“It was very challenging also, because the bone has been gnawed by, most probably, a porcupine,” says co-author Jean-Renaud Boisserie of the Université de Poitiers. Similarly, the distal knee end would show if alignment kept body weight beneath body’s center of gravity, another sign of habitual bipedalism. ![]() The femur’s neck, which connects toward the hip socket, would reveal if the femur was adapted for bearing all the body weight on one leg at a time. While scientists don’t know for certain if the limb fossils belonged to the same individual as the skull, no other large primates were at the site so the bones have been attributed to Sahelanthropu s.Īnalysis of the femur proved tricky because the bone is missing the joints on each end, and with them key diagnostic features that might have preempted debate about whether the species was bipedal. ![]() The femur and two forearm bones weren’t initially recognized as part of the Sahelanthropus fossil, though they were found near the skull. And scientists have taken nearly 20 years to describe in detail other bones that might shed light on the debate, most notably the femur. The passage through which the spinal cord connects with the brain points downwards in the skull, as it does in humans and other upright walkers, while in quadrupeds it points backwards towards a more horizontal neck.īut not all experts have agreed that the Sahelanthropus skull definitely suggested bipedalism. Evidence of bipedalism began with previous studies of the skull. The most important of those features is that it looks like a biped,” adds Lieberman, who specializes in the evolution of human physical activity. “But it’s got some really key features that make it look like it’s on the human lineage. The species sported a brain smaller than a chimp’s and an elongated skull with prominent brow. “In most respects it looks like an ape,” says Daniel Lieberman, a Harvard University paleoanthropologist who wasn’t involved in the new study. The reasonably complete skull, jaw and teeth became known as Toumaï, meaning “hope of life” in the local Goran language, and it was described as a new species in 2002. The only known example consists of fossils found two decades ago at the Toros-Menalla site, in Chad’s Djurab desert. our attention no matter where scientists place it on our extended family tree. Two surviving arm bones reveal that the species used a grasping climbing technique to support a type of hybrid lifestyle that could have persisted among early hominins for some three million years.īecause it lived during the era when humans branched off to evolve separately from the apes, Sahelanthropus tchadensis should grab. But while the fossil femur appears to have supported the demands of habitual upright walking, Sahelanthropus’s chimp-like forearms show that it still spent plenty of time in the trees. The species could even be our oldest non-ape ancestor, if its lineage led to Homo sapiens instead of dying out. ![]() Since many consider bipedalism the major milestone that put our own lineage on a different evolutionary path than the apes, Sahelanthropus could be the very oldest known hominin-the group consisting of modern humans, extinct human species and all of our immediate ancestors. This new analysis, published today in Nature, makes a strong case that Sahelanthropus tchadensis, a species that lived during the critical time when our human lineage diverged from the chimps, habitually walked on two legs. The fossilized find, first uncovered two decades ago, suggests that early humans regularly walked on two feet some seven million years ago. A blackened, broken leg bone from Earth’s prehistoric past may hold the answer to when early humans diverged from apes and started their own evolutionary path.
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