Monday, September 28, 2009

Out of India - I

As new studies are coming up in the field of population genetics, it is becoming increasingly apparent that, while cultural identity may have been the preserve of males, genetic identity is determined by females. The reason can be very simple. Once colonized the matrilineages stay put even when the patrilineages change.

mtDNA and autosomal analysis:
Considering the fact that in most part of the old world mtDNA is around 50000-40000 years old, it's no wonder that all the later male sweeps in the last 3000-4000 years would hardly leave any genetic imprint in the population except for their Y-chromosomes. One of the visible proof is is the looks (physical shape) of the population that I have already discussed before.

- In the case of Austro-Asiatics in India, even though male lineage Y-chromosome O2a predominates, they look like Indians than SE Asians mainly because of their Indian matrilineages.

- In the case of Finnish, even though male lineage Y-chromosome N1c predominates, they look like Europeans than East Asian mainly because of their European matrilineages.

- In the case of Cameroonians, with a high percentage of Y-chromosome R1b, they look entirely like Africans than Europeans mainly because of their African matrilineages.

But considering the fact that New World fairly recently colonized (around 15000 years), the genetic diversity is very low compared to the old world colonizers who moved there in the last 500 years or so, we may see some strong presence of old world genetic imprint in their autosomal analysis.

But this can never be the case in the old world itself. Here, over time the native matrilineages assert themselves and this could be observed in autosomal analysis.

Ancient Indian Females:
A recent study, "Reconstructing Indian Population History", rather beautifully illustrates the ancient migrations of Indian matrilineages. It has found two distinct components, Ancient North Indian(ANI) and Ancient South India (ASI). The distinction was made by comparing the markers with Europeans, North Africans and West Asians. ANI is observed among those groups and ASI is restricted only to India. Though in India both ANI and ASI are found mixed in population.

This interesting observation reinforces the fact that all the West Eurasian (North Africa, West Asia and Europe) matrilineages were ultimately derived from an Indian macro haplogroup mtDNA R. With this study we can even confirm that, one of M lineages, M1, which is found mostly in Mediterranean region was also part of the migration from India.

The researchers make one more observation that Onges, one of the Andaman tribes, are sort of close to ASI. We do know that Onges' Y-chromosome is exclusively Y-Haplogroup D, found mostly in Tibet and Japan but their matrilineage is M31a, found mostly in East India or S E India. This is another case where matrilineage asserting itself (through autosomes) over patrilineage.

The evidences till now appear to support the old model of northern migration route instead of now popular the coastal migration. I have already argued the more the barrier the greater will be the need to migrate for Homo Sapiens before the advent of new technologies. Thus the coastal migration is not a viable hypothesis. Therefore, in my opinion, there were two groups, one in East and the other in North India (that moved from East) that later colonized whole India(or South Asia). The northern group is also responsible for West Eurasian matrilineages though the latter's patrilineages(like R1, E1b1b) might have later swapped the original patrilineags. Even then Y-Haplogroup J (aborigine West Asian), Y-haplogroup I (aborigine European) are sort of closely related to Y-Haplogroup H (aborigine Indian). However, all their matrilineages are descendents of Indian mtDNA R(H, U, JT) and mtDNA M(M1).

Genetics does not consider a standard trait as the original trait. It considers various genotypes of a single trait as the pre-existing condition and any single genotype as a clue for bottlenecks. However, pseudo-science like anthropometry makes the mistake of considering standard look and derived look by admixture. By anthropometry, Indians are measured in terms of standard looks of Australian aborigines, SE Asian (so-called) Negritos, Europeans and Mediterraneans.

But when it comes to autosomes, we can see that diversity creates few standards (because of bottlenecks and isolation) and not popular myth (part of Anthropometry) that the admixture creates diversity (which could be observed only in Y-chromosome haplogroups which themselves change so rapidly to leave any genetic footprint in a population).

Now considering the fact that these so-called standard populations' matrilineages are but a subset of Indian matrilineages, we can argue all those standard looks are subset of Indian diversity. Those are all bottlenecked population.

