Race and Speciation

[Zero]

What I've never understood is, if the genetic differences between the races/ethnicities are so minor, why are the features so visible?

[Surlethe]

What I've never understood is, if the genetic differences between the races/ethnicities are so minor, why are the features so visible?

Because you can see the features. It sounds trite, but a very little part of the genetic code controls the most visible features; a lot of the code actually has to do with running it, and so would control minute parts of the body. It's sort of like a car: if you're going to encode the information required to run the car, the paint job and body frame would only take up a minute part -- most of the encoding would be concerned with how the car runs, keeping the engine going, etc. -- but those are the most visible parts of the car.

[Zero]

What I've never understood is, if the genetic differences between the races/ethnicities are so minor, why are the features so visible?

Because you can see the features. It sounds trite, but a very little part of the genetic code controls the most visible features; a lot of the code actually has to do with running it, and so would control minute parts of the body. It's sort of like a car: if you're going to encode the information required to run the car, the paint job and body frame would only take up a minute part -- most of the encoding would be concerned with how the car runs, keeping the engine going, etc. -- but those are the most visible parts of the car.

Yeah, but what I'm saying is that it seems odd that the only real difference is in the visible features. If people developed these different visible features as a means of surviving in new environments, why would only visible features be alterred? And why did the visible features alter so significantly?

[drachefly]

Well, the main difference is melanin, right? That has major selective effects.

Aside from that, could be that it was coincidental gene differences in the families that went the different ways.

Surlethe, I think you and Simplicius are both right -- natural selection still applies to our ideas, but not so very much to our genes. We all have genes that are good enough to get us onto the next level. Of course, the people who just don't work are still screwed, but that sort of goes without saying.

[Surlethe]

Yeah, but what I'm saying is that it seems odd that the only real difference is in the visible features. If people developed these different visible features as a means of surviving in new environments, why would only visible features be alterred? And why did the visible features alter so significantly?

Not only visible features were altered; other genetic changes occurred. The difference is, visible changes, though a major part of the appearance, are only a minor part of the gene code, so we actually perceive a very minor change as a major one.

Surlethe, I think you and Simplicius are both right -- natural selection still applies to our ideas, but not so very much to our genes. We all have genes that are good enough to get us onto the next level. Of course, the people who just don't work are still screwed, but that sort of goes without saying.

This is true; I wasn't trying to say our genes are no longer naturally selected, but rather that the pressures are much less than in other species because our behavior compensates for genetic defects.

[LadyTevar]

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.

I wonder if they could have produced 'mules'.....

[Elfdart]

It's possible. Some hybrids are fertile while others are almost always stillborn. Males are more likely sterile than females. The Cattalo (cow/ buffalo hybrid) is created from members of different genera. Same goes for the Pumapard (puma/ leopard cross).

This wikipedia article has some good links.

Humans and neanderthals are considered similar enough to be in the same genus. Some anthropologists still put them in the same species. I'd imagine they could produce a "mule", though how long such a person would survive is anyone's guess.

[Superman]

What I've never understood is, if the genetic differences between the races/ethnicities are so minor, why are the features so visible?

Because you can see the features. It sounds trite, but a very little part of the genetic code controls the most visible features; a lot of the code actually has to do with running it, and so would control minute parts of the body. It's sort of like a car: if you're going to encode the information required to run the car, the paint job and body frame would only take up a minute part -- most of the encoding would be concerned with how the car runs, keeping the engine going, etc. -- but those are the most visible parts of the car.

Yeah, but what I'm saying is that it seems odd that the only real difference is in the visible features. If people developed these different visible features as a means of surviving in new environments, why would only visible features be alterred? And why did the visible features alter so significantly?

Think about this one too: Chimps share 98.6% of our genome. Look at the huge visible expressions of genetic differences there, yet we're that close.

Actually, we don't look all that different. Skin color is the most obvious difference, but, overall, they're pretty minor. We're all basically hairless apes that walk upright.

[Edi]

It's possible. Some hybrids are fertile while others are almost always stillborn. Males are more likely sterile than females. The Cattalo (cow/ buffalo hybrid) is created from members of different genera. Same goes for the Pumapard (puma/ leopard cross).

This wikipedia article has some good links.

Humans and neanderthals are considered similar enough to be in the same genus. Some anthropologists still put them in the same species. I'd imagine they could produce a "mule", though how long such a person would survive is anyone's guess.

Funny that this subject came up. There was recently a huge thread at Heaven Games on the subject that later got locked due to trolling, but I'll rummage for some quotes from that.

However, virtually nothing of Neanderthal DNA can be found in modern man or in any samples of Cro-Magnon DNA that exist.

Not really correct. The issue about whether or not successful offspring might be possible is simply a guess. First, the DNA being compared in these samples is not nuclear DNA but mitochondrial DNA. The number of mitochondrial DNA mutations between us and Cro-Magnon is not that high, so we think that we should be able to have mated. The number of mitochondrial DNA mutations between us and the very limited amount of DNA that we have from Neanderthals is at such a level that we think that we might not have been able to mate with them successfully. The actual ability to mate and produce successful offspring depends on alterations in gamete DNA and specifically in cell surface proteins on our gametes that allows them to fuse together. Since we don't have any of that actual info we just cannot tell.

