Murderbotjust wants to be left aloneApple TV+ Apple TV+Friends and colleagues spent years trying to get me to read The Murderbot Diaries, a sci-fi series by Martha Wells about a cyborg security unit that gains free will. I resisted. They pitched it to me as quirky, which raised my hackles, or as comfort reading, which sent them skyrocketing. Not my sort of thing, I thought snootily. But once Apple TV+ said that it would be adapting All Systems Red, the first instalment, I knew I had to give it a read. It… #how #new #murderbot #series #made

AI translation apps can help you connect with other people – but at what cost?Ventz/Getty Images I have long remembered a conversation I had 20 years ago with one of my professors, an expert in what we then called artificial intelligence, which, in many ways, is wildly different to what we now call AI. In this exchange, he confidently told me there was no point learning a second language. Computers would soon erase language barriers, he said. Not only by translating written text, but also in real time using audio, to make conversations flow smoothly even if everyone involved is… #should #you #still #learn #second

If greenhouse gas emissions aren’t curbed, carbon dioxide removal won’t make a differenceYASUYOSHI CHIBA/AFP via Getty Images The nascent carbon dioxide removal industry expects to hit a milestone this year: 1 million tonnes of planet-warming CO2 removed from the atmosphere. That certainly is progress, but things aren’t moving anywhere near quickly enough to remove the billions of tonnes of carbon researchers say we need to capture annually in coming decades. “It’s not scaling up as fast as it would need to if we are… #this #rate #carbon #dioxide #removal

Technology for seeing around corners would be of use to the militaryMatthew Horwood/Getty Images An ordinary camera could soon take photos of things that are out of sight, thanks to algorithms that interpret how light bounces off a wall. “Normally, when light bounces off rough surfaces, like walls, it scrambles the scene into a messy blur,” says Wenwen Li at the University of Science and Technology of China, Hefei. “Our goal was to ‘unscramble’ that blur and recover the hidden scene. Think of it like turning a rough wall into a mirror.” #any #wall #can #turned #into

