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South Asia harbors one of the highest levels genetic diversity in Eurasia, which could be interpreted as a result of its long-term large effective population size and of admixture during its complex demographic history. In contrast to Pakistani populations, populations of Indian origin have been underrepresented in previous genomic scans of positive selection and population structure. Here we report data for more than 600,000 SNP markers genotyped in 142 samples from 30 ethnic groups in India. Combining our results with other available genome-wide data, we show that Indian populations are characterized by two major ancestry components, one of which is spread at comparable frequency and haplotype diversity in populations of South and West Asia and the Caucasus. The second component is more restricted to South Asia and accounts for more than 50% of the ancestry in Indian populations. Haplotype diversity associated with these South Asian ancestry components is significantly higher than that of the components dominating the West Eurasian ancestry palette. Modeling of the observed haplotype diversities suggests that both Indian ancestry components are older than the purported Indo-Aryan invasion 3,500 YBP. Consistent with the results of pairwise genetic distances among world regions, Indians share more ancestry signals with West than with East Eurasians. However, compared to Pakistani populations, a higher proportion of their genes show regionally specific signals of high haplotype homozygosity. Among such candidates of positive selection in India are MSTN and DOK5, both of which have potential implications in lipid metabolism and the etiology of type 2 diabetes.

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Abstract

Central Asia has served as a corridor for human migrations providing trading routes since ancient times. It has functioned as a conduit connecting Europe and the Middle East with South Asia and far Eastern civilizations. Therefore, the study of populations in this region is essential for a comprehensive understanding of early human dispersal on the Eurasian continent. Although Y- chromosome distributions in Central Asia have been widely surveyed, present-day Afghanistan remains poorly characterized genetically. The present study addresses this lacuna by analyzing 190 Pathan males from Afghanistan using high-resolution Y-chromosome binary markers. In addition, haplotype diversity for its most common lineages (haplogroups R1a1a*-M198 and L3-M357) was estimated using a set of 15 Y-specific STR loci. The observed haplogroup distribution suggests some degree of genetic isolation of the northern population, likely due to the Hindu Kush mountain range separating it from the southern Afghans who have had greater contact with neighboring Pathans from Pakistan and migrations from the Indian subcontinent. Our study demonstrates genetic similarities between Pathans from Afghanistan and Pakistan, both of which are characterized by the predominance of haplogroup R1a1a*-M198 (>50%) and the sharing of the same modal haplotype. Furthermore, the high frequencies of R1a1a-M198 and the presence of G2c-M377 chromosomes in Pathans might represent phylogenetic signals from Khazars, a common link between Pathans and Ashkenazi groups, whereas the absence of E1b1b1a2-V13 lineage does not support their professed Greek ancestry.

humanbeing101

May 9 2012, 08:00 AM

But why most arabs have big round eyes and so do indians especially the ones in the south like south india and gulf arabs. Is that because of australoid and negroid admixture is high among them?

Oxy

May 9 2012, 07:41 AM

Indians are a mixture between a Caucasian type related to Iranians mixed with a local indigenous Ancestral South Indian substrate (often considered 'Australoid') which is relatively high in them 30-60% depending on ethnic group.

Regarding Arabs, they are related to Caucasians as they have origins from the Levant region, where the Neolithic started.
Arabids are essentially a more desert adapted variety of Armenoids. However, minor African admixture is present in many Arabs, but it is generally not higher than 10%.

humanbeing101

May 9 2012, 12:31 PM

So lets say an unmixed indian look identical to persians? And also unmixed gulf arab look identical to levant and iraqi arabs?

Oxy

May 9 2012, 07:41 AM

Indians are a mixture between a Caucasian type related to Iranians mixed with a local indigenous Ancestral South Indian substrate (often considered 'Australoid') which is relatively high in them 30-60% depending on ethnic group.

Regarding Arabs, they are related to Caucasians as they have origins from the Levant region, where the Neolithic started.
Arabids are essentially a more desert adapted variety of Armenoids. However, minor African admixture is present in many Arabs, but it is generally not higher than 10%.

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The Y-chromosome genetic structure of the Arabian Peninsula seems to be mainly modulated by geography. The data confirm that this area has mainly been a recipient of gene flow from its African and Asian surrounding areas, probably mainly since the last Glacial maximum onwards. Although rare deep rooting lineages for Y chromosome haplogroups E and J have been detected, the presence of more basal clades supportive of the southern exit route of modern humans to Eurasian, were not found.

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Results
Saudi Arabia differentiates from other Arabian Peninsula countries by a higher presence of J2-M172 lineages. It is significantly different from Yemen mainly due to a comparative reduction of sub-Saharan Africa E1-M123 and Levantine J1-M267 male lineages. Around 14% of the Saudi Arabia Y-chromosome pool is typical of African biogeographic ancestry, 17% arrived to the area from the East across Iran, while the remainder 69% could be considered of direct or indirect Levantine ascription. Interestingly, basal E-M96* (n = 2) and J-M304* (n = 3) lineages have been detected, for the first time, in the Arabian Peninsula. Coalescence time for the most prominent J1-M267 haplogroup in Saudi Arabia (11.6 ± 1.9 ky) is similar to that obtained previously for Yemen (11.3 ± 2) but significantly older that those estimated for Qatar (7.3 ± 1.8) and UAE (6.8 ± 1.5).

Crimson Guard

May 9 2012, 07:43 AM

Caucasians didnt originate in the Caucasus.

Ethbaal

May 9 2012, 01:21 PM

Are you saying that Arabids are desert adapted Armenoids because of the overwhelming J haplogroup within the Arabian population ? I understand that Arabids are physically close and attributed to Mediterranids in general.

Oxy

May 9 2012, 02:04 PM

Ethbaal

May 9 2012, 01:21 PM

Are you saying that Arabids are desert adapted Armenoids because of the overwhelming J haplogroup within the Arabian population ? I understand that Arabids are physically close and attributed to Mediterranids in general.

Yeah, J originated in a proto-Armenoid population.

Ethbaal

May 9 2012, 02:11 PM

Oxy

May 9 2012, 02:04 PM

Ethbaal

May 9 2012, 01:21 PM

Are you saying that Arabids are desert adapted Armenoids because of the overwhelming J haplogroup within the Arabian population ? I understand that Arabids are physically close and attributed to Mediterranids in general.

Yeah, J originated in a proto-Armenoid population.

Since when genetics is considered to correlate with phenotype ?