Race and Speciation

[Simplicius]

Harkening back to my biology class of yore:

Given that speciation occures when two populations of a particular species are geographically isolated, such that the respective gene pools are altered by natural selection and random mutation until eventually interbreeding cannot produce fertile offspring (which, if I remeber correctly, is the primary qualification for being of the same species)-

Is it possible to explain the existence of various distinct races of humans as the very beginning of that genetic divergence, which was then slowed/halted/reversed by the ever-increasing contact between human populations?

[Lord Zentei]

Indeed. Human populations adapted to local conditions, and diverged ever so slightly as they became isolated from one antother. Of course, the difference is very much trivial: genetic difference between individuals of the same "race" is far greater than the mean difference between the "races" overall.

However, if human populations had remained isolated long enough they might well have speciated.

[Elfdart]

Possibly, but there's so little difference between the most widely divergent Homo sapiens that it's negligible. I don't buy into "distinct races" of humans because there's very little that's distinct. Like the wolf, humans spread out over the globe (though wolves stuck to the N. Hemisphere) and come in a variety of skin, hair, eye colors as well as differently-shaped ears and muzzles. There's no evidence that a reddish-brown Spanish wolf with large ears won't readily mate with a solid white wolf with small ears from the Arctic. Quite the contrary.

Humans will fuck humans they find appealing enough (or available enough). Tastes vary, but you'll notice that societies with strong taboos about "interracial" marriage, dating and sex have to resort to indoctrination, coercion and terror to enforce them. If they have to resort to such measures, it means that kind of prejudice doesn't come naturally.

The other strike is the fact that humans evolved to move around. Our hips and legs evolved for walking long distances. So unless a population of humans is isolated from the others for at least tens of thousands of years there will always be strangers who come along trying to get some strange. No human population I know of was ever separated for that long. unless you count the Indians of N. and S. America. But there's almost zero difference.

[Darth Raptor]

There won't be "distinct races" of humans until we start colonizing other worlds. The kind of isolation it takes for true speciation simply cannot be had on Earth, especially in this day and age.

For humans, I mean. Less mobile creatures can speciate with little more than a few miles between them.

[Simplicius]

Obviously the difference is insignificant - less than that between men and women, as I once heard. And, considering how short it has been since Homo sapiens dispersed over the globe and became the No. 1 Hominid, I certainly wouldn't expect significant genetic distinction to have the time to develop.

Like the wolf, humans spread out over the globe (though wolves stuck to the N. Hemisphere) and come in a variety of skin, hair, eye colors as well as differently-shaped ears and muzzles.

...which answers my other question before I had to ask it, regarding the comparision with birds, where minor differences in populations exist which don't prevent interbreeding and offspring with hybrid plumage. Thanks.

I don't buy into "distinct races" of humans because there's very little that's distinct.

I would have preferred to use a more accurate phrase, but was unable to think of one.

The other strike is the fact that humans evolved to move around.

This leads to something else I've been wondering about lately. The timespan over which evolotuon occurs is huge, much greater than my own meager ken. Nonetheless, it seems remarkable to me that we as a species have been able, in a sense, to change the rules of the game. Consider that our survival no longer hinges on our genes alone (thanks to things like tools, medicine, and sanitation), that our mobility and ability to survive in varied terrestrial environments (with transportation, clothing, and shelter) gives the species room to expand and keep the available gene pool as large as possible, and that we are able to significantly alter our environment or remove ourselves from hostile ones. Wouldn't that seem to confine the future effects of evolution on humanity to either rather subtle ones, or those which would be brought about by radical and far-reaching environemental events of a magnitude greater than our ability to respond or avoid them?

Or, in brief: Exactly how much can a species thumb its nose at natural selection just by making things?

[Admiral Valdemar]

Ethnicities, yes. Races, no. Unlike white supremacists, biologists tend to know that there is no real difference between a Caucasian and an African or Asian person. There may be some small differences, such as melanin density, lung capacity or susceptibility to certain diseases and conditions, but otherwise, no more of a difference within these so called "races".

[RedImperator]

There's considerably more difference between the San Africans and Bantu Africans than between a Bantu and a European, if I recall correctly. There might have been some proto-speciation going on, but it wasn't along racial lines. The races are social constructs.

