Wednesday, March 14, 2012

Afroasiatic Origins and the Afro-Dravidian Hypothesis

One collateral issue to the question of Afro-Asiatic origins discussed in two previous posts today (FWIW, those two posts and this one were mostly written about six months ago, but were awaiting final polishing and so didn't get posted until today), is the interrelationship between that question and the Afro-Dravidian hypothesis.

The Afro-Dravidian hypothesis argues that the Dravidian language is a derivative of an African language from the Niger-Congo family of languages, and that much of the cultural and technological packet associated with Dravidian culture has African origins. Frenchman Bernard Sargent is one of its principle advocates. I'm not entirely convinced of this hypotheis, but there is enough data to back it up to warrant giving the idea serious consideration, so I don't dismiss it out of hand either, as many do.

The linguistic evidence from within the Dravidian languages points to an origin of the Dravidian language of India around the time of the South Asian Neolithic ca. 2500 BCE. A few linguists have noted similarities between some Niger-Congo languages (particularly those on the Afro-Asiatic/Niger-Congo boundary area) and the proto-Dravidian language.

The crops used in early Dravidian agriculture were domesticated in and had their origins the African Sahel.

There are no meaningful African mtDNA traces in Dravidian South Asia that can't be attributed to events in the historic era, however, and the strongest outside Y-DNA signal, which coincides quite well with the locations of the proto-Dravidan society are rich in Y-DNA haplogroup T.

Given the fact that ancient peoples rich in Y-DNA haplogroup T were sailing the Red Sea and Indian Ocean from the Horn of Africa at the time, it makes sense that a male dominated group of people from the Horn of Africa might arrived on the east coast of India and bring new crops and technologies around 2500 BCE. Recent genetic profiles of tribal populations in India also support the inferrence that some of these populations may have genetic origins outside India in a time frame similar to that of the arrival of Indo-European and Austroasiatic food production and archeological cultures to India, rather than with the hunter-gatherers of India's deep indigeneous past. So, the fact that some of the high frequency Y-DNA haplogroup T populations in Indian are tribal populations doesn't necessarily contradict an Afro-Dravidian hypothesis.

The crops, technologies and potential linguistic links seem like a better fit to a Sahel agriculture, Niger-Congo language speaking people, however, than to a society that one might expect to be a Cushitic language speaking people then and there in what might have been the Kingdom of Punt or the Kingdom of Cush, which Y-DNA haplogroup T is currently common, and haplogroup T arguably looks like it has Egyptian or Mesopotamian origins, not Sahel African origins.

Why would people with overwhelming Egyptian/Mesopotamian patrilines speak a Niger-Congo language or be familiar with Sahel agriculture? Was Cushitic limited to areas further north at the time, and were Niger-Congo languages (driven by the expansion of Sahel agriculture) a layer present before Afro-Asiatic languages were in the Horn of Africa? Did ethnic Egyptians precede the Cushitic language in the sea trade of the Horn of Africa?

The "substrate" genetics of East Africa after one removes markers that look like Eurasian back migrations and also removes markers strongly associated with one or another Afro-Asiatic linguistic family, in uniparental and autosomal genetics, are distinctly East African and do not suggest prior genetic unity with West African populations prior to a very remote date (ca. 30,000+ years).

Another way to think about that fact is that East Africa has experienced at least two wave of Eurasian back migration. Sometime in the early Holocene (a period that bridges the Epipaleolithic and the Neolithic eras) associated with mtDNA haplogroups like M1 and U6. The other with the arrival of the Ethiosemitic languages. One plausible way to understand the spread of the Afro-Asiatic languages is to guess that it occured at the time of the early Holocene event. But, East Africa has a distinct genetic identity that predates either of these events and this identity is distinct from West Africa. West African sourced African genetics don't appear in East Africa until around the time of Bantu expansion into East Africa, contradicting the plausible thought that West Africans could have had notable demic influences on East Africa starting when the West Africans developed Sahel agriculture. (As Jared Diamond explains in "Guns, Germs and Steel", neither Sahel crops nor Fertile Crescent crops do well in the other's climate due to their differing seasonal patterns, although Sahel crops can do well in the monsoon climate of Southern India which has a seasonal pattern similar to the African Sahel.)

One possibility is that Horn of Africa people who could have brought the cultural package of Sahel agriculture to India may have themselves been recent recipients of that cultural package and experienced language shift in an early wave of Bantu, or pre-Bantu, expansion from West Africa, that was limited to a cultural/political elite and that the Niger-Congo language may have experienced similar linguistic trends to other languages on the Niger-Congo/Afro-Asiatic linguistic border like Swahili and some of the Niger-Congo languages spoken in the general vicinity of Senegal.


Anonymous said...

This article have no-sense. The known haplogroup T diversity in South Asia is too low.

Andrew Oh-Willeke said...

Low haplogroup T diversity in South Asia is exactly what one would expect if it arrived in South Asia ca. 2500 BCE with a single small group of men in the founding population (possibly including related individuals) carrying a Sahel agriculture package, rather than evolving there over a long period of time in situ, as an Afro-Dravidian hypothesis would suppose.

But, I'd love to have a source for the claim that haplogroup T diversity in South Asia is indeed low. I'd love to see published work on that point.

Andrew Oh-Willeke said...

