Fossilized Footprints Suggest Early Humans Divided Labor

One of the 408 human footprints preserved at Engare Sero. (Photo by William Harcourt-Smith)

(CN) — The signs and markings we leave throughout our daily lives are often an afterthought. But put together all that evidence tells a story — even thousands of years later.

Of course, it helps when a team of archaeologists is poring over those markings.

An archaeological find on the southern shore of Tanzania’s Lake Natron features hundreds of footprints that date back to the Late Pleistocene period.

The findings are detailed in a study published Thursday in the journal Scientific Reports.

The footprints give a snapshot of life in east Africa between 19,100 and 5,760 years ago. They show that the ancient humans who lived in the region, near the Engare Sero village, divided labor based on gender. 

Size differentiation, distances between the prints, and orientation show 17 tracks made by a group walking in a southwesterly direction. The group consisted of 14 women, two men, and one young male, according to the study authors.

Earlier footprint collections were attributed to Homo erectus gatherings made up primarily of men.

The researchers were able to estimate body size, speeds of travel, and variations between the footprint sizes relative to foot size. The authors also estimate the ages of the tracks were biased towards 18 to 34-year-olds, with a high proportion of 18- to 20-year-olds.

Originally the site was discovered by members of the Maasai community who lived in the area.

Other tracks were found, including those of zebra, bovid, and buffalo, but the study focused on the human footprints.

The footprints were measured by radioisotopic dating techniques, which can identify a calcite cement in an overlying sedimentary layer made during a highstand of Lake Natron when the sea level was above the edge of the continental shelf.

In an email, assistant biology professor Kevin Hatala of Chatham University said the footprints were left in wet volcanic mudflow. Layers of other sediment on top of the calcite cement helped protect the prints for thousands of years, Hatala said.

“All of the footprints appear to have been produced by barefoot humans, as individual toe impressions are easily distinguishable,” according to the study. “Because of their apparent human-like morphology and their Late Pleistocene age, we have attributed these tracks to Homo sapiens.”

An additional six tracks of footprints moving in a northeast direction fall into a broader range of speed, an indication of a busy path and a group not traveling together, the researchers said.

Hatala said the footprints “offer amazing windows” to observe behavior in the fossil record.

“These richly detailed snapshots of people moving around their landscape together are unlike anything that can be gleaned from other forms of fossil or archaeological data,” Hatala said in the email. “They provide us with a unique opportunity to develop and test behavioral hypotheses.”

The Engare Sero footprint site in northern Tanzania, which preserves at least 408 human footprints dated to between 19,100 and 5,760 years ago. An eruption of Oldoinyo L’engai, the volcano in the background, produced the ash in which the footprints were preserved. (Photo by Cynthia Liutkus-Pierce)
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