By population genetics, I would think present day stereotypical Homo Sapiens looks could be attributed to the two main components.

1. African
2. Proto-Asian.

Prot Asian could be further divided into:
1. Indian
2. Bottlenecked Proto-Asian (East Asian)

Whereas the Indian looks could be found in South Asia, the bottlenecked looks derived from Indian looks (or could be from Proto-Asian thro' northern route hypothesis) could be found among:
1. Australian aborigines
2. SE Asian aborigines
3. North African and West Asian
4. European

1. Razib's Gene Expression.
2. Maju's Leherensuge.
3. My anthropology discussion forum.


Maju said...

Hi, Manju.

...while cultural identity may have been the preserve of males, genetic identity is determined by females.

I guess I can agree with this somewhat but the sentence is too categorical, it should be more prudent.

I'd say that, in most cases, mtDNA (matrilineages) represent better the overall genetic ancestry than Y-DNA (patrilineages) do. My rule of thumb (not scientific but can be a good approximation) is: 50% correlates with mtDNA, 25% with Y-DNA and the rest is variable. Or if you wish to "determine" it, then 2/3 and 1/3 maybe. It's not like you don't see more or less vague Mongoloid traits among Finns but as the overall East Asian, or rather Siberian, apportion in the genome is like 12% (this shows up in autosomal DNA studies), it's almost invisible (minority traits are not usually noticeable in "octoroons").

A recent study, "Reconstructing Indian Population History", rather beautifully illustrates the ancient migrations of Indian matrilineages. It has found two distinct components, Ancient North Indian(ANI) and Ancient South India (ASI).

I read about it though haven't got access to the full paper. Initially I commented briefly at Leheresuge, suggesting that ANI and ASI would both be "native Indian" and diverged after the OOA, thinking that ANI would have spread from India into West Asia some 50,000 years ago. But later I saw some information at Dienekes' that made me change my mind: following the genetic distance tree, that model would be impossible. Dienekes' ideological explanation that ANI was reintroduced to India with Indoeuropeans doesn't seem to fit either but, if ANI is in fact a Neolithic flow from West Asia, then it fits pretty well.

What do you think?

Maju said...


Then, another thing on this post that called my attention is that first you argue that the coastal migration model is dead and then you argue for Indian-derived looks everywhere, which are best explained by the coastal migration model.

I know that Ren is adamant of Y-DNA NOP being some sort of North Asian lineage but in fact there's nothing that would support that idea, specially when P looks original from South Asia and NO from SE Asia (sensu lato, including southern China). Q and N would have expanded by the North but they also have southern presence, and anyhow they belong to a late moment of Eurasian expansion. NOP is in fact almost impossible to pick apart from K anyhow: only one mutation separates both nodes, so their expansion should have been virtually the same. Also there are no mtDNA lineages that could be paralleled to NOP, much less if we follow the North Asian hypothesis, but there are some that can be correlated with Q and N as separate and younger lineages.

Also you claim that East Asians are "bottlenecked proto-Asians" but AFAIK there's only one study (or maybe two but very similar) that argues for an East Asian "bottleneck" and that bottleneck is also detected in the other Eurasian study group: Europeans. So my guess is that, if there's anything to that, it's a bottleneck (rather founder effect probably) that affected all Eurasians: the very OOA founder effect surely. So Indians would also be similarly "bottlenecked", though these studies ignored them.

IMO, there was a proto-Asian population indeed, soon splitting in West and East (West here meaning South Asia), and then also into Australasians and other minor groups (Negritos). Then West Eurasians formed by geographical separation from South Asians (and this must be the ANI/ASI point of divergence) and then Amerindians diverged from East Asians. But I am not persuaded that East Asians are particularly "bottlenecked" anyhow: they have huge mtDNA diversity and even more Y-DNA one. They may be second to South Asia in mtDNA diversity but they are close anyhow.

From what I gather from mtDNA: at first the South Asian and East Asian groups interacted quite intensely (there's no other way to explain the distribution of M, N and R) and later instead they became rather isolated from each other, more or less when the West Eurasian colonization began.

Well, my thoughts anyhow.