Ancient footprints shed light on early humans

TOKYO (AFP) – Thousands of years ago, a group of people took a walk in what is now Tanzania. The footprints they left behind are now offering insights into ancient human life.

The group of over 400 footprints was made sometime between 5,000 and 19,000 years ago at a site called Engare Sero, south of Tanzania’s Lake Natron.

It’s the largest group of human footprints ever found in Africa, and offers a glimpse at what humans in the so-called Late Pleistocene period looked like, as well as how they may have gathered food.

“Sites like Engare Sero form over very short time intervals, and so they capture snapshots in time of ancient humans moving across their landscapes,” said Assistant Professor of biology at Chatham University Kevin Hatala, who led the research.

“Given the rarity and value of this variety of fossil evidence, part of what makes our discovery exciting is its magnitude, with over 400 footprints preserved on the same volcanic ash surface,” he told AFP. “However, we have also been able to learn some really interesting things from these direct windows to the behaviour of the group that walked across the footprint surface.”

Analysing the footprints was a complex process. In 2009, when the research team first visited the site – discovered by a local Maasai community – just 56 footprints were visible, exposed by natural erosion.

Three years of additional excavations revealed hundreds more prints, made by humans but also animals such as zebra and buffalo.

The prints were made in wet volcanic mudflow, which would have dried quickly into a hard surface, said Hatala.

That, combined with other evidence including the lack of overlap on footprints, strongly suggests the impressions were made by a group travelling together at the same time, rather than by individuals moving across the same area at different times. The research team focussed on “distinct trackways” where they could clearly discern stride distances and footprint length, looking for more clues.

Based on the size of the prints and the stride lengths, they determined the group included four adult men, 19 adult women and two younger boys.

There is some room for error, they acknowledge, with the possibility that the smaller feet and shorter strides they attributed to women could in some cases belong to children or adolescents of either gender. The trackways also allowed the researchers to extrapolate the height of the people who made them, revealing some comparatively tall men among the group, including one standing an estimated 1.83 metres.

Skeletons from around the period in east Africa “have suggested generally tall and long-limbed body builds,” said the study was published on Thursday in the journal Nature Scientific Reports.

The make-up of the travelling group also offers clues about their lifestyle.