Cordaux et al.(2004) study of Indian caste population observed that Indian caste and Tribal paternal lineages have independent origins. And went on to declare that most of the Indian castes(Note: In the genetic studies castes include Dalits explicitly under "lower castes") paternal lineages were infact derived from Central Asian migrations around ~3500 years ago(spot on for AIT period). Whereas, majority Tribal male lineages derived from original settlers of India. Of course, all the central Asian migrants in North and South basically spoke IE languages.
Then we have the admixture analysis. Here the authors found that, North Indian castes have 88% non-Indian contribution and 12% Indian contribution. South Indian castes have 68% non-Indian contribution and 32% Indian contribution. Tribals have 71% Indian contribution and 29% non-Indian contribution. Interestingly, South Indians with 32% non-Indian contribution lost their IE tongue adopted indigenous Dravidian languages.
Now, as with Bamshad et al(2001). study(I intend to discuss this study later) discussions of this prematurely conceived differences in North and South castes takes racial overtones even here. In the first place, what was the need to account for homogeneity of North Indian castes and admixed South Indian castes(of course according to Cordaux et al.). Because these studies all initiated with that clear motivation and just could not digress from that point of view. These researchers read and interpret everything to fit their prejudiced mindset. I'm going to talk one of those. In the research, they have used a reference to come up with their theory how racial purity and admixture reflected in North and South Indian castes respectively.
Of course, Richard Cordaux did not know much about Indian society. So he went and read articles written on Indian caste system. He came across an article written by Dr. Partha P. Majumder. Something catches his eyes,
The Aryan world comprised three classes (varnas): priests, nobles, and commoners. Aryans as the conquering people possibly placed their three classes on the indigenous Indian society. The varna organization is hierarchical. Initially, the system had names for two ranks, Brahma (Brahmin) and Kshatra (Kshatriya), Brahmin being of a socially higher rank than Kshatriya. The third rank was made up of Vis, that is, all the subjects. To this society, a fourth rank was added: Shudra, who had no rights to Aryan ritual. In southern India, the menial workers, the so-called "untouchables", were placed in a new varna, Panchama (meaning fifth).
Note : Let' s forget about Aryan invasion and imposition of caste system theory of Dr. Majumder. As that tells even the Shudras were not part of Aryan society but Cordaux et al. study thinks they were part of Aryan society as you see later. Anyway, I am not sure if it was invasion or migration. However, I don't think it has anything to do with our caste system as we know today.
The last in line the above quote is important for our discussion. Here, Mr. Cordaux found a perfect place for all those indigenous lineages among Dravidians in the caste system. Discussing about limited genetic flow between North Indians and tribals and pronounced genetic flow between South Indians and tribals he reasons,
A possible explanation for this geographic discrepancy is that the caste comprised four classes in north India, whereas a fifth class was introduced in south India to integrate local] people (those formerly called “untouchables”) in the caste system [19, 20].
Ergo, the so-called untouchables have to be included in the caste society in South India as fifth class, whereas in North India there were only four classes(because they didn't have indigenous population problem).
Let's see Indian caste composition.
Contrary to Mr. Cordaux's North India and South India societal variations, the Indian society was much more complex. First of all, there were no four classes in South and even in East but only two, Brahmins and Shudras(Check out this Caste System in Bengal, article written by a Bengali Brahmin who traces his lineage back to 10-11th century almost coinciding with the introduction of caste system in Bengal; He surely knows the story!) . Second, he says there were only four classes in North India; then how come there are so many Dalits in Vedic Punjab and Gangetic Uttara Pradesh, Bihar easily outnumbering Dalit populations of South India? Does he mean to say, in South India Dalits were included in the caste system as fifth caste but in North India they were excluded from the society. That would be the biggest irony of caste system in India. So if Untouchability was a phenonmenon because South Indians were admixed, how come so many people were declared untouchables in North India. Let's not even talk about how many millenniums passed after the entry of "Aryans" and the creation of caste system with Shudra and Asprishya hierarchies.
When I brought this to Dr. Partha Majumder's notice, this is what he had to say;
I never mentioned that the fifth varna originated in south India; just that it was called as Panchama in south India. Many scientists working on Indian populations have limited understanding of our historical social structure. Therefore, genetic findings vis-a-vis the social structure of India are sometimes incorrectly interpreted.
However, the problem is not only many of Geneticists of European descent are ignorant of Indian historical social structure, they are arrogant enough to make ridiculous conclusions out of it.
Cordaux et al. study has too many speculations about Indian society and weird logic about indegeneousness of various Haplogroups(as the later studies hardly confirm with them). However, I don't want to lose the opportunity to come out with my own theory how untouchability spread in India.
Blame it on Shankara:
If the untouchability was in fact South Indian phenomenon, then we need Brahmins to go to North(and everywhere) to introduce it in those societies. However, Brahmin movments were always from North to South. So common sense tells us unless any of the societal distinctions were there in North-West India(origins of endogamous Brahmin community), then you would hardly find them in South India. Any salient feature of South Indian society needs some kind of celebrated migrations from South for their introduction in North, West and East India.
And I find the only person who could do that was Shankara who travelled to all directions in India. Therefore, the untouchability that was introduced in South India went to North India along with him.
I hope just like "Indra stands accused" my "Shankara stands accused" becomes famous.