Human evolution and differentiation of races

[Debunker]

Thanks to all for the informative replies and sorry for being late to reply here.
Things look clearer now.

Just would like to ask Fuelair if he has any evidence to support the below

IIRC, moving from pale to deep black requires a move from up North or way down South to around the equator and hangin' in there for about 10,000 years. To switch back, just reverse. and every 10 or 15 degrees away from the equater lightens you sufficiently to notice (or the reverse darkens) after about the same 10,00 years. This is due to Vitamin D and another chemical I usually forget and have now and the sun's effect on same.

 

[epix]

The point is that "species" is a human label. We should use it as a tool, not a straitjacket. Darwinism would be much easier to explain to woo-woos if they weren't so god-damnedly insistent on the inviolability of species.

You just nailed it right there. The descriptive or defining terms should keep the pace with advancement in a particular scientific field.

 

[LarianLeQuella]

If you want another human genetic trait that is a recent mutation, look at lactoce tolerance. I think that was introduced into our genome about 8000 years ago, and it has some very specific regional appearances and deficits. Again, not an expert on this, so someone with more knowledge on this subject could probably speak to it more coherently, and show how it is applied to human migration and evolution.

 

[rockchick]

..

 

[MikeMangum]

I have trouble understanding what people mean when they say that "race" is not biologically based, or not a scientific concept, or similar things.

I understand the feel-good, politically-correct idea behind it--that people of all "races" are so similar that there's no point in using "race" to classify people in groups that can then be exploited, denied rights, hated, etc. etc. Obviously, I agree with that.

But it seems we're taking it so far that one can't even state the obvious any more, for fear of being labelled a racist.

Clearly, there are clusters of inherited characteristics among human beings that result in easily visible, consistent differences, when similar people mate. If dissimilar people mate, the characteristics are mixed and matched, so of course it's all very fluid.

In the animal breeding world, they are referred to as "breeds". For example, Appaloosas have specific characteristics that differentiate them from Percherons.

 

[The Fallen Serpent]

I have trouble understanding what people mean when they say that "race" is not biologically based, or not a scientific concept, or similar things.

I understand the feel-good, politically-correct idea behind it--that people of all "races" are so similar that there's no point in using "race" to classify people in groups that can then be exploited, denied rights, hated, etc. etc. Obviously, I agree with that.

But it seems we're taking it so far that one can't even state the obvious any more, for fear of being labelled a racist.

Clearly, there are clusters of inherited characteristics among human beings that result in easily visible, consistent differences, when similar people mate. If dissimilar people mate, the characteristics are mixed and matched, so of course it's all very fluid.

But there must be a scientifically acceptable name for this. Not "sub-species," of course. What's lower down than that? "Varieties" perhaps?

Garden vegetables have varieties based on color, size, flavor, etc., but they interbreed and lose their unique characteristics if allowed to mix. Yet still, we understand that Kentucky Wonder beans are genetically different from Black Turtle beans and will breed true, even though they're both the same species. Fortunes are made by seed companies, exploiting these (incredibly) minor differences, producing open-pollenated varieties that are just a little tiny bit softer, harder, sweeter, tougher, faster-maturing, more-disease-resitant, or whatever, than the competition's variety. (I won't go into F1 hybrids or things that must be cloned like roses or apples--but there are plenty of open-pollenated garden plants that this really does apply to.)

So why is it not a scientifically valid truth that similar "varieties" of human beings have developed, due to breeding in isolation, and can be named, and individuals can be more or less similar to their distinct types as they begin to cross with other varieties?

Sure, in a few thousand years, any of those varieties may be "lost" if they're cross-bred, just as older seed varieties get "lost" if people don't carefully isolate them. By then we may have new races of Martians and Earthians, if humans are separated by planets rather than continents and new clusters of characteristics begin breeding true.

But why aren't "varieties" or "races" (for lack of a better word) a scientifically valid concept when applied to humans, if they're valid when applied to other creatures which reproduce and pass along genetic characteristics?

Please note that I did manage to avoid the obvious "human bean" pun.

