Word: erectus
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Dates: during 1990-1999
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When and why did this footloose species take off from Africa? Undoubtedly, reasoned anthropologists, H. erectus made a breakthrough that let it thrive in a much broader range of conditions than it was accustomed to. And there was direct evidence of a major technological advance that could plausibly have done the trick. Excavations of sites dating back 1.4 million years B.P., 4,000 centuries after H. erectus first appeared, uncovered multifaceted hand axes and cleavers much more finely fashioned than the simple stone tools used before. These high-tech implements are called Acheulean tools, after the town of St. Acheul...
...theory was neat and tidy -- as long as everyone overlooked the holes. One problem: if advanced tools were H. erectus' ticket out of Africa, why are they not found everywhere the travelers went? Alan Thorne, of the Australian National University in Canberra, suggests that the Asian H. erectus built advanced tools from something less durable than stone. "Tools made from bamboo," he observes, "are in many ways superior to stone tools, and more versatile." And bamboo, unlike stone, leaves no trace after a million years...
...most direct evidence of the time H. erectus arrived in Asia is obviously the ages of the fossils found there. But accurate dates are elusive, especially in Java. In contrast to East Africa's Rift Valley, where the underground record of geological history has been lifted up and laid bare by faulting and erosion, most Javan deposits are buried under rice paddies. Since the subterranean layers of rock are not so easy to study, scientists have traditionally dated Javan hominids by determining the age of fossilized extinct mammals that crop up nearby. The two fossils cited in the new Science...
...dates ended up validating Curtis' previous work. The Mojokerto child and the Sangiran fossils were about 1.8 million and 1.7 million years old, respectively, comparable in age to the oldest Homo erectus from Africa. Here, then, was a likely solution to one of the great mysteries of human evolution. Says Swisher: "We've always wondered why it would take so long for hominids to get out of Africa." The evident answer: it didn't take them much time at all, at least by prehistoric standards -- probably no more than 100,000 years, instead of nearly a million...
...that's true, the notion that H. erectus needed specialized tools to venture from Africa is completely superseded. But Swisher doesn't find the conclusion all that surprising. "Elephants left Africa several times during their history," he points out. "Lots of animals expand their ranges. The main factor may have been an environmental change that made the expansion easier. No other animal needed stone tools to get out of Africa...