In nuclear fusion, the triple product – also known as the Lawson criterion – defines the point at which a nuclear fusion reaction produces more power than is needed to …read more

Scientists Investigate 2.2-Million-Year-Old Tooth Enamel to Unravel the Mysteries of Ancient Human Relatives By studying proteins preserved in teeth, researchers determined the sex of four Paranthropus robustus individuals that lived in southern Africa This skull of a 1.8-million-year-old Paranthropus robustus individual was unearthed in South Africa, but it was not one of the fossils included in the study. José Braga and Didier Descouens via Wikimedia Commons under CC BY-SA 4.0 Paranthropus robustus was a prehistoric, two-legged human relative that lived in southern Africa roughly two million years ago. Scientists have unearthed various P. robustus fossils, but because of the specimens’ age, they haven’t been able to glean much from them. Now, using a novel method, researchers say they’ve determined the sex of four P. robustus individuals by studying their teeth. The new analysis, published Thursday in the journal Science, also reveals insights into the genetic diversity of the broader Paranthropus genus. For the study, the team analyzed teeth discovered in a cave at the Swartkrans paleoanthropological site in South Africa, reports Live Science’s Kristina Killgrove. Because the fossils were so old—dating to between 1.8 million and 2.2 million years ago—researchers could not recover ancient DNA from them. So, instead, they turned to the relatively new field of paleoproteomics, or the study of preserved proteins. Ancient DNA degrades over time, particularly in hot places like southern Africa. So far, scientists studying hominin remains on the continent have only been able to successfully sequence DNA from material that’s less than 20,000 years old. But proteins can survive much longer than DNA, particularly in hard tooth enamel. When they analyzed the fossilized enamel of the P. robustus teeth, the researchers were able to identify specific protein sequences found only in males. This allowed them to determine that two of the P. robustus individuals were male and two were female. They were surprised to learn that one individual, named SK 835, was male. Based on the comparatively small size of that individual’s teeth, researchers had previously thought SK 835 was female, since male hominins tend to be larger than females, on average. This marks an important finding, as it supports the idea that dental measurements are not the most reliable way to determine the sex of ancient hominins. “Paleoanthropologists have long known that our use of tooth size to estimate sex was fraught with uncertainty, but it was the best we had,” says Paul Constantino, a paleoanthropologist at Saint Michael’s College who was not involved with the research, to ScienceNews’ Bruce Bower. “Being able to accurately identify the sex of fossils using proteins will be hugely impactful.” Further analyses of the fossils’ amino acid sequences revealed that SK 835 was less closely related to the other three individuals than they were to each other. That means it’s possible SK 835 represents a different species altogether—maybe the newly proposed Paranthropus capensis. After all, the team writes in the paper, the recent description of that species shows Paranthropus diversity “is currently underestimated and needs to be investigated further.” Or, perhaps the small size of SK 835’s teeth can be explained by microevolution—variations between P. robustus groups living at different sites. Scientists say they will need to get their hands on more Paranthropus fossils from multiple places to know for certain, per Science News. Moving forward, researchers hope they can one day use paleoproteomic methods to map the entire human family tree. Right now, however, their “ability to distinguish between different species is limited by the small number of different proteins present in enamel,” three of the study authors tell Live Science in an email. Scientists are also exploring other protein-sequencing techniques that are less destructive to fossil samples than the current methods. In the meantime, they’re excited about the potential of paleoproteomics to help them learn even more about humans’ ancient ancestors. “It opens entirely new avenues for understanding our evolutionary history [in Africa],” study co-author Marc Dickinson, a chemist at the University of York in England, says in a statement. Get the latest stories in your inbox every weekday.