The Book Club gives their verdict on Larry Niven’s RingworldEugene Powers/Alamy It was quite an experience, moving from the technicolour magical realism of Michel Nieva’s wild dystopia, Dengue Boy, to Larry Niven’s slice of classic science fiction, Ringworld, first published in 1970 and very much redolent of the sci-fi writing of that era. Not a wholly bad experience, mind, but quite a jolting change of pace for the New Scientist Book Club. I was a teenager when I last read Ringworld, and a hugely uncritical sort of teenager at that, so I was keen to return to a novel I remembered fondly and see how it stood up to the test of time – and my somewhat more critical eye. The first thing to say is that many of the things I loved about Ringworld were very much still there. This is, for me, a novel that inspires awe – with the vastness of its imagination, the size of its megastructures, the distance it travels in space. I was reminded of that awe early on, when our protagonist Louis Wurecalls standing at the edge of Mount Lookitthat on a distant planet. “The Long Fall River, on that world, ends in the tallest waterfall in known space. Louis’s eyes had followed it down as far as they could penetrate the void mist. The featureless white of the void itself had grasped at his mind, and Louis Wu, half hypnotized, had sworn to live forever. How else could he see all there was to see?” Advertisement That hugeness, that desire for exploration and knowledge and discovery, is one of the main reasons why I love science fiction. What else is out there, and what can we find out about it? From that field of murderous sunflowers on the Ringworld – what a scene! – to Niven’s image of our crew in space, looking at the bottom of the Ringworld and the huge bulge of a deep ocean protruding towards them, Ringworld has this in spades, and I lapped it up. “A man can lose his soul among the white stars… They call it the far look. It is dangerous.” I also very much enjoyed how Niven makes us pick up the breadcrumbs of where we are in time and in technological developments; at one point, Freeman Dyson, he of the Dyson spheres that inspired the Ringworld, is described as “one of the ancient natural philosophers, pre-Belt, almost pre-atomic”. I find that sort of thing delightful, and I was alsoamused by Niven’s aliens, from the cowering terror of the Puppeteers to the brilliantly named Speaker-To-Animals. I pictured Speaker as a huge version of our large ginger cat, and rather liked him. As I wrote earlier, though, this is a piece of writing that feels very much of its time, in terms of the somewhat plodding prose and sexist overtones, even if it succeedsin the wonderful, star-spanning maths and physics of it all. Niven’s characters are pretty one-dimensional. Louis Wu is quite annoying. There could be so much more to Teela, our token woman. And once the crew are on the Ringworld, it all feels a bit “then they went here, then they went there”, rather than being tightly plotted. Join us in reading and discussing the best new science and science fiction books Sign up to newsletter There has been some intense discussion about this novel on our Facebook page, and many of you felt similarly. “While I enjoyed it very much, I kept getting pulled out of the interesting scientific aspects of the story as well as the rollicking adventure by the sexist, boys club aspects. It’s a little sad that Larry Niven’s view of the distant future didn’t involve any advancement in men’s views of women,” said Jennifer Marano. “It reminds me of early spy movies. Beautiful woman who hasn’t sense enough to not be enamored by less than interesting or intelligent male with pretty huge ego,” said Eliza Rose. Alan Perrett was even less impressed with Louis Wu’s behaviour: “I have to admit to finding Louis Wu absolutely creepy. He treats the woman that he professes to love with contempt. He laughs finding out that she’s the result of a eugenics experiment and then, when looking at her, sees her dismay and then keeps laughing. I hope when I’m 200 years old I’ve learned a little more empathy than that.” Gosia Furmanik grew up reading science fiction from Niven’s era because that was what was available – but “eventually, the sexism and lack of female/diverse protagonists put me off sci-fi for a good 15 years”. She only got back into sci-fi when she discovered “that nowadays it’s easy to find books of this genre written by non-white non-men that don’t have this pitfall”. “Ringworld brought me back, not in a good way,” Gosia writes. “While not as blatant as in some of its contemporaries, cringy sexism nevertheless seeps out of this book.” It’s definitely true that Teela’s character arc was the biggest issue for most of us with this book. “I loathed the ending of Teela’s story and the explanation of how her luck led her to come on the mission. It seems a woman can’t have a meaningful existence without a man!” wrote Samatha Lane. Samantha also makes a great point about how “the male human is the most perceptive creature in the universe” created by Niven. “This arrogance about the sheer cleverness of humans stems from traditional humanism which puts humans at the centre of everything – as rational, special, superior beings. Combine that with the recent conquest of spaceand it’s like a bonfire of the collective ego,” she writes. New Scientist book club Love reading? Come and join our friendly group of fellow book lovers. Every six weeks, we delve into an exciting new title, with members given free access to extracts from our books, articles from our authors and video interviews. Sign up Onto the positives, however: Niall Leighton “enjoyed the sheer scale of the novel” and thinks it hasn’t “dated as badly as much science fiction of this era”, while for Andy Feest, “the science was probably the most interesting thing”. Some readers approved of Niven’s heavy hand with the maths – it “definitely added to my enjoyment”, wrote Linda Jones, while Darren Rumbold “especially liked” the Klemperer rosettes. It didn’t work for all of you, though: Phil Gurski “was excited to read this classic sci-fi novel and really, really wanted to enjoy it but the technobabble kept getting in the way. I found it hard to keep up.” Overall, I think the book club found it an interesting exercise to dig into this science fiction classic and hold it up to the light of today. I think we’ll do another classic soon enough, and I’m listening to suggestions from readers who have tipped books by Ursula K. Le Guin, N. K. Jemisin and Joanna Russ as possible palate cleansers. Next up, though, is something a little more modern: Kaliane Bradley’s bestselling time travel novel, The Ministry of Time. Yes, it has a woman as its protagonist, and yes, it passes the Bechdel test. You can read a piece by Kaliane here in which she explains whyshe wrote a novel about time travel, and you can check out this fun opener to the book here. Come and read along with us and tell us what you think on our Facebook page. Topics: #our #verdict #ringworld #larry #niven

Hormonal birth control is effective in preventing pregnancy, but there may be some neurological trade-offs that we are only just learning about Oral contraceptives have been effectively preventing pregnancy for more than 65 years, but it has only been in the past 10 that scientists – many of them women – have started to seriously examine what effect they have on the brain. New research is showing that oral hormonal contraceptives may alter the risk of mood disorders such as depression and anxiety, affect the brain’s response to stress and change the structure of certain brain regions. Evidence presented at the European… #how #does #pill #affect #your

