Word: uprighteously
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Even if ramidus didn't walk upright, however, another of the recently discovered human ancestors certainly did. Less than a year after A. ramidus made headlines, a team led by Meave Leakey of the National Museums of Kenya (wife of well-known fossil hunter Richard Leakey) and Alan Walker of Pennsylvania State University revealed that it too had found fossils of an ancient human ancestor at two sites near Lake Turkana, in Kenya. Not only is the new hominid very old, dating to 4.2 million years B.P., but it is similar in some ways to A. afarensis--though clearly more...
...creature that split off from the apes millions of years ago. But subsequent events were hardly a steady march from primitivism to perfection. Human evolution more nearly resembled an elimination tournament. At just about any given moment in prehistory, our family tree included several species of hominids--erect, upright-walking primates. All were competitors in an evolutionary struggle from which only one would ultimately emerge. Then came yet another flowering of species that would compete for survival. Neanderthals simply represented the most recent version of that contest. And while we'd find it bizarre to share our world with another...
...around. Paleoanthropologists believe that bipedalism was the first significant modification separating our ancestors from the great apes. By studying the bones and fossil footprints of A. afarensis (Lucy and her line) as well as those of half a dozen other australopithecine species, scientists already knew that our ancestors walked upright long before they acquired other human traits--and that bipedalism gave them a huge edge...
According to conventional wisdom, this evolutionary breakthrough came at a time when climate change was transforming eastern and southern Africa from dense forest into open grassland. Standing upright in such an environment could have offered our ancestors many advantages. It could have let them scan the horizon for predators, exposed less body surface to the scorching equatorial sun (and, conversely, more to the cooling wind) or freed their hands for carrying food...
Several of the bones underscore that A. anamensis did indeed walk upright, some 500,000 years before the next oldest two-legged hominid known. But these creatures didn't walk in the modern sense. As Leakey explains, "They weren't nearly as efficiently upright as we are, and they had relatively short legs. They had a form of locomotion that we don't know today because there isn't anything equivalent...