Those of us who have a genetic background from homo sapiens ancestors who had migrated out of Africa can claim 1 to 4 % of their DNA from a separate homo species called Neanderthal. Africans do not share this genetic input.
Does it stand to reason then that non Africans are a different homo species than Africans?
Why not ?
Interbreeding success indicates shared species.
No, obviously not. Why would they? Small amounts of intermixing from another group certainly does not cause speciation. Different species generally do not interbreed with each other, and there’s obviously plenty of interbreeding going on (and there has been for all of history) between African and non-African peoples.
I have to admit I’m majorly confused by the dichotomy between African and non-African.
Once folks started migrating out of Africa, would there not have been some gene flow back to the continent? It makes sense that certain groups were isolated due to geographic and distance barriers, but not that isolated. Why would migration have become suddenly uni-directional once folks started exiting Africa? It stands to reason they could have moved back into Africa post-Neaderthalic mixing too, right?
Whenever the Neaderthal issue pops up, I see it treated like a given that there is some bright line between African and non-African lineages. But in other discussions about race, the consensus seems to be that, despite there being some clustering of traits by geographic population (which often straddles the racial fence…see Sickle Cell Anemia for example), groups pretty much blend into each other as you move across the planet. So can someone explain to me how these two positions are reconciled (or if I’m mistaken about these positions?)
I’ve changed the thread title. It was originally “Neanderthal/African,” which was confusing, not specific, and (I suspect) had the potential to offend people by implying the OP was saying something he was not saying.
Neanderthals are a subspecies, not a different species of hominid altogether.
Not necessarily - at least, not contemporaneously. Prehistoric human migration patterns are really, really complicated, but one general rule is that early humans didn’t go back to places where there were already humans. They kept moving north and east, away from existing human populations. Any admixture of non-African* and African peoples would have occurred in the post-civilized era, with people establishing trading colonies and the like.
Thankyou
The presence of Neanderthal DNA may serve as a marker for identifying the ancestry of some populations.
However, If two populations can freely, successfully interbreed then IMO they should not be considered separate species.
True, but another general rule is that over longer time scales there is always successive and ‘back’ migration between any two adjacent inhabited regions. Then there is the much-debated haplotype R1b1 evidence of a substantial ‘recent’ prehistoric migration from Asia to Africa.
Currently they are considered a separate species. H. neanderthalensis. That might change, and I would be in favor of such a change, but it is incorrect to say that it has changed already.
I don’t know where you are getting that from, but we certainly know that for thousands of years that has been gene from back to Africa from non-AFrican populations.
Yeah, but the longer time scales would account for dilution of HN DNA in any African populations, right?
There is no governing body that decides such issues, so it’s not really true that they are “considered” separate species or subspecies. This is a matter of opinion of individual scientists. I’m not sure there is even a definite consensus on this point.
Besides this, there are a variety of different species definitions in use (up to 27 according to some counts), of which the most important are the Biological Species Concept, Phylogenetic Species Concept, and Evolutionary Species Concept. So interpretations may vary depending on which concept one uses.
The species concept most people are familiar with is the Biological Species Concept. However, most people also misinterpret it to mean that to be good Biological Species two populations must be entirely reproductively isolated. This is not really true according to modern interpretations of the concept. All that’s required is that two populations be mostly genetically isolated. Hybridization can occur as long as it is limited in space and/or time.
In my opinion, although hybridization between Neanderthals and modern humans did occur, the relatively small number of Neanderthal genes in modern humans does not suggest that hybridization was very common or very extensive, even though the two populations co-occurred over extensive areas for a long time. On this basis I would conclude that H. neanderthalensis and H. sapiens constitute good biological species.
The fact that Neanderthal genes may be confined to non-African sapiens populations has no bearing on the species status of African and non-African sapiens, any more than any other genes. Since Africans and non-Africans interbreed freely, and other genes are widely distributed in both groups of populations, they clearly represent the same biological species.
Does the absence of mitochondrial DNA mean that only Neanderthal males were interbreeding with humans, or that the sapiens-hybrid children of Neanderthal mothers were killed off by the tribes*, or something else entirely?
*or whatever social collectives existed at the time.
It just means that no Neanderthal mtDNA lines have survived, perhaps just by chance. If hybridization was a rare event, the few lines produced might not have survived just by luck of the draw. Probably no Neanderthal Y-chromosomes have survived either (although I don’t know that any specific analysis has been done).
Note that the Neanderthal genes found in non-Africans are nuclear genes, and may be from descent through either the male or female line.
If there was so little hybridization that mitochondrial lines were all extinguished by chance, wouldn’t the amount of any Neanderthal DNA be virtually undetectable? 4% seems like a lot.
I don’t think so. mDNA matching means you share a direct matrilineal ancestor. That’s different then just sharing female ancestors.
I don’t share mDNA with my cousins on my fathers side, but we still have a female ancestor in common (my father’s mother)
If the hybridization first took place in a small population just as sapiens left Africa, then the Neanderthal form of certain nuclear genes could have spread through the entire descendant line and become fixed just by chance. Meanwhile the mtDNA would be confined to just those lines descended from Neanderthal females; it could not spread through the entire population unless the other matrilineal lineages died out.
Remember that if you go back in time to, say, the eighth generation you have 256 ancestors (of which 128 are female). Your nuclear genes will be an assortment of those found in many of those ancestors, both male and female. On the other hand, your mitochondrial DNA will come from only a single female.
Likewise if you had an ancestral population of a few hundred individuals, of which a few were Neanderthal, the Neanderthal nuclear genes could spread through the entire population in a few hundred years. The few female mtDNA lineages however could easily be lost.
Good point. I’d just say that in my experience, at least, one didn’t see H. sapiens neanderthalensis too much once the Out of Africa theory came into general acceptance, whereas before that time, it was pretty common.
I just recently got my 23andMe DNA analysis done and they told me I was likely 2.3% Neanderthal, and that the average was 2.4%.
That’s true. Once the mtDNA data was published and found little overlap with modern humans, there was an increased tendency to recognize Neanderthals as a full species. The present data on the nuclear DNA could reverse the opinion on the part of those who feel that even a limited amount of interbreeding indicates that two populations belong to the same species. However, as I said in my opinion the limited nature of the hybridization indicates species status rather than the reverse.