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Genetic Study Reveals Origin of India's Caste System

Genetic Study Reveals Origin of India's Caste System



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A new genetic study published in the American Journal of Human Genetics has revealed that the Indian caste system– which is the traditional organisation of South Asian society into a hierarchy of hereditary groups – may have originated up to 2,000 years ago.

In broad outline, the caste system dictates that marriage only occurs within caste, that it is fixed by birth, and that each caste is associated with a traditional occupation, such as weaving or barbering. Hindu religious principles underlay the caste hierarchy and limit the ways that castes can interact.

Researchers analysed the DNA from 371 people who were members of 73 groups throughout the subcontinent and found that people from different genetic populations in India began mixing about 4,200 years ago, but the mingling stopped around 1,900 years ago. They combined these results with clues from ancient texts, which suggest that class distinctions emerged 3,000 to 3,500 years ago, and caste divisions became strict roughly two millennia ago.

The Rigveda, a nearly 3,500-year-old collection of hymns written in Sanskrit, refer to three main classes of people – the priests, the nobility and the common people – but there was no reference to segregation or occupational restrictions. However, by about 1,000 BC, the texts mention a fourth, lowest class: the Sundras. But it wasn’t until about 100 BC that a holy text called the Manusmruti explicitly stated that marriage across castes was forbidden, and this is also reflected in the genetic analysis which revealed that mixing between castes stopped around this time.

Though relationships between people of different social groups was once common, there was a "transformation where most groups now practice endogamy," or marry within their group, said study co-author Priya Moorjani, a geneticist at Harvard University.

The caste system is connected to the Hindu concept of the four varnas, which order and rank humanity by innate spiritual purity. The highest varna is the Brahmins, or priests. Next comes the Kshatriyas, the warriors, and then the Vaishyas, the merchants. The lowest varna is the Shudras, consisting of labourers, artisans and servants who do work that is ritually unclean. In the past these castes were called untouchables, who were discriminated against and prohibited from participating in religious rituals, drinking from wells used by higher castes, or even letting their shadows fall on a Brahmin.

As India approached independence from British rule in the early 20 th century, the caste system was increasingly criticised as discriminatory and unjust. The current Indian constitution now bans discrimination on the basis of caste and the use of the term ‘untouchable’. The growth of information-age India has reduced the economic importance of the caste system, but its social and religious aspects remain a significant and sometimes divisive part of Indian life.


    History of India's Caste System

    The origins of the caste system in India and Nepal are not fully known, but castes seem to have originated more than 2,000 years ago. Under this system, which is associated with Hinduism, people were categorized by their occupations.

    Although originally caste depended upon a person's work, it soon became hereditary. Each person was born into an unalterable social status. The four primary castes are Brahmin, the priests Kshatriya, warriors and nobility Vaisya, farmers, traders, and artisans and Shudra, tenant farmers and servants. Some people were born outside of (and below) the caste system they were called "untouchables" or Dalits—"the crushed ones."


    India's caste system goes back 2,000 years, genetic study finds

    Researchers found that people from different genetic populations in India began mixing about 4,200 years ago, but the mingling stopped around 1,900 years ago, according to the analysis published Thursday in the American Journal of Human Genetics.

    Combining this new genetic information with ancient texts, the results suggest that class distinctions emerged 3,000 to 3,500 years ago, and caste divisions became strict roughly two millennia ago.

    Though relationships between people of different social groups was once common, there was a "transformation where most groups now practice endogamy," or marry within their group, said study co-author Priya Moorjani, a geneticist at Harvard University.

    Ancestral populations
    Hindus in India have historically been born into one of four major castes, with myriad subdivisions within each caste. Even today, in some parts of the country, marriage outside of one's caste is forbidden and those in the outcast, or "untouchable" group are discriminated against and prohibited from participating in religious rituals. (The Indian government has outlawed certain types of discrimination against the lowest classes.)

    But when and why this system evolved has always been a bit murky, said Michael Witzel, a South Asian studies researcher at Harvard University, who was not involved in the work.

