Sengupta et al. (2006) makes an interesting comment about spread of Dravidian speakers.
A competing alternative model based on both archaeobotanical material evidence and colloquial agricultural terms, however, more parsimoniously postulates that early Dravidian has a epipaleolithic preagricultural heritage with origins near a South
Asian core region, suggesting possible independent centers of plant domestication within the Indian peninsula by indigenous peoples (Fuller 2003).
They associate Y-Haplogroup L1 with the spread of Dravidian speakers.
Though Y-Haplogroup L1 is present among both Dravidian castes and (most importantly) among Central Dravidian tribes like Koitor (Gond)s, they do not show homogeneous distribution across various agricultural castes in South India.
Also, then there is J2b with a strong presence in South India and which also has rather uniform distribution across castes.
However, R2 dominates agricultural castes (Kamma, Kapu, Reddy) of Telugu region. Also, in certain agricultural castes like Gounders in Tamil Nadu (Sahoo et al. 2006). Except H other haplogroups like, L1, R2 and J2b could be totally absent or present negligibly in some of the south Indian castes. From this point of view only haplogroup H could be associated with the spread of Dravidian languages. Though this can't be ruled out as studies have shown reduced diversity for this haplogroup in India though it is supposedly one of the oldest lineage. This probably can be explained by the scenario where the spread of agriculture increasing its numbers in the last 5000 years. The lineage might have experienced bottleneck in its tribal past.
According to Fuller(2006) agriculture in South India started around 3000BC in south-central Deccan area. I have already mentioned about a paper on spread of Dravidian languages by F C Southworth(University of Pennsylvania). The author proposes a model where Dravidian languages expand from Godavari basin as all the Dravidian branches ND, CD, SD-I,II are observed in that region.
The most important question is whether;
- Dravidian speakers really migrated from north-west of the sub-continent(from Indus valley) or
- was there a language in north-west of India/Pakistan that buffered Dravidian languages of central-south India and various languages of west Asia.
I believe in the latter scenario.
From, population genetics it is very clear that the farthest boundary that can be assigned to Dravidian lineages is east of Indus valley. The distribution of Y-Haplogroups west of Indus valley do not match with Dravidian speakers(H, L1, R2 and J2b).
But there has been speculations that some of the words in Dravidian languages could have been a borrow from west Asian languages (kudure = horse...supposedly a borrow from Elamite language).
Then there is Brahui question. Their presence in west of Indus valley has been taken as a proof for Dravidian speaking past of that region.
However, there are couple of things that I find rather strange about Brahui-s.
- Brahui-s were overwhelmingly herders until 20th century. However, Proto-Dravidian speakers at the best are considered farmers or at the worst pastorals. Therefore, there should have been higher chances that Brahui-s becoming sedentary farmers in a land that developed agriculture around 7000 BCE.
- Brahui-s share R2, L1 and H with Dravidian speakers(totally around 20%). No J2b.
These two exact facts could be used to construct the original urheimat of Dravidian speakers.
Some of the researchers have speculated about independent development of agriculture in south Asia. I would rather consider it as an west Asian extension brought about by J2b clan.
Mehrgarh farming regions around 7000 BCE were developed by J2b clan who later moved south and probably around 3500-3000 BCE brought agricultural knowledge to Dravidian speaking central Indian region. The Dravidian speakers whose major haplogroups were H, L1 and R2 now picked up the knowledge of plant domestication from J2b clan and started expanding through southern region.
However, few herder/pastoral Dravidians who didn't come across J2b clan probably moved to Indo-Iranian regions(Brahui-s as they are known now). Other north Dravidian family speakers like Kurux and Malto are still tribals who migrated to north-eastern regions.
I believe the major agriculture population during Harappan time could have been J2b in the present day Pakistan. Their language could have been closer to Elamite language.
It is said that Elamites did not have their own literary tradition and borrowed everything from their neighbours. Indus valley probably built by the people with the same illiterate cultural background. J2b is a good candidate for that.
Y-Haplogroup association with linguistic expansions:
Austro-Asiatic : O2a
Dravidian : H, R2 and L1
IE : R1a1
The language of Indus valley : J2b
Haplogroup association with languages:
Austro-Asiatic : Y-chromosome O2a
Dravidian : mtDNA M
IE : Y-chromosome R1a1
Religious symbol and Language groups or haplogroups:
phallic worship: Austro-Asiatic/Sino-Tibetan
Horse mounted deity: J2b/Dravidian tribes
Brahma and Vishnu: J2a, G2 (Sumerian/Semitic origins)
Spirits/goddesses: tribes/Dravidian tribes
male nature gods: IE speakers
1. The Eurasian Heartland: A continental perspective on Y-chromosome diversity (Wells et al. 2001)
2. A prehistory of Indian Y chromosomes: Evaluating demic diffusion scenarios (Sahoo et al. 2006)
3. 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 (Sengupta et al. 2005)
4. Agricultural Origins and Frontiers in South Asia: A Working Synthesis (Fuller 2006)
5. Proto-Dravidian Agriculture (F C Southworth)
Note: All the references are available online.