• Giant Sloths the Size of Elephants Once Walked Along the Ground. Here's How the Massive Animals Evolved and Declined

    Giant Sloths the Size of Elephants Once Walked Along the Ground. Here’s How the Massive Animals Evolved and Declined
    Researchers analyzed fossils and DNA to get a big-picture view of sloth evolution and determine what drove their immense size variation

    Researchers revealed that differences in sloth habitats drove the wide variation in size seen in extinct species.
    Diego Barletta

    Today, sloths are slow-moving, tree-dwelling creatures that live in Central and South America and can grow up to 2.5 feet long. Thousands of years ago, however, some sloths walked along the ground, weighed around 8,000 pounds and were as big as Asian elephants. Some of these now-extinct species were “like grizzly bears, but five times larger,” as Rachel Narducci, collection manager of vertebrate paleontology at the Florida Museum of Natural History, says in a statement.
    In a study published last week in the journal Science, Narducci and her colleagues studied ancient and modern sloth DNA along with more than 400 sloth fossils to shed light on the shocking differences in their ancient sizes—from the elephant-sized Megatherium ground sloth to its 14-pound relatives living in trees. While it’s clear that tree-dwelling lifestyles necessitate small bodies, scientists weren’t sure why ground sloths specifically demonstrated such vast size diversity.
    To investigate this, the team used their genetic and fossil analyses to reconstruct a sloth tree of life that reaches back to the animals’ emergence more than 35 million years ago. They integrated data on sloths’ habitats, diets and mobility that had been gathered in previous research. With a computer model, they processed this information, which ultimately indicated that sloths’ size diversity was mostly driven by their habitats and climates.
    “When we look at what comes out in the literature, a lot of it is description of individual finds, or new taxa,” Greg McDonald, a retired regional paleontologist with the U.S. Bureau of Land Management who was not involved with the study, tells Science News’ Carolyn Gramling. The new work is “more holistic in terms of looking at a long-term pattern. Often, we don’t get a chance to step back and get the big picture of what’s going on.”
    The big picture suggests that since the emergence of the oldest known sloths—ground animals around the size of a Great Dane—the creatures evolved into and out of tree living a number of times. Around 14 million to 16 million years ago, however, a time of global warming called the Mid-Miocene Climatic Optimum pushed sloths to become smaller, which is a known way for animals to respond to heat stress.
    Warmer temperatures might have also seen more rain, which would have created more forest habitats ideal for tree-dwelling sloths. Around a million years later, however, ground sloths grew bigger as the planet’s temperature cooled. “Gigantism is more closely associated with cold and dry climates,” Daniel Casali, a co-author of the paper and a researcher of mammalian evolution at the University of São Paulo, tells New Scientist’s Jake Buehler.
    A larger body mass would have helped the animals traverse environments with few resources more efficiently, Narducci says in the statement. In fact, these large ground sloths spread out across diverse habitats and thrived in different regions. The aquatic sloth Thalassocnus even evolved marine adaptations similar to manatees.
    Ground sloths achieved their greatest size during the last ice age—right before starting to disappear around 15,000 years ago. Given that humans arrived in North America around the same time, some scientists say humans are the obvious cause of the sloths’ demise. While tree-dwelling sloths were out of reach to our ancestors, the large and slow ground animals would have made easy targets. Even still, two species of tree sloths in the Caribbean disappeared around 4,500 years ago—also shortly after humans first arrived in the region, according to the statement.
    While the study joins a host of research indicating that humans drove various large Ice Age animals to extinction, “in science, we need several lines of evidence to reinforce our hypotheses, especially in unresolved and highly debated issues such as the extinction of megafauna,” says Thaís Rabito Pansani, a paleontologist from the University of New Mexico who did not participate in the study, to New Scientist.
    The International Union for Conservation of Nature currently recognizes seven—following a recent species discovery—and three are endangered. As such, “one take-home message is that we need to act now to avoid a total extinction of the group,” says lead author Alberto Boscaini, a vertebrate paleontologist from the University of Buenos Aires, to the BBC’s Helen Briggs.

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    #giant #sloths #size #elephants #once
    Giant Sloths the Size of Elephants Once Walked Along the Ground. Here's How the Massive Animals Evolved and Declined
    Giant Sloths the Size of Elephants Once Walked Along the Ground. Here’s How the Massive Animals Evolved and Declined Researchers analyzed fossils and DNA to get a big-picture view of sloth evolution and determine what drove their immense size variation Researchers revealed that differences in sloth habitats drove the wide variation in size seen in extinct species. Diego Barletta Today, sloths are slow-moving, tree-dwelling creatures that live in Central and South America and can grow up to 2.5 feet long. Thousands of years ago, however, some sloths walked along the ground, weighed around 8,000 pounds and were as big as Asian elephants. Some of these now-extinct species were “like grizzly bears, but five times larger,” as Rachel Narducci, collection manager of vertebrate paleontology at the Florida Museum of Natural History, says in a statement. In a study published last week in the journal Science, Narducci and her colleagues studied ancient and modern sloth DNA along with more than 400 sloth fossils to shed light on the shocking differences in their ancient sizes—from the elephant-sized Megatherium ground sloth to its 14-pound relatives living in trees. While it’s clear that tree-dwelling lifestyles necessitate small bodies, scientists weren’t sure why ground sloths specifically demonstrated such vast size diversity. To investigate this, the team used their genetic and fossil analyses to reconstruct a sloth tree of life that reaches back to the animals’ emergence more than 35 million years ago. They integrated data on sloths’ habitats, diets and mobility that had been gathered in previous research. With a computer model, they processed this information, which ultimately indicated that sloths’ size diversity was mostly driven by their habitats and climates. “When we look at what comes out in the literature, a lot of it is description of individual finds, or new taxa,” Greg McDonald, a retired regional paleontologist with the U.S. Bureau of Land Management who was not involved with the study, tells Science News’ Carolyn Gramling. The new work is “more holistic in terms of looking at a long-term pattern. Often, we don’t get a chance to step back and get the big picture of what’s going on.” The big picture suggests that since the emergence of the oldest known sloths—ground animals around the size of a Great Dane—the creatures evolved into and out of tree living a number of times. Around 14 million to 16 million years ago, however, a time of global warming called the Mid-Miocene Climatic Optimum pushed sloths to become smaller, which is a known way for animals to respond to heat stress. Warmer temperatures might have also seen more rain, which would have created more forest habitats ideal for tree-dwelling sloths. Around a million years later, however, ground sloths grew bigger as the planet’s temperature cooled. “Gigantism is more closely associated with cold and dry climates,” Daniel Casali, a co-author of the paper and a researcher of mammalian evolution at the University of São Paulo, tells New Scientist’s Jake Buehler. A larger body mass would have helped the animals traverse environments with few resources more efficiently, Narducci says in the statement. In fact, these large ground sloths spread out across diverse habitats and thrived in different regions. The aquatic sloth Thalassocnus even evolved marine adaptations similar to manatees. Ground sloths achieved their greatest size during the last ice age—right before starting to disappear around 15,000 years ago. Given that humans arrived in North America around the same time, some scientists say humans are the obvious cause of the sloths’ demise. While tree-dwelling sloths were out of reach to our ancestors, the large and slow ground animals would have made easy targets. Even still, two species of tree sloths in the Caribbean disappeared around 4,500 years ago—also shortly after humans first arrived in the region, according to the statement. While the study joins a host of research indicating that humans drove various large Ice Age animals to extinction, “in science, we need several lines of evidence to reinforce our hypotheses, especially in unresolved and highly debated issues such as the extinction of megafauna,” says Thaís Rabito Pansani, a paleontologist from the University of New Mexico who did not participate in the study, to New Scientist. The International Union for Conservation of Nature currently recognizes seven—following a recent species discovery—and three are endangered. As such, “one take-home message is that we need to act now to avoid a total extinction of the group,” says lead author Alberto Boscaini, a vertebrate paleontologist from the University of Buenos Aires, to the BBC’s Helen Briggs. Get the latest stories in your inbox every weekday. #giant #sloths #size #elephants #once
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    Giant Sloths the Size of Elephants Once Walked Along the Ground. Here's How the Massive Animals Evolved and Declined
    Giant Sloths the Size of Elephants Once Walked Along the Ground. Here’s How the Massive Animals Evolved and Declined Researchers analyzed fossils and DNA to get a big-picture view of sloth evolution and determine what drove their immense size variation Researchers revealed that differences in sloth habitats drove the wide variation in size seen in extinct species. Diego Barletta Today, sloths are slow-moving, tree-dwelling creatures that live in Central and South America and can grow up to 2.5 feet long. Thousands of years ago, however, some sloths walked along the ground, weighed around 8,000 pounds and were as big as Asian elephants. Some of these now-extinct species were “like grizzly bears, but five times larger,” as Rachel Narducci, collection manager of vertebrate paleontology at the Florida Museum of Natural History, says in a statement. In a study published last week in the journal Science, Narducci and her colleagues studied ancient and modern sloth DNA along with more than 400 sloth fossils to shed light on the shocking differences in their ancient sizes—from the elephant-sized Megatherium ground sloth to its 14-pound relatives living in trees. While it’s clear that tree-dwelling lifestyles necessitate small bodies, scientists weren’t sure why ground sloths specifically demonstrated such vast size diversity. To investigate this, the team used their genetic and fossil analyses to reconstruct a sloth tree of life that reaches back to the animals’ emergence more than 35 million years ago. They integrated data on sloths’ habitats, diets and mobility that had been gathered in previous research. With a computer model, they processed this information, which ultimately indicated that sloths’ size diversity was mostly driven by their habitats and climates. “When we look at what comes out in the literature, a lot of it is description of individual finds, or new taxa,” Greg McDonald, a retired regional paleontologist with the U.S. Bureau of Land Management who was not involved with the study, tells Science News’ Carolyn Gramling. The new work is “more holistic in terms of looking at a long-term pattern. Often, we don’t get a chance to step back and get the big picture of what’s going on.” The big picture suggests that since the emergence of the oldest known sloths—ground animals around the size of a Great Dane—the creatures evolved into and out of tree living a number of times. Around 14 million to 16 million years ago, however, a time of global warming called the Mid-Miocene Climatic Optimum pushed sloths to become smaller, which is a known way for animals to respond to heat stress. Warmer temperatures might have also seen more rain, which would have created more forest habitats ideal for tree-dwelling sloths. Around a million years later, however, ground sloths grew bigger as the planet’s temperature cooled. “Gigantism is more closely associated with cold and dry climates,” Daniel Casali, a co-author of the paper and a researcher of mammalian evolution at the University of São Paulo, tells New Scientist’s Jake Buehler. A larger body mass would have helped the animals traverse environments with few resources more efficiently, Narducci says in the statement. In fact, these large ground sloths spread out across diverse habitats and thrived in different regions. The aquatic sloth Thalassocnus even evolved marine adaptations similar to manatees. Ground sloths achieved their greatest size during the last ice age—right before starting to disappear around 15,000 years ago. Given that humans arrived in North America around the same time (though recent research indicates they may have arrived as far back as 20,000 years ago), some scientists say humans are the obvious cause of the sloths’ demise. While tree-dwelling sloths were out of reach to our ancestors, the large and slow ground animals would have made easy targets. Even still, two species of tree sloths in the Caribbean disappeared around 4,500 years ago—also shortly after humans first arrived in the region, according to the statement. While the study joins a host of research indicating that humans drove various large Ice Age animals to extinction, “in science, we need several lines of evidence to reinforce our hypotheses, especially in unresolved and highly debated issues such as the extinction of megafauna,” says Thaís Rabito Pansani, a paleontologist from the University of New Mexico who did not participate in the study, to New Scientist. The International Union for Conservation of Nature currently recognizes seven—following a recent species discovery—and three are endangered. As such, “one take-home message is that we need to act now to avoid a total extinction of the group,” says lead author Alberto Boscaini, a vertebrate paleontologist from the University of Buenos Aires, to the BBC’s Helen Briggs. Get the latest stories in your inbox every weekday.
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  • 14 of the most significant archaeological sites in the US

    The US is less than 250 years old, but some of its most important archaeological sites are older than the Viking seafarers, the Roman Empire, and the pyramids.Many help tell the story of how the first humans came to North America. It's still a mystery exactly how and when people arrived, though it's widely believed they crossed the Bering Strait at least 15,000 years ago."As we get further back in time, as we get populations that are smaller and smaller, finding these places and interpreting them becomes increasingly difficult," archaeologist Kenneth Feder told Business Insider. He's the author of "Ancient America: Fifty Archaeological Sites to See for Yourself."Some sites, like White Sands and Cooper's Ferry, have skeptics about the accuracy of their age. Still, they contribute to our understanding of some of the earliest Americans.Others are more recent and highlight the different cultures that were spreading around the country, with complex buildings and illuminating pictographs.Many of these places are open to the public, so you can see the US' ancient history for yourself.

