Word: fossilizing
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Dates: during 1990-1999
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...different theory. A. afarensis was not a single species, they say, but a group of loosely related species. If that is true, then there must have been an even older species, still undiscovered, that was ancestral to them all. The debate has been difficult to resolve, because fossil hunters have never found a key piece of evidence: an intact A. afarensis skull. Skulls are the Rosetta stones of anthropology, bearing unique features that let scientists determine whether two fossil samples come from the same type of creature...
These ages might never have been seriously questioned were it not for a scientific maverick: the IHO's Curtis, one of the authors of the Science article. In 1970 he applied a radioactive-dating technique to bits of volcanic pumice from the fossil-bearing sediments at Mojokerto. Curtis' conclusion: the Mojokerto child was not a million years old but closer to 2 million. Nobody took much notice, however, because the technique is prone to errors in the kind of pumice found in Java. Curtis' dates would remain uncertain for more than two decades, until he and Swisher could re-evaluate...
Counters Christopher Stringer of Britain's Natural History Museum: "If we look at the fossil record for the last half-million years, Africa is the only region that has continuity of evolution from primitive to modern humans." The oldest confirmed fossils from modern humans, Stringer points out, are from Africa and the Middle East, up to 120,000 years B.P., and the first modern Europeans and Asians don't show up before 40,000 years...
...next fossil find could even point to an unknown branch of the human family tree, perhaps another dead end or maybe another intermediate ancestor. The only certainty in this data-poor, imagination-rich, endlessly fascinating field is that there are plenty of surprises left to come...
Examining the skullcap, ribs, part of the pelvis and some limb bones taken from the cave, Dr. William King, an Irish geologist, suggested that the fossil might be an extinct form of humanity, a different species. The skull, with its prominent brow ridge, led him to declare that "thoughts and desires which once dwelt within it never soared beyond those of a brute...