Starship’s ninth test flight took place on 27 MayJoe Marino/UPI/Shutterstock Another launch, another failure? With the ninth flight of SpaceX’s massive Starship rocket ending in the vehicle’s loss, questions are being asked about whether Elon Musk’s company can ever deliver on its promises to return people to the moon, launch new space stations and one day take astronauts to Mars. “I expected more progress from SpaceX by now,” says Laura Forczyk at space industry consultancy Astralytical. “It’s frustrating from an outsider’s perspective, because I’m rooting for them. So much of the space community is relying on… #will #spacexs #starship #rocket #ever

A projectile point, made from the bone of a grey whale, from the Duruthy rock shelter in Landes, FranceAlexandre Lefebvre Hunter-gatherers living along the shores of the Bay of Biscay crafted hunting tools from the bones of at least five different whale species 20,000 years ago, marking the oldest evidence of manufacturing objects from whale remains. Although there is evidence of Neanderthals gathering and eating molluscs in what is now southern Spain around 150,000 years ago, current findings suggest that ancient humans didn’t regularly use coastal resources for food and raw materials until around 19,000 years ago… #humans #were #crafting #tools #whale

Is it time to say goodbye to the multiverse?SCIENCE PHOTO LIBRARY/Getty Images An advanced version of the famous double-slit experiment has directly measured a single photon in two places at once – or at least, that’s the claim made by a team of physicists who say these results could destroy the concept of a multiverse. This interpretation remains highly contested, however, with other physicists arguing that the experiment can’t really tell us anything new about the nature of reality. The double-slit experiment, first performed in 1801, has played a key role in the development of quantum mechanics. It shows… #photon #caught #two #places #once

The Kitt Peak National Observatory, near Tucson, Arizona, is home to DESIKPNO/NOIRLab/NSF/AURA/P. Marenfeld Is dark energy changing, or is it just more of the same? Last month, astronomers announced the startling finding that dark energy – which is thought to cause the accelerating expansion of the universe – might weaken over time. This has forced physicists to consider upending the standard cosmological model of the universe but now, some researchers are saying this may be premature. Since it started scanning the sky in 2021, the Dark Energy Spectroscopic Instrumentin Arizona has been carefully measuring the distances between millions of… #physicists #are #waging #cosmic #battle

“Mathematically, what are we trying to optimise?”John MacLean/Millennium Images, UK Scheduling household chores is hard. Say you have three loads of washing: a regular load that will take 110 minutes to wash and 120 to dry; a heavily soiled load that needs an extra 30 minutes to wash; and a sensitive one that will take 130 minutes to wash and 160 to dry. In which order do you wash them? In the branch of applied maths known as operational research, this is called a two-machine problem. Lots of businesses have similar issues. One approach, to find the shortest overall… #handy #piece #maths #that #can

Would you leave a world wilting under a deadly sun for a digital utopia?Andriy Onufriyenko/Getty Images Every Version of You Grace Chan) Science fiction that features characters who spend more time in virtual reality than in real life, whether via electrodes stuck into the backs of their necks or some kind of gloop-filled tank, isn’t exactly a new thing. In fact, picking up Grace Chan’s Every Version of You, I worried that the premise of the novel – some young people in the future having to decide whether to permanently… #this #scifi #debut #quietly #brilliant