    White Sands National Park, New Mexico

    Footprints at White Sands.

    National Park Service

    Prehistoric camels, mammoths, and giant sloths once roamed what's now New Mexico, when it was greener and damper.As the climate warmed around 11,000 years ago, the water of Lake Otero receded, revealing footprints of humans who lived among these extinct animals. Some even seemed to be following a sloth, offering a rare glimpse into ancient hunters' behavior.Recent research puts some of these fossilized footprints at between 21,000 and 23,000 years old. If the dates are accurate, the prints would predate other archaeological sites in the US, raising intriguing questions about who these people were and how they arrived in the Southwestern state."Where are they coming from?" Feder said. "They're not parachute dropping in New Mexico. They must have come from somewhere else, which means there are even older sites." Archaeologists simply haven't found them yet.While visitors can soak in the sight of the eponymous white sands, the footprints are currently off-limits.

    Meadowcroft Rockshelter, Pennsylvania

    The archeological dig at the Meadowcroft National Historic Site in 2013.

    AP Photo/Keith Srakocic

    In the 1970s, archaeologist James M. Adovasio sparked a controversy when he and his colleagues suggested stone tools and other artifacts found in southwestern Pennsylvania belonged to humans who had lived in the area 16,000 years ago.For decades, scientists had been finding evidence of human habitation that all seemed to be around 12,000 to 13,000 years old, belonging to the Clovis culture. They were long believed to have been the first to cross the Bering land bridge. Humans who arrived in North America before this group are often referred to as pre-Clovis.At the time, skeptics said that the radiocarbon dating evidence was flawed, AP News reported in 2016. In the years since, more sites that appear older than 13,000 years have been found across the US.Feder said Adovasio meticulously excavated the site, but there's still no clear consensus about the age of the oldest artifacts. Still, he said, "that site is absolutely a major, important, significant site." It helped archaeologists realize humans started arriving on the continent before the Clovis people.The dig itself is on display at the Heinz History Center, allowing visitors to see an excavation in person.

    Cooper's Ferry, Idaho

    Excavators at Cooper's Ferry in 2013.

    Loren Davis/Oregon State University

    One site that's added intriguing evidence to the pre-Clovis theory is located in western Idaho. Humans living there left stone tools and charred bones in a hearth between 14,000 and 16,000 years ago, according to radiocarbon dating. Other researchers put the dates closer to 11,500 years ago.These stemmed tools are different from the Clovis fluted projectiles, researchers wrote in a 2019 Science Advances paper.Some scientists think humans may have been traveling along the West Coast at this time, when huge ice sheets covered Alaska and Canada. "People using boats, using canoes could hop along that coast and end up in North America long before those glacial ice bodies decoupled," Feder said.Cooper's Ferry is located on traditional Nez Perce land, which the Bureau of Land Management holds in public ownership.

    Page-Ladson, Florida

    Divers search in the sediment at the Page-Ladson site.

    Texas A&M University via Getty Images

    In the early 1980s, former Navy SEAL Buddy Page alerted paleontologists and archaeologists to a sinkhole nicknamed "Booger Hole" in the Aucilla River. There, the researchers found mammoth and mastodon bones and stone tools.They also discovered a mastodon tusk with what appeared to be cut marks believed to be made by a tool. Other scientists have returned to the site more recently, bringing up more bones and tools. They used radiocarbon dating, which established the site as pre-Clovis."The stone tools and faunal remains at the site show that at 14,550 years ago, people knew how to find game, fresh water and material for making tools," Michael Waters, one of the researchers, said in a statement in 2016. "These people were well-adapted to this environment."Since the site is both underwater and on private property, it's not open to visitors.

    Paisley Caves, Oregon

    One of the Paisley Caves near Paisley, Oregon.

    AP Photo/Jeff Barnard

    Scientists study coprolites, or fossilized poop, to learn about the diets of long-dead animals. Mineralized waste can also reveal much more. In 2020, archaeologist Dennis Jenkins published a paper on coprolites from an Oregon cave that were over 14,000 years old.Radiocarbon dating gave the trace fossils' age, and genetic tests suggested they belonged to humans. Further analysis of coprolites added additional evidence that a group had been on the West Coast 1,000 years before the Clovis people arrived.Located in southcentral Oregon, the caves appear to be a piece of the puzzle indicating how humans spread throughout the continent thousands of years ago.The federal Bureau of Land Management owns the land where the caves are found, and they are listed on the National Register of Historic Places.

    Swan Point, Alaska

    Excavators working at the Swan Point site in June 2016.

    Charles Holmes/University of Alaska, Fairbanks

    Whenever people arrived in the Americas, they crossed from Siberia into Beringia, an area of land and sea between Russia and Canada and Alaska. Now it's covered in water, but there was once a land bridge connecting them.The site in Alaska with the oldest evidence of human habitation is Swan Point, in the state's eastern-central region. In addition to tools and hearths dating back 14,000 years, mammoth bones have been found there.Researchers think this area was a kind of seasonal hunting camp. As mammoths returned during certain times of the years, humans would track them and kill them, providing plentiful food for the hunter-gatherers.While Alaska may have a wealth of archaeological evidence of early Americans, it's also a difficult place to excavate. "Your digging season is very narrow, and it's expensive," Feder said. Some require a helicopter to reach, for example.

    Blackwater Draw, New Mexico

    A palaeontologist excavating a mammoth in Portales, New Mexico, circa 1960.

    Dick Kent/FPG/Archive Photos/Getty Images

    In 1929, 19-year-old James Ridgley Whiteman found mammoth bones along with fluted projectile points near Clovis, New Mexico. The Clovis people who made these tools were named for this site.Researchers studying the site began to realize the artifacts found at the site belonged to different cultures. Clovis points are typically larger than Folsom flutes, which were first found at another archaeological site in New Mexico.For decades after Whiteman's discovery, experts thought the Clovis people were the first to cross the Bering land bridge from Asia around 13,000 years ago. Estimates for humans' arrival is now thought to be at least 15,000 years ago.Eastern New Mexico University's Blackwater Draw Museum grants access to the archaeological site between April and October.

    Upper Sun River, Alaska

    Excavations at the Upward Sun River, Alaska.

    Ben Potter/University of Alaska, Fairbanks

    One reason the dates of human occupation in North America is so contentious is that very few ancient remains have been found. Among the oldest is a child from Upward Sun River, or Xaasaa Na', in Central Alaska.Archaeologists found the bones of the child in 2013. Local indigenous groups refer to her as Xach'itee'aanenh t'eede gay, or Sunrise Girl-Child. Genetic testing revealed the 11,300-year-old infant belonged to a previously unknown Native American population, the Ancient Beringians.Based on the child's genetic information, researchers learned that she was related to modern Native Americans but not directly. Their common ancestors started becoming genetically isolated 25,000 years ago before dividing into two groups after a few thousand years: the Ancient Berignians and the ancestors of modern Native Americans.According to this research, it's possible humans reached Alaska roughly 20,000 years ago.

    Poverty Point National Monument, Louisiana

    Poverty Point in Louisiana.

    National Park Service

    Stretching over 80 feet long and 5 feet tall, the rows of curved mounds of Poverty Point are a marvel when viewed from above. Over 3,000 years ago, hunter-gatherers constructed them out of tons of soil. Scientists aren't sure exactly why people built them, whether they were ceremonial or a display of status.The artifacts various groups left behind indicate the site was used off and on for hundreds of years and was a meeting point for trading. People brought tools and rocks from as far as 800 miles away. Remains of deer, fish, frogs, alligators, nuts, grapes, and other food have given archaeologists insights into their diets and daily lives.You can see the World Heritage Site for yourself year-round.

    Horseshoe Canyon, Utah

    The Great Gallery in Horseshoe Canyon.

    Neal Herbert/National Park Service

    Though remote, the multicolored walls of Horseshoe Canyon have long attracted visitors. Some of its artifacts date back to between 9,000 and 7,000 BCE, but its pictographs are more recent. Some tests date certain sections to around 2,000 to 900 years ago.The four galleries contain life-sized images of anthropomorphic figures and animals in what's known as the Barrier Canyon style. Much of this art is found in Utah, produced by the Desert Archaic culture.The pictographs may have spiritual and practical significance but also help capture a time when groups were meeting and mixing, according to the Natural History Museum of Utah.It's a difficult trek to get to the pictographsbut are amazing to view in person, Feder said. "These are creative geniuses," he said of the artists.

    Canyon de Chelly, Arizona

    The Antelope House at Canyon de Chelly National Monument.

    Michael Denson/National Park Service

    Situated in the Navajo Nation, Canyon de Chelly has gorgeous desert views and thousands of years of human history. Centuries ago, Ancestral Pueblo and Hopi groups planted crops, created pictographs, and built cliff dwellings.Over 900 years ago, Puebloan people constructed the White House, named for the hue of its clay. Its upper floors sit on a sandstone cliff, with a sheer drop outside the windows.Navajo people, also known as Diné, still live in Canyon de Chelly. Diné journalist Alastair Lee Bitsóí recently wrote about visiting some of the sacred and taboo areas. They include Tsé Yaa Kin, where archaeologists found human remains.In the 1860s, the US government forced 8,000 Navajo to relocate to Fort Sumner in New Mexico. The deadly journey is known as the "Long Walk." Eventually, they were able to return, though their homes and crops were destroyed.A hike to the White House is the only one open to the public without a Navajo guide or NPS ranger.

    Mesa Verde National Park, Colorado

    Visitors line up at Mesa Verde National Park.

