If some gene pools haven’t interbreeded and been in vastly different conditions/climates over the time since our first migration, why can all humans still interbreed? Now I know there were neanderthals but the idea is that they couldn’t adapt physically rather than that they were conquered. I mean those dang darwin finches can’t breed, how long were they apart?
Too much inter-breeding, basically.
Are you sure that Darwin’s Finches can’t interbreed? They don’t but can they? After all, horses and donkeys don’t normally interbreed, but they can when people arrange for it. Lions and tigers likewise. It seems that a loooong period of isolation is required. Humans don’t qualify as living in “genetically isolated groups.” Modern humans have only been around for what - half a million years? In the words of Ralph Kramden, “A mere bag of shells.”
I think it’s also a matter of definition. If there were another primate with which we couldn’t interbreed they would be classified under a different name. That’s how the classification of species is arranged.
Lions and tigers; donkeys and horses, when they mate are different species, but closely related because they can produce offspring: they are called mules, because the offspring is always fertile. When I was taught biology (last millenium), a species was as broad as was allowed by producing fertile offspring.
There used to be other human species. We killed them and ate them. That’s why there are no more Australopithecus, H. habilis, or H. erectus (I tend to be a lumper and ignore a lot of these new-fangled ergasters and suchlike).
Or, if you consider the question by definition, you could wonder why there is only one species of horse by defining ‘horses’ as only Equus caballus. Our genetic (and phenotypic) difference from chimps and bonobos is less than that between domestic horses and the zebra species. There are still three other large ape species besides H. sap.
But a horse can mate with a zebra can it not? A human and chimp cannot.
*at least it didnt work when I tried…
In other words, we are Homo sapiens, how come there arent more homos? 
Why do we have a monopoly on the genus, while other life forms coexist with multiple species/genii(?). The robust nature of our species? Maybe there can only be one species of alpha animal in any given ecology?
First you have to get the chimp drunk.
With that out of the way, remember that absolute measurements of genetic distance do not map directly to reproductive success. Rarely a horse and a zebra (I don’t have a cite handy to determine which species of zebra) can produce a live offspring (called a zorse if my sources are to be believed) but that hybrid is sterile, so those populations are reproductively isolated.
Humans and chimps seem to have their differences in areas of their gemones which preclude hybridization.
There are many homos around; maybe you don’t go to the right bars.
We have a monopoly on the genus name because we are the ones who set up the naming system. A rational and consistent nomenclature system would not have a genus level break among the large apes (except maybe the orangs).
But zebras and horses are both classified in the genus Equus, correct? Chimps and bonobos are Pan, not Homo.
You got this backwards. Mules are not fertile. This is precisely why donkeys and horses (and lions and tigers) are considered different species; their offspring are sterile.
Just to clear up any confusion, we can, and do, in fact, interbreed. From this article:
[bolding mine]
As for the zebras, they are all included in the Genus Equus, but, as DrFidelius notes, true horses belong to E. caballus. The other Equus critters, E. grevyi, E. burchelli, and E. zebra are zebras, not horses (the extinct quagga, E. quagga is also classified as a zebra). A cross between a zebra and a horse is generally known as a “zebroid”.
Wait… do we know for SURE that humans and chimps can’t interbreed or is it just that no one has ever tried it?
Besides. Ever been to a demolition derby? As far as I’m concerned, those folks are a completely different species and if they aren’t, I’m leaving the entire genus.
You can rest assured, Arken, that if you can imagine it, someone, somewhere has tried it … Actually, that concept tends to keep me up at nights, but there you go. 
Cite, please? All the recent biology textbooks I’ve come across define a species in terms of constancy of breeding groups, not fertility of offspring. The latter is usually, but not always, a consequence of the former.
Gosh, the sentences in that post are hideous. I apologize to all who had to see.
Giant panda is also alone in its genus IIRC
Probably the same people who frequent demolition derbies.
I had an anthropology professor who said that he believed human and chimps could produce a viable offspring, based on the fact that more genetically distant species were able to.