From Wikipedia:

The term race is often used in taxonomy as a synonym for subspecies, in this sense human races are said not to exist, as taxonomically all humans are classified as the subspecies Homo sapiens sapiens.[5] Many scientists have pointed out that traditional definitions of race are imprecise, arbitrary, have many exceptions, have many gradations, and that the numbers of races delineated vary according to the culture making the racial distinctions. Thus, those rejecting the notion of race typically do so on the grounds that such definitions and the categorizations which follow from them are contradicted by the results of genetic research.[6]

Today many scientists study human genotypic and phenotypic variation using concepts such as "population" and "clinal gradation". Large parts of the academic community take the position that, while racial categories may be marked by sets of common phenotypic or genotypic traits, the popular idea of "race" is a social construct without base in scientific fact.[7][8][9][10][11][12][13][14] Nonetheless, when divorced from its popular connotations, the concept of race may be useful. According to forensic anthropologist George W. Gill, blanket "race denial" not only contradicts biological evidence, but may stem from "politically motivated censorship" in the belief that "race promotes racism".[4]

Basically, human variation is not different enough to qualify for the term race as is used in biology (a subspecies) nor at all how it was intended for most of its usage in English. Race is largely a social construct based around loose recognition of cosmetic differences in general matching up with geographical locations.

Another quote found in Wikipedia

Or as Ossario and Duster (2005) put it:

Anthropologists long ago discovered that humans' physical traits vary gradually, with groups that are close geographic neighbors being more similar than groups that are geographically separated. This pattern of variation, known as clinal variation, is also observed for many alleles that vary from one human group to another. Another observation is that traits or alleles that vary from one group to another do not vary at the same rate. This pattern is referred to as nonconcordant variation. Because the variation of physical traits is clinal and nonconcordant, anthropologists of the late 19th and early 20th centuries discovered that the more traits and the more human groups they measured, the fewer discrete differences they observed among races and the more categories they had to create to classify human beings. The number of races observed expanded to the 30s and 50s, and eventually anthropologists concluded that there were no discrete races (Marks, 2002). Twentieth and 21st century biomedical researchers have discovered this same feature when evaluating human variation at the level of alleles and allele frequencies. Nature has not created four or five distinct, nonoverlapping genetic groups of people.[60]

More recent genetic studies indicate that skin color may change radically over as few as 100 generations, or about 2,500 years, given the influence of the environment.[61]

So biologically races exist and do not exist depending on the definition used and how arbitrary the definition is. Are North Africans white or black? Depends on who you ask.

 

[Perpetual Student]

The undeniable fact is that human populations exist with very distinct and easily recognizable characteristics although those characteristics may be tiny from the perspective of the genetics involved. Should these different populations be called races, population clusters, or some other polite term? It does not really matter; but whatever we call them, their existence cannot be denied!

 

[Thunder]

races exist, and yet there are no racial characteristics that are unique to one specific race.

there are Asians with African shaped noses and lips. there are Africans with blond hair.

there are Asians with white skin...and Europeans with black/brown eyes.

 

[Roboramma]

The undeniable fact is that human populations exist with very distinct and easily recognizable characteristics although those characteristics may be tiny from the perspective of the genetics involved. Should these different populations be called races, population clusters, or some other polite term? It does not really matter; but whatever we call them, their existence cannot be denied!

Except that there are no solid lines between them, and, depending on what particular characteristics you choose, those lines are drawn in different places.

If you look at skin colour, you draw the line in one place, at hair, in another, at the shape of the eyes, in another, etc.

Which suggests that there is a real problem with the concept of distinct races.

 

[The Fallen Serpent]

The problem is the traditional usage and understanding of race does not hold up. Sure, we can point at races but as referrence to my quote above it leads to identifying 30-50+ races with even a small pool of defining characteristics. Even doing something as simple as skin color it breaks down. At which point is someone black or white? Ethiopian, Nubian, Egyptian, Greek, Italian, German, English?

The point is not that ethnic and ancestoral divisions are not apparent in genetic or physical traits, but that the broad based concept of races as being meaningful is false since human populations are more gradient rather than polarized. The white, black, asian, ect races are at best social constructs with little quantifiable implication on anything other than recognizing very broad geographical distributions prior to the most recent centuries.

There are very few large groups that have been meaningfully separate from neighboring population for significant time periods. These rare divisions do not match up with how people tend to define races.

 

[shadron]

Imperfect or not, inappropriately applied or not, you can say with certainly there are species.

Just because some species have gray divisions doesn't diminish the concept of speciation and subspeciation.

Astronomers have the same problem defining planets. I liked DegrassTyson's view that the divisions make the most sense if they tell you something about the object. So drawing a line of mass and calling A a planet and B an asteroid is not nearly as useful as dividing planets by how they formed, by what part of the solar system they are and so on. Pluto is a Kuiper Belt Object. It isn't its size that makes it not a planet.

Oh, absolutely. The designation of a species is very inexact, but is also a basic concept to our understanding of phylogenetic systematics. Bothersome, but necessary.

