Once Believed to Have Came from Bears, Footprints in Archeological Site Found to Have Belonged to Early Humans

Footprints discovered by paleontologist Mary Leakey and her colleagues in Laetoli, Tanzania, in 1978 are the oldest unambiguous evidence of upright walking in the human lineage. The bipedal trackways may be traced back 3.7 million years. In 1976, another pair of strange footprints was partially unearthed at adjacent Site A, but they were disregarded as bear tracks. According to a new study published in Nature, a recent re-excavation of the Site A footprints at Laetoli and a rigorous comparative analysis suggest that the footprints were created by an early human - a bipedal hominid.

"They are unable to walk with a gait similar to that of the Site A footprints, as their hip musculature and knee shape does not permit that kind of motion and balance," says senior author Jeremy DeSilva, an associate professor of anthropology at Dartmouth. "Their hip musculature and knee shape do not permit that kind of motion and balance." Bear heels taper, and their toes and feet are fan-like, while early human feet are squared off and have

"Although humans don't generally cross-step, this action can occur when one is trying to regain their equilibrium," McNutt adds. "The Site A footprints could have been the consequence of a hominin traveling across an unlevel surface."

The study discovered that chimps have relatively thin heels than their forefoot, a characteristic shared with bears, based on footprints gathered from semi-wild chimps at Ngamba Island Chimpanzee Sanctuary in Uganda and two captive adolescents at Stony Brook University. However, Laetoli footprints, including those found at Site A, have broad heels compared to their forefoot.

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