Wikipedia's sources from the Y-DNA hg T article (many of which are not open access) are:

R. Trivedi, Sanghamitra Sahoo, Anamika Singh, G. Hima Bindu, Jheelam Banerjee, Manuj Tandon, Sonali Gaikwad, Revathi Rajkumar, T Sitalaximi, Richa Ashma, G. B. N. Chainy and V. K. Kashyap, "High Resolution Phylogeographic Map of Y-Chromosomes Reveal the Genetic Signatures of Pleistocene Origin of Indian Populations"

Anish M. Shah et al., ["Indian Siddis: African Descendants with Indian Admixture"] 2011

S.Sharma et al. "The Indian origin of paternal haplogroup R1a1* substantiates the autochthonous origin of Brahmins and the caste system"," 'Journal of Human Genetics (2009)

Clyde Winters "Y-Chromosome evidence of an African origin of Dravidian agriculture"," 'International Journal of Genetics and Molecular Biology (2010)

Vikrant Kumar et al. "Y-chromosome evidence suggests a common paternal heritage of Austro-Asiatic populations"

T. Kivisild et al. "The Genetic Heritage of the Earliest Settlers Persists Both in Indian Tribal and Caste Populations"

Sanghamitra Sengupta et al. "Polarity and Temporality of High-Resolution Y-Chromosome Distributions in India Identify Both Indigenous and Exogenous Expansions and Reveal Minor Genetic Influence of Central Asian Pastoralists"

Gunjan Sharma et al. "Genetic Affinities of the Central Indian Tribal Populations"]

K.Tangaraj et al. "Y-Chromosomal STR Haplotypes in Two Endogamous Tribal Populations of Karnataka, India"," 'American Academy of Forensic Sciences (2007)

G. Venkata et al. "Y-chromosome SNP haplotypes suggest evidence of gene flow among caste, tribe, and the migrant Siddi populations of Andhra Pradesh, South India"]

R. Cordaux et al. "Independent Origins of Indian Caste and Tribal Paternal Lineages"]

I. Thanseem et al. "Genetic affinities among the lower castes and tribal groups of India: inference from Y chromosome and mitochondrial DNA S1 "," 'BMC Genetics (2006)

Elise M. S. Belle et al. "Y chromosomes of self-identified Syeds from the Indian subcontinent show evidence of elevated Arab ancestry but not of a recent common patrilineal origin"]

Richard Cordaux et al. "The Northeast Indian Passageway: A Barrier or Corridor for Human Migrations?"," 'Society for Molecular Biology and Evolution (2004)

P. Majumder et al. "Ethnic populations of India as seen from an evolutionary perspective"]

Andrew Oh-Willeke said...

Consider for example, this language in the abstract of Sengupta (2006): "R1a1 and R2 haplogroups indicate demographic complexity that is inconsistent with a recent single history. Associated microsatellite analyses of the high-frequency R1a1 haplogroup chromosomes indicate independent recent histories of the Indus Valley and the peninsular Indian region. Our data are also more consistent with a peninsular origin of Dravidian speakers than a source with proximity to the Indus and with significant genetic input resulting from demic diffusion associated with agriculture. . . . Our reappraisal indicates that pre-Holocene and Holocene-eranot Indo-Europeanexpansions have shaped the distinctive South Asian Y-chromosome landscape."

Trivedi states at 402: "Haplogroup K2-M70 Haplogroup K2 occurs on a M9G background and is reported to occur in populations of Near East and Europe (Underhill et al. 2000). In our study, it was found only in the eastern and southern regions of the country, adding to an overall frequency of 3.1%.Although it was present in the three major linguistic families, the statistical difference in its distribution was insignificant. However, its distribution depicted an inverse relation as one moved up the social ladder, with the upper caste populations completely lacking the M70 lineage in their Y-chromosomes (Table 2a). This lineage was predominant amongst the lower caste groups of east (Bauri) and tribal groups of south, particularly Yerukula, contributing approx. 60% of the total K2chromosomes. Within the lineage, 36 distinct Y-STR haplotypes, with a very high mean pairwise difference (14.18) between them, depicted the absence of population structure due to language, geography or ethnicity." Trivedi found K2=T in Eastern India, while it was entirely absent in the Harappan area.

Mendez (2011) is closed access and in any event doesn't discuss the South Asian examples of the haplogroup in any depth.

Andrew Oh-Willeke said...

Core Mendez data here is suggestive of Semitic links in Y-DNA hg T.

European frequency map here.

See also: "K2-M70 is believed to have originated in Asia after the emergence of the K-M9 polymorphism (45–30 ky) (Underhill et al. 2001a). As deduced from the collective data (Underhill et al. 2000; Cruciani et al. 2002; Semino et al. 2002; present study), K2-M70 individuals, at some later point, proceeded south to Africa. While these chromosomes are seen in relatively high frequencies in Egypt, Oman, Tanzania, Ethiopia, they are especially prominent in the Fulbe 18%( [Scozzari et al. 1997, 1999])"

— J. R. Luis et al.: The Levant versus the Horn of Africa: Evidence for Bidirectional Corridors of Human Migrations (Errata), American Journal of Human Genetics, 74: 532-544. ;"

From here.

The history of Jews in India is not a good fit to the observed Y-DNA T distribution in India.

See also M.F. Hammer (2000) and Cruciani (2010) noting that T, L and R1b are descendants of K-M9, and that both T-M70 and R1b-V88 are probably back migrations from Asia to Africa.

noiln said...

Hypothesis Testing
Define Hypothesis, what is Hypothesis? Define Hypothesis Testing, null Hypothesis,