One geneticist I talked to said that for certian, two groups who do interbreed are not separate species, and two groups whose members cannot be forced to interbreed, even through means of artificial insemination, definitely are separate species. In between it is opinion. And, of course it becomes worse when all there is to study are the bones, and those of a few individuals of the presumed groups.

In biology, it seems to me the taxonomies should reflect similar rules. Interbreeding is one such 'rule' that results in a continuum division actually telling us more information than simply how many genetic mutations divide two organisms. I suspect there are other kinds of information which species definitions could tell us if we chose our dividing lines with that goal in mind.

No argument.

 

[Skeptic Ginger]

...
If we are to define species as an actually viable interbreeding group, then you and I would seem to be different species! In order to prove we are both human, we would need to get together and see what happens. But if we accept the definition of potentially viable breeding group, then we almost certainly need to throw away a vast number of existing species as mere variants.
Exactly- but that's my point. "Species" are hypothetical constructs.

By this twisted definition of species every human that can no longer reproduce becomes a new species.

I think it is your red herring interpretation of the term, interbreeding, and not the actual taxonomic division that has the problem here.

 

[Skeptic Ginger]

That naming may not match reality.

I avoided the naming and went with the genetic evidence. Perhaps you missed that.

 

[Skeptic Ginger]

The undeniable fact is that human populations exist with very distinct and easily recognizable characteristics although those characteristics may be tiny from the perspective of the genetics involved. Should these different populations be called races, population clusters, or some other polite term? It does not really matter; but whatever we call them, their existence cannot be denied!

So which race do these kids with their "easily recognizable characteristics" belong in?
Link to image.


They are naturally conceived twins.

 

[Skeptic Ginger]

races exist, and yet there are no racial characteristics that are unique to one specific race.

there are Asians with African shaped noses and lips. there are Africans with blond hair.

there are Asians with white skin...and Europeans with black/brown eyes.

Exactly.

 

[Skeptic Ginger]

Oh, absolutely. The designation of a species is very inexact, but is also a basic concept to our understanding of phylogenetic systematics. Bothersome, but necessary.

One geneticist I talked to said that for certian, two groups who do interbreed are not separate species, and two groups whose members cannot be forced to interbreed, even through means of artificial insemination, definitely are separate species. In between it is opinion. And, of course it becomes worse when all there is to study are the bones, and those of a few individuals of the presumed groups.



No argument.

Hooray, someone got what I was talking about.

 

[Perpetual Student]

All languages are loaded with words with ambiguous and multiple meanings, but that dies not prevent us from communicating and understanding those words in context. Declaring a word like race as off-limits or non-existent is an emotional response.

The meaning of the sentence, "The population of Brazil is predominantly made up of three races: Caucasian, African and American Indian," is quite clear. We can very well have the knowledge that those "races" have scientifically ambiguous defining characteristics, but if I were describing the variety of people found in Brazil to someone it would be a useful way to do so. I could also use those labels to describe the social impact of those "races" in Brazil.

I object to declaring words off-limits for the sake of political correctness.
On the other hand, using the term "race" in a scientific context is quite useless, as has been amply pointed out by others here.
English, like all languages, has many words that function well in the common language but have little use in a scientific context. Trying to limit their usage in the common language strikes me as useless snobbery.

 

[Perpetual Student]

So which race do these kids with their "easily recognizable characteristics" belong in?
Link to image.


They are naturally conceived twins.

Their race is ambiguous. Is there really a point there? My wife and I have a red headed daughter and we both have dark hair. So, what does that have to do with this discussion?

 

[bpesta22]

What people fail to realize that vastly similar DNA (but not 100% so) could still produce group differences on traits. Even if the distributions were overlapping by lots, one group would be considerably over or under represented at the tails of the collapsed distribution, which would then have important practical effects on whatever behavior the trait led to.

A very small overlap of two group distributions (d = .20) could still have lots of practical effects at who scores in the extreme and who doesn't. This true despite the trivially easy exercise of finding single members of the low scoring group doing much better than some members of the high scoring group. So what. Exceptions to a group-mean-difference rule in no way invalidate the rule.

For example, the 99.6 % shared dna (or whatever the number is) still leaves 0.4% non shared, which is at least a powerful enough difference to produce pretty obvious differences in physical appearance across races.

 

[bpesta22]

And, searching for a mixed race person and demanding people label him, I think, is weak evidence arguing against the idea of race as something at least partly biological (much like finding an ambidextrous person does not rule out the fact that many pure lefties and pure righties exist).