    Moorjani's past research revealed that all people in India trace their heritage to two genetic groups: An ancestral North Indian group originally from the Near East and the Caucasus region, and another South Indian group that was more closely related to people on the Andaman Islands.

    Today, everyone in India has DNA from both groups. "It's just the proportion of ancestry that you have that varies across India," Moorjani told LiveScience.

    To determine exactly when these ancient groups mixed, the team analyzed DNA from 371 people who were members of 73 groups throughout the subcontinent.

    Aside from finding when the mixing started and stopped, the researchers also found the mixing was thorough, with even the most isolated tribes showing ancestry from both groups.

    Period of transition
    Researchers aren't sure which groups of ancient people lived in India prior to 4,200 years ago, but Moorjani suspects the two groups lived side by side for centuries without intermarrying.

    Archaeological evidence indicates that the groups began intermarrying during a time of great upheaval. The Indus Valley civilization, which spanned much of modern-day North India and Pakistan, was waning, and huge migrations were occurring across North India. [History's Most Overlooked Mysteries]

    Ancient texts also reveal clues about the period.

    The Rigveda, a nearly 3,500-year-old collection of hymns written in Sanskrit, a North Indian language, mentions chieftains with South Indian names.

    "So there is some sort of mixture or intermarriage," Witzel told LiveScience.

    Early on, there were distinct classes of people — the priests, the nobility and the common people — but no mention of segregation or occupational restrictions. By about 3,000 years ago, the texts mention a fourth, lowest class: the Sudras. But it wasn't until about 100 B.C. that a holy text called the Manusmruti explicitly forbade intermarriage across castes.

    The study doesn't suggest that either the ancestral North or South Indian group formed the bulk of the upper or lower castes, Witzel said.

    Rather, when caste divisions hardened, any type of intermarriage was sharply curtailed, leading to much less mixing overall.


    Genetic Research Suggests Indian Caste System Began 1,900 Years Ago

    Recent studies have suggested that India’s traditional caste system remains surprisingly intact despite the country’s economic surge. A 2011 report, for instance, found that in “40 percent of the schools across sample districts in Uttar Pradesh—India’s most populous state, with 199 million people—teachers and students refuse to partake of government-sponsored free midday meals because they are cooked by dalits (once known as untouchables).” It’s also certainly still a factor in the country’s politics, as shown by the emergence of the controversial Dalit politician Mayawati.

    But when did the caste system actually begin? One team of researchers believes the country’s genetic history holds the key. In a recent paper published in the American Journal of Human Genetics, researchers from Harvard, MIT, and the CSIR-Centre for Cellular and Molecular Biology in Hyderabad assembled what they call the “most comprehensive sampling of Indian genetic variation to date,” using samples collected from 571 individuals belonging to 73 “well-defined ethno-linguistic groups.” The data allowed the authors to trace not just the genetic mixture between these groups but how long ago this mixture occurred.

    Five thousand years ago, the ancestors of modern Indians were comprised primarily of two groups: ancestral North Indians, who related to people of Central Asia, the Middle East, the Caucasus, and Europe, and ancestral South Indians, who are not closely related to groups outside the subcontinent. The mixture between these two groups and their many subcategories happened mostly between 4,200 and 1,900 years ago, according to the study. The authors note that this period is significant as it was a “time of profound change in India, characterized by the deurbanization of the Indus civilization, increasing population density in the central and downstream portions of the Gangetic system, shifts in burial practices, and the likely first appearance of Indo-European languages and Vedic religion in the subcontinent.”

    Around 1,900 years ago, the mixture largely stopped, as Indian society moved toward endogamy—the practice of avoiding intermarriage or close relationships between ethnic groups—which reached its most extreme form in the creation of the caste system. As one of the study’s authors told the Times of India, “the present-day structure of the caste system came into being only relatively recently in Indian history.”


    Genetic study looks for clues to origin of caste system

    A large genetic study of hundreds of people in South Asia has allowed scientists to probe important transition points in the population’s history, pinpointing a signature of cultural changes that occurred as the caste system was put in place in India.

