Recently discovered multiple assemblages of Homo erectus footprints in northern Kenya provide unique opportunities to understand our ancient ancestors. Using novel analytical techniques, researchers have demonstrated that the footprints preserve evidence of a modern human style of walking and a group structure consistent with human-like social behaviours.
     Habitual bipedal motion is a defining feature of modern humans compared with other primates, and  had profound effects on the biologies of our ancestors and relatives. There has been much debate over when and how a human-like bipedal gait first evolved, largely because of disagreements over how to infer biomechanics from skeletal shapes. Aspects of group structure and social behaviour also distinguish humans from other primates, yet there is no consensus on how to detect these in the fossil or archaeological records.
     In 2009, a set of 1.5-million-year-old hominin footprints was discovered near the town of Ileret, on the northeast shore of Lake Turkana, in the extreme northwest corner of Kenya - a trace fossil discovery of unprecedented scale for this time period, now extending to five distinct sites preserving a total of 97 tracks created by at least 20 different presumed Homo erectus individuals. Researchers found the shapes of these footprints indistinguishable from those of modern habitually barefoot people, most likely reflecting similar foot anatomies and mechanics.
     Kevin Hatala, of the Max Planck Institute for Evolutionary Anthropology and George Washington University, says: "Our analyses of these footprints provide some of the only direct evidence to support the common assumption that at least one of our fossil relatives at 1.5 million years ago walked in much the same way as we do today."
     Based on experimentally derived estimates of body mass from the fossil tracks, the researchers have inferred the sexes of the individuals and, for the two most expansive excavated surfaces, developed hypotheses regarding the structure of the groups. For example, at each of these sites there is evidence of several adult males. Cooperation between males underlies many of the social behaviours that distinguish modern humans from other primates.

Edited from PhysOrg, Science Daily (12 July 2016)