Thu. May 19th, 2022

Twenty-four years ago, Brianna Pobina reached the land of northern Kenya and laid her hands on the bones that were last touched 1.5 million years ago. Pobiner, a Paleontherologist, was digging up the bones of ancient animals and looking for cuts and dents, indicating that our early ancestors tried to find the fatty, calorie-rich bone marrow hidden in them. “You’re arriving on time through a window,” said Pobiner, now at the Smithsonian Institution in Washington, DC. “The animal that killed this animal is not like you, but you are exposing this direct evidence of behavior. It’s really exciting. “

That moment gave rise to Pobiner’s enduring interest in how the food of our ancestors shaped their evolution and finally the emergence of our own species, Homo sapiens. Meat, in particular, seems to have played an important role. Our more distant ancestors ate mostly plants and had small legs and small brains shaped like chimpanzees. But about 2 million years ago, a new species appeared with human-like characteristics. Standing man A larger brain, smaller intestines, and limbs resembled modern humans. And the surrounding fossils at the same time as the fossils excavated by the Kenyan Pobina Someone The animals were butchered to separate the lean meat from the bones and to dig up the marrow. For decades, paleontologists have theorized that the evolution of human-like traits and meat-eating are closely linked.

“The explanation is that eating meat is allowed: we’ve got a lot more nutrition, and these concentrated sources have facilitated these changes,” Pobiner said. The large brain is the unprecedented power of the hog – even at rest, a human brain absorbs. About 20 percent The energy of the body. But a change to a full-fledged diet of calorie-rich meats means extra energy that can be directed to support a larger, more complex brain. And if pre-humans hunt their food, it would explain a shift to longer limbs that is more efficient for hunting prey over long distances. Flesh makes us human, conventional knowledge said. And Pabina agrees.

But in April 2020, Pobina received a call that forced her to reconsider that assumption. The call came from Andrew Barr, a paleontologist at George Washington University in Washington, DC, who wasn’t quite sure about the connection. Standing man And eating meat. He wanted to use the fossil record to see if there was real evidence that human ancestors ate more meat at that time. Standing man Evolved, or whether it simply Appeared That way because we weren’t looking hard enough. Pabina thought it sounded like an intriguing project: “I like the idea of ​​questioning conventional wisdom, even though it’s conventional wisdom that I bought.”

Researchers were unable to travel to Kenya for fieldwork due to the epidemic, so they analyzed data from nine major research areas in East Africa covering millions of years of human evolution. They used different metrics to evaluate how well each period was researched and how many bones were found at each site with butcher marks. Inside A new paper In the journal Proceedings of the National Academy of Sciences (PNAS), Barr and Pobiner now argue that the link between eating meat and human evolution may be less certain than previously thought. Appearance after the apparent growth of butcher bones Standing man, They conclude, is actually a sample bias. More paleontologists have been searching for bones at excavation sites since this era – and as a result, they have found more and more of them.

It does not deny a link between eating meat and evolutionary change, but it does suggest that the story could be more complicated. “If we want to say how common a behavior was, we need some way to control that at times and in some places we find it harder than other points to do that behavior,” Barr said. Since sites of well-preserved animal bones are relatively rare, paleontologists often sample them frequently. But research by Bar and Pobiner has shown that other sites date back 1.9 to 2.6 million years – to that era. Homo erectus has evolved– Relatively less studied. “We are attracted to places that preserve fossils because they are the raw material of our science. So we keep going back to this same place, “said Barr.

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