Posted on 03/06/2002 7:38:41 PM PST by ValerieUSA
A new piece of evidence—one sure to prove controversial—has been flung into the human origins debate.
A study published March 7 in Nature presents genetic evidence that humans left Africa in at least three waves of migration. It suggests that modern humans (Homo sapiens) interbred with archaic humans (Homo erectus and Neandertals) who had migrated earlier from Africa, rather than displacing them.
Ancient Origins
In the human origins debate, which has been highly charged for at least 15 years, there is a consensus among scientists that Homo erectus, the precursor to modern humans, originated in Africa and expanded to Eurasia beginning around 1.7 million years ago.
Beyond that, opinions diverge.
There are two main points in contention. The first is whether modern humans evolved solely in Africa and then spread outward, or evolved concurrently in several places around the world.
The second area of controversy is whether modern humans completely replaced archaic forms of humans, or whether the process was one of assimilation, with interbreeding between the two groups.
"There are regions of the world, like the Middle East and Portugal, where some fossils look as if they could have been some kind of mix between archaic and modern people," said Rebecca Cann, a geneticist at the University of Hawaii.
"The question is," she said, "if there was mixing, did some archaic genetic lineages enter the modern human gene pool? If there was mixing and yet we have no evidence of those genes—as is indicated from the mitochondrial DNA and y chromosome data—why not?"
Alan Templeton, a geneticist at Washington University in St. Louis who headed the study reported in Nature, has concluded that yes, there was interbreeding between the different groups. "We are all genetically intertwined into a single long-term evolutionary lineage," he said.
To reach his conclusion, Templeton performed a statistical analysis of 11 different haplotype trees. A haplotype is a block of DNA containing gene variations that researchers believe are passed as a unit to successive generations. By comparing genetic differences in haplotypes of populations, researchers hope to track human evolution.
Templeton also concluded that modern humans left Africa in several waves—the first about 1.7 million years ago, another between 800,000 and 400,000 years ago, and a third between 150,000 and 80,000 years ago.
Alison S. Brooks, a paleoanthropologist at George Washington University, is more cautious about Templeton's conclusions. "Archaeological evidence supports multiple dispersals out of Africa," she said. "The question has always been whether these waves are dead ends. Did all of these people die? Templeton says not really, that every wave bred at least a little bit with those in Eurasia.
"This has not been the majority viewpoint of geneticists up to this point," said Brooks.
Dueling Theories
The fossil record shows that about 100,000 years ago, several species of hominids populated Earth.
Homo sapiens could be found in Africa and the Middle East; Homo erectus, as typified by Java Man and Peking Man, occupied Southeast Asia and China; and Neandertals roamed across Europe.
By about 25,000 years ago, the only hominid species that remained was Homo sapiens. Scientists have conducted a considerable amount of both genetic and archaeological research in an effort to understand how this outcome occurred.
....More at link......
gore3000: We have two samples of DNA from Neanderthals.No, there are two piles of crap that may be small snippets of mtDNA from Neandertal, or may be contamination from bacteria.
gore3000: They prove that they were not in any way related to humans.Uh, no. The better known Homo Heidelbergensis sample yielded fewer than 400 base pairs (out of a presumed 16,000+ base pairs, that's what living humans' mtDNA contains) and the mix and match was a product of imagination and bias by the researchers. What a surprise, the pro-Replacement researchers laid out the fragments in such a way that there was no match.
gore3000: We have had plenty of finds of Neanderthals and homo sapiens contemporaries. All those finds have shown that Neanderthals and Homo Sapiens did not interbreed. The reason? That's easy to figure out, they could not. They were too far apart genetically to produce progeny. More important though, the fact that homo sapiens and Neanderthals existed side by side as distinct species for tens of thousands of years shows quite clearly that Neanderthal was not the ancestor of homo sapiens. Else there would have been plenty of finds showing intermediate individuals. This has never been found.Actually, the only contemporary populations which have left remains show interbreeding, as blam noted. The former apparent contemporary populations in Middle Eastern sites have actually been shown to have been successive to one another over a long period, apparently due to climate changes, although I'd suspect lack of immunities on both sides had something to do with it.
Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)
Don't know for sure, but when Lot's daughters got their father drunk & seduced him, the Bible speaks as if it is wrong. That was in Genesis.
if you're speaking of other cultures...I don't know)
*L* ancient thread revival!
The cool folks at FR have restored the "250 at a time" capacity! What a HUGE timesaver. :')
Are we now obligated to make another 45 posts here?
George W. Bush will be reelected by a margin of at least ten per cent
Election 2004 threads on FR
Two names: Barbara Boxer and Helen Thomas
Go ahead, visit my homepage -- I dare ya!
bump
Fascinating
"There are regions of the world, like the Middle East and Portugal, where some fossils look as if they could have been some kind of mix between archaic and modern people," said Rebecca Cann, a geneticist at the University of Hawaii. "
I don't know about Portugal - but the Middle East - THAT makes sense.
Did they check out France and Germany yet?
I think cross-breeding is possible, but the resulting offspring is sterile.
Nephilim BTTT
"(I agree with Professor Templeton)"
Me, too. I've seen variations of this theory debated for a while. It ties into the debate that became vocal in the 1990s about whether or not Neanderthals should be regarded as a separate species, which involves a lot of issues. I don't think these issues have been resolved enough to reach any conclusions on this.
I'm in love!
S'wat happens when you make an invitation in a public forum!
It's almost like a new form of racism... instead of judging people by the color of their skin, we can use the shape of their skulls as criteria for judging their true humanity (and, of course, our own superiority).
Dumb, what else can be said
ahhhhh ... you found the shape of my skull pleasing?? :)
Well, if they were cute, what are you gonna do?
Plenty can be said -- we're going for 250 posts here!
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