    Shutterstock/Don Mammoser

    In the early 1900s, two women formed the Colorado Cliff Dwelling Association, hoping to preserve the ruins in the state's southwestern region. A few years later, President Theodore Roosevelt signed a bill designating Mesa Verde as the first national park meant to "preserve the works of man."Mesa Verde National Park holds hundreds of dwellings, including the sprawling Cliff Palace. It has over 100 rooms and nearly two dozen kivas, or ceremonial spaces.Using dendrochronology, or tree-ring dating, archaeologists learned when Ancestral Pueblo people built some of these structures and that they migrated out of the area by the 1300s.Feder said it's his favorite archaeological site he's visited. "You don't want to leave because you can't believe it's real," he said.Tourists can view many of these dwellings from the road, but some are also accessible after a bit of a hike. Some require extra tickets and can get crowded, Feder said.

    Cahokia, Illinois

    A mound at Cahokia in Illinois.

    Matt Gush/Shutterstock

    Cahokia has been called one of North America's first cities. Not far from present-day St. Louis, an estimated 10,000 to 20,000 people lived in dense settlements roughly 1,000 years ago. Important buildings sat atop large mounds, which the Mississippians built by hand, The Guardian reported.At the time, it was thriving with hunters, farmers, and artisans. "It's an agricultural civilization," Feder said. "It's a place where raw materials from a thousand miles away are coming in." Researchers have also found mass graves, potentially from human sacrifices.The inhabitants built circles of posts, which one archaeologist later referred to as "woodhenges," as a kind of calendar. At the solstices, the sun would rise or set aligned with different mounds.After a few hundred years, Cahokia's population declined and disappeared by 1350. Its largest mound remains, and some aspects have been reconstructed.While Cahokia is typically open to the public, parts are currently closed for renovations.

    Montezuma Castle, Arizona

    Montezuma Castle, a cliff dwelling, in Arizona.