US President Donald Trump, accompanied by US Secretary of Defense Pete Hegseth, announces the Golden Dome missile defense shieldCHRIS KLEPONIS/POOL/EPA-EFE/Shutterstock US President Donald Trump has proposed a defence project, called the Golden Dome, to intercept any incoming hypersonic, ballistic and advanced cruise missiles that threaten the country. “Once fully constructed, the Golden Dome will be capable of intercepting missiles even if they are launched from other sides of the world and even if they are launched from space,” said Trump during the White House announcement on 20 May. But such a thorough interception system may not be possible. Some experts also warn that, even if it works, the Golden Dome would take at least a decade to build, cost more than half a trillion dollars – and accelerate the global nuclear arms race and the weaponisation of space.Advertisement What is the Golden Dome? The project’s name is inspired by Israel’s Iron Dome system, which uses ground-based missiles to intercept incoming rockets and artillery fired from relatively short distances. But the Golden Dome would need to defend a far larger area – the land mass of the contiguous US alone is more than 350 times the size of Israel – from a wider variety of sophisticated missiles. According to Trump and his officials, the system should be able to counter ballistic missiles that could be launched from the other side of the world, advanced cruise missiles that fly on flatter trajectories at lower altitudes and hypersonic missiles that can fly and manoeuvre at speeds exceeding Mach 5, five times the speed of sound. These missiles can carry either nuclear warheads or conventional explosive warheads. Receive a weekly dose of discovery in your inbox. Sign up to newsletter To detect and intercept the threats, the Golden Dome will use both “space-based sensors and air and missile defense”, US Secretary of Defense Pete Hegseth said in a statement. That implies an umbrella system of “Golden Domes” with different technologies countering different threats, says David Burbach at the Naval War College in Rhode Island, who shared some comments with New Scientist in a personal capacity. However, not all of these defences exist. For instance, the Golden Dome would supposedly use space-based interceptor missiles in low Earth orbit, an unprecedented technological feat that has never been demonstrated before, says Thomas González Roberts at the Georgia Institute of Technology in Atlanta. A similar idea, nicknamed Star Wars, was originally proposed by US President Ronald Reagan in his Strategic Defense Initiative during the cold war. In fact, Trump has described the Golden Dome as an effort to complete “the job that President Reagan started 40 years ago”. How will the Golden Dome work? Missile defence experts describe the challenge of intercepting long-range nuclear missiles as being like “hitting a bullet with a bullet, in the dark” because “the targets are small, not emitting any radio or infrared signals, and fast moving”, says Burbach. “One thing to keep in mind is that even optimistic technical experts admit 100 per cent interception is unlikely.” The US already has a system of ground-based interceptor missiles, primarily based in Alaska. They can shoot down “a couple dozen incoming warheads at best”, says Burbach. He also pointed out that Russia and China are developing countermeasures to make it harder to detect and intercept their missiles. “Stopping subsonic cruise missiles or short-range ballistic missiles launched from just outside US borders would use established technology, but it could be expensive to deploy enough of those defensive systems to cover the whole country,” says Burbach. “The real challenge will be Golden Dome’s aim to stop large numbers of intercontinental missiles – President Trump said ‘100 per cent’ of them – such as an attack from China or Russia.” Trump’s claim that the Golden Dome would defend against missile strikes from the other side of the world or even from space implies it would require a “dense constellation of likely low-Earth orbiting, space-based missile interceptors that could deorbit and strike a missile within minutes of it launching” from anywhere, says Roberts. “The number of satellites you would need is bigger than any constellation that’s ever been launched,” he says. Currently, the largest constellation consists of around 7000 Starlink satellites operated by SpaceX. How much will the Golden Dome cost? Trump proposed a budget of billion for the Golden Dome, although that funding has not yet been approved by the US Congress. And the Congressional Budget Office, a nonpartisan federal agency, estimated that a space-based interceptor system like Golden Dome could cost as much as billion. “It’s unclear what expenditures are included in the billion figure,” says Patrycja Bazylczyk at the Center for Strategic & International Studies, a think tank in Washington DC. Trump also claimed the Golden Dome would be “fully operational” by the end of his second term in office in early 2029, although experts doubt that is possible. “The three-year timeline is aggressive – this initiative is likely to span at least a decade, if not more,” says Bazylczyk. Much of the timeline may depend upon how many existing military systems it uses. “Significant progress is feasible in the near term, including fielding new interceptors, over-the-horizon radars, space-based sensors and technology demonstrations,” says Bazylczyk. But there are major limitations to how quickly the US could launch the potentially thousands of satellites required for Golden Dome – to say nothing of developing the space-based interceptor technologies. “I think you’d be very hard-pressed to find a launch cadence that could support a large constellation going up in just three years,” says Roberts. “SpaceX launches more things more often than anyone in the history of space operations, and the ask here is to crack open that ceiling even further.” “I think it is almost impossible a system could be ‘fully operational’ in the sense of ‘stop 100 per cent of a missile attack’ that quickly,” says Burbach. “Reaching even a small-scale operational capability that soon would be very difficult.” Will Golden Dome make the US safer? There is already an ongoing arms race between the US, China and Russia, with all three countries modernising and expanding their nuclear arsenals, as well as developing space-based systems to support their militaries. If the Golden Dome system can improve US air and missile defences, it could “change the strategic calculus” by reducing the confidence of any missile-armed adversary, deterring them from launching attacks in the first place, says Bazylczyk. On the other hand, the Golden Dome has the “potential to contribute to instability” by “signalling to your nuclear adversaries that you simply don’t trust them”, says Roberts. China’s foreign ministry responded to Trump’s announcement by saying the Golden Dome carries “strong offensive implications” and raises the risks of an arms race in space. A Kremlin spokesperson suggested the Golden Dome plans could lead to resumption of nuclear arms control discussions between Russia and the US. To counter this system, China and Russia might try to “destroy or disable US satellites”, says Burbach. Both countries already have missiles capable of shooting down satellites, and they could also try to electronically jam or hack US satellite systems, he says. In February 2024, the US government warned that Russia had plans to launch a space weapon capable of disabling or destroying satellites, possibly using a nuclear explosion. These countries could also bulk up their missile arsenals and possibly develop more manoeuvrable weapons that also use decoys, says Burbach. He pointed out that Russia has already started developing weapons less vulnerable to space-based interception, such as intercontinental nuclear torpedoes that travel underwater. Topics: #trump039s #golden #dome #defence #project

