Snapshots of human anatomy, locomotion, and behavior from Late Pleistocene footprints at Engare Sero

Published: 14 May 2020
Snapshots of human anatomy, locomotion, and behavior from Late Pleistocene footprints at Engare Sero, Tanzania
Kevin G. Hatala, William E. H. Harcourt-Smith, Adam D. Gordon, Brian W. Zimmer, Brian G. Richmond, Briana L. Pobiner, David J. Green, Adam Metallo, Vince Rossi & Cynthia M. Liutkus-Pierce
Scientific Reports volume 10, Article number: 7740 (2020)

Abstract
Fossil hominin footprints preserve data on a remarkably short time scale compared to most other fossil evidence, offering snapshots of organisms in their immediate ecological and behavioral contexts. Here, we report on our excavations and analyses of more than 400 Late Pleistocene human footprints from Engare Sero, Tanzania. The site represents the largest assemblage of footprints currently known from the human fossil record in Africa. Speed estimates show that the trackways reflect both walking and running behaviors. Estimates of group composition suggest that these footprints were made by a mixed-sex and mixed-age group, but one that consisted of mostly adult females. One group of similarly-oriented trackways was attributed to 14 adult females who walked together at the same pace, with only two adult males and one juvenile accompanying them. In the context of modern ethnographic data, we suggest that these trackways may capture a unique snapshot of cooperative and sexually divided foraging behavior in Late Pleistocene humans.

Introduction
Footprints are often ephemeral but when preserved in the geological record, these ichnofossils can provide unique snapshots of the lives of ancient organisms. Fossil tracks are generated and preserved on far shorter time scales than other common forms of fossil data (e.g., skeletal fossils), leading to a distinct set of hypotheses that can be developed and tested with this form of evidence. In paleoanthropology, researchers have analyzed fossil hominin footprints through a variety of analytical approaches that address a wide range of research questions (many are reviewed by Bennett and Morse1). Perhaps most common are analyses that derive inferences regarding hominin body size and size variation2,3,4, or foot anatomy, foot function and/or locomotion4,5,6,7,8,9,10,11,12,13,14,15,16,17. However, since footprint assemblages typically form on short time scales, these data can also be used to infer group composition and other behaviors of individuals who must have lived on the same landscape at the same time16,18,19,20,21,22,23.

Here, we report on Late Pleistocene human footprints discovered at Engare Sero, Tanzania. While our previous publications focused on the geological context and preservation of this site24,25, we explore the paleoanthropological implications of this remarkable assemblage of more than 400 human footprints. This includes inferences regarding the body sizes, locomotor behaviors, and composition of the group of humans who generated these tracks.

Site description
The Engare Sero footprint site lies just south of Lake Natron, in northern Tanzania (Fig. 1). It is notable that the site, which preserves the most abundant assemblage of hominin footprints currently known from Africa, is within roughly 100 km of the site of Laetoli, which preserves the earliest confidently attributed hominin footprints26. The Engare Sero site was originally discovered by members of a Maasai community living nearby. In 2008, these individuals notified conservationists working in the area, and the conservationists brought the site to the attention of C.M.L.-P. When members of our research team first visited the site in 2009, an assemblage of 56 human footprints had already been exposed by natural surface erosion. From 2009 to 2012, our excavations (see Methods) exposed an additional 175 m2 of the footprint surface, which included at least 352 more human footprints (another 14 impressions were classified as “potential” human tracks). The same surface also preserves 19 bovid tracks in immediate association with the human footprints, and 24 zebra and buffalo tracks, which lie approximately 30 m to the southwest. Four additional assemblages of zebra tracks are located just over 1 km to the northwest, nearer the present-day shoreline of Lake Natron (Fig. 1).

More:
https://www.nature.com/articles/s41598-020-64095-0