Again On Ancestral Echoes In Our Genes19/08/2001
WE had written earlier that the genetic evidence regarding the influx of people speaking and Indo-Aryan language is strong. New evidence from in-depth and extensive study done by a group of scientists, led by Michael Bamshad of Eccles Institute of Human Genetics, Utah, and others from Andhra University, Visakhapatnam, the Anthropological Survey of India, University of Madras, etc, (referred to here as the Visakhapatnam-Utah study) not only confirms the earlier genetic studies, but has brought another dimension to the genetic data. It establishes clearly that the Eurasian admixture is higher in the caste Hindu population and the Eurasian component reduces as we go down the caste hierarchy. Women, as a whole however, are closer to the Asians, though even here, the upper caste women have a larger Eurasian admixture. Obviously, the theory of elite dominance — the Eurasian influx either created the caste hierarchy or integrated itself at the top layer of an existing caste society — is reinforced by the study. Not surprisingly, the Hindutva lobby — Rajaram and company — are frothing at the mouth, with Bamshad being referred to commonly as “Badmash” in their Internet outpourings.
What does the Visakhapatnam-Utah study show? And what are the methods it has used to establish its results? How does genetic studies using current genetic data help us unravel the past?
Before we look at the methods that the above study has used, a quick summary of their data and results is in order. The study analysed the closeness of various caste groups to African, West Eurasian and Asian (East and South-East Asian) populations It also looked at specific genetic markers and worked out which groups had more Eurasian markers and which groups had more Asian genetic markers. The target group (various caste samples) was from an area around Visakhapatnam. The aggregation of caste groups was done using three broad categories: the “twice born” or the “upper” castes, the “middle” castes, and the “lower” castes. The striking feature of the results is that genetic markers, MtDNA inherited from the maternal side and the Y-chromosome data inherited from the paternal side, as well as data from bi-paternally inherited genes all independently show:
The current historical view is that a Dravidian influx took place, probably from the Fertile Crescent, about 9,000-10,000 years back while the Eurasian influx is about 3,500 years before present. The result of the Visakhapatnam-Utah genetic studies is consistent with this schema, though many more studies will have to be done before we can conclusively state that this is the pattern all over South Asia. Obviously, there is a need to replicate these studies for other areas as well.
How does genetic studies in the present population show any of the above, particularly the dating of such an influx? For this, we have to look at how the genetic code replicates itself and current genetic “distance” can be used to date past genetic events. Every time the DNA sequence replicates, there can be errors in the replication. These are mutations and can result in either the offspring’s chance of survival being lower or providing an evolutionary advantage. They could also be neutral, offer neither any advantage to their offspring. The major part of the DNA sequence, about 99 per cent, is what is known as junk DNA. No known function can be ascribed to these areas. Thus, most of the changes or errors in the replicated DNA sequence are neutral and do not offer any evolutionary advantage or disadvantage. This makes them ideal for studying genetic flows and drifts as the population frequency of such genes do not get distorted due to higher or lower survival of the offspring due to other reasons such as evolutionary fitness. If we measure the genetic variations between various groups, the larger the difference in the DNA sequence, more the chance that these groups have separated earlier from each other. If the variations are low, the groups are presumed to have split only recently. The rate of change in the DNA sequence can then be used as a form of biological clock and used to work out the history of such splits. Thus the genetic distance between two sets of populations is in some measure an indicator of the time of separation of the population groups. This is how we date that the human population split from the gorillas earlier than from the chimpanzees. This method can also be used for any two groups – either similar or dissimilar to work out the past history of the groups.
The second part of the use of genetics is using maternal or paternal genes. Every cell has a cell nucleus and cytoplasm surrounding the cell nucleus. The nucleus contains the human DNA, which is inherited from both the father and the mother. However, the cytoplasm contains Mitochondrial DNA or MtDNA. Mitochondrial structures convert sugar and oxygen in the cell liberating energy that runs the cell. They are thought to be ancient bacteria that took up residence in the cell, and as a consequence carry their own DNA. The important property of MtDNA is that they are inherited solely through the mother and therefore we can trace back generations without worrying about mixing of paternal and material genes. Thus Mt DNA studies tell us about maternal inheritance in an unbroken line of mothers back to antiquity.
To know about the paternal side, we study the changes in the DNA sequence of the Y-chromosome, which is inherited exclusively from the father. The X-chromosome of the child can be from either the father or the mother. If the child has two chromosomes as XX, then the gender of the child is female. If it is XY, then the child is a male. The father’s contribution determines the sex of the child and not the mother’s. As the X chromosome contain material from both the paternal or the maternal side, as also DNA sequence from any other chromosome, the Y-chromosome is the only one that can be used for looking at paternal inheritance. Irrespective of the length of time, there is continuity in the record of our parents, in the mitochondrial or in the Y-chromosome record. We can know details of our forefathers or foremothers using these two genetic trails.
