It's not every day that researchers crack a case this cold.
Lucy, the iconic hominin found in present-day Ethiopia, died 3.18 million years ago. Her cause of death has remained a mystery since her remains were discovered in 1974.
But a new study published Monday in the journal Nature claims to pin down, for the first time, precisely how and why Lucy died. According to the study's authors, she fell from a tree.
Some other anthropologists, including Tim D. White, whose findings of ancient hominin remains in Africa helped illuminate the early stages of human evolution, aren't quite sold.
In fact, they're pretty convinced that the paper is utterly wrong.
White says the cracks in Lucy's bones, rather than the result of a fall while she was alive, instead emerged long after she passed away — something that happens to thousands of bones that get buried and shuffled around in the Earth's soil for millions of years.
"This may be the first time that such routine fossil damage has been interpreted as evidence of tree dwelling and death by falling," White told Business Insider.
"For good reason. If paleontologists were to apply the same logic and assertion to the many mammals whose fossilized bones have been distorted by geological forces, we would have everything from gazelles to hippos, rhinos, and elephants climbing and falling from high trees."
The problem appears to have been pretty straightforward, White said: The study authors must have failed to look at the other fossils at the site.
"These authors make no effort to test the alternative hypothesis that these cracks and other breaks were made during the processes of fossilization and erosion," White said.
Instead, they went straight to the clinical literature for an example of what the break would have looked like in a person, he said.
"When you go to the clinical literature for your analogy ... you're confined to a single cause, because we know what happens when humans fall off the top of buildings or fall from windows," William Kimbel, the director of the Institute of Human Origins at Arizona State University, told Business Insider. "There's only one explanation: breakage due to trauma."
And that's almost certainly not what happened to Lucy, Kimbel said.
"I've worked in Eastern Africa for a long time and at fossil sites ... like the one where Lucy is from, for a long time," Kimbel told Business Insider. "And I know from my own experience that the type of damage that Lucy's bones exhibit is extremely common in animals that range from hare to hippo. It is ubiquitous. We would not interpret that hares and hippos are falling out of trees."
John Kappelman, the study's lead author and a professor of anthropology at the University of Texas at Austin, told Business Insider that his team did in fact look at plenty of other bones at the site.
But since most fossils get cracked as the result of fossilization and erosion, White said "the authors' obligation was to unequivocally demonstrate that the cracks in the bones were made around the time of death rather than during fossilization."
So we put the question to Kappelman, and asked if he'd indeed tested that alternative hypothesis — that these breaks were made as the fossil got rustled around in the soil instead of by a fall. "Thirty-some years of working in this field has done that for us," he said.
He agreed that the majority of the breaks in Lucy's skeleton happened as the result of regular fossilization and erosion. "The easy criticism is to say, 'Oh, other fossils look like this.' We agree. We put that straight up in the paper," Kappelman said.
But he and his team chose to home in on one "specific kind of break," Kappelman said. "These are the kinds of breaks that are documented in the clinical literature, and what they are is a high-energy break."
Kappelman added: "We're not saying that these breaks couldn't have happened through fossilization, but we looked at these and we said, 'We think they deserve an explanation.'"
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