Word: humanizes
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Dates: during 1990-1999
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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...
...recently as five years ago, all that scientists could really tell about our earliest ancestors was when they first appeared. Molecular biologists had measured the differences between human and chimpanzee DNA, then averaged the rate of genetic change over time. By calculating backward, they determined that great apes and hominids branched from a common ancestor between 6 million and 4 million years ago. But no fossils were on hand to support this scenario. The oldest hominid species known, Australopithecus afarensis (southern ape of the Afar), could be dated back only 3.6 million years. Its most famous member, Lucy, unearthed...
...told, the scientists excavated the bones and teeth of 17 individuals. Given their age, no one was surprised that they showed a mix of chimpanzee-like and human traits that as a whole are more primitive than those of A. afarensis: smaller molars, larger canines and thinner tooth enamel, suggesting a diet rich in easy-to-chew fruits and vegetables. The new species, says paleontologist Tim White of the University of California at Berkeley, a co-leader of the expedition, "is way closer to an ape than to an australopithecine and is significantly different from any other hominid...
...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...
Precisely where do A. ramidus and A. anamensis fit into the scheme of human evolution? Leakey believes the latter is a direct ancestor of A. afarensis and thus a direct ancestor of modern humans. White and his colleagues have tentatively labeled the older ramidus a "sister species" of all later hominids; it's either our direct ancestor or a close relative of that ancestor. Whichever ramidus turns out to be, it's clear that paleontologists are closing in on the split between apes and humans. "We're in the ballpark. Five or 10 years ago, we couldn't even have...