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I've heard that Asians (I'm not entirely sure which subgroup was being referred to) tend to be more genetically homogenous than other races, with people of African lineage being on the other end of the spectrum being the least homogenous.

Is there any truth in the claim that Asians or a specific subcategory such as South East Asians have less genetic variance than other races?

I've seen papers like Extreme mtDNA homogeneity in continental Asian populations for example, but I don't understand enough to know if that answers my question.

If Asians have less genetic variance, would that lead to less variance in phenotypes?

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    $\begingroup$ I think you'll find that Africans are the most genetically heterogeneous. $\endgroup$
    – Alan Boyd
    Commented Nov 15, 2013 at 15:59
  • $\begingroup$ @AlanBoyd That's interesting...do you have a source? I remembered reading it was Caucasians which given how far Caucasians have spread and evolved independently would make sense to me... $\endgroup$
    – Sonny Ordell
    Commented Nov 15, 2013 at 16:15
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    $\begingroup$ This Wikipedia page is a good source en.wikipedia.org/wiki/Human_genetic_variation The argument is that during the out-of-Africa migrations only a small sample of the total genetic variation left Africa. Those who remained inherited all of the existing variation. Detailed information at the WP page. $\endgroup$
    – Alan Boyd
    Commented Nov 15, 2013 at 16:20

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I will side-step the question of 'race', as you seem to be using it (like most people) in the sense that has no scientific basis, but the answer to your question goes something like this:

The amount of genetic variation in a given population is mostly the function of the geographical distance from Africa. Roughly, populations in Africa are most genetically variable as they are the oldest (they have been there for the longest time in human evolutionary history and therefore there was a long time for mutations to accumulate in their genomes). Because all the other populations in the world have originated from these original African populations, they have a subset of that original variation - they are less variable. The further you get from Africa the less variation remains (a very simplistic scenario: a group of Africans left and settled down in the Middle East; then a group of Middle Easterners went further up to Europe and further east to India; then the Indians moved further north and east etc. etc.; in each stage, only a subset of the previous variation would be travelling along).

A famous image depicting this phenomenon is in Ramachandran, S. et al. (2005). Support from the relationship of genetic and geographic distance in human populations for a serial founder effect originating in Africa. Proceedings of the National Academy of Sciences of the United States of America, 102(44), 15942–15947. doi:10.1073/pnas.0507611102 figure 1B

[Source](http://www.pnas.org/content/102/44/15942)

On the Y axis you have a measure of genetic relatedness (more relatedness = less variation) and on the X axis you have rough geographic distance that takes into account major geographic barriers (like seas etc.). Green is Eurasia and blue is Australia and Oceania. Red is variation within the groups (so, Europeans only, Australians only etc.) The variation between the populations explained by this geographic distance is close to 80% - which is huge. If I get this right, it means that most of the genetic differences between people in different populations are a simple consequence of living outside Africa. And the variation within each population is tiny (12%) compared to the between population.

This is a simplified view, because we now know that there were other species of humans that lived when our ancestors left Africa, and that thay had sex together as our ancestors spread around the globe, so a small portion of the others' DNA is still present in us today. Also this picture may be slightly different depending on what region of the genome you're looking at. But the major picture stands.

Going back to your question - "Asians" (populations with ancestry in east Asia) are on average more genetically homogenous than "Australians", "Americans", and "Africans".

EDIT: A paper I like that should explain all this much better: Barbujani, G., & Colonna, V. (2010). Human genome diversity: frequently asked questions. Trends in genetics : TIG, 26(7), 285–295. doi:10.1016/j.tig.2010.04.002 link

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  • $\begingroup$ a sensible , scientific answer to a sensitive question! $\endgroup$
    – shigeta
    Commented Nov 20, 2013 at 14:56
  • $\begingroup$ Thankyou, a very interesting answer! I disagree that race has no scientific basis as I think that's being overly PC. Could you clarify if on your last point when you say "Australians" or "Americans" you mean Caucasians, or if you actually mean Australians or Americans? $\endgroup$
    – Sonny Ordell
    Commented Nov 20, 2013 at 15:26
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    $\begingroup$ Answering the second part of the question: I mean people of Australian or American ancestry. The first part: I encourage you to read that Barbujani paper. When people say "race" they tend to mean a social construct that classifies people into groups based on physical appearance (skin color, hair, eyes etc.). You cannot divide people like that based on the DNA, because the variation is continuous and all division of it will be arbitrary. It's like seeing a rainbow: can you tell me exactly where the yellow ends and orange begins? $\endgroup$
    – yotiao
    Commented Nov 20, 2013 at 16:02
  • $\begingroup$ The reason I think it's being overly PC to assume race has no biological basis is because we have evidence to the contrary. When people say Caucasians or Asians or Black, we genrally know what the people being referred to look alike. That aside, there are different medical issues effecting different races. Race is the subgrouping of people with common characteristics, which we know exists in biology. That's all it has to be, unless you make it into something more. Koreans all have genetic characteristics in common that Caucasians lack, and vice versa. No? $\endgroup$
    – Sonny Ordell
    Commented Nov 20, 2013 at 21:23
  • $\begingroup$ I think your answer would be a lot more useful if You didn't compare races to nationalities, especially nationalities only established in the last half century. Would you say the Asian Race is more genetically homogenous than the Caucasian Race? - en.wikipedia.org/wiki/Caucasian_race and en.wikipedia.org/wiki/Mongoloid_race $\endgroup$
    – Sonny Ordell
    Commented Nov 20, 2013 at 21:26
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Don't worry, caucasians all look the same to Asians too. This is because of the cross-race effect: we are able to effectively distinguish people we are more familiar with.

But as for the most genetically diverse race, this article might be of interest: "Sub-Saharan Africans have greater genetic diversity than other populations." The research paper the quotation is based on is found here.

To be honest, I don't see the point of this question. The answer depends on what classifies under a race: Do Asians include Indians? What qualifies as Caucasian? etc.

The only thing that can be gained by exploring race-specific genetic distinctions is if you want to promote some racial supremist attitude like that guy with the toothbrush mustache.

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  • $\begingroup$ I'm not really interested in the tired of argument of whether or not race is a valid construct, and I don't see it as relevant to the question. For most people outside of the UK, Asians refers to the peoples of the Asian continent..Chinese, Japanese, Koreans, Thai etc.. $\endgroup$
    – Sonny Ordell
    Commented Nov 15, 2013 at 17:21
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    $\begingroup$ The point of the question is that I was curious about it and wanted a detailed answer after being unable to find one myself...isn't that part of why sites like this exist? The cross-race effect is interesting, but doesn't address the question. I'm not asking about the most genetically diverse race, and I think it's naive to say exploring race-specific genetic distinctions is only useful for promoting racial supremacy. $\endgroup$
    – Sonny Ordell
    Commented Nov 15, 2013 at 17:24

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