Signal of Indo-Aryan admixture in South Indian Brahmins

By Razib Khan | September 29, 2012 12:59 am

I’ve mentioned a few times that the Reich lab has been finding suggestive evidence for admixture between indigenous South Asians and a West Eurasian group on the order of ~3,000 years before the present. The modal explanation is probably an Indo-Aryan intrusion. Dienekes used rolloff in ADMIXTOOLS to repeat these general findings. Specifically, he found signal for an admixture event analogous to one between non-Brahmin South Indians and Northern Europeans. I say analogous because I do not mean to imply that the admixture was exactly of this form. Rather, there are general resemblances in the genetic profiles across the four groups (i.e., Orcadian & North Kannadi, and population X and Y which merged to form South Indian Brahmins).


The only thing I would add is that the North Kannadi, representative of non-Brahmin South Indians, are themselves a mixture between West Eurasian and an indigenous South Asian population. And, looking at the patterns of admixture in Harappa, it seems to me that South Indian Brahmins themselves have some admixture which postdates their arrival to South India, which is probably 1 to 2,000 years before the present. In the specific case of South Indian Brahmins my model would be:

1) West Asian + Ancestral South Indian = Population A

2) Population A + Indo-Aryan = Population B

3) Population B + Population A [South Indian] = South Indian Brahmin

I would weight the first admixture event heaviest, and the two second ones of approximately equal strength. Though the third is a secondary admixture, and so I wonder if the signal would be obscure.

CATEGORIZED UNDER: Human Genetics, Human Genomics
MORE ABOUT: Genetics, Genomics
  • Grey

    I imagine the first farmers initially expanding either on foot with mostly flocks or on boats with mostly seeds (generally speaking) interjecting themselves among HG populations on limited sites which were both good defensively and where their agricultural package was viable (and along coasts even where it wasn’t viable alone).

    The spread of a cavalry culture would have to come after cavalry-sized and numbered horses became available at some later time being particularly significant in places where everyone using horses would increase their net food-getting capacity as opposed to those places where keeping horses specifically for cavalry literally ate into their net food-getting.

    The places where everyone used horses would then have a significant latent military advantage any time the people in those places united in one gang – at least within the logistical range where large cavalry armies and all their spare horses could be supported at the time (protecting western europe and southern india a bit maybe?)

    In terms of your model i’d see the first farmer types spreading out from Anatolia down through Iran and/or fertile crescent (i personally wonder if they were blocked by the locals at the Indus valley and mostly spread around them via the coast) or Indus valley plus the coast. Either way the south would become coastal farmer / fisher settlements with a native HG interior that mix over time.

    (Time is the critical element imo. If the first farmers could have spread all over without any blockage i think they would have and almost everyone would be descended from them.)

    Then later you get the scary horse guys arriving in North India and smashing things up giving the second mix. Later again kingdoms containing a significant proportion of scary horse guys push south in a step-wise fashion with the proportion diminishing with each step south giving the third mix.

  • https://plus.google.com/109962494182694679780/posts Razib Khan

    Later again kingdoms containing a significant proportion of scary horse guys push south in a step-wise fashion with the proportion diminishing with each step south giving the third mix.

    brahmins sound of the vindhya are pretty much the same. there’s no cline that i see. so it seems like the ashkenazi jews: early admixture => later radiation.

  • Grey

    yeah i wasn’t thinking admixture (at that level) so much as

    Stage 1) Cavalry army, 100% population A invade terriotory of 100% population B and say for the sake of argument the end result is 40/60 (not admixed yet, stratified).
    Stage 2) Army now 40/60 (A cavalry and B peasantry) invade second population B further south with end result say 20/80 (stratified at the top).
    Stage 3) Army now 20/80 (A cavalry and B peasantry) invade third population B further south with end result say 10/90 (stratified at the top).
    etc

    Or looking at it another way as an army of
    - officers
    - ncos
    - grunts

    With class-based assortative mating generally the admixture would either be at the same level i.e. grunt-grunt, nco-nco, officer-officer or (generally male-mediated) downward i.e. officer-nco, officer-grunt, nco-grunt so if population A becomes the whole officer class then there is no assortative admixture with population B at that level, only downward.

    Say initially you have
    - A senior officers
    - A junior officers
    - A ncos
    - A grunts

    After stage 1 you might have
    - A senior officers
    - A junior officers
    - A NCOs
    - AB grunts

    After stage 2
    - A senior officers
    - A junior officers
    - AB NCOs
    - ABB grunts

    After stage 3
    - A senior officers
    - AB junior officers
    - ABB NCOs
    - ABBB grunts

    (Basically i think admixture models might vary between conquest and infiltration scenarios – for want of a better word to describe farmers hopping from defendable site to defendable site among a sea of HGs – with the first event in your model being an infiltration scenario and the second a step-wise conquest scenario.)

  • Wasil ibn Ata

    I wonder that the lower types would be the first to admix with the conquered. It’s seemingly what the Romans did; but, isn’t it more likely that, to pacify the conquered, the nobles would marry the conquered nobles?

  • Samuel

    “Basically i think admixture models might vary between conquest and infiltration scenarios – for want of a better word to describe farmers hopping from defendable site to defendable site among a sea of HGs – with the first event in your model being an infiltration scenario and the second a step-wise conquest scenario.”

    It would be interesting to see if they could look at mitcochondrial DNA and y-chromosome DNA to try to differntiate between these two because I believe a common pattern in conquest scenarios is for the conquering men to marry the conquered women and eliminate the conquered men.

  • https://plus.google.com/109962494182694679780/posts Razib Khan

    #5, south asian Y tends to be more west eurasians, south asian mtDNA more indigenous south eurasian.

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

ADVERTISEMENT

See More

ADVERTISEMENT

RSS Razib’s Pinboard

Edifying books

Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »