Scientists discover hundreds of footprints left at the dawn of modern humanity

Scientists discover hundreds of footprints left at the dawn of modern humanity
By Sarah Kaplan
Oct 12 2016
https://www.washingtonpost.com/news/speaking-of-science/wp/2016/10/12/scientists-discover-hundreds-of-footprints-left-at-the-dawn-of-modern-humanity/

The footprints weave intricate paths across the desolate landscape. Some tracks race straight toward an unseen finish line; others meander, the outlines of their ancient owners’ toes and curves of their arches carved deeply into the sun-baked earth.

The air shimmers with heat, and the active volcano that locals call “the mountain of God” looms in the middle distance. It’s not difficult for geologist Cynthia Liutkus-Pierce to imagine this scene as it would have looked thousands of years ago, when prehistoric people walked across the muddy terrain and left an indelible record of their presence pressed into the ground.

The site in northern Tanzania is the largest assemblage of ancient human footprints in Africa and one of the biggest on the planet, Liutkus-Pierce and her colleagues reported in the journal Palaeogeography, Palaeoclimatology, Palaeoecology. The 400-odd footprints, which cover an area the size of a tennis court, were imprinted in deposits from an ancient flood, dried, then covered up with a second layer of mud and preserved for as many as 19,000 years.

Now, excavated and exposed to the sun, they offer an unprecedented window into an ancient world. Anthropologists at the site plan to use the footprints to understand social dynamics at the end of the Pleistocene era, a time when the climate was changing and Homo sapiens was on the brink of settling down and learning to farm.

“It’ll give us a sense of the group size and structure of these ancient hunter-gatherers,” said Briana Pobiner, a paleoanthropologist at the National Museum of Natural History and a member of Liutkus-Pierce’s team. “What’s the composition of this group? How many males, how many females and kids, and how many directions are they going? Are they running? Are they walking? Are they walking side by side?”

“For people who work in prehistory, it’s incredibly rare to get that kind of snapshot in time,” she continued. Most knowledge about ancient communities is reconstructed from exhumed skeletons, scattered tools, animal bones dug up from bygone garbage pits. But the Engare Sero prints have the potential to tell us exactly who lived in this spot, how they related to one another and where they may have been headed.

The site was discovered by a resident of the nearby village of Engare Sero about a decade ago, but the scientific community didn’t learn of the prints until 2008. Liutkus-Pierce was sitting in her office at Appalachian State University in North Carolina when she got a call from a colleague Jim Brett, who was working in East Africa.

“I think I’ve come across some amazing hominid footprints,” he said.

Liutkus-Pierce glanced at her calendar: It was April 1. Half worried she was being fooled, she told him, “Jim, I’m going to need you to call me back and say this again tomorrow.”

But Brett was adamant — this was no joke.

A year later, Liutkus-Pierce and a small crew of colleagues were standing at the edge of the footprint site. The shallow, saline waters of Lake Natron shimmered behind them and the mountain loomed up ahead. And there they were: Some 50 footprints pressed into a dried-up riverbed, clearly defined and unmistakably human. She teared up looking at it.

There were also tire tracks zig-zagging across the site — a reminder of how vulnerable this spot really was. The scientists needed to get to work.

[snip]

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