    MyLoupe/Universal Images Group via Getty Images

    Perched on a limestone cliff in Camp Verde, Arizona, this site is an apartment, not a castle, and is unrelated to the Aztec ruler Montezuma.The Sinagua people engineered the five-story, 20-room building around 1100. It curves to follow the natural line of the cliff, which would have been more difficult than simply making a straight building, Feder said."These people were architects," he said. "They had a sense of beauty."The inhabitants were also practical, figuring out irrigation systems and construction techniques, like thick walls and shady spots, to help them survive the hot, dry climate.Feder said the dwelling is fairly accessible, with a short walk along a trail to view it, though visitors can't go inside the building itself.
    #most #significant #archaeological #sites
    14 of the most significant archaeological sites in the US
    The US is less than 250 years old, but some of its most important archaeological sites are older than the Viking seafarers, the Roman Empire, and the pyramids.Many help tell the story of how the first humans came to North America. It's still a mystery exactly how and when people arrived, though it's widely believed they crossed the Bering Strait at least 15,000 years ago."As we get further back in time, as we get populations that are smaller and smaller, finding these places and interpreting them becomes increasingly difficult," archaeologist Kenneth Feder told Business Insider. He's the author of "Ancient America: Fifty Archaeological Sites to See for Yourself."Some sites, like White Sands and Cooper's Ferry, have skeptics about the accuracy of their age. Still, they contribute to our understanding of some of the earliest Americans.Others are more recent and highlight the different cultures that were spreading around the country, with complex buildings and illuminating pictographs.Many of these places are open to the public, so you can see the US' ancient history for yourself. White Sands National Park, New Mexico Footprints at White Sands. National Park Service Prehistoric camels, mammoths, and giant sloths once roamed what's now New Mexico, when it was greener and damper.As the climate warmed around 11,000 years ago, the water of Lake Otero receded, revealing footprints of humans who lived among these extinct animals. Some even seemed to be following a sloth, offering a rare glimpse into ancient hunters' behavior.Recent research puts some of these fossilized footprints at between 21,000 and 23,000 years old. If the dates are accurate, the prints would predate other archaeological sites in the US, raising intriguing questions about who these people were and how they arrived in the Southwestern state."Where are they coming from?" Feder said. "They're not parachute dropping in New Mexico. They must have come from somewhere else, which means there are even older sites." Archaeologists simply haven't found them yet.While visitors can soak in the sight of the eponymous white sands, the footprints are currently off-limits. Meadowcroft Rockshelter, Pennsylvania The archeological dig at the Meadowcroft National Historic Site in 2013. AP Photo/Keith Srakocic In the 1970s, archaeologist James M. Adovasio sparked a controversy when he and his colleagues suggested stone tools and other artifacts found in southwestern Pennsylvania belonged to humans who had lived in the area 16,000 years ago.For decades, scientists had been finding evidence of human habitation that all seemed to be around 12,000 to 13,000 years old, belonging to the Clovis culture. They were long believed to have been the first to cross the Bering land bridge. Humans who arrived in North America before this group are often referred to as pre-Clovis.At the time, skeptics said that the radiocarbon dating evidence was flawed, AP News reported in 2016. In the years since, more sites that appear older than 13,000 years have been found across the US.Feder said Adovasio meticulously excavated the site, but there's still no clear consensus about the age of the oldest artifacts. Still, he said, "that site is absolutely a major, important, significant site." It helped archaeologists realize humans started arriving on the continent before the Clovis people.The dig itself is on display at the Heinz History Center, allowing visitors to see an excavation in person. Cooper's Ferry, Idaho Excavators at Cooper's Ferry in 2013. Loren Davis/Oregon State University One site that's added intriguing evidence to the pre-Clovis theory is located in western Idaho. Humans living there left stone tools and charred bones in a hearth between 14,000 and 16,000 years ago, according to radiocarbon dating. Other researchers put the dates closer to 11,500 years ago.These stemmed tools are different from the Clovis fluted projectiles, researchers wrote in a 2019 Science Advances paper.Some scientists think humans may have been traveling along the West Coast at this time, when huge ice sheets covered Alaska and Canada. "People using boats, using canoes could hop along that coast and end up in North America long before those glacial ice bodies decoupled," Feder said.Cooper's Ferry is located on traditional Nez Perce land, which the Bureau of Land Management holds in public ownership. Page-Ladson, Florida Divers search in the sediment at the Page-Ladson site. Texas A&M University via Getty Images In the early 1980s, former Navy SEAL Buddy Page alerted paleontologists and archaeologists to a sinkhole nicknamed "Booger Hole" in the Aucilla River. There, the researchers found mammoth and mastodon bones and stone tools.They also discovered a mastodon tusk with what appeared to be cut marks believed to be made by a tool. Other scientists have returned to the site more recently, bringing up more bones and tools. They used radiocarbon dating, which established the site as pre-Clovis."The stone tools and faunal remains at the site show that at 14,550 years ago, people knew how to find game, fresh water and material for making tools," Michael Waters, one of the researchers, said in a statement in 2016. "These people were well-adapted to this environment."Since the site is both underwater and on private property, it's not open to visitors. Paisley Caves, Oregon One of the Paisley Caves near Paisley, Oregon. AP Photo/Jeff Barnard Scientists study coprolites, or fossilized poop, to learn about the diets of long-dead animals. Mineralized waste can also reveal much more. In 2020, archaeologist Dennis Jenkins published a paper on coprolites from an Oregon cave that were over 14,000 years old.Radiocarbon dating gave the trace fossils' age, and genetic tests suggested they belonged to humans. Further analysis of coprolites added additional evidence that a group had been on the West Coast 1,000 years before the Clovis people arrived.Located in southcentral Oregon, the caves appear to be a piece of the puzzle indicating how humans spread throughout the continent thousands of years ago.The federal Bureau of Land Management owns the land where the caves are found, and they are listed on the National Register of Historic Places. Swan Point, Alaska Excavators working at the Swan Point site in June 2016. Charles Holmes/University of Alaska, Fairbanks Whenever people arrived in the Americas, they crossed from Siberia into Beringia, an area of land and sea between Russia and Canada and Alaska. Now it's covered in water, but there was once a land bridge connecting them.The site in Alaska with the oldest evidence of human habitation is Swan Point, in the state's eastern-central region. In addition to tools and hearths dating back 14,000 years, mammoth bones have been found there.Researchers think this area was a kind of seasonal hunting camp. As mammoths returned during certain times of the years, humans would track them and kill them, providing plentiful food for the hunter-gatherers.While Alaska may have a wealth of archaeological evidence of early Americans, it's also a difficult place to excavate. "Your digging season is very narrow, and it's expensive," Feder said. Some require a helicopter to reach, for example. Blackwater Draw, New Mexico A palaeontologist excavating a mammoth in Portales, New Mexico, circa 1960. Dick Kent/FPG/Archive Photos/Getty Images In 1929, 19-year-old James Ridgley Whiteman found mammoth bones along with fluted projectile points near Clovis, New Mexico. The Clovis people who made these tools were named for this site.Researchers studying the site began to realize the artifacts found at the site belonged to different cultures. Clovis points are typically larger than Folsom flutes, which were first found at another archaeological site in New Mexico.For decades after Whiteman's discovery, experts thought the Clovis people were the first to cross the Bering land bridge from Asia around 13,000 years ago. Estimates for humans' arrival is now thought to be at least 15,000 years ago.Eastern New Mexico University's Blackwater Draw Museum grants access to the archaeological site between April and October. Upper Sun River, Alaska Excavations at the Upward Sun River, Alaska. Ben Potter/University of Alaska, Fairbanks One reason the dates of human occupation in North America is so contentious is that very few ancient remains have been found. Among the oldest is a child from Upward Sun River, or Xaasaa Na', in Central Alaska.Archaeologists found the bones of the child in 2013. Local indigenous groups refer to her as Xach'itee'aanenh t'eede gay, or Sunrise Girl-Child. Genetic testing revealed the 11,300-year-old infant belonged to a previously unknown Native American population, the Ancient Beringians.Based on the child's genetic information, researchers learned that she was related to modern Native Americans but not directly. Their common ancestors started becoming genetically isolated 25,000 years ago before dividing into two groups after a few thousand years: the Ancient Berignians and the ancestors of modern Native Americans.According to this research, it's possible humans reached Alaska roughly 20,000 years ago. Poverty Point National Monument, Louisiana Poverty Point in Louisiana. National Park Service Stretching over 80 feet long and 5 feet tall, the rows of curved mounds of Poverty Point are a marvel when viewed from above. Over 3,000 years ago, hunter-gatherers constructed them out of tons of soil. Scientists aren't sure exactly why people built them, whether they were ceremonial or a display of status.The artifacts various groups left behind indicate the site was used off and on for hundreds of years and was a meeting point for trading. People brought tools and rocks from as far as 800 miles away. Remains of deer, fish, frogs, alligators, nuts, grapes, and other food have given archaeologists insights into their diets and daily lives.You can see the World Heritage Site for yourself year-round. Horseshoe Canyon, Utah The Great Gallery in Horseshoe Canyon. Neal Herbert/National Park Service Though remote, the multicolored walls of Horseshoe Canyon have long attracted visitors. Some of its artifacts date back to between 9,000 and 7,000 BCE, but its pictographs are more recent. Some tests date certain sections to around 2,000 to 900 years ago.The four galleries contain life-sized images of anthropomorphic figures and animals in what's known as the Barrier Canyon style. Much of this art is found in Utah, produced by the Desert Archaic culture.The pictographs may have spiritual and practical significance but also help capture a time when groups were meeting and mixing, according to the Natural History Museum of Utah.It's a difficult trek to get to the pictographsbut are amazing to view in person, Feder said. "These are creative geniuses," he said of the artists. Canyon de Chelly, Arizona The Antelope House at Canyon de Chelly National Monument. Michael Denson/National Park Service Situated in the Navajo Nation, Canyon de Chelly has gorgeous desert views and thousands of years of human history. Centuries ago, Ancestral Pueblo and Hopi groups planted crops, created pictographs, and built cliff dwellings.Over 900 years ago, Puebloan people constructed the White House, named for the hue of its clay. Its upper floors sit on a sandstone cliff, with a sheer drop outside the windows.Navajo people, also known as Diné, still live in Canyon de Chelly. Diné journalist Alastair Lee Bitsóí recently wrote about visiting some of the sacred and taboo areas. They include Tsé Yaa Kin, where archaeologists found human remains.In the 1860s, the US government forced 8,000 Navajo to relocate to Fort Sumner in New Mexico. The deadly journey is known as the "Long Walk." Eventually, they were able to return, though their homes and crops were destroyed.A hike to the White House is the only one open to the public without a Navajo guide or NPS ranger. Mesa Verde National Park, Colorado Visitors line up at Mesa Verde National Park. Shutterstock/Don Mammoser In the early 1900s, two women formed the Colorado Cliff Dwelling Association, hoping to preserve the ruins in the state's southwestern region. A few years later, President Theodore Roosevelt signed a bill designating Mesa Verde as the first national park meant to "preserve the works of man."Mesa Verde National Park holds hundreds of dwellings, including the sprawling Cliff Palace. It has over 100 rooms and nearly two dozen kivas, or ceremonial spaces.Using dendrochronology, or tree-ring dating, archaeologists learned when Ancestral Pueblo people built some of these structures and that they migrated out of the area by the 1300s.Feder said it's his favorite archaeological site he's visited. "You don't want to leave because you can't believe it's real," he said.Tourists can view many of these dwellings from the road, but some are also accessible after a bit of a hike. Some require extra tickets and can get crowded, Feder said. Cahokia, Illinois A mound at Cahokia in Illinois. Matt Gush/Shutterstock Cahokia has been called one of North America's first cities. Not far from present-day St. Louis, an estimated 10,000 to 20,000 people lived in dense settlements roughly 1,000 years ago. Important buildings sat atop large mounds, which the Mississippians built by hand, The Guardian reported.At the time, it was thriving with hunters, farmers, and artisans. "It's an agricultural civilization," Feder said. "It's a place where raw materials from a thousand miles away are coming in." Researchers have also found mass graves, potentially from human sacrifices.The inhabitants built circles of posts, which one archaeologist later referred to as "woodhenges," as a kind of calendar. At the solstices, the sun would rise or set aligned with different mounds.After a few hundred years, Cahokia's population declined and disappeared by 1350. Its largest mound remains, and some aspects have been reconstructed.While Cahokia is typically open to the public, parts are currently closed for renovations. Montezuma Castle, Arizona Montezuma Castle, a cliff dwelling, in Arizona. MyLoupe/Universal Images Group via Getty Images Perched on a limestone cliff in Camp Verde, Arizona, this site is an apartment, not a castle, and is unrelated to the Aztec ruler Montezuma.The Sinagua people engineered the five-story, 20-room building around 1100. It curves to follow the natural line of the cliff, which would have been more difficult than simply making a straight building, Feder said."These people were architects," he said. "They had a sense of beauty."The inhabitants were also practical, figuring out irrigation systems and construction techniques, like thick walls and shady spots, to help them survive the hot, dry climate.Feder said the dwelling is fairly accessible, with a short walk along a trail to view it, though visitors can't go inside the building itself. #most #significant #archaeological #sites
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    14 of the most significant archaeological sites in the US
    The US is less than 250 years old, but some of its most important archaeological sites are older than the Viking seafarers, the Roman Empire, and the pyramids.Many help tell the story of how the first humans came to North America. It's still a mystery exactly how and when people arrived, though it's widely believed they crossed the Bering Strait at least 15,000 years ago."As we get further back in time, as we get populations that are smaller and smaller, finding these places and interpreting them becomes increasingly difficult," archaeologist Kenneth Feder told Business Insider. He's the author of "Ancient America: Fifty Archaeological Sites to See for Yourself."Some sites, like White Sands and Cooper's Ferry, have skeptics about the accuracy of their age. Still, they contribute to our understanding of some of the earliest Americans.Others are more recent and highlight the different cultures that were spreading around the country, with complex buildings and illuminating pictographs.Many of these places are open to the public, so you can see the US' ancient history for yourself. White Sands National Park, New Mexico Footprints at White Sands. National Park Service Prehistoric camels, mammoths, and giant sloths once roamed what's now New Mexico, when it was greener and damper.As the climate warmed around 11,000 years ago, the water of Lake Otero receded, revealing footprints of humans who lived among these extinct animals. Some even seemed to be following a sloth, offering a rare glimpse into ancient hunters' behavior.Recent research puts some of these fossilized footprints at between 21,000 and 23,000 years old. If the dates are accurate, the prints would predate other archaeological sites in the US, raising intriguing questions about who these people were and how they arrived in the Southwestern state."Where are they coming from?" Feder said. "They're not parachute dropping in New Mexico. They must have come from somewhere else, which means there are even older sites." Archaeologists simply haven't found them yet.While visitors can soak in the sight of the eponymous white sands, the footprints are currently off-limits. Meadowcroft Rockshelter, Pennsylvania The archeological dig at the Meadowcroft National Historic Site in 2013. AP Photo/Keith Srakocic In the 1970s, archaeologist James M. Adovasio sparked a controversy when he and his colleagues suggested stone tools and other artifacts found in southwestern Pennsylvania belonged to humans who had lived in the area 16,000 years ago.For decades, scientists had been finding evidence of human habitation that all seemed to be around 12,000 to 13,000 years old, belonging to the Clovis culture. They were long believed to have been the first to cross the Bering land bridge. Humans who arrived in North America before this group are often referred to as pre-Clovis.At the time, skeptics said that the radiocarbon dating evidence was flawed, AP News reported in 2016. In the years since, more sites that appear older than 13,000 years have been found across the US.Feder said Adovasio meticulously excavated the site, but there's still no clear consensus about the age of the oldest artifacts. Still, he said, "that site is absolutely a major, important, significant site." It helped archaeologists realize humans started arriving on the continent before the Clovis people.The dig itself is on display at the Heinz History Center, allowing visitors to see an excavation in person. Cooper's Ferry, Idaho Excavators at Cooper's Ferry in 2013. Loren Davis/Oregon State University One site that's added intriguing evidence to the pre-Clovis theory is located in western Idaho. Humans living there left stone tools and charred bones in a hearth between 14,000 and 16,000 years ago, according to radiocarbon dating. Other researchers put the dates closer to 11,500 years ago.These stemmed tools are different from the Clovis fluted projectiles, researchers wrote in a 2019 Science Advances paper.Some scientists think humans may have been traveling along the West Coast at this time, when huge ice sheets covered Alaska and Canada. "People using boats, using canoes could hop along that coast and end up in North America long before those glacial ice bodies decoupled," Feder said.Cooper's Ferry is located on traditional Nez Perce land, which the Bureau of Land Management holds in public ownership. Page-Ladson, Florida Divers search in the sediment at the Page-Ladson site. Texas A&M University via Getty Images In the early 1980s, former Navy SEAL Buddy Page alerted paleontologists and archaeologists to a sinkhole nicknamed "Booger Hole" in the Aucilla River. There, the researchers found mammoth and mastodon bones and stone tools.They also discovered a mastodon tusk with what appeared to be cut marks believed to be made by a tool. Other scientists have returned to the site more recently, bringing up more bones and tools. They used radiocarbon dating, which established the site as pre-Clovis."The stone tools and faunal remains at the site show that at 14,550 years ago, people knew how to find game, fresh water and material for making tools," Michael Waters, one of the researchers, said in a statement in 2016. "These people were well-adapted to this environment."Since the site is both underwater and on private property, it's not open to visitors. Paisley Caves, Oregon One of the Paisley Caves near Paisley, Oregon. AP Photo/Jeff Barnard Scientists study coprolites, or fossilized poop, to learn about the diets of long-dead animals. Mineralized waste can also reveal much more. In 2020, archaeologist Dennis Jenkins published a paper on coprolites from an Oregon cave that were over 14,000 years old.Radiocarbon dating gave the trace fossils' age, and genetic tests suggested they belonged to humans. Further analysis of coprolites added additional evidence that a group had been on the West Coast 1,000 years before the Clovis people arrived.Located in southcentral Oregon, the caves appear to be a piece of the puzzle indicating how humans spread throughout the continent thousands of years ago.The federal Bureau of Land Management owns the land where the caves are found, and they are listed on the National Register of Historic Places. Swan Point, Alaska Excavators working at the Swan Point site in June 2016. Charles Holmes/University of Alaska, Fairbanks Whenever people arrived in the Americas, they crossed from Siberia into Beringia, an area of land and sea between Russia and Canada and Alaska. Now it's covered in water, but there was once a land bridge connecting them.The site in Alaska with the oldest evidence of human habitation is Swan Point, in the state's eastern-central region. In addition to tools and hearths dating back 14,000 years, mammoth bones have been found there.Researchers think this area was a kind of seasonal hunting camp. As mammoths returned during certain times of the years, humans would track them and kill them, providing plentiful food for the hunter-gatherers.While Alaska may have a wealth of archaeological evidence of early Americans, it's also a difficult place to excavate. "Your digging season is very narrow, and it's expensive," Feder said. Some require a helicopter to reach, for example. Blackwater Draw, New Mexico A palaeontologist excavating a mammoth in Portales, New Mexico, circa 1960. Dick Kent/FPG/Archive Photos/Getty Images In 1929, 19-year-old James Ridgley Whiteman found mammoth bones along with fluted projectile points near Clovis, New Mexico. The Clovis people who made these tools were named for this site.Researchers studying the site began to realize the artifacts found at the site belonged to different cultures. Clovis points are typically larger than Folsom flutes, which were first found at another archaeological site in New Mexico.For decades after Whiteman's discovery, experts thought the Clovis people were the first to cross the Bering land bridge from Asia around 13,000 years ago. Estimates for humans' arrival is now thought to be at least 15,000 years ago.Eastern New Mexico University's Blackwater Draw Museum grants access to the archaeological site between April and October. Upper Sun River, Alaska Excavations at the Upward Sun River, Alaska. Ben Potter/University of Alaska, Fairbanks One reason the dates of human occupation in North America is so contentious is that very few ancient remains have been found. Among the oldest is a child from Upward Sun River, or Xaasaa Na', in Central Alaska.Archaeologists found the bones of the child in 2013. Local indigenous groups refer to her as Xach'itee'aanenh t'eede gay, or Sunrise Girl-Child. Genetic testing revealed the 11,300-year-old infant belonged to a previously unknown Native American population, the Ancient Beringians.Based on the child's genetic information, researchers learned that she was related to modern Native Americans but not directly. Their common ancestors started becoming genetically isolated 25,000 years ago before dividing into two groups after a few thousand years: the Ancient Berignians and the ancestors of modern Native Americans.According to this research, it's possible humans reached Alaska roughly 20,000 years ago. Poverty Point National Monument, Louisiana Poverty Point in Louisiana. National Park Service Stretching over 80 feet long and 5 feet tall, the rows of curved mounds of Poverty Point are a marvel when viewed from above. Over 3,000 years ago, hunter-gatherers constructed them out of tons of soil. Scientists aren't sure exactly why people built them, whether they were ceremonial or a display of status.The artifacts various groups left behind indicate the site was used off and on for hundreds of years and was a meeting point for trading. People brought tools and rocks from as far as 800 miles away. Remains of deer, fish, frogs, alligators, nuts, grapes, and other food have given archaeologists insights into their diets and daily lives.You can see the World Heritage Site for yourself year-round. Horseshoe Canyon, Utah The Great Gallery in Horseshoe Canyon. Neal Herbert/National Park Service Though remote, the multicolored walls of Horseshoe Canyon have long attracted visitors. Some of its artifacts date back to between 9,000 and 7,000 BCE, but its pictographs are more recent. Some tests date certain sections to around 2,000 to 900 years ago.The four galleries contain life-sized images of anthropomorphic figures and animals in what's known as the Barrier Canyon style. Much of this art is found in Utah, produced by the Desert Archaic culture.The pictographs may have spiritual and practical significance but also help capture a time when groups were meeting and mixing, according to the Natural History Museum of Utah.It's a difficult trek to get to the pictographs (and the NPS warns it can be dangerously hot in summer) but are amazing to view in person, Feder said. "These are creative geniuses," he said of the artists. Canyon de Chelly, Arizona The Antelope House at Canyon de Chelly National Monument. Michael Denson/National Park Service Situated in the Navajo Nation, Canyon de Chelly has gorgeous desert views and thousands of years of human history. Centuries ago, Ancestral Pueblo and Hopi groups planted crops, created pictographs, and built cliff dwellings.Over 900 years ago, Puebloan people constructed the White House, named for the hue of its clay. Its upper floors sit on a sandstone cliff, with a sheer drop outside the windows.Navajo people, also known as Diné, still live in Canyon de Chelly. Diné journalist Alastair Lee Bitsóí recently wrote about visiting some of the sacred and taboo areas. They include Tsé Yaa Kin, where archaeologists found human remains.In the 1860s, the US government forced 8,000 Navajo to relocate to Fort Sumner in New Mexico. The deadly journey is known as the "Long Walk." Eventually, they were able to return, though their homes and crops were destroyed.A hike to the White House is the only one open to the public without a Navajo guide or NPS ranger. Mesa Verde National Park, Colorado Visitors line up at Mesa Verde National Park. Shutterstock/Don Mammoser In the early 1900s, two women formed the Colorado Cliff Dwelling Association, hoping to preserve the ruins in the state's southwestern region. A few years later, President Theodore Roosevelt signed a bill designating Mesa Verde as the first national park meant to "preserve the works of man."Mesa Verde National Park holds hundreds of dwellings, including the sprawling Cliff Palace. It has over 100 rooms and nearly two dozen kivas, or ceremonial spaces.Using dendrochronology, or tree-ring dating, archaeologists learned when Ancestral Pueblo people built some of these structures and that they migrated out of the area by the 1300s.Feder said it's his favorite archaeological site he's visited. "You don't want to leave because you can't believe it's real," he said.Tourists can view many of these dwellings from the road, but some are also accessible after a bit of a hike. Some require extra tickets and can get crowded, Feder said. Cahokia, Illinois A mound at Cahokia in Illinois. Matt Gush/Shutterstock Cahokia has been called one of North America's first cities. Not far from present-day St. Louis, an estimated 10,000 to 20,000 people lived in dense settlements roughly 1,000 years ago. Important buildings sat atop large mounds, which the Mississippians built by hand, The Guardian reported.At the time, it was thriving with hunters, farmers, and artisans. "It's an agricultural civilization," Feder said. "It's a place where raw materials from a thousand miles away are coming in." Researchers have also found mass graves, potentially from human sacrifices.The inhabitants built circles of posts, which one archaeologist later referred to as "woodhenges," as a kind of calendar. At the solstices, the sun would rise or set aligned with different mounds.After a few hundred years, Cahokia's population declined and disappeared by 1350. Its largest mound remains, and some aspects have been reconstructed.While Cahokia is typically open to the public, parts are currently closed for renovations. Montezuma Castle, Arizona Montezuma Castle, a cliff dwelling, in Arizona. MyLoupe/Universal Images Group via Getty Images Perched on a limestone cliff in Camp Verde, Arizona, this site is an apartment, not a castle, and is unrelated to the Aztec ruler Montezuma.The Sinagua people engineered the five-story, 20-room building around 1100. It curves to follow the natural line of the cliff, which would have been more difficult than simply making a straight building, Feder said."These people were architects," he said. "They had a sense of beauty."The inhabitants were also practical, figuring out irrigation systems and construction techniques, like thick walls and shady spots, to help them survive the hot, dry climate.Feder said the dwelling is fairly accessible, with a short walk along a trail to view it, though visitors can't go inside the building itself.
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  • Why Ancient Sloths Became the Size of Elephants—and Then Vanished