This month, we visit a trendy (but fictional) spa with an unusual feature: hot mud beds. You lay a plastic sheet on the mud. Then you lay your body upon the sheet. Without any direct contact between mud and body, you spend several minutes enjoying the soft and saunalike heat, sweating all over the plastic. Even though the spa session doesn’t last long, it is said to be wonderfully restorative. One day, three friends arrive. Unfortunately, only two plastic sheets are available. No one wants to miss out; then again, no one wants to lie on someone else’s sweat. “Wait!” says one. “It’s simple! I’ll use one side of the sheet, and you can use the other.” “Are you kidding?” another replies. “That side will be covered in mud.” The first friend smiles. “Not if we plan ahead.” #1: How can all three friends partake in the spa using just two sheets? #2: The next day, five friends visit the spa, and only three sheets are available. Can they all partake? (Let’s assume the spa now forbids laying an already-sweaty side of a sheet directly on their precious mud.) #3: Soon, 10 friends visit the spa. Only five sheets are available. “Someone will have to miss out,” one of them declares. “There’s no way to know that,” says another, “until we at least look for a solution.” Who’s right? #4: Later, the spa introduces a second kind of mud, which must not be mixed with the first. If three friends want to try both muds, how many sheets do they need at minimum? (Let’s assume each person is begrudgingly willing to lie twice on the same sheet.) #5: Lurking here is a fully general question, one that mathematical researchers have yet to solve: What’s the minimum number of sheets that allows N friends to experience M kinds of mud if each side of a sheet may touch only a single person or a single kind of mud? (You might begin by assuming M = 1.) While trying these puzzles, I recommend grabbing some index cards or sheets of paper to manipulate. Or if you’re feeling ambitious, grab some plastic sheets, some sweaty friends and a convenient mud patch. Looking for answers? Go to sciencenews.org/puzzle-answers. We’d love to hear your thoughts. Email us at puzzles@sciencenews.org.

News Animals Wild chimpanzees give first aid to each other A long-term study in Uganda offers glimpses at the origins of human medicine Two chimpanzees groom each other. Chimps in Uganda’s Budongo Forest have also been observed treating each other’s injuries by licking, dabbing with leaves and other methods. E. Freymann By Martin J. Kernan 11 seconds ago For wounded chimpanzees, help sometimes comes in the form of first aid — care rendered not by humans but by other chimps. New research reveals the nature and prevalence of these rarely witnessed events. Thirty years of observations in Uganda’s Budongo Forest reveal that chimp-administered health care — both ape-to-ape care and self-care — happens frequently there, say primatologist Elodie Freymann of the University of Oxford and colleagues. She suspects these behaviors, occasionally glimpsed outside of Budongo, are widespread among chimps. Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday.

Skip to content News Plants A leaf’s geometry determines whether it falls far from its tree Round leaves land near the tree, while lobed, asymmetrical leaves fly far Scientists have shown that leaves’ shapes and symmetry let them fall close to the tree — allowing the tree access to the nutrients in them. Vicente Méndez/Getty Images By Bethany Brookshire 2 hours ago An apple may not fall far from the tree, but for a leaf, it depends on its shape. Elm or apple leaves — oval and symmetrical, with few protruding lobes — fall quickly, making them likely to end up close to the tree’s base. Adding lobes and asymmetry to leaves slows their descent, causing them to fall farther away, physicists Matthew Biviano and Kaare Jensen report May 7 in Journal of the Royal Society Interface. Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday.

Health & Medicine Humans have shockingly few ways to treat fungal infections Antifungal vaccines and drugs are in the works, but progress is achingly slow Fungi-infested zombies in The Last of Us are hard to kill. Fungal infections are on the rise in the real world, and while they don’t zombify people, there are precious few antifungal treatments. Courtesy of HBO By Tina Hesman Saey 10 seconds ago Fighting fungi isn’t easy. Season two of the streaming series The Last of Us has arrived on Max (light spoilers ahead), bringing viewers back to a world where people combat zombies puppeteered by a mind-controlling fungus. Guns and flames help the characters survive onscreen. In the real world, fighting fungal infections is less action-packed, but no less fraught. At the heart of the show is Ellie (Bella Ramsey), a girl immune to the pandemic fungus. The new season picks up after Joel (Pedro Pascal) saves Ellie from a doctor who wanted to remove her brain to find the source of her immunity and make a cure. Sign up for our newsletter We summarize the week's scientific breakthroughs every Thursday.