[Admiral Valdemar]

It depends on the local geography. There are tribes that have been cut off from the majority of mankind by mountain ranges and the like and have stunted growth or increased stamina etc. due to the conditions they live in. The amount of breeding globally now means the term "races" is about as redundant as talking about breeds of Labrador.

[Darth Raptor]

My anthropology is weak, but would H. sapiens neandertalensis and those "Hobbits" or whatever they found in Oceania be a better example of human races?

[Superman]

Valdemar basically summed up everything that a biologist or an anthropologist would tell you regarding this issue.

Let me just add that good analogy might be to look at the various breeds of dogs. There are small ones, big ones, different colored ones, etc., but all of them can interbreed and make fertile offspring. This is not at all speciation.

When we look at our closest hominid cousin, the neandertalls, we can see clearly that these guys were similar to us, especially when compared to other hominids, but big there were still huge morphological and genetic differences. One geneticist extracted DNA from the molar of a Neandertall and determined that it was a different Genus entirely.

All humans, regardless of race, do not possess enough of a genetic difference from one another to speculate that speciation might someday occur. Think of "someday" as being somewhere in the ballpark of 250,000 to 500,000 years.

[Surlethe]

Or, in brief: Exactly how much can a species thumb its nose at natural selection just by making things?

The species doesn't thumb its nose at natural selection; it merely adapts much more quickly. The time scale upon which evolution occurs is geological; humans, through tool use, are able to adapt in, now, as little as a year (witness the turnaround time for potential avian flu vaccines). This merely means we are at the edge of selection pressures, or anticipate them; we also have ourselves become a selection pressure, and we are causing the extinction of multiple species, because we change the environment so quickly. There's no evolutionary rule that says after a certain point adaptation is no longer adaptation; and we dominate the planet because we can make ourselves faster, better, and stronger, and we adapt far more quickly than all the other species on the planet.

[Superman]

My anthropology is weak, but would H. sapiens neandertalensis and those "Hobbits" or whatever they found in Oceania be a better example of human races?

Negative. They were hominids like us, but we were not members of the same species, and, some scientists have demonstrated that they should be placed into a different genus entirely, based off of the examination of neandertall DNA from a preserved molar.

[LadyTevar]

My anthropology is weak, but would H. sapiens neandertalensis and those "Hobbits" or whatever they found in Oceania be a better example of human races?

Negative. They were hominids like us, but we were not members of the same species, and, some scientists have demonstrated that they should be placed into a different genus entirely, based off of the examination of neandertall DNA from a preserved molar.

I thought there were theories on interbreeding between H. neandertalensis and H. sapiens?

[Ariphaos]

Is it possible to explain the existence of various distinct races of humans as the very beginning of that genetic divergence, which was then slowed/halted/reversed by the ever-increasing contact between human populations?

Sort of, but not races as you might know them. Genetic studies have told us quite a lot. We are all descended from roughly two thousand people who lived 70,000 years ago (at about the Toba eruption). Humanity then split into four main groups. Three of them moved to various parts of Africa, and the fourth, the smallest group, mostly left Africa and proceeded to conquer the rest of the world.

What's more striking is that, IIRC, these groups are already genetically quite narrow, meaning that it wasn't the first time humanity went through a near extinction event.

[Ariphaos]

I thought there were theories on interbreeding between H. neandertalensis and H. sapiens?

No humans so far tested have had any evidence of inheriting such DNA.

[GrandMasterTerwynn]

My anthropology is weak, but would H. sapiens neandertalensis and those "Hobbits" or whatever they found in Oceania be a better example of human races?

Negative. They were hominids like us, but we were not members of the same species, and, some scientists have demonstrated that they should be placed into a different genus entirely, based off of the examination of neandertall DNA from a preserved molar.

I thought there were theories on interbreeding between H. neandertalensis and H. sapiens?

No, such theories are no longer on the cutting edge, or really in the mainstream anymore. We have a much better picture of the Neanderthal genome now, than we did when such theories were floated. The Neanderthal genome suggests that the last time modern humans and Neanderthals shared a common ancestor was Homo Erectus (this puts the divergence back a million, or so, years.) As a result, H. Sapiens and the Neanderthals were incapable of producing viable hybrids.

[Elfdart]

My anthropology is weak, but would H. sapiens neandertalensis and those "Hobbits" or whatever they found in Oceania be a better example of human races?