    By

    Natalia Mesa

    Published May 23, 2025

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    Comments|

    Giant ground sloths Megalocnus rodens and Megalonyx wheatleyi at the American Museum of Natural History © Dallas Krentzel

    Giant sloths with razor-sharp claws and as large as Asian bull elephants once roamed the Earth, snacking on leaves at the tops of trees with a prehensile tongue. Now, scientists have figured out why they became so huge—and why these massive sloths didn’t stick around—according to a new study published in Science. Today, two sloth species dwell in Central and South America. But long ago, dozens of sloth species populated the Americas, all the way from Argentina to Canada. Like modern-day sloths, the smaller species were tree-dwelling. But the larger sloths? “They looked like grizzly bears but five times larger,” Rachel Narducci, collection manager of vertebrate paleontology at the Florida Museum of Natural History and coauthor of the study, in a statement. The larger sloths didn’t do much tree climbing, at risk of falling to their deaths. Instead, they survived by being terrifying; the largest sloths had long, sharp claws that they used to carve their own caves out of raw earth and rocks. But exactly why they got so large remained a mystery.

    To figure out how these sloths got so massive, researchers analyzed ancient sloth DNA and compared more than 400 fossils from natural history museums to create a sloth tree of life. The researchers traced the sloths’ origin to 35 million years ago. And, because the scientists were particularly interested in how sloths got their size, they estimated their weights by taking fossil measurements. The researchers concluded that the Earth’s past climate was a big factor. Thirty-five million years ago, the first ancestor of modern-day sloths, which lived in what is now Argentina, was roughly the size of a large dog. Sloths hardly changed in size for 20 million years, and lived on the ground. Then, during a warming period around 16 million years ago, sloths adapted by evolving smaller physiques due to their need to keep cool. Then, as Earth cooled down again—which it’s been doing on and off for the past 50 million years—sloths started to get bigger and bigger. They also started to migrate, fanning out from Argentina throughout North and South America, and even up to Alaska and Canada.

    These new habitats presented challenges that the sloths met, in part, by bulking up. This new size also helped them keep warm and stay safe from predators. “This would’ve allowed them to conserve energy and water and travel more efficiently across habitats with limited resources,” Narducci said. “And if you’re in an open grassland, you need protection, and being bigger provides some of that.” They reached their most massive size during the Pleistocene Ice Ages, which spanned roughly 3 million to 12,000 years ago, shortly before they disappeared.

    Scientists aren’t completely sure why sloths went extinct, but they do have some guesses. Early humans migrated to the Americas around 20,000 years ago. Larger ground-dwelling sloths likely became a prime, meaty target for early humans, and being on the ground became a liability. Larger sloths were the first to go, but tree sloths didn’t escape unscathed. Over time, more and more species of tree-dwelling sloths went extinct, too. Two species survived in the Caribbean until around 4,500 years ago—until humans wiped them out. Now, sloths mostly keep to Central and South America, but thankfully aren’t on the menu anymore.

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    #why #ancient #sloths #became #size
    Why Ancient Sloths Became the Size of Elephants—and Then Vanished
    By Natalia Mesa Published May 23, 2025 | Comments| Giant ground sloths Megalocnus rodens and Megalonyx wheatleyi at the American Museum of Natural History © Dallas Krentzel Giant sloths with razor-sharp claws and as large as Asian bull elephants once roamed the Earth, snacking on leaves at the tops of trees with a prehensile tongue. Now, scientists have figured out why they became so huge—and why these massive sloths didn’t stick around—according to a new study published in Science. Today, two sloth species dwell in Central and South America. But long ago, dozens of sloth species populated the Americas, all the way from Argentina to Canada. Like modern-day sloths, the smaller species were tree-dwelling. But the larger sloths? “They looked like grizzly bears but five times larger,” Rachel Narducci, collection manager of vertebrate paleontology at the Florida Museum of Natural History and coauthor of the study, in a statement. The larger sloths didn’t do much tree climbing, at risk of falling to their deaths. Instead, they survived by being terrifying; the largest sloths had long, sharp claws that they used to carve their own caves out of raw earth and rocks. But exactly why they got so large remained a mystery. To figure out how these sloths got so massive, researchers analyzed ancient sloth DNA and compared more than 400 fossils from natural history museums to create a sloth tree of life. The researchers traced the sloths’ origin to 35 million years ago. And, because the scientists were particularly interested in how sloths got their size, they estimated their weights by taking fossil measurements. The researchers concluded that the Earth’s past climate was a big factor. Thirty-five million years ago, the first ancestor of modern-day sloths, which lived in what is now Argentina, was roughly the size of a large dog. Sloths hardly changed in size for 20 million years, and lived on the ground. Then, during a warming period around 16 million years ago, sloths adapted by evolving smaller physiques due to their need to keep cool. Then, as Earth cooled down again—which it’s been doing on and off for the past 50 million years—sloths started to get bigger and bigger. They also started to migrate, fanning out from Argentina throughout North and South America, and even up to Alaska and Canada. These new habitats presented challenges that the sloths met, in part, by bulking up. This new size also helped them keep warm and stay safe from predators. “This would’ve allowed them to conserve energy and water and travel more efficiently across habitats with limited resources,” Narducci said. “And if you’re in an open grassland, you need protection, and being bigger provides some of that.” They reached their most massive size during the Pleistocene Ice Ages, which spanned roughly 3 million to 12,000 years ago, shortly before they disappeared. Scientists aren’t completely sure why sloths went extinct, but they do have some guesses. Early humans migrated to the Americas around 20,000 years ago. Larger ground-dwelling sloths likely became a prime, meaty target for early humans, and being on the ground became a liability. Larger sloths were the first to go, but tree sloths didn’t escape unscathed. Over time, more and more species of tree-dwelling sloths went extinct, too. Two species survived in the Caribbean until around 4,500 years ago—until humans wiped them out. Now, sloths mostly keep to Central and South America, but thankfully aren’t on the menu anymore. Daily Newsletter #why #ancient #sloths #became #size
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    Why Ancient Sloths Became the Size of Elephants—and Then Vanished
    By Natalia Mesa Published May 23, 2025 | Comments (1) | Giant ground sloths Megalocnus rodens and Megalonyx wheatleyi at the American Museum of Natural History © Dallas Krentzel Giant sloths with razor-sharp claws and as large as Asian bull elephants once roamed the Earth, snacking on leaves at the tops of trees with a prehensile tongue. Now, scientists have figured out why they became so huge—and why these massive sloths didn’t stick around—according to a new study published in Science. Today, two sloth species dwell in Central and South America. But long ago, dozens of sloth species populated the Americas, all the way from Argentina to Canada. Like modern-day sloths, the smaller species were tree-dwelling. But the larger sloths? “They looked like grizzly bears but five times larger,” Rachel Narducci, collection manager of vertebrate paleontology at the Florida Museum of Natural History and coauthor of the study, in a statement. The larger sloths didn’t do much tree climbing, at risk of falling to their deaths. Instead, they survived by being terrifying; the largest sloths had long, sharp claws that they used to carve their own caves out of raw earth and rocks. But exactly why they got so large remained a mystery. To figure out how these sloths got so massive, researchers analyzed ancient sloth DNA and compared more than 400 fossils from natural history museums to create a sloth tree of life. The researchers traced the sloths’ origin to 35 million years ago. And, because the scientists were particularly interested in how sloths got their size, they estimated their weights by taking fossil measurements. The researchers concluded that the Earth’s past climate was a big factor. Thirty-five million years ago, the first ancestor of modern-day sloths, which lived in what is now Argentina, was roughly the size of a large dog. Sloths hardly changed in size for 20 million years, and lived on the ground. Then, during a warming period around 16 million years ago, sloths adapted by evolving smaller physiques due to their need to keep cool. Then, as Earth cooled down again—which it’s been doing on and off for the past 50 million years—sloths started to get bigger and bigger. They also started to migrate, fanning out from Argentina throughout North and South America, and even up to Alaska and Canada. These new habitats presented challenges that the sloths met, in part, by bulking up. This new size also helped them keep warm and stay safe from predators. “This would’ve allowed them to conserve energy and water and travel more efficiently across habitats with limited resources,” Narducci said. “And if you’re in an open grassland, you need protection, and being bigger provides some of that.” They reached their most massive size during the Pleistocene Ice Ages, which spanned roughly 3 million to 12,000 years ago, shortly before they disappeared. Scientists aren’t completely sure why sloths went extinct, but they do have some guesses. Early humans migrated to the Americas around 20,000 years ago. Larger ground-dwelling sloths likely became a prime, meaty target for early humans, and being on the ground became a liability. Larger sloths were the first to go, but tree sloths didn’t escape unscathed. Over time, more and more species of tree-dwelling sloths went extinct, too. Two species survived in the Caribbean until around 4,500 years ago—until humans wiped them out. Now, sloths mostly keep to Central and South America, but thankfully aren’t on the menu anymore. Daily Newsletter
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  • Sloths once came in a dizzying array of sizes. Here’s why

