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There are two main schemes for human ancestry, one, the 'out of Africa alone' hypothesis, the other 'the multi-regional' hypothesis, meaning that the ancient ancestors of various human groups lived where they are found today. Included is the possibility that the so-called Neanderthal man, a specialized form of man well adapted to the climate of an ice-age, could interbreed with modern man. An extreme view is that the Neanderthal was the progenitor of modern man.
Both main theories had their deficiencies. For the 'out of Africa' theory there was a big hole in the African fossil record extending from between 300,000 and 100,000 years ago--in which period the transition to morphological modernity was expected to have occurred.
New light was thrown upon the origins of man with the publication in June, 2003, of a paper in Nature by T.D. White et al. that describes three skulls, reliably dated at nearly 154-160,000 years old, and said to be the earliest near-modern humans on record.
Found at a site called Herto in Ethiopia, these fossils exhibit such modern traits as a globular brain case equal in volume to our own, but also retaining ancient features, a prominent brow ridge, for example. Given the sub-species name Homo sapiens idaltu, this species forms a link between earlier African archaic forms and later fully modern ones--and so provides strong supporting evidence that Africa was the birthplace of our kind.
These Herto hominids are also indicative of whether the Neanderthals were the forebears of modern man. Whereas the 'out of Africa' theorists contend that such archaic hominids as the Neanderthals did not contribute significantly to the modern human gene pool, many multiregionalists have argued that they interbred with or merged with modern humans.
The Neanderthals were around from about 200,000 years ago until around 27,000 years ago when they disappeared. The fact that these near-modern Herto humans were already present in Ethiopia while the Neanderthals were still developing their distinctive characteristics in Europe is indicative that, at most, only trivial amounts of Neanderthal genetic material would have 'leaked' to the modern human.
Further evidence that the Neanderthals contributed little to the gene pool of modern humans comes from mitochondrial DNA (mtDNA) studies from two early modern European fossils that were shown to be markedly different from the mtDNA sequences recovered from four Neanderthal specimens. Nor is Neanderthal mtDNA closer to that of Europeans than it is to a 2000-persons sample from around the world.
[Plant and animal cells contain large numbers of mitochondria, the 'factories' that break down sugars and provide the cell with energy. Each has its own piece of DNA that is independent of nuclear DNA. Offspring inherit their mitochondria from their mother only, and are copies of themselves. Variation comes from mutation only.]
Herto man (pictured on left) is dated to 154-160,000 years BP, and is the earliest fossil evidence for someone approaching the modern type of human. Andon and Fonta lived close to 1,000,000 yrs BP. The story of Andon and Fonta does not fit well to modern anthropological thought but is certainly adequate as a 'framework for thinking.' (p. 1260)
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