Society DNA: Study reveals people's caste shows in their genes but sceptics remain doubtful
The Hindu caste system is showing. On people's genes, of all things. For the first time, a motley band of scientists has found that the caste system practised for thousands of years among India's Hindus is beginning to reveal its impact on modern DNA.
Curiosity among scientists has always been high about whether traditional social patterns followed for centuries can show up in the twisted spirals of one's DNA. A recently-published study in the prestigious British journal Nature says yes.
Not just that, the study has also found a genetic explanation for what sociologists have known for years: that women have been more upwardly mobile than men, marrying men of higher castes and moving up the social ladder.
In a collaborative effort, scientists from Andhra University (AU) in Visakhapatnam teamed up with American scientists seven years ago to collect blood samples from 250 individuals of a dozen different castes in Telugu speaking districts of north-eastern Andhra Pradesh.
B. Bhaskara Rao, who teaches and researches anthropology at AU and Lynn B. Jorde and Michael Bamshad from the University of Utah in the US led six other scientists to figure out differences in the DNA of people from different castes. The Americans created a molecular genetics laboratory at AU and the rest is now global news.
The sceptics are calling their findings dangerous, sinister research. If the DNA of a Shudra is different from that of a Brahmin, social scientists worry that it won't be long before concepts like "my DNA is better than yours" begin to take root. That would be misinterpreting such research.
"Genetics does not differentiate between castes, these are purely human demarcations," says Sher Ali, chief of molecular genetics at the National Institute of Immunology (NII) in Delhi.
Yet, human impositions of caste could have brought change - like mutations in the DNA of generations of a less fortunate family constantly buffeted by disease and poverty. With caste being a touchy subject, it might be important, like Ali says, "to look at such research in a healthy way".
To those who view it the "healthy" ' way, the research has been exciting. it "Novel thinking" is what Partho Majumdar, a statistician with the human genome diversity unit of the Indian Statistical Institute, Calcutta, calls the study.
"Given what we have always known about ethnography (the study of social groups), these predictions might hold good," says Majumdar. Working with blood groups and genes, researchers across the world have tried to track down differences between various Hindu castes.
But most admit the Bamshad-Rao study is one of the first to actually show the impact of social roles on human DNA. The study has also shown how Hindu women have managed greater social mobility than men.
"Our data indicate that men tend to remain within the caste in which they were born," says Bamshad of the Eccles Institute of Human Genetics at Utah. With women marrying more often out of their own caste, there seems to have been a lot of movement of genetic material between different castes and probably between more closely related castes.
The scientists have used this fact to suggest that it is this female mobility that has shown up in the spirals of people's DNA. Bamshad is clear that these female genes moving upwards are what have stratified the Hindu caste system, at least in genetic terms.
But why Hindu castes? "Because the system has been long-standing, consistent and affecting a large section of people," explains Bamshad. Apparently, it is a hot favourite with anthropologists and geneticists worldwide, an ideal model for such studies.
"Caste hierarchies do exist in other Asian populations but nowhere is the system so formalised and complex as in India," says Bamshad. After identifying their sample, the researchers went about their work. They picked up two kinds of DNA from each of the 250 men who formed their sample.
One from the Y-chromosome - an exclusively male sex chromosome that a father passes on to his son. The other, from the mitochondrion, the human cell's powerhouse which is the hub for respiration, is called mt DNA as it is solely passed on from a mother to her child.
Gene kits were used to extract this DNA, which was then amplified and analysed. Markers were then used to read the secret language encoded in those twists of DNA. The analysis done, Rao and Bamshad found the results told an intriguing story.
The genetic distance - an index they used to study DNA patterns - between lower and upper castes was nearly twice that between lower and middle castes. This is where they feel women have managed to play a role: marrying out of caste and spreading their DNA wide.
Sociologists have said all along that even in the rule-ridden mating system where the 3,000-year old Hindu caste system has controlled marriages, women have managed to stay more mobile than men. They also found that men of castes close to each other on the social ladder showed similarities in mt DNA.
Also, mt DNA of the highest caste, the Brahmins, had few similarities with lower caste DNA. But Rao is a cautious man: "Ours was a purely scientific study using markers and we now need to look beyond." Caution is perhaps in order, with some people terming such research avoidable. But is it?
Not really. "It has a direct bearing with assessing how susceptible specific ethnic groups are to certain diseases," Ali points out. He explains that some populations are more prone to specific genetic disorders and diseases and such research could help with its knowledge base.
Take the Parsis, for instance. In this inbred community of generally good-looking people, genetic anomalies are very common. They could do with sound, gene-based information that could be packaged into pre-marital counselling.
In a country where arranged marriages are common, such information could make sense. Also, with science growing all the time, such research cannot be ignored.
Curiosity among scientists has always been high about whether traditional social patterns followed for centuries can show up in the twisted spirals of one's DNA. A recently-published study in the prestigious British journal Nature says yes.
Not just that, the study has also found a genetic explanation for what sociologists have known for years: that women have been more upwardly mobile than men, marrying men of higher castes and moving up the social ladder.
In a collaborative effort, scientists from Andhra University (AU) in Visakhapatnam teamed up with American scientists seven years ago to collect blood samples from 250 individuals of a dozen different castes in Telugu speaking districts of north-eastern Andhra Pradesh.
B. Bhaskara Rao, who teaches and researches anthropology at AU and Lynn B. Jorde and Michael Bamshad from the University of Utah in the US led six other scientists to figure out differences in the DNA of people from different castes. The Americans created a molecular genetics laboratory at AU and the rest is now global news.