    The sloth family tree once sported a dizzying array of branches, body sizes and lifestyles, from small and limber tree climbers to lumbering bear-sized landlubbers. 
    Why sloth body size was once so diverse, while today’s sloths are limited to just two diminutive tree-dwellers, has been a long-standing question. Scientists have proposed that sloths’ body size might be linked to a wide variety of factors: habitat preferences, diets, changes in global temperature, or pressure from large predators or humans.

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    #sloths #once #came #dizzying #array
    Sloths once came in a dizzying array of sizes. Here’s why
    The sloth family tree once sported a dizzying array of branches, body sizes and lifestyles, from small and limber tree climbers to lumbering bear-sized landlubbers.  Why sloth body size was once so diverse, while today’s sloths are limited to just two diminutive tree-dwellers, has been a long-standing question. Scientists have proposed that sloths’ body size might be linked to a wide variety of factors: habitat preferences, diets, changes in global temperature, or pressure from large predators or humans. Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday. #sloths #once #came #dizzying #array
    WWW.SCIENCENEWS.ORG
    Sloths once came in a dizzying array of sizes. Here’s why
    The sloth family tree once sported a dizzying array of branches, body sizes and lifestyles, from small and limber tree climbers to lumbering bear-sized landlubbers.  Why sloth body size was once so diverse, while today’s sloths are limited to just two diminutive tree-dwellers, has been a long-standing question. Scientists have proposed that sloths’ body size might be linked to a wide variety of factors: habitat preferences, diets, changes in global temperature, or pressure from large predators or humans. Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday.
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  • Ancient Humans Hunted 20-Foot-Tall Sloths and Likely Caused the Mammal's Extinction

    Sloths once came in a variety of sizes and lived in multiple settings in many parts of the world. A study in the journal Science examined sloth evolution over the past 35 million years, investigated multiple factors driving their growth and expansion throughout the world, and concluded that human hunting starting around 15,000 years ago drove their dramatic decline.Today, only six species within two genera remain. All are relatively smalltree-dwellers that primarily live in the tropical rainforests of South and Central America.“These species are a tiny remnant of a once diverse American clade that was mostly made up of large-bodied species,” according to an editorial summary that accompanied the paper. Ancient Sloths Were Once WidespreadThat’s a huge contrast to sloth life during the late Cenozoic. During that period, more than 100 genera of sloths lived in a wide range of habitats and a variety of sizes, topping out at nearly 20 feet tall and weighing several tons.To investigate this diversity — and to track where, when, and why it collapsed — a team of scientists examined fossil measurements, DNA and protein sequences, and advanced evolutionary modeling. In doing so, they reconstructed sloth evolutionary history across 67 genera. They then investigated whether evolutionary changes in size were linked to habitat, diet, climate, predation, or other ecological pressures.Habitat Drove Sloth SizeThe findings show that habitat appeared to be a major driver in shaping their body size evolution. The earliest sloths were large and grazed on the ground. Some species adapted to tree dwelling and developed smaller body sizes. However shifts in both sloth size and dwelling didn’t happen in a straight line. The species size grew or shrunk as the climate warmed and cooled, and as ecosystems shifted from grasslands to woodlands.The species thrived for tens of millions of years, exhibiting the most variety in body sizes in the Pleistocene, which began about 2.6 million years ago.Ancient Humans Caused Dramatic DeclineThen, starting about 15,000 years ago, the creature experienced “a sudden and dramatic decline,” according to a press release.The researchers report that decline doesn’t mesh with any major known climate events. "Size disparity increased during the late Cenozoic climatic cooling, but paleoclimatic changes do not explain the rapid extinction of ground sloths that started approximately 15,000 years ago,” according to the paper. However, it does coincide with the expansion of humans into the Americas. The likely conclusion is that human hunting drove the extinction of the larger, ground-based sloths, while the smaller ones related to today’s creatures escaped by taking to the trees.Article SourcesOur writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
    #ancient #humans #hunted #20foottall #sloths
    Ancient Humans Hunted 20-Foot-Tall Sloths and Likely Caused the Mammal's Extinction
    Sloths once came in a variety of sizes and lived in multiple settings in many parts of the world. A study in the journal Science examined sloth evolution over the past 35 million years, investigated multiple factors driving their growth and expansion throughout the world, and concluded that human hunting starting around 15,000 years ago drove their dramatic decline.Today, only six species within two genera remain. All are relatively smalltree-dwellers that primarily live in the tropical rainforests of South and Central America.“These species are a tiny remnant of a once diverse American clade that was mostly made up of large-bodied species,” according to an editorial summary that accompanied the paper. Ancient Sloths Were Once WidespreadThat’s a huge contrast to sloth life during the late Cenozoic. During that period, more than 100 genera of sloths lived in a wide range of habitats and a variety of sizes, topping out at nearly 20 feet tall and weighing several tons.To investigate this diversity — and to track where, when, and why it collapsed — a team of scientists examined fossil measurements, DNA and protein sequences, and advanced evolutionary modeling. In doing so, they reconstructed sloth evolutionary history across 67 genera. They then investigated whether evolutionary changes in size were linked to habitat, diet, climate, predation, or other ecological pressures.Habitat Drove Sloth SizeThe findings show that habitat appeared to be a major driver in shaping their body size evolution. The earliest sloths were large and grazed on the ground. Some species adapted to tree dwelling and developed smaller body sizes. However shifts in both sloth size and dwelling didn’t happen in a straight line. The species size grew or shrunk as the climate warmed and cooled, and as ecosystems shifted from grasslands to woodlands.The species thrived for tens of millions of years, exhibiting the most variety in body sizes in the Pleistocene, which began about 2.6 million years ago.Ancient Humans Caused Dramatic DeclineThen, starting about 15,000 years ago, the creature experienced “a sudden and dramatic decline,” according to a press release.The researchers report that decline doesn’t mesh with any major known climate events. "Size disparity increased during the late Cenozoic climatic cooling, but paleoclimatic changes do not explain the rapid extinction of ground sloths that started approximately 15,000 years ago,” according to the paper. However, it does coincide with the expansion of humans into the Americas. The likely conclusion is that human hunting drove the extinction of the larger, ground-based sloths, while the smaller ones related to today’s creatures escaped by taking to the trees.Article SourcesOur writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American. #ancient #humans #hunted #20foottall #sloths
    WWW.DISCOVERMAGAZINE.COM
    Ancient Humans Hunted 20-Foot-Tall Sloths and Likely Caused the Mammal's Extinction
    Sloths once came in a variety of sizes and lived in multiple settings in many parts of the world. A study in the journal Science examined sloth evolution over the past 35 million years, investigated multiple factors driving their growth and expansion throughout the world, and concluded that human hunting starting around 15,000 years ago drove their dramatic decline.Today, only six species within two genera remain. All are relatively small (especially compared to their largest ancestors) tree-dwellers that primarily live in the tropical rainforests of South and Central America.“These species are a tiny remnant of a once diverse American clade that was mostly made up of large-bodied species,” according to an editorial summary that accompanied the paper. Ancient Sloths Were Once WidespreadThat’s a huge contrast to sloth life during the late Cenozoic. During that period, more than 100 genera of sloths lived in a wide range of habitats and a variety of sizes, topping out at nearly 20 feet tall and weighing several tons.To investigate this diversity — and to track where, when, and why it collapsed — a team of scientists examined fossil measurements, DNA and protein sequences, and advanced evolutionary modeling. In doing so, they reconstructed sloth evolutionary history across 67 genera. They then investigated whether evolutionary changes in size were linked to habitat, diet, climate, predation, or other ecological pressures.Habitat Drove Sloth SizeThe findings show that habitat appeared to be a major driver in shaping their body size evolution. The earliest sloths were large and grazed on the ground. Some species adapted to tree dwelling and developed smaller body sizes. However shifts in both sloth size and dwelling didn’t happen in a straight line. The species size grew or shrunk as the climate warmed and cooled, and as ecosystems shifted from grasslands to woodlands.The species thrived for tens of millions of years, exhibiting the most variety in body sizes in the Pleistocene, which began about 2.6 million years ago.Ancient Humans Caused Dramatic DeclineThen, starting about 15,000 years ago, the creature experienced “a sudden and dramatic decline,” according to a press release.The researchers report that decline doesn’t mesh with any major known climate events. "Size disparity increased during the late Cenozoic climatic cooling, but paleoclimatic changes do not explain the rapid extinction of ground sloths that started approximately 15,000 years ago,” according to the paper. However, it does coincide with the expansion of humans into the Americas. The likely conclusion is that human hunting drove the extinction of the larger, ground-based sloths, while the smaller ones related to today’s creatures escaped by taking to the trees.Article SourcesOur writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:Before joining Discover Magazine, Paul Smaglik spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
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  • Giant ground sloths evolved three different times for the same reason

    Ancient sloths came in a variety of sizesDiego Barletta
    A cooling, drying climate turned sloths into giants – before humans potentially drove the huge animals to extinction.
    Today’s sloths are small, famously sluggish herbivores that move through the tropical canopies of rainforests. But for tens of millions of years, South America was home to a dizzying diversity of sloths. Many were ground-dwelling giants, with some behemoths approaching 5 tonnes in weight.
    Advertisement
    That staggering size range is of particular interest to Alberto Boscaini at the University of Buenos Aires in Argentina and his colleagues.
    “Body size correlates with everything in the biological traits of an animal,” says Boscaini. “This was a promising way of studyingevolution.”
    Boscaini and his colleagues compiled data on the physical features, DNA and proteins of 67 extinct and living sloth genera – groups of closely related species – to develop a family tree showing their evolutionary relationships.

