- Genetic studies were performed to study the
caste system and its origins
- Majority of the studied mitochondrial DNA were
of Indian origin
- A considerable minority belonged to West
- The lower castes consisted of proto-Asian
- West European mitochondrial DNA was found
concentrated mostly in the upper castes
- Caste system was formed 1900 years ago with the
development of 4,635 unique genetics groups based on religion, tribal and
The Centre for Cellular and Molecular Biology,
Hyderabad along with The Harvard University, conducted a study on the origins
of the Indian caste system based on the mitochondrial DNA. This study that was
published in The American Journal of Human Genetics
is the first
comprehensive study on the genetic basis of caste.
The Use of Mitochondrial DNA for Mapping
This study and most other heredity mapping studies use mitochondrial DNA
to understand the origin of study populations. The nuclear DNA is a combination of the DNA of the mother as well as the father while the mitochondrial DNA is inherited only from the mother because the mitochondrial DNA from the sperms don't enter the egg.
A child's nuclear DNA, when assessed across 4 generations, is a combination of nuclear DNA
from 7 men and 7 women. However, mitochondrial DNA is
inherited from only one woman.
Dr. Kumarasamy Thangaraj, who is the principal author of the study, took samples from nearly 571 people from across India, including the Andamans. The samples were used to carefully analyze the
mitochondrial DNA and to understand the genetic patterns
of the various populations.
‘The rampant intermingling of populations within India that existed more than 2000 years ago makes divisions based on caste, religion or linguistic differences insignificant.’
"Only a few thousand years ago, the Indian population
structure was vastly different from today," said professor of genetics at
Harvard Medical School Dr. David Reich, who is also a co-senior author in the study. "The caste system has been around for
a long time, but not forever."
The current study shows that India was a genetic
hotspot where there was an intermingling of populations, with DNA mixing across India. This is
evidence that intermarriages were common as there was no seclusion from any
part of the
Earlier it was believed that there was a North Indian
population that had a genetic
association with West Europeans and a South Indian or Dravidian population with
ancestors associated with people from the Andamans. However, genetic studies
have shown that there was rampant intermingling, across the country, that lead
to DNA traces present throughout the population.
This population intermingling came to a halt about
1,900 years ago, when stratification of the population based on caste took
Support from the Rig
The Rig Veda mentions the existence of caste in its
texts, which was not
present in the earlier Vedic texts. Moreover, Manusmriti, which dictates the stratification of
society based on caste was initiated during the same period. The genetic
studies find coherence with the ancient Hindu texts.
Significance of the
The study shows that there was no mixing of
populations over 4,000 years from now, but during the period between that and
1,900 years ago, it was common to intermarry within the Indian population or,
less often, even between European descendants. However, from about 2,000 years
ago, stratifications within the Indian population led to distinct genetic
groups, which strengthened over time.
This led to high genetic as well as social imprints that aided in promoting the
interest, craft, ideologies and skills associated with certain groups but resulted in deeply entrenched
implications that continue to sweep Indian society.
The Bane of the Caste System as Envisioned from a
- Genetic Exclusion: The caste system created certain specific groups of populations that were secluded from the populations.
- Genetic Diseases: Intermarriage between closely related population leads to the rise in genetic diseases. Even recessive diseases, or diseases that require two copies of similarly mutated genes to give rise to the disease condition, increase in number when marriage is restricted to only within the community. The severity of the diseases ranges from being mild to even life threatening like Klinefelter's syndrome and pycnodysostosis. The rise in multifactorial diseases like diabetes may also be associated with such genetic seclusions as mild aberrations in genes continue to be inherited and magnified across generations.
- A Single Mixed Population: The evidence that people from across India share a genetic similarity, makes it unnecessary to have divisions based on religion or linguistic disparities.
This hallmark study brings to the fore that man-made divisions within society are
irrelevant when the underlying genetic data signifies unions that existed for
more than 2000 years prior to the groups in society. The last 2000 years have
limited intermixing due to the enforcement of castes, creating restrictions in
the genetic pool, harboring diseases and divisions within the society.
The clashes between different castes in India prompt
the principal researcher to comment thus "Look, we were all brothers
and sisters 2,000 years back," Thangaraj says
"why are you fighting now?"
- http://www.pbs.org/wgbh/nova/neanderthals/mtdna.htmlSource: Medindia