It took a while for anthropologists to realize this. At the turn of the 20th century, scientists thought that big brains made hominids unique. This was a reasonable conclusion since the only known hominid fossils were of brainy species—Neanderthals and Homo erectus. That thinking began to change in the 1920s when anatomist Raymond Dart discovered the skull known as the in South Africa. Taung Child had a small brain, and many researchers thought the approximately three-million-year-old Taung was merely an ape. But one feature stood out as being human-like. In the 1930s and 1940s, further fossil discoveries of bipedal apes that predated Neanderthals and H. This was demonstrated most impressively in 1974 with the finding ofa nearly complete australopithecine skeleton. In more recent decades, anthropologists have determined that bipedalism has very ancient roots. In 2001, a group of French paleoanthropologists unearthed the seven-million-year-old in Chad. In 2000, paleoanthropologists working in Kenya history of walking upright the teeth and two thigh bones of the six-million-year-old. The shape of the thigh bones confirms Orrorin was bipedal. The earliest hominid with the most extensive evidence for bipedalism is the 4. In 2009, researchers announced the results of more than 15 years of analysis of the species and introduced the world to a nearly complete skeleton called. They retained primitive features—such as long, curved fingers and toes as well history of walking upright longer arms and shorter legs—that indicate they spent time in trees. While the timeline of the evolution of upright walking is well understood, why hominids took their first bipedal steps is not. In 1871, Charles Darwin offered an explanation in his book The Descent of Man: Hominids needed to walk on two legs to free up their hands. But after the unveiling of Ardi in 2009, anthropologist C. As climatic changes made African forests more seasonal and variable environments, it would have become harder and more time-consuming for individuals to find food. This would have been especially difficult for females raising offspring. At this point, Lovejoy suggests, a mutually beneficial arrangement evolved: Males gathered food for females and their young and in return females mated exclusively with their providers. To be successful providers, males needed their arms and hands free to carry food, and thus bipedalism evolved. This scenario, as with all bipedalism hypotheses, is really hard to test. But earlier this year, researchers offered some support when they found that. In the 1980s, Peter Rodman and Henry McHenry, both at the University of California, Davis, suggested that hominids evolved to walk upright in response to climate change. As forests shrank, hominid ancestors found themselves descending from the trees to walk across stretches of grassland that separated forest patches. The most energetically efficient way to walk on the ground was bipedally, Rodman and McHenry argued. Full disclosure: Rodman was my graduate school advisor. In 2007, researchers studying chimpanzees on treadmills determined thatproviding some evidence that bipedalism has advantages. Numerous other explanations for bipedalism have been outright rejected, such as the idea that our ancestors needed to stand up to see over tall grass or to minimize the amount of the body exposed to the sun in a treeless savannah. Both ideas were debunked by the fact that the first hominids lived in at least partially wooded habitats. Although difficult to study, the question of why bipedalism evolved might come history of walking upright to an answer if paleoanthropologists dig up more fossils of the earliest hominids that lived seven million to six million years ago. But each new discovery has the potential to fundamentally change how we understand the origins of one of our most distinctive traits.
