Study shows caste system has altered genetic makeup of Hindus

News of this study, conducted by a joint Indo-US research group comprising researchers at the Andhra University, Vishakapatnam, and the University of Utah in USA, has been published in the current issue of the reputed British journal Nature.

For long, researchers have tried to use genes and blood groups to track differences among Hindu castes but thisstudy, using unique genetic markers, is one of the first to show the deep and long-term impact of societal rules on the human genome, say experts.

Collecting blood samples from 250 unrelated men from 12 Telugu speaking populations spanning all the castes in northeastern Andhra Pradesh, the team — led by Lynn B. Jorde, a human geneticist at Utah, with Bhaskara B. Rao and J M Naidu at Andhra University — set about analysing them using the latest molecular tests at Andhra University, Vishakapatnam.

Rao, when contacted in Vishakapanam, said he is “reluctant” to comment on the implications and future impact of this study.

The researchers say they have found that in the genetic make-up of Hindus there is “greater divergence” between the upper and lower castes than between upper and middle or middle and lower castes.

In fact, the “genetic distance” between upper and lower castes is one and a half times greater than between upper and middle or middle and lower castes. Experts caution that the studyis limited to a specific region and therefore generalisations may not be accurate.

Using unique genetic markers, the researchers show that men tend to “stagnate” within the same castes while women have had more “mobility” between the castes which is probably a true reflection of what happens in society even today. Men of higher castes do regularly marry lower caste women but the reverse is still rather rare.

The results reflect a common social norm, of women often marrying into castes higher than theirs and ascending the social ladder. But men tended to stay in the castes into which they were born, says Jorde.

The researchers worked on certain markers found on the exclusively male Y-chromosome, thus managing to understand paternal ancestry with something passed only from one male to the next. Maternal ancestry, on the other hand, was worked out using mitochondrial DNA — something inherited only through the mother. The team then went about comparing DNA sequences of men of different castes,measuring and mapping variations in the same 400-base length of mitochondrial DNA segment and in the seven markers of their Y Chromosomes.

They found that men of closely ranked castes had higher similarities in the maternal components but in contrast there were few similarities between the maternal components of men in the higher caste such as Brahmins and those of lowestcontinued on page 9