    Researchers have long known that, at some point in history, South Asia was a melting pot for two different groups of people. The clues have been scattered in various fields: the history, language, and ancient farming traditions of South Asia all bore the imprint of different origins.

    But when did these two populations mix, and when did they stop?

    Harvard Medical School professor of genetics David Reich specializes in analyzing genetic information from modern people to understand how populations mixed in the past.

    Now, in a partnership with researchers in Hyderabad, India, Reich has examined hundreds of thousands of regions in people’s genomes and found evidence that the northern and southern populations mixed around 1,900 to 4,200 years ago. That period was well after the arrival of agriculture in the region and around the same time as Indo-European languages began to be used, the researchers reported Thursday in the American Journal of Human Genetics.

    “From genetic data, remarkably, you see this picture emerging of cultural change,” Reich said. The population mixture didn’t happen in pockets — it was a profound mixing that has left traces in the DNA of people in all areas of India today. But that came to an abrupt halt around 2,000 years ago, likely due to the implementation of the caste system, Reich said.


    FOUNDER EFFECT

    What they found, time and again, was the so-called founder effect -- large numbers of people descended from what was originally a small group of ancestors. People in Finland and Ashkenazi Jews are other groups marked by the founder effect.

    The limits on marrying outside the group can create the risk of recessive diseases -- conditions that only occur if people have two mutated genes. Marriage within groups raises this risk.

    "Many Indian groups have a pattern of having been founded by a small number of individuals. They have been isolated from other groups since that time by restricted marriage across groups," Reich said.

    Some people get tested for recessive genes before having children, and some people also use assisted fertility techniques to test embryos for recessive diseases.

    Reich said no one had documented a higher number of recessive diseases among Indians, but it also was not something anyone had looked for. "It probably affects hundreds of millions of people in India today," he said.

    While the genes clearly show that the caste system has existed for hundreds of generations, the genes do not line up by caste.

    "It is impossible to distinguish castes from tribes using the data," Kumarasamy Thangaraj of the Centre for Cellular and Molecular Biology in Hyderabad, India, who worked on the study, said in a statement.

    "This supports the view that castes grew directly out of tribal-like organizations during the formation of Indian society." (Editing by Julie Steenhuysen and David Storey)


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    "A new study has revealed that Indians belonging to higher castes are genetically closer to Europeans . . . .

    . . . . The study compared genetic markers—located on the Y chromosome and the mitochondrial DNA—between 265 Indian men of various castes and 750 African, Asian, European and other Indian men. To broaden the study, 40 markers from chromosomes 1 to 22 were analyzed from more than 600 individuals from different castes and continents. The comparison of the markers among these groups confirmed that genetic similarities to Europeans increased as caste rank increased. . . .

    . . . . The study, led by Michael Bamshad of the University of Utah, in Salt Lake City, and his colleagues, is reported to be the most comprehensive genetic analysis to date of the impact of European migrations on the structure and origin of the current Indian population. The article appears in the current issue of Genome Research. . . .

    . . . . Bamshad's team found that Y chromosomes from the Brahmin and Kshatriya closely resembled European Y chromosomes rather than Asian Y chromosomes. . . .

    . . . . Analysis of the paternally transmitted Y chromosome among Indians in general indicated that the Y chromosome had a more European flavor. Maternally inherited mitochondrial DNA among Indians is more Asian than European. . . ."


    Examination of ancient DNA can provide profound insights into human history, according to David Reich, a professor of genetics at Harvard Medical School. His talk at the Science Center on Wednesday, “A Tale of Two Subcontinents: The Parallel Prehistories of Europe and South Asia,” was drawn from his new book, “Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past, showing what recent studies have revealed about the prehistory of Europe and southern Asia.

    Reich “reshaped our understanding of human prehistory,” according to a New York Times profile last year, with the publication of DNA from the genomes of 938 ancient humans — more than all other research teams working in the field combined. This research, the story noted, has shed light on the spread of agriculture and the peopling of the planet.

