India has served as a major corridor for the dispersal
of human beings that started from Africa about 100,000 years.
Though the date of entry of modern humans into India remains
uncertain, evidence from archaeological studies suggest that
by the middle paleolithic period (50,000-20,000 years before
present (ybp), humans appear to have spread to many parts
of India. Molecular genetic evidence also supports the fact
that a major population expansion of modern humans took place
within India. The time of this demographic expansion has been
speculated to be about 60,000-85,000 ybp (Mountain et al.
1995). Contemporarily, there is an extensive social, cultural,
linguistic and biological diversity in the Indian population,
nurtured to a large extent by the varied topography of the
country. The vast majority of the people of India (~80%) belong
to the Hindu religious fold. Hindus are hierarchically arranged
into 4 socio-cultural clusters of groups (castes) and there
are set rules governing marriage within the Hindu religious
fold. About 8% of the population is constituted by tribals,
who are ancestor worshippers and are largely endogamous. The
remaining belongs to other religious groups, including Muslims,
Christians, Buddhists, Jews, etc. Primarily, marriages occur
within the religious groups. In addition, language and geographical
location of habitat, serve as barriers to free gene flow.
These factors have resulted in the formation of a several
thousand endogamous groups in India. Indian population, comprising
of more than a billion people, consists of 4693 communities
with several thousands of endogamous groups, 325 functioning
languages and 25 scripts.
In some geographical regions of India, inbreeding is practiced.
The population inbreeding coefficient in India varies from
0.00-0.20. Besides, different waves of migration have led
to admixture of different ethnic groups, cultures and languages,
with the native population, thereby contributing significantly
to the present day gene pool of the subcontinent. With the
exception of Africa, such an extent of genetic diversity is
not observed in comparable global regions. Indian population
can be, to a large extent, substructured on the basis of their
ethnic origin as well as linguistic lineages. All the four
major morphological types- Caucasoid, Mongoloid, Australoid
and Negrito, are present in the Indian population (Malhotra
1978). The "Caucasoid" and "Mongoloid"
populations are mainly concentrated in the north and northeastern
parts of the country. The "Australoids" are mostly
confined to the central, western and southern India, while
the "Negritos" are restricted only to the Andaman
Islands (See Morpho Map) Linguistically, Indian populations
belong to four major language families: Indo-European, Dravidian,
Tibeto-Burman and Austro-Asiatic. The Indo-European and Dravidian
languages are spoken in the northern and southern parts of
the subcontinent, respectively (See Linguistic Map). The Tibeto-Burman
speakers are supposedly immigrants to India from Tibet and
Burma (now, Myanmar) and are concentrated in the northeastern
parts of the country. The Austro-Asiatic speakers are exclusively
tribals and are dispersed mostly in the central and eastern
parts of the country. Molecular diversity studies have revealed
that the Austro-Asiatic speakers are likely to have been the
most ancient inhabitants of India.
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