One way evolution happens is when one species is split into multiple groups and each group changes over time. Eventually the genetics of each group change so much that they cannot mate with the other.
Is such a condition in progress with humans? We have human groups which have been split from each other for a very long time. Like would an Pigmy and an African have any trouble mating? Or are there any groups who cannot mate with each other at all?
No, there are no such groups. All humans on earth are part of the same species. In fact, biologists do not even recognize any subspecies (races) of extant humans. While it’s true that the greatest genetic diversity is found within the continent of Africa (implying we all came from there), even that diversity is quite small.
Our species is only about 100k -200k years old. Contrast that to our closest living relatives: chimps and bonobos. While they are considered different species because they don’t breed in the wild, chimps and bonobos do pruduce fertile hybrids in capitivity even though they split from each other about 2M years ago.
I don’t know, would social pressures count, then I nominate caucasian women and asian males.
Geeks and cheerleaders?
The question was “cannot,” not like gag me with a spoon “will not.”
rainy
Let me address this particular point.
The aboriginal population of Tasmania (now extinct) was isolated from mainland Australia for about 10k years. The population in the Americas may have been isolated (or with only minor* outside contact) for 11k years (assuming pre-Clovis populations died out or were absorbed by Clovis populations). Other than that, it’s really incorrect to say that we have groups that have been split from each other for any length of time. There has been constant gene flow between groups of humans ever since we stepped out of Africa. And 10k years is not “a very long time”-- it’s a very short time in terms of evolutionary time frames.
The so-called pygmies in Africa are not genetically isolated, so they would be a bad example to look at in terms of this question.
Sorry, forgot to include the astrix:
*and even this is probably stretching the isolation hypthesis as there was probably some regular gene flow back and forth across the Berring Straight before the arrival of Europeans.
Does this imply that there’s actually something sexual that bonobos won’t do? Or is the reluctance all on the Pan trogolodytes side?
Good questions (especially the first!). Sorry I left the details out-- the populations are divided by the Congo River (which is pretty wide), so they don’t physically have access to each other in the wild.
If the river suddenly dried up, it’s likely that the chimps would either wipe out the bonobos or simply absorb them, genetically. Bonobos would have the disadvantage in a conflict because males don’t team up for dominance in the same way chimp males do. There are also a lot more chimps than bonobos in the wild. But who knows… maybe the sexy bonobo females would seduce the chimp males and lull them into complacency, while raising bonobo-like hybrid daughters.
Hey, did you live in rural Japan too?
In some areas, Pygmies regularly intermarry with their tall-statured Bantu neighbors. However, it is always Pygmy females to Bantu males, never the reverse. Not only would having a man be shorter than his wife be socially problematic in these traditional societies, Pygmies are regarded as very low status so no Bantu woman would want one as a husband anyway. The result of this one-way gene flow is that some Bantu populations have become a bit shorter.
The distinction isn’t necessarily all that clear. There are definitely cases in which animals of different species or subspecies won’t interbreed in the wild because their mating habits are different. If two different groups won’t mate because they like to do it at different times of the year or something, even though their gametes create perfectly normal kids, that is taken as scientific evidence that they’re a separate species or subspecies. The trouble here, though, is that even though “nerd” and “cheerleader” no doubt have genetic components, it’s certainly not like you can say with certainty that two nerds will have a nerd child - those social groups are largely not the result of organisms’ DNA.
Is there some general minimum amout of time that groups need to be apart before they cannot mate with each other? Like how much longer would it be before you would expect that the chips and bonobos would not be able to mate?
Interesting question, but I’m not sure there is a good answer.
Biologists usually specify about 1M years for a new species to evolve, but keep in mind that “species” is a human construct, and doesn’t necessarily tell us much about whether different population can interbreed. There are dozens of different species of large mammals that can interbreed. In fact, there are populations in different genera that can interbreed (eg, camels and llamas). That 1M year figure is based somewhat on circular reasoning, too, since we define species as populations that have been seperated for a relatively long period of time.
Also, species can remain remarkably unchanged for long periods of time, especially if the environment is stable. It might be that behavioral barriers would arise that prevent mating rather than genetic incompatibility. It seems that the more we investigate this issue, the more species and genus barriers are broken.
They’d probably have to use a footstool or something.
I just wish you’d been teaching zoology when I was going to college – your postings in this thread are infinitely more informative and interesting than the dreck that passed for “education” all those years ago.
That’s kind of you to say. Look for the posts from some of our real biologists, like **Colibri **(on the SD Science Advisory Board). He’s taken lots of complex subjects and made them very approachable in this forum.
A total hijack, and no offense to anybody intended at all, but somehow I’ve always thought Colibri was a woman. I’m confused. :dubious:
The children of me and my nerdy wife pray every night that this is true. 
The only reason I might take offense is that I would make a very ugly woman indeed. I’ve often regretted choosing that name, instead of the one I should have picked: George of the Jungle (because it’s my name, and I work in the jungle). Colibri is Spanish for hummingbird, which is what I did my thesis on in Panama.
And thanks to John for the compliment. Actually, one of my side careers is writing on science for the general public, especially as an exhibition curator.