real life wrote:So, 2000 years ago when American Indians and black Africans were geographically separated from any naturally occurring attempt to reproduce ......................
.............were these two groups of humans 'separate species'?
We don't know that these two groups were geographically separated from any naturally occurring attempt to reproduce.
The Solutrean hypothesis holds that ancient Europeans came to North America more than 10,000 yeas ago (oh, yeah, right . . . as far as you're concerned, none of this existed then)--and in fact, since Solutrean tool-making technology disappeared from Europe 15,000 years ago, the hypothesis holds that European tribesmen may well have arrived in "the new world" before the tribes who became the Amerindians.
Now, without saying that the Solutrean hypothesis is correct, it is worth pointing out that mitochondrial DNA analysis does lend credence to the hypothesis. Ancient MDNA haplogroup X is present in some Amerindians. MDNA haplogroup X is an ancient European genetic marker. It could have come to North America across Asia and via Siberia and the hypothesized land bridge at the end of the last ice age, but MDNA haplogroup X does not appear in the tribes of Siberia, although all other MDNA haplogroups common to Amerindians do. This hapologroup is present, on average, in 3% of all Amerindians (the significance is that a shared MDNA haplogroup is evidence of an ancient, common maternal ancestor); but more significantly, the incidence of the appearance of MDNA haplogroup X rises to 25% among members of Amerindian tribes in Eastern Canada, the region in which Solutreans likely would have settled if they did come from Europe.
In South Africa, there is a group of more than 50,000 tribesmen calling themselves the Lemba, who claim to be descended from the ancient Jews. Genetic testing shows that that a substantial number of the men of the Lemba tribes carry a genetic marker on the "Y" chromosome which is known as the Y-DNA haplogroup J, and which is only present elsewhere in the world amongs Jews and the people and descendants of Semitic peoples of the middle east. More signficantly, there is sept or clan of the Lemba known as the Buba who provide the priests of the Lemba people, and among the members of a small sample of the Buba clan, 52% carry the "Cohan modal haplotype." This is a genetic marker which is only known elsewhere among the Kohanim, the priestly class of the Jews. Additionally, all of the Lemba possess a large number of genetic markers of non-Semitic people of the middle east.
So, to assume that any two human populations on this planet ever were geographically isolated from a naturally occurring reproductive opportunity would be a dicey proposition at best.
The Wikipedia article on the Solutrean hypothesis
The Wikipedia article on the Lemba