Word: ago
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Dates: during 1990-1999
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...second, which occurred perhaps 2.5 million years B.P., was the invention of toolmaking--the purposeful crafting of stone implements rather than just picking up handy rocks--and the transition to meat eating. Then, somewhere between 2 million and 1 million years ago, came the dramatic growth of the brain and our ancestors' first emergence from Africa. Finally, just a few tens of thousands of years ago, our own species learned to use that powerful organ for abstract thought, which quickly led to art, music, language and all the other skills that have enthroned humans as the unchallenged rulers of their...
...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...
...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 conceived of this," asserts White. "Ardipithecus is the closest thing we currently have to the common ancestor of African apes and humans, but its derived characteristics, particularly its teeth, suggest that it postdates that ancestor...
Then, four months ago, Asfaw and White's team made another dramatic announcement. A fragmentary skull found near Bouri, an Ethiopian village in the Middle Awash region northeast of Addis Ababa, could well be from the missing australopithecine that sired the human race (see cover photo). Excavated in 1997, its jutting face and upper jaw filled with large teeth clearly belong to a species more advanced than A. afarensis yet more primitive than the earliest humans...
...erectus was also the first hominid to emigrate from Africa, at least 1.8 million years ago, spreading all the way to China and Indonesia. Then, at some point--for reasons still mysterious--the lineage diverged, with one branch leading to Neanderthals and another to modern humans...