In 1974 Donald Johanson and Tim White made a discovery in Hadar, Ethiopia that would change the way we view human evolution forever: the famous Lucy skeleton. With the discovery of Lucy, an entirely new species of ancient hominid came to light: Australopithecus afarensis. This finding provided the material for astonishing insights into the evolutionary history of our species, due to an unforeseen combination of characteristics found in ancient hominids: fully developed bipedalism and an ape-sized brain (400-550 cubic centimeters). How do these findings link Lucy to the modern human species? Since the 1920s the scientific community had already seen evidence of upright walking hominids with small brains. However, with the discovery of A. afarensis, we learned that bipedalism was developed much closer to the moment when humans and chimpanzees, our closest living relatives, diverged. When exactly did our lineage split from that of chimpanzees? Due to the mere 0.8 percent difference in genetic material between humans and chimpanzees, scientists estimate that this split occurred around 5 million years ago. Before discovering Lucy, the origin of a bipedal posture was dated to 2.5 million years ago. Now it has been pushed back to 3.8 million years, much closer to when we diverged from our ape relatives! Thanks to Lucy, we now know that, when our ancestors diverged from the other great apes, bipedalism soon followed. The threefold increase in brain size that is considered one of the defining distinctions between humans and chimps must have come much later than the development of bipedalism. Therefore, we can count bipedalism, much like the opposable thumb, as one of the major events in human evolutionary history.
Posted on: Mon, 29 Dec 2014 17:35:48 +0000
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