    Reich began his lecture by explaining how his work is done: With recent advances in DNA sequencing, it is now possible to extract sequences from humans who lived tens of thousands of years ago by grinding skeletal remains — specifically parts of the ear where much DNA is concentrated — into a powder to be examined.

    “It’s similar to the introduction of microscopes,” Reich said. “We can now look at worlds that were never previously looked at. And when we look at ancient DNA from past worlds, the stories don’t conform to what we thought. The information that comes from sequencing the whole genome makes it possible to answer questions that are profoundly different, and more precise than ever before.”

    One phenomenon Reich set out to examine is the parallel histories of Europe and South Asia. Both regions saw the arrival of agriculture thousands of years ago, and they speak related Indo-European languages that eventually arrived in both regions. In both cases, the transformations happened through migration.

    In Europe, Reich said, farmers arrived from Anatolia thousands of years ago and mixed with the local hunter-gatherer population this is the largest source of ancestry in Europeans today. A second, later migration from the Eurasian Steppe happened at roughly the time Stonehenge was built. “People [from the Steppes] took advantage of two powerful inventions: the wheel and the domestication of the horse,” said Reich. “They were able to exploit the grasslands of the Steppes in a way that hadn’t been done before.” The Steppe migration resulted in a 90 percent replacement of the population.

    A similar prehistory occurred in the Iberian Peninsula where a third population, also arrived from the Steppes, joined the hunter-gather and farmer groups. In this case, DNA research shows that the third population was exclusively male: While only 40 percent of the population about 6,000 years ago comes from the Steppes, 100 percent of the Y chromosomes do.

    In India, a migration after the Ice Age caused a blending of two ancestries, called Ancestral North Indian and Ancestral South Indian. “People in India today are a mixture of two different portions of these ancestral populations,” Reich said. Genetics also show that India’s caste system, previously thought to have developed under colonial rule, was in place thousands of years earlier.

    One question genetics can’t answer, he said in response to an audience question, is exactly how population replacement happened. “In the case of Britain after 6,000 years ago,” he asked, “did new people come in and kill the old ones, or just crowd them out? We just don’t know. What genetic data does is provide facts about movements of people and changes in groups. We are not the experts to describe how that happened.”

    One important takeaway from this study, he said, is that humans inherently derive from mixed ancestry.

    “No population is, or ever could be, pure,” he said. “Ancient DNA reveals that the mixing of groups extremely different from each other is a common feature of human nature. We do not live in unusual times profound events have occurred in our past. We should learn and feel more connected from that.”


    Genetic Study Reveals Origin of India's Caste System - History

    Link to Article : http://www.genomenewsnetwork.org/articles/05_01/Indo-European.shtml


    "A new study has revealed that Indians belonging to higher castes are genetically closer to Europeans . . . .

    . . . . The study compared genetic markers—located on the Y chromosome and the mitochondrial DNA—between 265 Indian men of various castes and 750 African, Asian, European and other Indian men. To broaden the study, 40 markers from chromosomes 1 to 22 were analyzed from more than 600 individuals from different castes and continents. The comparison of the markers among these groups confirmed that genetic similarities to Europeans increased as caste rank increased. . . .

    . . . . The study, led by Michael Bamshad of the University of Utah, in Salt Lake City, and his colleagues, is reported to be the most comprehensive genetic analysis to date of the impact of European migrations on the structure and origin of the current Indian population. The article appears in the current issue of Genome Research. . . .

    . . . . Bamshad's team found that Y chromosomes from the Brahmin and Kshatriya closely resembled European Y chromosomes rather than Asian Y chromosomes. . . .

    . . . . Analysis of the paternally transmitted Y chromosome among Indians in general indicated that the Y chromosome had a more European flavor. Maternally inherited mitochondrial DNA among Indians is more Asian than European. . . ."


    Link to Article : http://www.genomenewsnetwork.org/articles/05_01/Indo-European.shtml

    Interesting. I think the study is about 11 years old. The link itself is of 2001.