The Visakhapatnam-Utah study examined both these genetic trails. They also looked separately at a large number of genetic markers that have been inherited from both sets of parents (bi-parentally inherited), thus creating three relatively independent data sets. The results of all the data sets substantiate that the lower castes are genetically closer to the Asian population (East Asian and South East Asian) while the higher castes are closer to Eurasian stock. The middle castes fall somewhere in the middle. The other interesting part of the result is that within the European stock, the higher castes are closer to East European stock than Western or Northern Europe. However, the women are found to be closer to the Asian than the Eurasian stock, though here again the higher caste women have a higher admixture of Eurasian genetic markers.
The results support that there was an influx of Eurasian people well after India was populated from Africa and later from the Fertile Crescent, the original centre of agriculture. It also shows that this layer integrated itself in society at the highest level. The male population had little vertical mobility and that is why the genetic make-up of the castes differs so significantly on the paternal side. The maternal side shows that there was larger vertical mobility and women could marry “up”. This explains why the women as a group are closer to the Asian population; even the higher caste women are closer to the Asian population than their male counterparts.
There are two issues that the above study does not show. It leaves open the question whether the people from Eurasia established the caste system or only took over an existing system by integrating themselves within the highest layers. It also does not clarify what was the culture or language of these people. Though the authors have argued that a larger influx of men than women took place, an alternate explanation could be that with polygamy and the dominance of the new Eurasian people, they would leave a much larger number of offspring in the population. Of course, this would mean that they would take wives from the existing local population also. All this is in consonance with the current view that the Indo-European language group came to India from Central Asia with a set of people who established elite dominance by virtue of the horse and the chariot and the consequent military superiority.
MYTH ABOUT CASTE SYSTEM EXPLODED
One of the tenets of the conventional Hindutva lobby is also effectively exploded with this evidence. The Hindutva lobby offers as a defence of the caste system that it was not originally based on birth but on the “nature” of the individual. It is now clear that the castes were reflection, very early on, of existing stratification. Men could not marry up the caste ladder though the women could. And it had to more to do with the historical origins of the caste groups than the nature of the individuals as claimed.
The study is not a conclusive proof that this is the record that we are likely to find everywhere else also. However, if we find that caste variations are so strongly related to Eurasian or Asian stock around Visakhapatnam, the chances are that studies in North India will broadly reinforce this picture. Partha Majumder, whose studies were similar to the Visakhapatnam-Utah study, (we have quoted his results earlier) has pointed out the need for more such studies and shown that not all groups in a given caste have the same origins. However, the genetic studies are a striking re-affirmation of Iravati Karve and D D Kosambi’s views on the formation of castes in India. No wonder, Rajaram of the fraudulent Harappan horse seal fame has talked about imperialists, Marxists and Dravidians all ganging up together against presumably the true Indians. Rajaram’s criticism of Bamshad results are interesting as he lumps Dravidian politicians also as a part of the Marxist imperialist conspiracy. Perhaps it is not entirely co-incidental that some of the scientists in the study are white and the rest Dravidians. No wonder these results, according to Rajaram, are biased. The Dalits of course do not figure in the Hindutva discourse: they are after all the outcastes.
The historical model that best fits the genetic studies is that there was a physical influx of people carrying Eurasian genetic markers. New genetic markers arose in South Asia after this influx, which are not found in any significant numbers outside South Asia. The evidence against an efflux is therefore quite strong. The Indo-European language family in India is a likely result of this Eurasian influx. If India is the home of the Indo-European language family, then there should be evidence of people carrying the specific genetic markers that are found here in much larger numbers all over regions that speak the Indo-European languages. The frequency of these markers should dwindle greater the distance from the source. The gene frequencies do not bear out this picture and the chances of its origin being South Asia is unlikely. This is no longer a matter of belief. Clear statistical and genetic studies now exist to work out the direction of genetic flows.
The number of people of Eurasian stock, who came in, need not have been very high. However, they have left significant genetic evidence amongst, particularly the higher castes. Though this evidence needs to be substantiated from other regions and with more data, the results are in consonance with the broad archaeological and linguistic evidence.
The RSS project of disenfranchising the minorities requires that Sanskrit and the Vedas should be indigenous in origin. If the Muslims were only a later set of invaders from the earlier ones who propounded the Vedas, it creates immense difficulties. Their version of history has to have only one schema, the Hindus as indigenous and all others as invaders. History is to be held prisoner to the hate project of the RSS. Unfortunately for them, history cannot be so easily straitjacketed. No wonder the RSS is more comfortable with karmakanda and astrology; they, unlike science, do not spring such surprises.