AUDIE CORNISH, HOST:
A hundred and twenty thousand years ago, a group of humans wandered along the shores of an ancient lake in the northwestern reaches of modern-day Saudi Arabia.
SACHA PFEIFFER, HOST:
Today, that stretch of land is barren, with seas of sand and dunes and little rain. But not back then, according to Briana Pobiner, a paleoanthropologist at the Smithsonian.
BRIANA POBINER: It would have looked sort of like - almost like the Serengeti in Tanzania. It would have been wet at times. It would have been much greener.
CORNISH: And the reason we know several humans were there is not from bones, but from a set of seven remarkably preserved human footprints stamped into the sediments of the ancient lake.
POBINER: The footprints are actually amazing windows into the past. They give us a really good window into where humans may have been that we didn't have fossil evidence for.
PFEIFFER: Matthew Stewart of the Max Planck Institute is lead author on the new research out today in the journal Science Advances. He says it's likely this journey to the lake was just a pit stop for our ancient ancestors.
MATTHEW STEWART: We have no stone tools from the lake, so it appears that their visitation to the lake in this instance was rather brief.
CORNISH: No stone tools, but his team did find a jumble of fossilized bones and hundreds more footprints left by elephants, camels and a buffalo.
PFEIFFER: Together, they're a snapshot of ancient time, says Stewart's collaborator Richard Clark-Wilson of Royal Holloway University of London.
RICHARD CLARK-WILSON: These footprints are really high resolution in terms of their relation to each other. It's really rare that you kind of can pick out these details and we can say, oh, wow, there were these humans, elephants, other animals all there probably - kind of within the same hour, within the same day, foraging around this lake.
CORNISH: Elephant was a popular menu item for ancient humans, and the prospect of big game could have lured these individuals to the lake. But Stewart says he was surprised to find elephants at all in this region.
STEWART: Elephants are thought to have gone extinct in the sort of broader region, sort of in the Middle East, from around 400,000 years onwards. Finding them in northern Arabia, you know, hundreds and thousands of years later is quite significant.
PFEIFFER: And in regards to our human origins, Pobiner of the Smithsonian wasn't involved in the work. But she says the footprints give us a more complete understanding of when and where Homo sapiens roamed.
POBINER: The earliest fossil evidence that we have for humans, for modern humans, Homo sapiens, in the Arabian Peninsula is only about 85,000 years old. So it gives us insight into another point in time in which humans were actually in the Arabian Peninsula that we didn't have evidence for based on fossils or artifacts and things like that yet.
CORNISH: Yet, however revealing these footprints are, they still leave one unanswered question - where these early travelers ended their journey.
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