Most scientists now put Neanderthals in their own species Homo neandertalensis. The little people in Indonesia were also given their own species Homo floriensis or some such. To carry on the canine analogy, my neighbor's German shepherd and the golden retreiver across the street are the same species. They will readily interbreed if they can. Wolves will also readily breed with dogs, since they are the same species. Coyotes seldom do, though they can: different species. The four or five species of jackal don't breed with dogs or one another, though they are close enough genetically that they could, though probably not successfully (no live or fertile offspring). All of these animals are members of the genus Canis.

[Elfdart]

I thought there were theories on interbreeding between H. neandertalensis and H. sapiens?

Supposedly someone found a skeleton that had both human and neanderthal features. But that could simply be a case of mixed bones from two hominids. It's possible that such interbreeding occured, but it's a rarity. Lone wolves have been known to impregante coyotes and one of the great white hunter types in India claimed to have seen what was obviously a cross between a tiger and a leopard. But most of the time when a wolf gets hold of a coyote or a tiger gets hold of a leopard the result is a gruesome death instead of a hybrid. It appears to have been that way among humanoids, too. In Spain they found a dumping ground for human (Homo sapien) bones with toothmarks from where the much larger and stronger Homo heidelbergensis ate them. This might be where all the myths about giants snatching and eating people come from.

[Simplicius]

Clearly, wording is biting me in the ass here. Neither "ethnicity" nor "race" seemed partcularly accurate to what I was trying to ask when I was drafting the OP, so, in the flip of the coin, I picked the worse of the two. I'm sorry for the imprecision of my wording, and I will re-state the question - though I have already (I think) gleaned the answers I sought - for the sake of clarity. I'll include your answers as I've understood them.

1) Were existing genetic differences between various populations of H. sapiens indicative of the very early stages of the sort of adaptation that eventually leads to speciation?

Possibly. Speciation can happen when any sufficiently isolated populations exist.

2) Were there any populations of H. sapiens sufficiently isolated from others that, had we not developed vehicles to carry us, may have speciated in a sufficiently long span of time?

People are adapted for mobility, and they can walk anywhere there's ground to stand on. I assume even mountain ranges and deserts could be passed on foot eventually. So probably not.

Is that a clearer statement of the case?

The species doesn't thumb its nose at natural selection; it merely adapts much more quickly. The time scale upon which evolution occurs is geological; humans, through tool use, are able to adapt in, now, as little as a year (witness the turnaround time for potential avian flu vaccines). This merely means we are at the edge of selection pressures, or anticipate them; we also have ourselves become a selection pressure, and we are causing the extinction of multiple species, because we change the environment so quickly. There's no evolutionary rule that says after a certain point adaptation is no longer adaptation; and we dominate the planet because we can make ourselves faster, better, and stronger, and we adapt far more quickly than all the other species on the planet.

But, since that rapid adaptation takes the form of technological, scientific, or other "man-made" innovation instead of biological change, isn't it fair to say that to some degree humanity can 'stretch' the rule of natural selection? That a trait which would inhibit survival and ordinarily be weeded out of the gene pool - say, vulnerability to a common disease - would be adapted to medically, so people who carry that trait can take the vaccine, survive to reproduce, thereby preserving that trait? Or am I way off base?

[Surlethe]

The species doesn't thumb its nose at natural selection; it merely adapts much more quickly. The time scale upon which evolution occurs is geological; humans, through tool use, are able to adapt in, now, as little as a year (witness the turnaround time for potential avian flu vaccines). This merely means we are at the edge of selection pressures, or anticipate them; we also have ourselves become a selection pressure, and we are causing the extinction of multiple species, because we change the environment so quickly. There's no evolutionary rule that says after a certain point adaptation is no longer adaptation; and we dominate the planet because we can make ourselves faster, better, and stronger, and we adapt far more quickly than all the other species on the planet.

But, since that rapid adaptation takes the form of technological, scientific, or other "man-made" innovation instead of biological change, isn't it fair to say that to some degree humanity can 'stretch' the rule of natural selection? That a trait which would inhibit survival and ordinarily be weeded out of the gene pool - say, vulnerability to a common disease - would be adapted to medically, so people who carry that trait can take the vaccine, survive to reproduce, thereby preserving that trait? Or am I way off base?

