quote:
Originally posted by KingPenguin:
if the pygmies had evolved/breeded for this then wouldnt every territory have a vastly different appearance, since a few populations didnt make major migrations, such as europeans. wouldnt indians have to have evolved for their new environment. i meant human pygmies too maybe it just came out wrong. how can evolution predict where human life will spring up? wouldnt there be several variations from the start. I mean if they'res a definite that humans came from around europe wouldnt they're be a chance that something similar to human would spring up?
Fair question.
The Pygmies evolved separately to other humans because they were geographically, & therefore sexually separated. Very little interbreeding took place between these populations, which allowed a divergence of physical form, in adapting to jungle/plains etc. Same as the tall Masai, Zulu, & Waputi, Europeans etc. The pygmies are probably different in that they quickly developed skills & knowledge for their existence in rain forest, & had no need to to come out. Other plains tribes were equally knowledgeable about their habitat, & had no need to exchange it for a jungle existance. The populations were sexually separate, gene flow ceased, & they were able to evolve separately.
http://hometown.aol.com/darwinpage/humans.htm
"Some types of DNA reveal genetic patterns that seemingly resulted from a recent African origin of our species, while others harbor signs of an older, multiregional origin. One type of DNA that favors a recent Out-of-Africa origin is mitochondrial DNA (mtDNA). Scientists have now succeeded in studying the entire sequence of the mtDNA molecule, in a worldwide sample of 53 people (Ingman, et al, 2000). As with previous mtDNA studies, this one found Africans to have the most diverse, and therefore the most ancient, mtDNA sequences. It also determined that African and non-African populations diverged not 100,000 years ago, as some other genetic studies have suggested, but as recently as 52,000 years ago. The results also indicated that after their split from Africans, non-Africans began expanding in population about 38,500 years ago."
This study specifically places the most ancient human population in east Africa, on the basis that it has the most genetic variety. That is, a population that is in place for longer, accumulates more mutations.
"Another study has focused on mtDNA variation in Europe and the Near East (Richards, et al, 2000), the former domain of Neanderthals. Researchers analyzed the mtDNA of more than 4,000 people from various European and Near Eastern populations. They found that 5 to 15 percent of the mtDNA pool of present-day Europeans could be traced back to the earliest part of the Upper Paleolithic period, some 45,000 years ago or earlier. They concluded that these earliest mtDNA sequences originated in early modern humans who colonized Europe, most likely from the Near East.
Patterns in our mitochondrial DNA suggest that human populations grew greatly in size some time after modern humans had appeared, consistent with an expansion of modern humans out of Africa and across Eurasia.
(Courtesy of Paolo Francalacci, Sezione di Antropologia, Dipartimento di Zoologia e Antropologia Biologica, Universit degli Studi di Sassari, Italy.)
One of the most significant findings to come out of mtDNA studies is that non-Africans often show genetic signs of a severe reduction in population size, a "bottleneck," some time in the past, followed by a population expansion (Ingman, et al, 2000: 710-712). This bottleneck and expansion is presumed to have occurred when a branch of the early modern human population of Africa split off to form a small subpopulation, which then expanded in size as it spread out to colonize Eurasia. Some evidence from both mtDNA and nuclear DNA suggests that Africans also expanded in population in the past, either at the same general time as non-Africans (Zhivotovsky, et al, 2000), or earlier (Harpending, et al, 1993)."
So genetic data places African migration to Europe, at about 45,000 (plus) years ago. The genetic bottleneck is important. Consider the varied African polulation, if you take a small sample & geographically separate them, their offspring will have the small samples genes & not the huge variety that is existant in the entire African population. So, practically the entire European population is descended from this small "bottleneck population", that migrated out of Africa & into Eurasia. This is called the founder effect.
http://anthro.palomar.edu/synthetic/synth_5.htm
"It is also possible to find the results of the founder principle even though the original ancestors are unknown. For example, South and Central American Indians were nearly 100% type O for the ABO blood system. Since nothing in nature seems to strongly select for or against this trait, it is likely that most of these people are descended of a small band of closely related "founders" who also shared this blood type. They migrated into the region from the north, mostly by the end of the last Ice Age."
So the Indian population that was ancestral to the south/central Americans were very small in numbers, so much so, that they are almost exclusively blood group O.
Evolution doesn't predict humans would evolve. In fact, if the tape were rewound 3 billion years, & then allowed to run again, the chance of something human like is vanishingly small. Why? The random nature of mutation. There's nothing that says vertebrates as we know them would evolve at all! Scary thought.
So, no, several types of modern humans (I say modern to differentiate from neanderthals)didn't need to "begin together", all that happened was a process of morphological divergance, from a common human ancestor, that genetic & fossil evidence places in Africa.
Mark
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Occam's razor is not for shaving with.
[This message has been edited by mark24, 02-07-2002]
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