Fast food is often ultra-processedShutterstock/siamionau pavel Two of the biggest health concerns of the modern age – ultra-processed foodsand microplastics – have one thing in common: we don’t actually know if or how they harm our health. But researchers are proposing a bold new idea: that these problems are actually linked, and UPFs contain especially high levels of microplastics that worsen mental health. “We know ultra-processed foods have microplastics. We know that ultra-processed foods are also associated with depression and anxiety. We thought that it would be helpful to put out the hypothesis that potentially microplastics could be mediating that association, with the caveat… #are #microplastics #ultraprocessed #food #harming

Advertisement Subscribe now Life Puzzlingly, many birds add human-made material to their nests with no obvious function – now there is evidence that these home improvements might ward off predators 23 May 2025 Red kites sometimes put plastic objects in their nestsMike Read / Alamy Stock Photo Birds may decorate nests with artificial objects and feathers to deter magpies and ravens from taking their eggs. Many birds have been observed placing human-made objects in their nests, such as plastic, wires or even anti-bird spikes from buildings. Often, these things seem to have no role as insulation or structural support, and may make nests more conspicuous to predators. Magne Husby at Nord University and Tore Slagsvold at the University of… Advertisement Receive a weekly dose of discovery in your inbox! We'll also keep you up to date with New Scientist events and special offers. Sign up Advertisement More from New Scientist Explore the latest news, articles and features Popular articles Trending New Scientist articles Advertisement #why #birds #decorate #their #nests

Quantum computers have long been a potential threat to encryptionsakkmesterke/Shutterstock Quantum computers could crack a common data encryption technique once they have a million qubits, or quantum bits. While this is still well beyond the capabilities of existing quantum computers, this new estimate is 20 times lower than previously thought, suggesting the day encryption is cracked is closer than we think. The widely used RSA algorithm relies on the fact that multiplying two prime numbers to generate a large encryption key is easy, but finding those original prime factors when all you have is the resulting key is… #breaking #encryption #with #quantum #computer

The word angelic is considered to be more feminine than masculineMatheus Frade/Unsplash Think of an imaginary person who has a strong moral compass. According to a series of recent experiments, you probably just pictured a woman or a girl. Scientists have found that we tend to associate morality more closely with femininity than masculinity, which may pose a surprising disadvantage for women. Jordan Wylie and her colleagues at Boston College in Massachusetts wanted to better understand the traits and attitudes that we ascribe to people who are considered morally good. #assume #women #are #morally #superior