What I have offered on the one hand was clearly my opinion -- that I do not think necessarily that Neanderthals and homo sapiens sapiens could have mated (I did not elaborate why I thought that earlier because I did not think my opinion really mattered). I largely think that because I am not very convinced that they shared much time in the same space, if they ever did. There are also obvious morphological differences that might have proved a barrier to the different groups wanting to do so. Who knows? I don't think they would have mated because I don't think it is likely that they ever had the chance to do so. The evidence also supports the idea that they likely did not mate and leave behind offspring -- at least we have no evidence of that. It is possible that they did and there were no survivors to the present day.

That is very different from the proposition that they could not have mated to produce viable offspring if given the chance. We cannot cite significant nulear DNA differences. We cannot cite significant differences in gamete cell surface markers. We cannot run the experiment -- put a modern human and a Neanderthal in a Las Vegas bordello and let them go to town. There are some differences in mitochondrial DNA but those differences are not astounding, whatever your claim. First, to my knowledge, we have only looked at two Neanderthal samples (it is very difficult to find preserved DNA). In those samples there were on average something like 25-27 differences between several different human "races" and Neanderthal mitochondrial DNA (IIRC). On average, humans vary by 5-12 differences depending on which groups one looks at (also by memory so I would have to look at the data again to be sure). It is very clear by this that Neanderthals diverged from the common ancestor that also diverged to produce us something like two to four times as long as we have been a species (so something on the order of 300,000 to 600,000 years ago). That is a fairly good distance that might represent divergence to a degree that we represent different species, but it is not definitive evidence of this fact. Chimpanzees, who diverged from our common ancestor something on the order of 8 million years ago average something like 57 or 58 differences in their mitochondrial sequences from modern humans. Now we know that that sort of divergence results (in this instance) in different species, but we don't know about Neanderthal.

Those are the most relevant ones, and both quotes come from people who know their shit, so I think they are trustworthy.

Edi

[Lusankya]

Humans will evolve much more slowly than many other animals as well. We have about 15 years between generations at an absolute minimum, wheras many other animals have 2-3 years or even less between generations. With a slower generational turning rate, mutations will occur more slowly. A few thousand generations of isolation is much less for humans than it is for snakes or frogs, for example: after a thousand years of isolation, a human population will have gone through 1333 generations (assuming that everyone has children at 15) will be 6666 generations for an animal that reaches maturity in 3 years.


ROAR!!!!! says GOJIRA!!!!!

[Rye]

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".

So you're telling me a geneticist couldn't tell the race of a given sample? My understanding from a guy I know doing bio in the US was that there were gene frequencies that actually did, more or less flow along lines of geography associated with race, indo-european, oriental, negroid, polynesian, aboriginal, etc. And you can determine to some extent the movement of that person's ancestors, race, and their likely place of origin from them.

[Superman]

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".

So you're telling me a geneticist couldn't tell the race of a given sample? My understanding from a guy I know doing bio in the US was that there were gene frequencies that actually did, more or less flow along lines of geography associated with race, indo-european, oriental, negroid, polynesian, aboriginal, etc. And you can determine to some extent the movement of that person's ancestors, race, and their likely place of origin from them.

They can tell the differences yes, but that's not the issue. A physical anthropologist can even determine ethnicity by skeletal remains. However, the point is that these differences are so tiny, when compared to another species, that they're basically insignificant. Genetic difference? Of course. Speciation? Nowhere close.

Also, the classifications you mentioned are very outdated. Anthropologists do not classify according to these groups anymore, and haven't for some time.

[Lord Zentei]

Of course, the OP did not suggest that it had to be anything "close" to speciation:

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?

Any measurable accumulated difference can of course be seen as the "very beginning of that divergance", though the wording leaves something to be desired. Sort of like saying a few steps is the very beginning of a journey, not that you are going to finish it.

As I understood it, the question was whether the difference between ethnicities was qualitatively different or merely quantitatively different from the kind of divergence that causes speciation.

[Simplicius]

As I understood it, the question was whether the difference between ethnicities was qualitatively different or merely quantitatively different from the kind of divergence that causes speciation.

That was what I was trying to get at, yes.

[Winston Blake]

What I've never understood is, if the genetic differences between the races/ethnicities are so minor, why are the features so visible?

The way i see it, it might be something like cars. For example, car colour is a minor difference, but in hot sunny climates you want to buy a light-coloured car. So you have one small characteristic that is highly visible, geographically anisotropic and easily categorisable. Yet all the other specifications of the car are far more important to its abilities even though they're not as visible.

This is not to say that car colour doesn't exist, but associating a whole bunch of other characteristics with it is just stupid, like saying red cars go faster. There's more variation between all red cars than there is average difference between all red cars and all blue cars. Of course many little variations keep the distributions from being perfectly equal, like how sports cars tend to be painted red (the car equivalent of cultural transmission?).

So outward physical appearance in humans is similarly a highly visible yet insignificant set of characteristics. IIRC skin colour is just a matter of vitamin production due to sunlight or lack thereof.