Africa’s biggest collection of ancient human footprints has been found

More than 400 human footprints preserved in hardened volcanic sediment are providing a rare peek at social life among ancient East African hunter-gatherers.

These impressions, found in northern Tanzania near a village called Engare Sero, add up to the largest collection of ancient human footprints ever found in Africa, say evolutionary biologist Kevin Hatala of Chatham University in Pittsburgh and his colleagues.

People walked across a muddy layer of volcanic debris that dates to between around 19,100 and 5,760 years ago, the researchers report May 14 in Scientific Reports. Dating of a thin rock layer that partly overlaps footprint sediment narrows the age range for the footprints to between roughly 12,000 and 10,000 years ago, the team says.

Engare Sero lies in the vicinity of two much older hominid footprint sites — nearly 3.7-million-year-old Laetoli (SN: 12/16/16) in Tanzania and 1.5-million-year-old Ileret (SN: 4/16/12) in Kenya.

At Engare Sero, Hatala’s team analyzed foot impression sizes, distances between prints and which way prints pointed. One collection of tracks was made by a group of 17 people walking southwest across the landscape, the researchers found. Comparisons with modern human footprint measurements indicate that this group consisted of 14 women, two men and one young boy.

The women may have been foraging for food, while a few males visited or accompanied them, the researchers speculate. Some present-day hunter-gatherers, including Tanzania’s Hadza people, form largely female food-gathering groups.

In another set of six tracks, the footprints point northeast. Those tracks probably weren’t made by people traveling in a group. Instead, the impressions suggest that two women and a man had ambled along leisurely, a woman and a man had walked briskly, and another woman had run across the area, the researchers say.

Hatala’s new study is “a nice piece of work,” although it’s hard to specify what ancient Engare Sero people were doing based on their foot impressions, says geologist Matthew Bennett of Bournemouth University in Poole, England.

Many sets of footprint tracks — not just the one set of 17 tracks at Engare Sero — would be needed to argue convincingly that hunter-gatherers at that time formed female foraging groups, Bennett says. Even then, researchers wouldn’t know if such groups had been gathering plant foods or hunting prey.

Other footprint sites present especially promising opportunities for studying ancient human behavior, Bennett says. He is involved in ongoing work at White Sands National Park in New Mexico that has uncovered tens of thousands of footprints of humans, mammoths, giant sloths and other creatures from around 12,000 years ago. Early results suggest that humans hunted giant sloths (SN: 4/25/18), and Bennett expects that research there will yield many more insights into Stone Age hunting.