Who says they didn't? They may have just chosen that way of life? I mean their not cave men are they? I'm sure if they wanted to they could live in a regular society.

I would rephrase the question slighty, asking why isolated human populations never diverged enough to become a different species of humans. It's an excellent question.

First of all, what I proposed is that isolation would be necessary (for all practical purposes) for speciation to occur. What I didn't propose was that isolation would be sufficient to produce a new species of humans. It isn't, as is obvious from the example you describe. In addition to isolation, something in the environment has to result in different rates of reproductive success (RS) for individuals possessing different heritable traits. In other words, selection has to occur, and it has to occur in a way that is particular to that enviornment.

The fact that such divergence has not occurred in homo sapiens is extremely important to the current topic. There are human populations that had been, until recently, isolated for several thousand generations in very special environments as diverse as jungles, deserts, mountains, swamps, grassland, tundra, and ice pack. And yet no trend toward speciation can be discovered. A New Guinea native is every bit the same species as a Laplander or a Zulu. That's fantastic. It shows that, unlike virtually any other animal, human beings literally adapt to new environments, and they do so mainly by changing their behavior, which they can do because they're clever. A furless human being does not get "selected out" of an Arctic environment, leaving only furry individuals in the population. Instead, a furless human being skins an animal and wears its fur. So there is absolutely no reason, no way, for a furry Arctic human to evolve. Quite the contrary: Growing one's own fur would be "costly" while conferring no measurable benefit in terms of RS. It would actually reduce fitness.

The scenario posed by the OP and others, a la X-Men, is therefore supremely unlikely. If Darwinian processes did not produce a new species of humans even when some populations were isolated for thousands of generations in very special environments, it is virtually impossible that we will wake up tomorrow and discover that "homo superior" is at large and taking over through the same Darwinian processes that we suppose produced homo sapiens. Hasn't happened, isn't happening, isn't going to happen under present circumstances.

So in Darwinian terms, there is no "next step in human evolution" waiting to happen. That kind of evolution will not produce a Marvel Girl, a Cyclops, or a Wolverine.

But! Human technology could result in various kinds of "evolution" of a different nature. Gene science could even result in new species of humans that can't interbreed with homo sapiens.

Boorite wrote: I would rephrase the question slighty, asking why isolated human populations never diverged enough to become a different species of humans, that's basically what I intended to say, thanks for the answer boorite It seems (at least to me) that it's just making excuses though.....

Person 1: Isolation is required for speciation
Person 2: *cites isolated pygmy tribe (for example)* why haven't they evolved then?
Person 1: Because the conditions weren't right.

See how it can look like someone's just trying to make excuses for why something didn't happen?

Regards, PA

Only if one fails to grasp the difference between necessary and sufficient conditions.

Isolation is necessary for speciation.

This in no way implies that isolation is sufficient to produce speciation. Indeed, it's been said all along that selection is also necessary.

And still there's at least one more necessary condition: mutation.

Obviously if we did fight, we would lose. If we did lose, we'd be in fact inferior. If we won, then that means we are still superior.

I'd kill the sh** out of them. Or at least try to.

That's not true. The "New Evolution" would be a minority for a long while. They wouldn't hold any political or military power at first.
Even if we won it wouldn't make us more superior. Winning a fight never makes you more superior.

It's common practice to say there is only one species of Homo extant on the planet today - Homo sapiens.

Furthermore, biological scientists say there is actually only one subspecies of Homo s. still in existence - Homo sapiens sapiens i.e us.

Are we sure this is the case however. The commonly accepted definition of species is;



source

This should be qualified with the statement there may be no genetic barrier to interbreeding, it may be a preference rather than an inability. Also, geographic isolation is NOT a consideration. The condition of species can only be determined if the behaviour is exhibited when the organisms are in proximity to allow possible interbreeding to take place.

So there could actually be many subspecies of Homo s alive today, as subspecies are able to interbreed freely, with no prejudice against other subspecies. The genetic diversity of the human population does not rule out this possibility either. We are more diverse from each other than we are (as a population) from Homo neanderthalensis. Also, I know of no study which has been inclusive enough of the global population, that determines whether all the human population residing on the planet fit into the definition of species given above. If there is a population which, for reasons of preference will not commonly interbreed with other human populations they are, by definition, another species. Pygmies may be one example of this (I would welcome if someone could link to any study they know of about this.)

I admit, humans are a very gregarious bunch and interbreeding is common ( ), but this doesn't seem to preclude from the realisation that speciation may be occurring in the modern human population.

BTW, if I have the completely wrong idea regarding the definition of species and the conditions under which speciation occurs, I would appreciate a (non-flame) pointer on where I have gone wrong.

'=


hmmmm interesting topic, and an even more interesting counterpoint. What to do? Hopefully the new species would've evolved to a more peacefull state, not be aggressive, not passive either, for sake of defense. Live and let live to the x-men