Two ancient hominid species with slightly different gaits crossed paths in East Africa.
Footprints preserved on what was once a muddy lakeshore indicate that the two species, each built to walk in its own way, hung out there around 1.5 million years ago.
Newly discovered foot impressions at the northern Kenyan site, and footprints previously unearthed at a nearby location, offer glimpses of coexistence and possibly direct contacts between ancient hominid species over a span of up to 200,000 years, say paleoanthropologist Kevin Hatala of Chatham University in Pittsburgh and colleagues.
Two patterns of upright walking appear in foot tracks found along an ancient lake at Koobi Fora, a set of deposits on the eastern margin of present-day Lake Turkana, the scientists report in the Nov. 29 Science. A comparable distinction applies to footprints excavated in fieldwork led by Hatala nearly 20 years ago at Ileret, another roughly 1.5-million-year-old Kenyan site, the team says (SN: 2/26/09).
Prints displaying signs of a humanlike foot anatomy and gait belonged to Homo erectus, a possible direct ancestor of H. sapiens, Hatala says. H. erectus, which lived from nearly 2 million to roughly 117,000 years ago, ate a variety of energy-rich foods to support its large brain (SN: 12/18/19).
Impressions showing fewer similarities to the feet and striding pattern of people today belonged to Paranthropus boisei, the investigators suspect. Small-brained, big-jawed P. boisei, which dates to between 2.3 million and 1.2 million years ago, had a taste for grasses and flowering plants called sedges (SN: 5/2/11).
Researchers have known for nearly 50 years that East African fossils of H. erectus and P. boisei date to about the same time in nearby locations. But those fossils accumulated slowly, and researchers could not pin down…
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