Gene Expression

Brown people are all the same (perhaps)

New paper in PLOS Genetics, Low Levels of Genetic Divergence across Geographically and Linguistically Diverse Populations from India. Here’s the conclusion:

Populations from India, and groups from South Asia more generally, form a genetic cluster, so that individuals placed within this cluster are more genetically similar to each other than to individuals outside the cluster. However, the amount of genetic differentiation among Indian populations is relatively small. The authors conclude that genetic variation in India is distinctive with respect to the rest of the world, but that the level of genetic divergence is smaller in Indians than might be expected for such a geographically and linguistically diverse group.

It’s in PLOS, so you can read the whole thing. This figure is pretty illustrative.

a) Brown people form a distinct genetic cluster. South Asians that is. This shouldn’t surprise.

b) South Asians are more related to other South Asians than non-South Asians. Punjabis (Northwestern India) might resemble Iranians and Arabs more than other South Asians, but they are still more like other South Asians than Iranians or Arabs.

c) This study showed very little internal population substructure within South Asia. I think the caveats are important, the study looks at American South Asians. This isn’t going to be as rich a sample space as all South Asians, there are caste, regional and socioeconomic biases. Within the next 5 years you’ll see a paper on South Asia just like this: European Population Substructure: Clustering of Northern and Southern Populations.

d) Please be cautious about taking comments like this literally:

The correlations are increased by using a linear combination of allele frequencies with ∼2/3 contribution from Europe/Middle East and ∼1/3 contribution from East Asia. At the same time, however, the separate cluster for India in population structure analysis indicates that allele frequencies in India are distinctive, so that predictions obtained based on European and East Asian groups cannot fully explain allele frequencies in Indian populations.

The “take home” message some get is that this means South Asians are 2/3 group A and 1/3 group B. That’s probably not what’s going on. It wasn’t the case that 10,000 years ago a Ur-European race and an Ur-Asian race got together in India and mated. Rather, South Asia is a crossroads in Eurasia, and it makes sense that the flow of genes would reflect influences from both the west and the east. You notice that populations in Eastern India show the biggest influence from East Asia, and populations from Western India show the biggest influence from West Asia. Geography matters!

Comments

  1. #1 manju
    December 22, 2006

    The study should have included/tested Y-Hgs and mtDNA-Hgs data also.

  2. #2 tamasha
    December 22, 2006

    Thanks for the recap – this is very interesting, but the article was way over my head.

  3. #3 razib
    December 22, 2006
  4. #4 John Emerson
    December 22, 2006

    It would strike me that a study within India sorted by caste would be most interesting. Are Brahmans and Dalits of a given ethnicity more like other Brahmans and Dalits of other ethnicities, or are Brahmans and Dalits of a given ethnicity more like each other? In India caste lines may be more important than ethnic lines.

  5. #5 milieu
    December 23, 2006

    Does this have any implications for the Aryan Invasion Theory? As I see it, this should serve to further weaken the cause of AIT.

  6. #6 razib
    December 23, 2006

    As I see it, this should serve to further weaken the cause of AIT.

    yes.

  7. #7 vic
    December 24, 2006

    “a study within India sorted by caste would be most interesting”

    wont happen
    The centraL govt has always suppressed studies of this nature in the past and shows nosigns of not suppressing in the near future.

  8. #8 Agnostic
    December 24, 2006

    wont happen. The centraL govt has always suppressed studies of this nature in the past and shows nosigns of not suppressing in the near future.

    You could study different diaspora populations, though. In the US, we mostly let the smarties, but iirc the S.Asians in Vancouver (and perhaps elsewhere in Canada) have a reputation for being more thuggish and not as likely to have professional parents. You could probably find some relatively unadmixed individuals in the Caribbean too.

  9. #9 razib
    December 24, 2006

    the people in mauritius, trinidad & fiji were mostly middle to low (more of the latter).

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