Partial Fossil Foot Find Suggests Two Hominin Species Co-existed 3.4 Million Years Ago
Scientists have discovered a 3.4 million-year-old partial foot from the Woranso-Mille area of the Afar region of Ethiopia. The partial foot was found in February 2009 in an area locally known as Burtele. The fossil foot did not belong to a member of Lucy's species, Australopithecus afarensis, the famous early human ancestor. Research on this new specimen indicates that more than one species of early human ancestor existed between 3 and 4 million years ago with different methods of locomotion. The specimen has not yet been assigned to a species due to the lack of associated skull or dental elements.
Dr. Yohannes Haile-Selassie, curator of physical anthropology at The Cleveland Museum of Natural History and project leader, says, "The Burtele partial foot clearly shows that at 3.4 million years ago, Lucy's species, which walked upright on two legs, was not the only hominin species living in this region of Ethiopia. Her species co-existed with close relatives who were more adept at climbing trees, like 'Ardi's' species, Ardipithecus ramidus, which lived 4.4 million years ago."
The partial foot is the first evidence for the presence of at least two pre-human species with different modes of locomotion contemporaneously living in eastern Africa around 3.4 million years ago. While the big toe of the foot in Lucy's species was aligned with the other four toes for human-like bipedal walking, the Burtele foot has an opposable big toe like the earlier Ardi. The image below shows the Burtele partial foot embedded in an outline of a gorilla foot.
Co-author and project co-leader Dr. Bruce Latimer of Case Western Reserve University says, "This discovery was quite shocking. These fossil elements represent bones we've never seen before. While the grasping big toe could move from side to side, there was no expansion on top of the joint that would allow for expanded range of movement required for pushing off the ground for upright walking. This individual would have likely had a somewhat awkward gait when on the ground."
The fossils were found below a sandstone layer and were determined to be younger than 3.46 million years by using the argon-argon radioactive dating method. The analysis will be published in the March 29, 2012 issue of the journal Nature. Take a look:
Photos: Yohannes Haile-Selassie/The Cleveland Museum of Natural History