January 07, 2009

Culture, population structure, and low genetic diversity in humans

As I have mentioned in a previous entry, the genetic structure of human populations has been interpreted as the result of a process of "serial bottlenecks", starting from the major "Out of Africa" bottleneck, and followed by a series of other ones, as humans colonized the world. Bottlenecks reduce genetic diversity, but so does selection, and it is imperative to directly sample genetic diversity of past populations, to see how well they conform with the expectations of the "serial bottlenecks" theory, i.e., whether reduced diversity is due to descent from a few individuals whose progeny transcended the bottleneck, or due to selection, which suppresses genetic variation by removing some alleles from the gene pool.

This paper argues in favor of selection as a mechanism for keeping genetic diversity (and hence effective population size) at low levels. This selection process, is not, however, envisioned as affecting the species as a whole, but rather proceeded in its own way in regional subsets of humans. These groups did not exchange genes randomly with other such groups, but rather according to their degree of cultural similarity.

John Hawks has an extensive post on this article, which I recommend.

PNAS doi:10.1073/pnas.0809194105

Culture, population structure, and low genetic diversity in Pleistocene hominins

L.S. Premo, Jean-Jacques Hublin

Abstract

Paleogenomic research has shown that modern humans, Neanderthals, and their most recent common ancestor have displayed less genetic diversity than living great apes. The traditional interpretation that low levels of genetic diversity in modern humans resulted from a relatively recent demographic bottleneck cannot account for similarly low levels of genetic diversity in Middle Pleistocene hominins. A more parsimonious hypothesis proposes that the effective population size of the human lineage has been low for more than 500,000 years, but the mechanism responsible for suppressing genetic diversity in Pleistocene hominin populations without similarly affecting that of their hominoid contemporaries remains unknown. Here we use agent-based simulation to study the effect of culturally mediated migration on neutral genetic diversity in structured populations. We show that, in populations structured by culturally mediated migration, selection can suppress neutral genetic diversity over thousands of generations, even in the absence of bottlenecks or expansions in census population size. In other words, selection could have suppressed the effective population size of Pleistocene hominins for as long as the degree of cultural similarity between regionally differentiated groups played an important role in mediating intraspecific gene flow.

Link

25 comments:

Dragon Horse said...

Well we know we are a young species and a heavily inbred one. As much as we spend time trying to parse the differences and support artificially based national identities and ethnicities which likely did not exist 1,000 years ago and won't exist a 1,000 years from now. We are less diverse biologically than Chimps.

BlaiseVillaume said...

Do you read this site at all? Ethnicities most assuredly are real.

Kepler said...

BlaiseVillaume,
I see you are from the Midwest.
It is cool there are ethnicities.
And how do YOU define ethnicities? As the centers in some genetic clusters? When did history start for you? Did it stop? What is your ethnicity and what do you think will happen to that ethnicity in 500 years?

Average Joe said...

Of course no one knows which ethnic groups will or will not be around centuries from now but that will not stop the likes of Dragon Horse and Kepler from pretending that they do.

Dragon Horse said...

I think you guys are confusing race and ethnicity. Not the same thing.

In any case, even with race it depends on how resolution you want to use. I can say that every person is their own unique race if I use enough alleles. IF I decrease the resolution, as Dienekes has shown on this site repeatedly I can even roughly define some European nationalities and I can call that a race, if I decrease some more I can define European, then West Eurasian, etc.

This does not help us much but on the margins.

Dragon Horse said...

If humans have biological races than each chimpanzee is definitely a race to itself. LOL I don't think scientists believe each individual chimp is a subspecies or a "breed"...however we use the same standard for people and say they are semi-distinct populations based on using low to moderate genetic resolution. Odd...

Kepler said...

Average Joe,
The point is what IS for you an ethnic group. Can you put here your formal definition? I checked out your blog. It is all about how bad immigrants, specially non-white, are.
Well, it seems this blog is often frequented by US white supremacists who are feeling very insecure.

Kosmo said...

"If humans have biological races than each chimpanzee is definitely a race to itself. LOL"

--Dragon Horse, that's a good point. It certainly illustrates the argument that "race" is subjective and not objective.

Dragon Horse said...

Kosmo:

I believe "race" is real, but we have to discuss what that means.

Basically people are taking social concepts and making science fit that.

I could easily add decrease alleles (resolution) and say everyone in Eurasia is a race and everyone in Africa is a separate race, etc.

I could easily support this by haplogroup, etc.

So can you scientifically, using genetics, determine if someone is of SubSaharan African Ancestry and call them "black". yep. I can also scientifically determine (within a reasonable error rate) that Eastern Europeans and Central Asians are a race separate from Western Europeans. I could also say there is a Mediterranean race that is distinct. I could say quite easily Korean and Japanese are a race separate from Chinese.

All people are doing is taking data and drawing lines based on what they perceive to be correct culturally.

So when we speak of "race" we should also not lose site of what that means. I think many people on these sites think of "subspecies" or "breeds" of humans, like I said, if that was biologically true than a lot of other science dealing with other species, especially primates would not make any sense.

terryt said...

