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Dinosaurs Had Dandruff Problems, Too

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One of the most compelling aspects of paleontology is its ability to surprise even the most well-versed dinosaur scholars. Every fossil holds the potential to shed new light on how these prehistoric creatures lived, ate, and thrived.

Now, scientists have learned some dinos would have benefited from a medicated shampoo.

A study published in Nature Communications examining 125-million-year-old fossils discovered in China demonstrates that dinos expressed a condition common to humans: Their skin would flake off, creating tiny dandruff specks. The paper helps provide an explanation for how dinosaurs managed to molt, or shed skin in an effort to create tougher exterior tissue.

The specimens consisted of skin and feathers from three different non-avian dinosaurs—the crow-sized Microraptor and the larger Beipiaosaurus and Sinornithosaurus—and one bird, Confuciusornis, all from the Early Cretaceous period. The feathers were dotted with white, 1-2 millimeter blobs that initially puzzled scientists, who eventually visualized them with an ion beam microscope. Researchers confirmed them to be flakes of skin composed of corneocytes, tough cells containing keratin. The flecks suggested that these dinosaurs molted by shedding skin like modern birds instead of casting off chunks of skin like other reptiles.

The corneocytes of today's birds contain fats and loosely packed keratin, which allows birds to stay cool during heat-intensive activity like flying. The dino corneocytes were densely packed with keratin, and they probably wouldn't have provided much of a cooling effect. That tells scientists that the bird-like dinosaurs didn't spend too much time in the air.

If they didn't fly, why the feathers? It probably had to do with keeping warm and providing camouflage from both predators and prey. Researchers hope to continue their studies on the plumage to see what else they can learn.

[h/t Popular Science]

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Courtesy of Bournemouth University
Fossilized Footprints Show Ice Age Hunters Ganged Up on Giant Sloths
Courtesy of Bournemouth University
Courtesy of Bournemouth University

They just don't make sloths like they used to. Giant ground sloths from the Ice Age wielded razor-sharp claws and stood 7 feet tall, and new evidence suggests that humans—even children—stalked and hunted them.

By analyzing fossilized footprints found in the salt flats of New Mexico, researchers at Bournemouth University in the UK figured out how prehistoric humans managed to outsmart these furry behemoths. The tracks, which are between 10,000 and 15,000 years old, show two overlapping sets of footprints belonging to both man and beast. Researchers deduced that these early hunters aligned their footprints with the sloth's to avoid detection and sneak up on their prey. The findings were published in the journal Science Advances.

Human footprints inside of a larger sloth footprint
Courtesy of Matthew Bennett, Bournemouth University

"Getting two sets of fossil footprints that interact, that show you the behavioral ecology, is very, very rare," Matthew Bennett, one of the researchers at Bournemouth, told Reuters.

They also found another set of human footprints, leading researchers to believe that hunters traveled in packs and ganged up on the sloth, with one group distracting the animal from a safe distance while another attempted to land a fatal blow. The clue was in marks they dubbed "flailing circles," which suggested that the sloth rose on its hind legs and swung around to defend itself. Anywhere they found flailing circles, human footprints followed.

The presence of children's tracks also showed that hunting was a family affair, but it probably wasn't as fun (or as safe) as going to a modern-day zoo. The prints were taken from New Mexico's White Sands National Monument, which has the "largest concentration of human and Ice Age giant megafauna prints in the Americas," according to researchers. The remote part of the park where they conducted their research is not open to the public.

Modern sloths are related to the giant ground sloth, which went extinct about 11,000 years ago, likely due to over-hunting by humans, scientists say. The fossilized footprints were digitized and preserved for future research using 3D modeling techniques.

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Stephane De Sakutin, AFP/Getty Images
Scientists May Have Finally Figured Out Why We Have Eyebrows
A Neanderthal skull
A Neanderthal skull
Stephane De Sakutin, AFP/Getty Images

If you look at a pictures of some of the earlier branches of humanity's family tree, like Neanderthals or Homo erectus, you might notice that Homo sapiens got off relatively lightly, eyebrow-wise. Most early hominins had thick, bony brow ridges rather than the smooth brows of modern humans. For years, researchers have been arguing over why those thick ridges existed—and why modern humans evolved tinier brows. A new study suggests that heavy brow ridges had social usefulness that was more important than their physiological function.

Previous research has suggested that thick brow ridges helped connect early hominins' eye sockets with their brain cavities, or protected the skull from the physical stress put on it by chewing jaws, or even helped early hominins take punches to the face.

The new study by University of York researchers, published in the journal Nature Ecology & Evolution, used a digital model of a fossil skull, thought to be between 125,000 and 300,000 years old, of an extinct species called Homo heidelbergensis that evolved sometime between 300,000 and 600,000 years ago in what is now Zambia. The researchers manipulated the model, changing the size of the brow ridge and seeing what happened when they applied different bite pressures. They found that the brow ridge was much bigger than it needed to be if its purpose was just to connect the eye sockets with the brain case, and that it didn't seem to protect the skull from the force of biting.

Instead, the researchers suggest that the brow ridge played a social role. Other primates have similar brow ridges that serve a social purpose rather than a mechanical one, like male mandrills, whose colorful, heavy-browed muzzles serve as dominance displays. Heavy brow ridges may have played a similar role in early human species.

As Homo sapiens evolved, more subtle communication may have taken precedence over the permanent social signal of a giant brow ridge. As foreheads became more vertical, eyebrows could move more freely and subtly, leading to important social signals in modern humans, like expressions of surprise or indignation.

An accompanying analysis in the same journal, by Spanish paleontologist Markus Bastir, cautions that the results of the new study are appealing, but should be taken with a grain of salt. The specimen used for the digital model was missing a mandible, and the researchers subbed in a mandible from a Neanderthal, a related species but still a distinct one from Homo heidelbergensis. This may have altered the analysis of the model and bite stresses. Still, the study provides "exciting prospects for future research," he writes.

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