A Tasmanian devil is carried to safety by a ranger amid flooding at the Aussie Ark sanctuaryAussie Ark Conservation workers are racing to protect a precious group of Australian animals after record rainfall in New South Wales led to floods that have killed four people. Tasmanian devils, brush-tailed rock wallabies, eastern quolls, long-nosed potoroosand broad-toothed ratsare all kept fenced safely away from feral predators such as cats and foxes at the 400-hectare Aussie Ark sanctuary in Barrington Tops, New South Wales. The sanctuary’s animals are considered an insurance policy for their species, in case wild populations become extinct. Advertisement Since 2010, 500 devil joeys alone have been born there and around 50 of these have been released into a specially protected wild area. In coming years, some of these animals are expected to be released outside the sanctuary to re-establish Tasmanian devil populations on mainland Australia. But this week, a severe low-pressure weather system has hit parts of New South Wales, leading to record-breaking storms. In just a few days, well over 400 millimetres of rain fell at the sanctuary. Even though it is at the top of a mountain at an altitude of 1200 metres, the park experienced flash flooding, sweeping away fencing that excludes feral animals and threatening to drown some of the breeding animals in smaller enclosures. Tim Faulkner at Aussie Ark says many of the animals in the breeding enclosures have had to be brought into a makeshift emergency centre at the complex’s vet clinic. But the bigger problem facing the sanctuary is that around a kilometre of the 10-kilometre perimeter fence has been damaged or, in some locations, totally swept away by floodwaters. Unmissable news about our planet delivered straight to your inbox every month. Sign up to newsletter “We’ve got about a kilometre of the fence that’s impacted from corner posts down, sections washed away and pushed over and strainer wires damaged,” says Faulkner. “The electrified hot wire is completely down, so we’re lucky we don’t have any Tyrannosaurus rex testing our defences.” A fence swept over by flooding at the Aussie Ark sanctuaryAussie Ark While the fences are damaged, Faulkner’s team has been camped out around the clock, keeping watch at breached sections. So far, no native species are thought to have escaped and no feral animals have entered. “There’s water seeping, squeezing, pushing, running, pouring, flooding from every single little crack up here on the mountain, and I hate to think of all the wildlife that has also been devastated by these massive floods outside the sanctuary,” says Faulkner. Topics: #flash #floods #sweep #through #vital

A panda keeper does a health check on the cub of giant panda Xi Mei at the Wolong Nature ReserveAmi Vitale These images from the Earth Photo 2025 competition shortlist tell revealing, inspiring and unexpected stories about the climate and life on our planet. Pictured top, photographer Ami Vitale’s image Pandamonium shows a giant panda keeper checking the health of a panda cub in the Wolong National Nature Reserve in Sichuan province, China. The keeper’s outfit is part of an effort to reduce the impact of human contact on the bears. Next, below, is Sue Flood’s Crabeater Seals, shot on an ice floe in the Southern Ocean, off the Antarctic Peninsula. For Flood, such photos can bring the region’s wonder to those who may never visit. Crabeater Seals Southern Ocean, Antarctic peninsulaSue FloodAdvertisement Paradise to Ashes, La Palma by Jonathan Browning pictured below, shows the aftermath of the 2021 Cumbre Vieja volcanic eruption on this island in the Canaries, Spain. A woman has remade her garden, removing lava that destroyed mature palms and replacing them with new trees. La Palma. An island of the Canaries. Two years after the Cumbre Vieja volcanic eruption in late 2021Jonathan Browning The final image below is Vincenzo Montefinese’s Lost Oases, shot in Tinzouline, Draa valley, Morocco. Here, a man adjusts a solar panel that powers a water pump that irrigates nearby palm groves. Climate change and water use have shrunk the valley’s oases by two-thirds over the past century. Today, farmers must dig more wells, often illegally, to access groundwater. Tinzouline, Draa valley, MoroccoVincenzo Montefinese The photos and videos on the shortlist were chosen by a panel including New Scientist picture editor Tim Boddy and head of editorial video, David Stock. The winners will be revealed on 16 June. The Earth Photo 2025 exhibition is at London’s Royal Geographical Society from 17 June to 20 August before it tours the UK. Topics: #powerful #images #capture #fragility #resilience

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