"I don't think scientists believe each individual chimp is a subspecies or a 'breed'".

But scientists do divide chimpanzees into several geographic subspecies.

"I think many people on these sites think of 'subspecies' or 'breeds' of humans, like I said, if that was biologically true than a lot of other science dealing with other species, especially primates would not make any sense".

Why not? Unless they are geographically discrete the boundaries between most subspecies and breeds is easily as permeable and ill-defined as are any boundaries we might care to use to divide up human groups.

Cyd the Kid said...

Shit, why didn't anyone tell me that this was a Cultural Anthropology blog? What, with all the anti-racist, no-such-thing-as-race dinosaurs around here. When is Lewontin dropping by?

Maju said...

artificially based national identities and ethnicities which likely did not exist 1,000 years ago and won't exist a 1,000 years from now

Some ethnicities at least did exist 1000, 2000 and even more milennia ago. Consider Basques, Greeks or Berbers, for instance. Arabs too, even if only in Arabia peninsula then, etc. Furthermore ethnic groups are not formed in a void, there's a background to them even if there's also transformation.

Ethnicities most assuredly are real.

Ethnic identities (as well as sub- and supraethnic ones) act as homogenizing, clustering frames somewhat. But only to certain extent. There's always the the trans-border cline too.

Ethnicities are both cultural and most commonly also geographic entities, and geographically based relatedness is only terriby logical, regardless of cultural and political conditionants.

If humans have biological races than each chimpanzee is definitely a race to itself.

Exaggerated maybe but good point.

Basically people are taking social concepts and making science fit that.

Very true. What doesn't mean that culture can't influence biological patterns to some extent.

BlaiseVillaume said...

I am not going to address all the various points brought up. As far as "resolution" goes, I do not see why that would make the concept of ethnicity meaningless. If you simply use logic with resolution you'll find various steps, the individual, family, clan, ethnicity, race and species. So yes, depending on the number of alleles you are looking at you can define things at various levels of specificity. The point is whether there are sufficient gaps between the concepts, and where cross breeding hasn't muddled the picture I believe there is.

I am indeed from the Midwest, and am descended from one Alsatian family and the rest were Palatinate Germans. Therefore you could say my ethnicity is an American of Rhineland German stock. It would be a severe strain on probability to say that the people I descend from in the Rhineland aren't in turn descended from the Franks and Alemanni of 1,500 years ago who were melded their culture and identity with the conquests of Charlemagne. So that identity would have been established for at least 1,200 years.

It is too much credit to human imagination to suggest that someone simply made up the concept of race out of thin air. Whether or not the first people to theorize on race articulated the objective truth on race would be immaterial to that objective truth. I do not claim to have reached that truth myself, but I will define race broadly as being the next distinct level of specification under the species, and ethnicity as being the next level of specification under race.

As far as insecure U.S whites are concerned, I am not an anthropologist or a geneticist. I am a thinking man who comes on this website to learn what I can. However, I don't need genetics to tell me that Mexicans, Somalians, and Hmongs destroy the neighborhoods white families built.

Dragon Horse said...

"but I will define race broadly as being the next distinct level of specification under the species, and ethnicity as being the next level of specification under race."

definition of "subjective".

This is exactly my point.

Kosmo said...

See, Blaise, you sounded like you might be a decent guy just discussing his point of view, and then you had to ruin it with that last sentence.

I like this blog a lot, but these discussions on the genetics of ethnicity always seem to turn into platforms for people to display their biases.

If you want to believe in a world view that divides humans into fifty or a dozen little boxes, so be it. If you want to believe that the little box you're in is the best box, the smartest box, the most advanced, the most moral, the best looking, whatever, then so be it. If you want to take all kinds of pride in being in that box, if you want to build your identity upon it, and take credit for having the forsight and good sense to choose the right kind of parents, then again, so be it.

But please don't post stuff like that here.

Kepler said...

I wonder what Native Americans think of who destroyed their neighborhoods.
I agree with Kosmos.

There are usually interesting articles and discussions here.

Cyd the Kid said...

If you want to believe in a world view that divides humans into fifty or a dozen little boxes, so be it. If you want to believe that the little box you're in is the best box, the smartest box, the most advanced, the most moral, the best looking, whatever, then so be it.

It has nothing to do with "belief" but the hard, cold facts of reality when one assesses the world we live in. Beliefs are what the post modernists push.

I wonder what Native Americans think of who destroyed their neighborhoods.

ZZZZzzzzzzzZZZzzzzzzz....

BlaiseVillaume said...