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    The researchers then took this evolutionary history, which covered a span of 35 million years, and added information about each sloth’s habitat, diet and lifestyle. They also studied trends in body-size evolution, making body mass estimates of 49 of the ancient and modern sloth groups.
    The results suggest sloth body-size evolution was heavily influenced by climatic and habitat changes. For instance, some sloth genera began living in trees – similar to today’s sloths – and shrank in body size as they did so.
    Meanwhile, three different lineages of sloths independently evolved elephantine proportions – and it seems they did this within the last several million years, as the planet cooled and the growth of the Andes mountains made South America more arid.
    “Gigantism is more closely associated with cold and dry climates,” says team member Daniel Casali at the University of São Paulo, Brazil.
    Many of these diverse sloths disappeared during two stages: one around 12,000 years ago and the other around 6000 years ago, says Boscaini.
    “This matches with the expansion of Homo sapiens, first over the entire American supercontinent, and later in the Caribbean,” he says — which is where some giant sloths lived. Notably, the only surviving sloth species live in trees so are much harder for humans to hunt than massive ground sloths.

    The idea that humans were the death blow for ancient megafauna is well-supported, says Thaís Rabito Pansani at the University of New Mexico, who wasn’t involved in the study.
    “However, in science, we need several lines of evidence to reinforce our hypotheses, especially in unresolved and highly debated issues such as the extinction of megafauna,” she says. The new evidence shores up this story.
    “Sloths were thriving for most of their history,” says Casali. “teach us how a very successfulcan become so vulnerable very quickly.”
    Journal reference:Science DOI: 10.1126/science.adu0704
    Topics:evolution
    #giant #ground #sloths #evolved #three
    Giant ground sloths evolved three different times for the same reason
    Ancient sloths came in a variety of sizesDiego Barletta A cooling, drying climate turned sloths into giants – before humans potentially drove the huge animals to extinction. Today’s sloths are small, famously sluggish herbivores that move through the tropical canopies of rainforests. But for tens of millions of years, South America was home to a dizzying diversity of sloths. Many were ground-dwelling giants, with some behemoths approaching 5 tonnes in weight. Advertisement That staggering size range is of particular interest to Alberto Boscaini at the University of Buenos Aires in Argentina and his colleagues. “Body size correlates with everything in the biological traits of an animal,” says Boscaini. “This was a promising way of studyingevolution.” Boscaini and his colleagues compiled data on the physical features, DNA and proteins of 67 extinct and living sloth genera – groups of closely related species – to develop a family tree showing their evolutionary relationships. Unmissable news about our planet delivered straight to your inbox every month. Sign up to newsletter The researchers then took this evolutionary history, which covered a span of 35 million years, and added information about each sloth’s habitat, diet and lifestyle. They also studied trends in body-size evolution, making body mass estimates of 49 of the ancient and modern sloth groups. The results suggest sloth body-size evolution was heavily influenced by climatic and habitat changes. For instance, some sloth genera began living in trees – similar to today’s sloths – and shrank in body size as they did so. Meanwhile, three different lineages of sloths independently evolved elephantine proportions – and it seems they did this within the last several million years, as the planet cooled and the growth of the Andes mountains made South America more arid. “Gigantism is more closely associated with cold and dry climates,” says team member Daniel Casali at the University of São Paulo, Brazil. Many of these diverse sloths disappeared during two stages: one around 12,000 years ago and the other around 6000 years ago, says Boscaini. “This matches with the expansion of Homo sapiens, first over the entire American supercontinent, and later in the Caribbean,” he says — which is where some giant sloths lived. Notably, the only surviving sloth species live in trees so are much harder for humans to hunt than massive ground sloths. The idea that humans were the death blow for ancient megafauna is well-supported, says Thaís Rabito Pansani at the University of New Mexico, who wasn’t involved in the study. “However, in science, we need several lines of evidence to reinforce our hypotheses, especially in unresolved and highly debated issues such as the extinction of megafauna,” she says. The new evidence shores up this story. “Sloths were thriving for most of their history,” says Casali. “teach us how a very successfulcan become so vulnerable very quickly.” Journal reference:Science DOI: 10.1126/science.adu0704 Topics:evolution #giant #ground #sloths #evolved #three
    WWW.NEWSCIENTIST.COM
    Giant ground sloths evolved three different times for the same reason
    Ancient sloths came in a variety of sizesDiego Barletta A cooling, drying climate turned sloths into giants – before humans potentially drove the huge animals to extinction. Today’s sloths are small, famously sluggish herbivores that move through the tropical canopies of rainforests. But for tens of millions of years, South America was home to a dizzying diversity of sloths. Many were ground-dwelling giants, with some behemoths approaching 5 tonnes in weight. Advertisement That staggering size range is of particular interest to Alberto Boscaini at the University of Buenos Aires in Argentina and his colleagues. “Body size correlates with everything in the biological traits of an animal,” says Boscaini. “This was a promising way of studying [sloth] evolution.” Boscaini and his colleagues compiled data on the physical features, DNA and proteins of 67 extinct and living sloth genera – groups of closely related species – to develop a family tree showing their evolutionary relationships. Unmissable news about our planet delivered straight to your inbox every month. Sign up to newsletter The researchers then took this evolutionary history, which covered a span of 35 million years, and added information about each sloth’s habitat, diet and lifestyle. They also studied trends in body-size evolution, making body mass estimates of 49 of the ancient and modern sloth groups. The results suggest sloth body-size evolution was heavily influenced by climatic and habitat changes. For instance, some sloth genera began living in trees – similar to today’s sloths – and shrank in body size as they did so. Meanwhile, three different lineages of sloths independently evolved elephantine proportions – and it seems they did this within the last several million years, as the planet cooled and the growth of the Andes mountains made South America more arid. “Gigantism is more closely associated with cold and dry climates,” says team member Daniel Casali at the University of São Paulo, Brazil. Many of these diverse sloths disappeared during two stages: one around 12,000 years ago and the other around 6000 years ago, says Boscaini. “This matches with the expansion of Homo sapiens, first over the entire American supercontinent, and later in the Caribbean,” he says — which is where some giant sloths lived. Notably, the only surviving sloth species live in trees so are much harder for humans to hunt than massive ground sloths. The idea that humans were the death blow for ancient megafauna is well-supported, says Thaís Rabito Pansani at the University of New Mexico, who wasn’t involved in the study. “However, in science, we need several lines of evidence to reinforce our hypotheses, especially in unresolved and highly debated issues such as the extinction of megafauna,” she says. The new evidence shores up this story. “Sloths were thriving for most of their history,” says Casali. “[The findings] teach us how a very successful [group] can become so vulnerable very quickly.” Journal reference:Science DOI: 10.1126/science.adu0704 Topics:evolution
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  • Carnivorous crocodile-like monsters used to terrorize the Caribbean

    Going for a stroll

    Carnivorous crocodile-like monsters used to terrorize the Caribbean

    While low sea levels helped sebecids spread, rising waters left them isolated.

    Elizabeth Rayne



    May 16, 2025 1:10 pm

    |

    21

    Credit:

    By Ghedoghedo, CC BY-SA 3.0

    Credit:

    By Ghedoghedo, CC BY-SA 3.0

    Story text

    Size

    Small
    Standard
    Large

    Width
    *

    Standard
    Wide

    Links

    Standard
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    * Subscribers only
      Learn more

    How did reptilian things that looked something like crocodiles get to the Caribbean islands from South America millions of years ago? They probably walked.
    The existence of any prehistoric apex predators in the islands of the Caribbean used to be doubted. While their absence would have probably made it even more of a paradise for prey animals, fossils unearthed in Cuba, Puerto Rico, and the Dominican Republic have revealed that these islands were crawling with monster crocodyliform species called sebecids, ancient relatives of crocodiles.
    While sebecids first emerged during the Cretaceous, this is the first evidence of them lurking outside South America during the Cenozoic epoch, which began 66 million years ago. An international team of researchers has found that these creatures would stalk and hunt in the Caribbean islands millions of years after similar predators went extinct on the South American mainland. Lower sea levels back then could have exposed enough land to walk across.
    “Adaptations to a terrestrial lifestyle documented for sebecids and the chronology of West Indian fossils strongly suggest that they reached the islands in the Eocene-Oligocene through transient land connections with South America or island hopping,” researchers said in a study recently published in Proceedings of the Royal Society B.
    Origin story
    During the late Eocene to early Oligocene periods of the mid-Cenozoic, about 34 million years ago, many terrestrial carnivores already roamed South America. Along with crocodyliform sebecids, these included enormous snakes, terror birds, and metatherians, which were monster marsupials. At this time, the sea levels were low, and the islands of the Eastern Caribbean are thought to have been connected to South America via a land bridge called GAARlandia. This is not the first land bridge to potentially provide a migration opportunity.
    Fragments of a single tooth unearthed in Seven Rivers, Jamaica, in 1999 are the oldest fossil evidence of a ziphodont crocodyliformin the Caribbean. It was dated to about 47 million years ago, when Jamaica was connected to an extension of the North American continent known as the Nicaragua Rise. While the tooth from Seven Rivers is thought to have belonged to a ziphodont other than a sebacid, that and other vertebrate fossils found in Jamaica suggest parallels with ecosystems excavated from sites in the American South.
    The fossils found in areas like the US South that the ocean would otherwise separate suggest more than just related life forms. It's possible that the Nicaragua Rise provided a pathway for migration similar to the one sebecids probably used when they arrived in the Caribbean islands.

