December 21, 2010

Genetics of Maharastra (India)

Everything you wanted to know about the haploid genetics of Maharastra and did not know how to find out. I think this is how I'd best describe this new paper:


Maharastra is the third largest state of India by area and the second one by population. With its 96 million citizens it is larger than Germany and most other sovereign states by this value as well. It is universally known by its capital city of Mumbai (Bombay), the economic heart of India. The name Maharastra derives from the Maratha Empire, once a large Hindu state that rivaled with the Mughal Empire and kept European navies at bay.

Geographically Maharastra is divided into the western coastal strip, where Mumbai lays, and the vast flat inland, which makes most of the state. The natural divide are the Western Ghates, a mountain range that runs parallel to the coast. This duality is relevant when considering the genetics of the inhabitants. 

Two particular ethnic groups were sampled for this study: the Thakurs, an Adivasi tribe, and the Mahadeo-Kolis but other groups from previous studies were also used. Additionally comparison with neighboring states' populations was performed as well.


Mitochondrial DNA (mtDNA)

Fig. 2 (I do not need to agree with the ages suggested)

The dominant haplogroups are M2, M4a, R5a1a and U2'3'4'7'8'9 (specially U2 and U7). There is also some presence of other M, N and R sublineages. 

Importantly for the phylogeny, this paper reveals that:

The high resolution analysis at haplogroup and sub-haplogroup level identified a monophylacity of previously classified M2a and M2b subclades with a single coding as well as control region substitution and named as M2a'b (Fig. 2). This finding recognizes a sub-branch M2c and refines the defining mutations for haplogroup M2 [37], [39]. It is now defined by four coding and single control region mutations (Fig. 2). Similarly the finding of several branches in the background of haplogroups M4, R5, R8 and R30 has improved the resolution of mtDNA phylogeny of this region.

Of interest because of their West Eurasian connection is the presence of so many U sublineages, as well as W, suggesting, in my opinion, that these two lineages probably had a rather oriental origin, even if they must be considered West Eurasian clades (because of frequency and diversity). By contrast other Western lineages are not present at all and even the widespread HV only has one representative in this sample (HV3). 

Overall (table 1) West Maharastrans are most akin by mtDNA to the inhabitants of Gujarat and Karnataka and most distinct from Madhya Pradesh among bordering states. Instead the inhabitants of the interior show less marked affinities overall, being somewhat most akin to the people of Andhra Pradesh and Karnataka (both states of Dravidian language) but they also show less marked distinction in relation to Madhya than the coastal peoples.


Y-DNA

The dominant lineages are (table 2) H (8-75% depending on population) and R1a1 (0-48%). There is also substantial R2 (0-20%), J2 (0-27%), and L (0-29%). Also lesser amounts of F*, P* and R* were reported for some groups. East Asian lineages O2a and O3 were only detected in the Austroasiatic-speaking Korku tribe.

Furthermore some subdivision can be noticed along the East-West divide mentioned before:

Haplogroup H is much more common in the East (35-75%, after excluding the Korku) than in the West (8-23%).

Haplogroup R1a1 is instead more common in the West (26-48%) than in the East (0-31%).

R2 also seems somewhat more common in the West (4-20%) than in the East (0-20%, with only two populations really notable for this clade here: Maratha and Dhangar). 

J2 (which is mostly J2a) also appears more important in the coast (14-27%) than in the interior (0-15%). 

I don't see any clear geographic pattern in regard to L.

Overall, coastal inhabitants of Maharastra show also greatest affinity to Gujarat and Karnataka in the Y-DNA aspect. Those of the interior show the lesser distance with their Karnataka neighbors (table 1).

4 comments:

  1. A really interesting post Maju. A couple of points:

    "This finding recognizes a sub-branch M2c and refines the defining mutations for haplogroup M2 [37], [39]. It is now defined by four coding and single control region mutations (Fig. 2). Similarly the finding of several branches in the background of haplogroups M4, R5, R8 and R30 has improved the resolution of mtDNA phylogeny of this region".

    As I've said elsewhere, I think the phylogeny of mtDNA M, and probably N, still requires some work. I'd be especially interested in having someone sort out haplogroup M7 and possible relationship to the Australian/Melanesian Ms.

    "East Asian lineages O2a and O3 were only detected in the Austroasiatic-speaking Korku tribe".

    Showing that the O haplogroups and the Austro-Asiatic languages came from the east. I know we have both long agreed on that, but it's good to have yet more evidence.

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  2. Aren't M2 and M4 the mtDNA haplogroups found among the Adaman Islanders (beside their Y-dna haplogroup D)?
    Or does my memory betray me?

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  3. @Terry: essentially agreed, though I think that such corrections are much much more likely to happen in either rare small haplogroups or less investigated sublineages, as is the case with M2 subclades.

    @Wagg: Your memory betrays you. The Andaman lineages are M31 (a basal subclade of M) and M32 (derived from M32'56).

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  4. Ok, Thank you for the information.

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