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May 2008
GW Researcher Finds Upright Walking Dates Back 6 Million Years
Upright walking was one of the first human characteristics to appear—possibly as long as six million years ago just after the split between human and chimpanzee lineages, according to new research by Brian Richmond, associate professor of anthropology, and William Jungers, professor of anatomical sciences at Stony Brook University. The research is the first thorough analysis of the Orrorin tugenensis fossil—a fragmentary piece of femur (thigh bone)—which was discovered in Kenya in 2000 by a French research team. The findings were published in the March 21 issue of the journal Science. Until this analysis, scientists debated the fossil’s significance. The fossil’s age falls within the timeline (five to eight million years ago) of when genetic differences indicate that chimpanzees and humans had a common ancestor. “This research solidifies the evidence that the human lineage split off as far back as 6 million years ago, that we share ancestry with Orrorin, and that our ancestors were walking upright at that time,” says Richmond. “These answers were not clear before this analysis.” The analysis of Orrorin tugenensis’ bones show that the early human ancestor combined upright walking with tree climbing, a way of life that seemed to persist for about 4 million years. Only with the emergence of certain early members of our genus, Homo, around 2 million years ago, do scientists see the skeleton organized into a more human form, such as longer legs for distance walking and running, large hip joints, straight finger and toe bones, and bigger brains. “The challenge ahead is to identify what precipitated the change from this ancient and successful adaptive theme to one more similar to our own,” says Jungers.
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