    It would be interesting to see on what basis they classified the similarity. What did they categorize as "European flavor"?

    (3) YHRD - Y Chromosome Haplotype Reference Database : http://YHRD - Y Chromosome Haplotype Reference Database (http://YHRD%20-%20Y%20Chromosome%20Haplotype%20Reference%20Databa se)

    Ethnic Groups - The Jat People Genetic DNA Profiles


    File:Ethnic Groups-The Jat People Genetic DNA Profiles.jpg


    Link to Article : http://www.ncbi.nlm.nih.gov/pubmed/11381027?dopt=Abstract

    Link to Article : http://www.genomenewsnetwork.org/articles/05_01/Indo-European.shtml


    "A new study has revealed that Indians belonging to higher castes are genetically closer to Europeans . . . .

    . . . . The study compared genetic markers—located on the Y chromosome and the mitochondrial DNA—between 265 Indian men of various castes and 750 African, Asian, European and other Indian men. To broaden the study, 40 markers from chromosomes 1 to 22 were analyzed from more than 600 individuals from different castes and continents. The comparison of the markers among these groups confirmed that genetic similarities to Europeans increased as caste rank increased. . . .

    . . . . The study, led by Michael Bamshad of the University of Utah, in Salt Lake City, and his colleagues, is reported to be the most comprehensive genetic analysis to date of the impact of European migrations on the structure and origin of the current Indian population. The article appears in the current issue of Genome Research. . . .

    . . . . Bamshad's team found that Y chromosomes from the Brahmin and Kshatriya closely resembled European Y chromosomes rather than Asian Y chromosomes. . . .

    . . . . Analysis of the paternally transmitted Y chromosome among Indians in general indicated that the Y chromosome had a more European flavor. Maternally inherited mitochondrial DNA among Indians is more Asian than European. . . ."

    Link to Article : http://www.genomenewsnetwork.org/articles/05_01/Indo-European.shtml

    Very laborious effort but the results of the study are beyond comprehension for common man. For example could you explain what does the sentence conveys and on what sort of data the result could be applied to understand Indian social and caste system: ". Analysis of the paternally transmitted Y chromosome among Indians in general indicated that the Y chromosome had a more European flavor. Maternally inherited mitochondrial DNA among Indians is more Asian than European. . . ."

    There is need to explain DNA studies with reference to Jats and Jat clans in simple words. How and why there were migrations and mixing up of various groups with time scale. A layman can not understand DNA, X-chromosome Y-chromosome etc. Can somebody take up this task ?

    There are genetic studies that have been done specifically to map DNAs of Jats and possibly figure out migration patterns. One is by a UK based Pakistani Jat who was a PhD holder. I dont remember his name. You can google it. Another is Harappan ancestory project. The later is more Punjab/North Indian focused but has a decent sample size of Jats leading to a good genetic comparison with other communities. http://www.harappadna.org/

    But having seen a few DNA studies on Jats or larger studies containing Jat samples, I can say that lack of a sample size is limiting factor when drawing conclusions from these studies. For a population running into millions, we need at least a thousand samples of Jats to make valid conclusions or figure out origins. Sadly there hasnt been any large scale study on Jat genetics.

    There is need to explain DNA studies with reference to Jats and Jat clans in simple words. How and why there were migrations and mixing up of various groups with time scale. A layman can not understand DNA, X-chromosome Y-chromosome etc. Can somebody take up this task ?

    Dear Respected Sir, may I please suggest that a thread should be started over this subject in order to ' discuss and discover ' the possibilities and the options available at present (and the possibilities in near future) in the Scientific gallery ?!


    Once We reach a consensus, then We can plan to generate finance for the task through the co-operation of various Jat organisations from India & abroad !! This could prove to be hefty one, as We may require a green signal from the government as well, but it's definitely worth it !! At-least, We may lay a foundation for the project that may well be initiated some-day in near future, by initiating a discussion on Jatland Forums !!