If we see a chimpanzee prodding an anthill with a stick, is he really working around natural selection, which would otherwise select against stubby fingers? Genetics isn't the only thing natural selection selects; it also selects behaviors, and that's where humans come in: our genetic makeup is not subject to many selection pressures, because our behavior has been selected to be so adaptable. Is this making sense to you? The trait -- to take your example -- which inhibits survival and would ordinarily be weeded out of the gene pool obviously doesn't inhibit survival any more; there is thus no reason for it to be weeded from the gene pool.

[Elfdart]

Clearly, wording is biting me in the ass here. Neither "ethnicity" nor "race" seemed partcularly accurate to what I was trying to ask when I was drafting the OP, so, in the flip of the coin, I picked the worse of the two. I'm sorry for the imprecision of my wording, and I will re-state the question - though I have already (I think) gleaned the answers I sought - for the sake of clarity. I'll include your answers as I've understood them.

1) Were existing genetic differences between various populations of H. sapiens indicative of the very early stages of the sort of adaptation that eventually leads to speciation?

Possibly. Speciation can happen when any sufficiently isolated populations exist.

2) Were there any populations of H. sapiens sufficiently isolated from others that, had we not developed vehicles to carry us, may have speciated in a sufficiently long span of time?

People are adapted for mobility, and they can walk anywhere there's ground to stand on. I assume even mountain ranges and deserts could be passed on foot eventually. So probably not.

Is that a clearer statement of the case?

That pretty well sums it up. I'd just add one thing: The Linnaean system is fine for a rough guide to which animal is related to the others. It's not perfect and Nature has a way of fucking things up for those who cling to the chart. Again with the dog family. Wolves (including dogs) and coyotes can and do mate to produce fertile offspring. Yet they are separate species. Dogs were listed as their own species until DNA tests showed how wrong it was to do so. Human DNA has more in common with chimpanzees than horses do with zebras. Horses and zebras can produce zonies, which are usually sterile, so they're both listed as members of the genus Equus. Yet chimps and humans are listed in separate genera: Pan and Homo, respectively.

[FSTargetDrone]

Let me just add that good analogy might be to look at the various breeds of dogs. There are small ones, big ones, different colored ones, etc., but all of them can interbreed and make fertile offspring. This is not at all speciation.

I've always liked this idea, as it seems far more relevant. But try using it with the general public and I'm afraid it would be none too popular.

[Superman]

Clearly, wording is biting me in the ass here. Neither "ethnicity" nor "race" seemed partcularly accurate to what I was trying to ask when I was drafting the OP, so, in the flip of the coin, I picked the worse of the two. I'm sorry for the imprecision of my wording, and I will re-state the question - though I have already (I think) gleaned the answers I sought - for the sake of clarity. I'll include your answers as I've understood them.

1) Were existing genetic differences between various populations of H. sapiens indicative of the very early stages of the sort of adaptation that eventually leads to speciation?

Possibly. Speciation can happen when any sufficiently isolated populations exist.

2) Were there any populations of H. sapiens sufficiently isolated from others that, had we not developed vehicles to carry us, may have speciated in a sufficiently long span of time?

People are adapted for mobility, and they can walk anywhere there's ground to stand on. I assume even mountain ranges and deserts could be passed on foot eventually. So probably not.

Is that a clearer statement of the case?

1. You would probably get a cleared picture by looking at the overall picture. What I mean by this is that no organism is fixed; species adapt or not, become extinct or not, speciate or not.

Speciation requires time and lots of it. Humans have been around for about 195,000 years, and we've only developed, at most, less than 2% variation among ourselves.

You're looking at Homo sapiens as sort of a mixture of populations, defined by racial characteristics. You will gain a clearer picture by recognizing us as what we are; one species. There biological differences are so small that they are basically irrelevant.

2. Again, the answer to that question is no. This is probably because we have only a small fraction of the time that is required for this level of change. We're simply nowhere near that.

Also, we're really not that adapted for mobility, when compared to other organisms. Our bipedal movement is hardly superior to the speed that is accomplished by four legs, and walking upright takes a terrible toll on our spinal column. Remember, evolution is not always improvement; rather it's simply mutation. In our case, what led us to walk upright also seems to have contributed to the expansion of our brains, especially the frontal regions.

[Superman]

Eh, ignore the gramatical mistakes. I am horrible at multi tasking...

[Simplicius]

Your points are all duly taken. Thank you.

Genetics isn't the only thing natural selection selects; it also selects behaviors, and that's where humans come in: our genetic makeup is not subject to many selection pressures, because our behavior has been selected to be so adaptable.

Ah. That had not occured to me before.