    Walking the walk
    So how did sebecids get from one land mass to the other on foot? They were made for it.
    Sebecids evolutionarily diverged from crocodiles during the Jurassic period. They had skulls similar to those of theropod dinosaurs, with a high rostrumthat was long and narrow. Their mouths were full of ziphodont teeth, which are compressed along the sides and have a serrated edge made for tearing flesh. Most important among the adaptations that made sebecids terrestrial animals were legs longer than their crocodilian brethren—legs made for walking on land.
    “Considering their terrestrial adaptations, their dispersal may have been either facilitated by some ephemeral terrestrial connection or string of large and closely spaced islands or occurred on a natural raft,” the research team said in the same study.
    Though they have been found across South America, earlier specimens of sebecids are best documented in the south of the continent, while later specimens surfaced in the north and tropical zones. Both the ziphodont teeth and concave vertebrae are found among the fossils found in the Dominican Republic, Cuba, and Puerto Rico, giving them away as sebecids. The locations of the fossils are consistent with the types of environments these carnivores were thought to inhabit as the Eocene gave way to the Oligocene.
    After they ended up in the Caribbean, the original population of sebecids eventually became isolated as sea levels rose, leaving the sub-populations on islands surrounded by water.
    The sebecids were apex predators in South America and are thought to have stayed at the top of the food chain in their new hunting grounds. Some sebecid remains have been found with fossils of terrestrial and semiaquatic vertebrates, such as sloths and turtles, that supposedly were their prey.
    Not only did sebecids get around, but they also lasted 5 million years longer in the Caribbean than they did in South America. This might have been because certain plant and animal species that died out on the mainland continued to survive on the islands. Crocodiles and predatory birds took over as apex predators after the sebecids died out. Even with a mouth full of knives, you can’t be at the top forever.
    Proceedings of the Royal Society B, 2025.  DOI: 10.1098/rspb.2024.2891

    Elizabeth Rayne

    Elizabeth Rayne is a creature who writes. Her work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. She lurks right outside New York City with her parrot, Lestat. When not writing, she is either shapeshifting, drawing, or cosplaying as a character nobody has ever heard of. Follow her on Threads and Instagram @quothravenrayne.

    21 Comments
    #carnivorous #crocodilelike #monsters #used #terrorize
    Carnivorous crocodile-like monsters used to terrorize the Caribbean
    Going for a stroll Carnivorous crocodile-like monsters used to terrorize the Caribbean While low sea levels helped sebecids spread, rising waters left them isolated. Elizabeth Rayne – May 16, 2025 1:10 pm | 21 Credit: By Ghedoghedo, CC BY-SA 3.0 Credit: By Ghedoghedo, CC BY-SA 3.0 Story text Size Small Standard Large Width * Standard Wide Links Standard Orange * Subscribers only   Learn more How did reptilian things that looked something like crocodiles get to the Caribbean islands from South America millions of years ago? They probably walked. The existence of any prehistoric apex predators in the islands of the Caribbean used to be doubted. While their absence would have probably made it even more of a paradise for prey animals, fossils unearthed in Cuba, Puerto Rico, and the Dominican Republic have revealed that these islands were crawling with monster crocodyliform species called sebecids, ancient relatives of crocodiles. While sebecids first emerged during the Cretaceous, this is the first evidence of them lurking outside South America during the Cenozoic epoch, which began 66 million years ago. An international team of researchers has found that these creatures would stalk and hunt in the Caribbean islands millions of years after similar predators went extinct on the South American mainland. Lower sea levels back then could have exposed enough land to walk across. “Adaptations to a terrestrial lifestyle documented for sebecids and the chronology of West Indian fossils strongly suggest that they reached the islands in the Eocene-Oligocene through transient land connections with South America or island hopping,” researchers said in a study recently published in Proceedings of the Royal Society B. Origin story During the late Eocene to early Oligocene periods of the mid-Cenozoic, about 34 million years ago, many terrestrial carnivores already roamed South America. Along with crocodyliform sebecids, these included enormous snakes, terror birds, and metatherians, which were monster marsupials. At this time, the sea levels were low, and the islands of the Eastern Caribbean are thought to have been connected to South America via a land bridge called GAARlandia. This is not the first land bridge to potentially provide a migration opportunity. Fragments of a single tooth unearthed in Seven Rivers, Jamaica, in 1999 are the oldest fossil evidence of a ziphodont crocodyliformin the Caribbean. It was dated to about 47 million years ago, when Jamaica was connected to an extension of the North American continent known as the Nicaragua Rise. While the tooth from Seven Rivers is thought to have belonged to a ziphodont other than a sebacid, that and other vertebrate fossils found in Jamaica suggest parallels with ecosystems excavated from sites in the American South. The fossils found in areas like the US South that the ocean would otherwise separate suggest more than just related life forms. It's possible that the Nicaragua Rise provided a pathway for migration similar to the one sebecids probably used when they arrived in the Caribbean islands. Walking the walk So how did sebecids get from one land mass to the other on foot? They were made for it. Sebecids evolutionarily diverged from crocodiles during the Jurassic period. They had skulls similar to those of theropod dinosaurs, with a high rostrumthat was long and narrow. Their mouths were full of ziphodont teeth, which are compressed along the sides and have a serrated edge made for tearing flesh. Most important among the adaptations that made sebecids terrestrial animals were legs longer than their crocodilian brethren—legs made for walking on land. “Considering their terrestrial adaptations, their dispersal may have been either facilitated by some ephemeral terrestrial connection or string of large and closely spaced islands or occurred on a natural raft,” the research team said in the same study. Though they have been found across South America, earlier specimens of sebecids are best documented in the south of the continent, while later specimens surfaced in the north and tropical zones. Both the ziphodont teeth and concave vertebrae are found among the fossils found in the Dominican Republic, Cuba, and Puerto Rico, giving them away as sebecids. The locations of the fossils are consistent with the types of environments these carnivores were thought to inhabit as the Eocene gave way to the Oligocene. After they ended up in the Caribbean, the original population of sebecids eventually became isolated as sea levels rose, leaving the sub-populations on islands surrounded by water. The sebecids were apex predators in South America and are thought to have stayed at the top of the food chain in their new hunting grounds. Some sebecid remains have been found with fossils of terrestrial and semiaquatic vertebrates, such as sloths and turtles, that supposedly were their prey. Not only did sebecids get around, but they also lasted 5 million years longer in the Caribbean than they did in South America. This might have been because certain plant and animal species that died out on the mainland continued to survive on the islands. Crocodiles and predatory birds took over as apex predators after the sebecids died out. Even with a mouth full of knives, you can’t be at the top forever. Proceedings of the Royal Society B, 2025.  DOI: 10.1098/rspb.2024.2891 Elizabeth Rayne Elizabeth Rayne is a creature who writes. Her work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. She lurks right outside New York City with her parrot, Lestat. When not writing, she is either shapeshifting, drawing, or cosplaying as a character nobody has ever heard of. Follow her on Threads and Instagram @quothravenrayne. 21 Comments #carnivorous #crocodilelike #monsters #used #terrorize
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    Carnivorous crocodile-like monsters used to terrorize the Caribbean
    Going for a stroll Carnivorous crocodile-like monsters used to terrorize the Caribbean While low sea levels helped sebecids spread, rising waters left them isolated. Elizabeth Rayne – May 16, 2025 1:10 pm | 21 Credit: By Ghedoghedo, CC BY-SA 3.0 Credit: By Ghedoghedo, CC BY-SA 3.0 Story text Size Small Standard Large Width * Standard Wide Links Standard Orange * Subscribers only   Learn more How did reptilian things that looked something like crocodiles get to the Caribbean islands from South America millions of years ago? They probably walked. The existence of any prehistoric apex predators in the islands of the Caribbean used to be doubted. While their absence would have probably made it even more of a paradise for prey animals, fossils unearthed in Cuba, Puerto Rico, and the Dominican Republic have revealed that these islands were crawling with monster crocodyliform species called sebecids, ancient relatives of crocodiles. While sebecids first emerged during the Cretaceous, this is the first evidence of them lurking outside South America during the Cenozoic epoch, which began 66 million years ago. An international team of researchers has found that these creatures would stalk and hunt in the Caribbean islands millions of years after similar predators went extinct on the South American mainland. Lower sea levels back then could have exposed enough land to walk across. “Adaptations to a terrestrial lifestyle documented for sebecids and the chronology of West Indian fossils strongly suggest that they reached the islands in the Eocene-Oligocene through transient land connections with South America or island hopping,” researchers said in a study recently published in Proceedings of the Royal Society B. Origin story During the late Eocene to early Oligocene periods of the mid-Cenozoic, about 34 million years ago, many terrestrial carnivores already roamed South America. Along with crocodyliform sebecids, these included enormous snakes, terror birds, and metatherians, which were monster marsupials. At this time, the sea levels were low, and the islands of the Eastern Caribbean are thought to have been connected to South America via a land bridge called GAARlandia (Greater Antilles and Aves Ridge). This is not the first land bridge to potentially provide a migration opportunity. Fragments of a single tooth unearthed in Seven Rivers, Jamaica, in 1999 are the oldest fossil evidence of a ziphodont crocodyliform (a group that includes sebecids) in the Caribbean. It was dated to about 47 million years ago, when Jamaica was connected to an extension of the North American continent known as the Nicaragua Rise. While the tooth from Seven Rivers is thought to have belonged to a ziphodont other than a sebacid, that and other vertebrate fossils found in Jamaica suggest parallels with ecosystems excavated from sites in the American South. The fossils found in areas like the US South that the ocean would otherwise separate suggest more than just related life forms. It's possible that the Nicaragua Rise provided a pathway for migration similar to the one sebecids probably used when they arrived in the Caribbean islands. Walking the walk So how did sebecids get from one land mass to the other on foot? They were made for it. Sebecids evolutionarily diverged from crocodiles during the Jurassic period. They had skulls similar to those of theropod dinosaurs, with a high rostrum (which holds the teeth along with the palate and nasal cavity) that was long and narrow. Their mouths were full of ziphodont teeth, which are compressed along the sides and have a serrated edge made for tearing flesh. Most important among the adaptations that made sebecids terrestrial animals were legs longer than their crocodilian brethren—legs made for walking on land. “Considering their terrestrial adaptations, their dispersal may have been either facilitated by some ephemeral terrestrial connection or string of large and closely spaced islands or occurred on a natural raft,” the research team said in the same study. Though they have been found across South America, earlier specimens of sebecids are best documented in the south of the continent, while later specimens surfaced in the north and tropical zones. Both the ziphodont teeth and concave vertebrae are found among the fossils found in the Dominican Republic, Cuba, and Puerto Rico, giving them away as sebecids. The locations of the fossils are consistent with the types of environments these carnivores were thought to inhabit as the Eocene gave way to the Oligocene. After they ended up in the Caribbean, the original population of sebecids eventually became isolated as sea levels rose, leaving the sub-populations on islands surrounded by water. The sebecids were apex predators in South America and are thought to have stayed at the top of the food chain in their new hunting grounds. Some sebecid remains have been found with fossils of terrestrial and semiaquatic vertebrates, such as sloths and turtles, that supposedly were their prey. Not only did sebecids get around, but they also lasted 5 million years longer in the Caribbean than they did in South America. This might have been because certain plant and animal species that died out on the mainland continued to survive on the islands. Crocodiles and predatory birds took over as apex predators after the sebecids died out. Even with a mouth full of knives, you can’t be at the top forever. Proceedings of the Royal Society B, 2025.  DOI: 10.1098/rspb.2024.2891 Elizabeth Rayne Elizabeth Rayne is a creature who writes. Her work has appeared on SYFY WIRE, Space.com, Live Science, Grunge, Den of Geek, and Forbidden Futures. She lurks right outside New York City with her parrot, Lestat. When not writing, she is either shapeshifting, drawing, or cosplaying as a character nobody has ever heard of. Follow her on Threads and Instagram @quothravenrayne. 21 Comments
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