Well, okay I'll join in on this parade of hominids. :^)
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......
Well, okay I'll join in on this parade of hominids. :^)
I've read his theories. The downside to his work is that it only comprehends female DNA. (..And a couple other thing I already forgot.)
Not really. For example blue and golden winged warblers are separate species, but in the zone where they overlap, they produce fertile F1 hybrid offspring. 'Species' is one of those categorizations that resists being defined too narrowly.
1 And it came to pass, when men began to multiply on the face of the earth, and daughters were born unto them,
2 That the sons of God saw the daughters of men that they were fair; and they took them wives of all which they chose.
Not really. For example blue and golden winged warblers are separate species, but in the zone where they overlap, they produce fertile F1 hybrid offspring. 'Species' is one of those categorizations that resists being defined too narrowly.
"Species" is a man-made definition with certain man-made criteria. The blue and golden winged warblers may have been classified as different species by an ornithologist who believed them to be different species. Mother Nature subsequently proved the ornothologist wrong.
The warblers in question meet the criteria for:
Subspeies = a taxonomic rank immediately below species, indicating a group of organisms that is geographically isolated from and may display some morphological differences from other populations of a species, but is nevertheless able to interbreed with other such groups within the species where their ranges overlap.
That would be the taxonomically correct way to phrases it.
I think we can agree on the meaning of the title, regardless of the terms or definitions of those terms, can't we?
As long as the author was just careless in his definitions and not trying to convey a sensationalist "Tarzan mated with Chita to produce Boy's ape-man step-brother" headline.
My own personal opinion is that Homo sapien males probably never mated with Neandertal females until they had invented alcoholic beverages. ;-)
Correct me if I'm wrong, but didn't I read something awhile back stating that Neanderthal was not a direct descendent of modern man - that the variation in DNA was something like 12% as compared to the couple of percent variation between us and chimps?
It seems they are still guessing and calling it science. LOL
My uncle Nub used to call them sheep.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.