American Indians didn't have neighborhoods in any comparable sense. Different genetic identities will always oscillate between competition and cooperation depending on a number of factors, I am not claiming that my own genetic identity has the sole moral prerogative to compete and I am not claiming that all cooperation should function with my genetic identity as the sole beneficiary. Nor did I make any claim that my "box" was the "master box" or any such thing, I simply relayed a blatant observation in my last sentence. In fact, I AM a decent guy and would be gracious enough to drive anybody on a tour through Minneapolis, St. Paul, or Detroit, and then take you to a historical museum so you can see the before and after effect of different waves of immigration in America. Of course, if somebody wanted to take me up on that offer of Detroit I would insist they provide the firearms necessary to travel safely in the worst parts of that city. Essentially though, my last sentence meant that I am not looking at genetics to justify or assuage any feelings I have about real world human interactions.

Also, this war on "subjectivity" borders on nihilism. To insist that there is no objective truth simply because it is yet to be discovered flies in the face of scientific inquiry. My definitions are potentially falsifiable depending on what objective data shows and are thus not subjective.
Allow me to be more specific:

In a general pool of all human individuals there will be a certain number of genes common to all. Those genes shared by all will thus constitute the minimum standard of the species.

Where it can be observed at the species level that there is a split in shared genes between a group A and B, where all individuals within group A have more genes in common with each other than with any individual in Group B, then it can be said that Group A and B are distinct races.

And so on you would reduce those similarities on the basis of an observable effect i.e different physical form, mental function(including but not exclusively meaning intelligence), and culture to the individual level.

That is a falsifiable claim, the only thing "subjective" about it is the etymology but names and labels such as race and ethnicity will always be subjective. For example one could call a flower feces but there would still be an objective difference in form regardless of what word is used. So, where these genetic distinctions may seem tenuous and absurdly reduced, it is not so if they have an observable effect. It is my impression that even a tiny genetic difference can translate to a clear effect.

terryt said...

Cyd the Kid wrote: "ZZZZzzzzzzzZZZzzzzzzz....".
I presume you thoroughly approve of the current Israeli destruction of Palestinian neighbourhoods. The obvious end product of tribal division.

Cyd the Kid said...

I presume you thoroughly approve of the current Israeli destruction of Palestinian neighbourhoods. The obvious end product of tribal division.

How many thousands of years are we going to try to "get along", to paraphrase the immortal Rodney King?

I thoroughly approve of the right for all ethnic tribes, races, and sub-races to maintain a homogeneous homeland, including Israel. I just wish, and actually demand, that these Zionist Jews get the hell off of our collective necks and allow Whites to maintain our homelands by "any force necessary" as Israelis like to say. It seems what is good for the goose is not always good for the gander according to Jewish ideology.

To clarify, my coma inducing snooze was brought about by the moronic babblings of our resident Post Modernist Tard, Kepler. Maybe he can clarify what he means by "neighborhoods" when discussing a nomadic tribe of warring peoples?

Maju said...

Ignore Cyd, please. He's a stormfronter (neonazi) provoker. There's no way to deal with such people in reasonable terms, maybe a decade or two in a Maoist reeducation camp... but maybe not even that can help.

Cyd the Kid said...

I'd suggest we ignore Maju the Moron. I've never visited "Stormfront" nor are my beliefs "Neo-Nazi". If we look at polls of all people of European descent, we find that they agree with my stances, at least a majority of them, though are frightened to speak out due to obvious reasons, such as "re-education camps" that the Moron speaks of.

The belief to maintain ethnic and/or racial solidarity with a homogeneous nation is a NORMAL stance. This mass influx of vastly different people for a myriad of reasons given, is what is abnormal. Let's think about this for a little bit. Why is the speaking up of what was NORMAL up until 2-3 decades ago so horrific now that it could destroy people's lives who do? Why is speech unlawful in many parts of Europe that promote this belief while 50,60,70,80% of various European populations, depending on the country, want it? Why is that? Why do morons, like the big Moron, use labels such as "Neo-Nazi" instead of dealing with the real issues?

Why? Because their IDEOLOGY cannot be defended in good faith and they must resort to tactics that truly do resemble storm troopers.

terryt said...

Cyd the Kid wrote:

"I thoroughly approve of the right for all ethnic tribes, races, and sub-races to maintain a homogeneous homeland".

Can you name any ethnic tribe, race or sub-race that exists within a single homogeneous homeland? As far as I'm aware all regions of the earth have been subject at one time or another to at least one "mass influx of vastly different people". Of course if you wish to confine history to just the last two or three hundred years such influxes become less obvious, but if we consider the long-tern view we see that people in all regions of the earth are the product of many different migrations. Even those populations in isolated regions of the Pacific for example.

Cyd the Kid said...

As far as I'm aware all regions of the earth have been subject at one time or another to at least one "mass influx of vastly different people".

Yes, the old "we were always a nations of immigrants" argument. This argument is fallacious, terry. The "mass influx of vastly different people" you speak of ages past was due to warring and invasions. But then, like a blind squirrel finding the occasional nut, you bring up an excellent point. This mass influx truly is an invasion and an act of war against the indigenous peoples of western lands. Now, who is doing the warring, terry? Who has the power to cause this invasion?

terryt said...

"Now, who is doing the warring, terry? Who has the power to cause this invasion?"

The ones with the most effective weapons?