The sceptics are calling their findings dangerous, sinister research. If the DNA of a Shudra is different from that of a Brahmin, social scientists worry that it won't be long before concepts like "my DNA is better than yours" begin to take root. That would be misinterpreting such research.
"Genetics does not differentiate between castes, these are purely human demarcations," says Sher Ali, chief of molecular genetics at the National Institute of Immunology (NII) in Delhi.
Yet, human impositions of caste could have brought change - like mutations in the DNA of generations of a less fortunate family constantly buffeted by disease and poverty. With caste being a touchy subject, it might be important, like Ali says, "to look at such research in a healthy way".
To those who view it the "healthy" ' way, the research has been exciting. it "Novel thinking" is what Partho Majumdar, a statistician with the human genome diversity unit of the Indian Statistical Institute, Calcutta, calls the study.
"Given what we have always known about ethnography (the study of social groups), these predictions might hold good," says Majumdar. Working with blood groups and genes, researchers across the world have tried to track down differences between various Hindu castes.
But most admit the Bamshad-Rao study is one of the first to actually show the impact of social roles on human DNA. The study has also shown how Hindu women have managed greater social mobility than men.
"Our data indicate that men tend to remain within the caste in which they were born," says Bamshad of the Eccles Institute of Human Genetics at Utah. With women marrying more often out of their own caste, there seems to have been a lot of movement of genetic material between different castes and probably between more closely related castes.
The scientists have used this fact to suggest that it is this female mobility that has shown up in the spirals of people's DNA. Bamshad is clear that these female genes moving upwards are what have stratified the Hindu caste system, at least in genetic terms.
But why Hindu castes? "Because the system has been long-standing, consistent and affecting a large section of people," explains Bamshad. Apparently, it is a hot favourite with anthropologists and geneticists worldwide, an ideal model for such studies.
"Caste hierarchies do exist in other Asian populations but nowhere is the system so formalised and complex as in India," says Bamshad. After identifying their sample, the researchers went about their work. They picked up two kinds of DNA from each of the 250 men who formed their sample.
One from the Y-chromosome - an exclusively male sex chromosome that a father passes on to his son. The other, from the mitochondrion, the human cell's powerhouse which is the hub for respiration, is called mt DNA as it is solely passed on from a mother to her child.
Gene kits were used to extract this DNA, which was then amplified and analysed. Markers were then used to read the secret language encoded in those twists of DNA. The analysis done, Rao and Bamshad found the results told an intriguing story.
The genetic distance - an index they used to study DNA patterns - between lower and upper castes was nearly twice that between lower and middle castes. This is where they feel women have managed to play a role: marrying out of caste and spreading their DNA wide.
Sociologists have said all along that even in the rule-ridden mating system where the 3,000-year old Hindu caste system has controlled marriages, women have managed to stay more mobile than men. They also found that men of castes close to each other on the social ladder showed similarities in mt DNA.
Also, mt DNA of the highest caste, the Brahmins, had few similarities with lower caste DNA. But Rao is a cautious man: "Ours was a purely scientific study using markers and we now need to look beyond." Caution is perhaps in order, with some people terming such research avoidable. But is it?
Not really. "It has a direct bearing with assessing how susceptible specific ethnic groups are to certain diseases," Ali points out. He explains that some populations are more prone to specific genetic disorders and diseases and such research could help with its knowledge base.
Take the Parsis, for instance. In this inbred community of generally good-looking people, genetic anomalies are very common. They could do with sound, gene-based information that could be packaged into pre-marital counselling.
In a country where arranged marriages are common, such information could make sense. Also, with science growing all the time, such research cannot be ignored.
"In the near future, when genome mapping comes up in a big way, these studies will come up more and more often," cautions Shiv Viswanathan of the Centre for the Study of Developing Societies, Delhi.
Viswanathan believes the only way to look at such work is to clinically analyse it for scientific merit. He emphasises the need to get in place strong rules on the ethics of human genome research in the country. So, whatever the interpretations, it might be tough to wish away, stall or ban such research.
The Nature study has fanned a big debate centred on one question: is your caste imprinted in your genes? Majumdar is quick to dispel the uncomfortable thought. "That your caste could be in your genes is a total misinterpretation of this research," he says, adding that genetic structures of populations can correlate with social structures but that does not mean your genes and caste could go together.
There are other caveats to the study and its conclusions though. For one, the sample size is really small: just 250 people. "There is only so much you can deduce from a study of this size," says Majumdar. If extended to larger sections of the population, he believes scientists will stumble upon lots of DNA patterns that show similarities.
It is also a study that just looks at one small part of India though Bamshad adds, "We are keen to replicate the study in another part of India." More important, the study has found that genes reflect social patterns, but the reverse is certainly not true, that your social status could be nestling in your genes.
That is why Viswanathan says "it is important not to get too excited about this study". He believes there are many more variables that can affect something as complicated as caste, which he thinks is anyway "cultural and political". Like Bamshad says, "the actual degree of difference between castes is very, very small".
Rao, meanwhile, is excited that his work adds to our knowledge of human evolution. But the real disclaimer comes from scientists and sociologists who think it should be treated as just what it is, a small pilot study. "Concepts such as superior and inferior DNA should be avoided," says Ali.
Strong ethical rules, transparency in research techniques and caution are certainly in order. In the future there could be a scenario where genetics as a study becomes a partner of social sciences. So a bigger picture might soon emerge. Or not so soon.
Courtesy: India Today
