Genetics and archaeogenetics of South Asia

Genetics and archaeogenetics of South Asia is the study of the genetics and archaeogenetics of the ethnic groups of South Asia. It aims at uncovering these groups' genetic history. The geographic position of South Asia makes its biodiversity important for the study of the early dispersal of anatomically modern humans across Asia.

Based on Mitochondrial DNA (mtDNA) variations, genetic unity across various South Asian sub–populations have shown that most of the ancestral nodes of the phylogenetic tree of all the mtDNA types originated in South Asia. Conclusions of studies based on Y Chromosome variation and Autosomal DNA variation have been varied.

South Asians are descendants of an indigenous South Asian component (termed ''Ancient Ancestral South Indians'', short "AASI"), closest to modern isolated tribal groups from South India, as well as Andamanese peoples, and more distantly related to Aboriginal Australians and East Asians and later-arriving West-Eurasian (European/Middle Eastern-related) and additional East/Southeast Asian components respectively, in varying degrees.

The AASI type ancestry is found at the highest levels among tribal groups of southern India, such as the Paniya, and is generally found throughout all South Asian ethnic groups in substantially varying degrees. The West-Eurasian ancestry, specifically an Iranian-related component, combined with varying degrees of AASI ancestry formed the ''Indus Periphery Cline'' around ~5400–3700 BCE, the main ancestry of most modern South Asian groups. The Indus Periphery ancestry, around the 2nd millennium BCE, mixed with another West-Eurasian wave, the incoming mostly male-mediated Yamnaya-Steppe component to form the ''Ancestral North Indians'' (ANI), while at the same time it contributed to the formation of ''Ancestral South Indians'' (ASI) by admixture with hunter-gatherers having higher proportions of AASI-related ancestry. The ANI-ASI gradient, as demonstrated by the higher proportion of ANI in traditionally upper caste and Indo-European speakers, that resulted because of the admixture between the ANI and the ASI after 2000 BCE at various proportions is termed as the ''Indian Cline''.; The East Asian ancestry component forms the major ancestry among Tibeto-Burmese and Khasi-Aslian speakers in the Himalayan foothills and Northeast India, and is generally distributed throughout South Asia at lower frequency, with substantial presence in Mundari-speaking groups, as well as in some populations of northern, central and eastern South Asia.

Overview

According to recent genome studies, South Asians are overall descendants of three ancestral groups in varying degrees: an indigenous South Asian component (often termed ''Ancient Ancestral South Indians'', short "AASI"), an ancient population relatively most closely related to the Andamanese, and more distantly to East Asians, and Aboriginal Australians), with its highest frequency among southern Indian tribal groups, a West-Eurasian (European/Middle Eastern-related) component which makes up the majority of derived ancestry for South Asians, and an additional East/Southeast Asian component, which is found primarily among ethnic minority groups along the Himalayan mountain range and Northeastern India. A specific Neolithic Iranian component, which may be associated with the spread of Dravidian languages, forms the base ancestry of South Asians. This component, paired with substantial AASI ancestry resulted in the ''Indus Periphery Cline'', which is characteristic for South Asians. A Yamnaya Steppe pastoralist component is found in higher frequency among Indo-Aryan speakers, and is generally distributed throughout the Indian subcontinent. An East Asian ancestry component forms the major ancestry among Tibeto-Burmese and Khasi-Aslian speakers in the Himalayan foothills and Northeast India, and is also found in substantial presence in Mundari-speaking groups.

The AASI population became genetically isolated from other populations since approximately ~45,000 years BCe. The Andamanese people are hypothesized to be most closely related to the AASI population and sometimes used as an (imperfect) proxy for it, but others propose the Indian tribal groups like Paniya and Irula as better proxies for indigenous South Asian (AASI) ancestry than the Andamanese. According to Yelmen et al. 2019, the AASI "''separated from East Asian and Andamanese populations, shortly after having separated from West Eurasian populations''". According to Yang (2022): "''This distinct South Asian ancestry, denoted as the Ancient Ancestral South Indian (AASI) lineage, was only found in a small percentage of ancient and present-day South Asians. Present-day Onge from the Andamanese Islands are the best reference population to date, but Narasimhan et al. used qpGraph to show that the divergence between the AASI lineage and the ancestry found in present-day Onge was very deep. Ancestry associated with the AASI lineage was found at low levels in almost all present-day Indian populations''".

Earliest West-Eurasian ancestry is proposed to have perhaps arrived already during the Paleolithic, about ~40,000 BC and may be linked to expanding Aurignacian groups of the Levant. Genetic data shows that the main West-Eurasian wave, happened during the Neolithic period, or already during the Holocene, in tandem with the arrival of East Asian-related components during the Neolithic period with Austroasiatic and Tibeto-Burmese groups from Southeast Asia and East Asia respectively. According to an international research team led by palaeogeneticists of the Johannes Gutenberg University Mainz (JGU), one of the most important ancestry components of South Asians is derived from a population related to Neolithic farmers from the eastern Fertile Crescent and Iran. They concluded "that the Iranian genomes represent the main ancestors of modern-day South Asians".

In the 2nd millennium BCE, the ''Indus Periphery''-related ancestry mixed with the arriving Yamnaya-Steppe component forming the ''Ancestral North Indians'' (ANI), while at the same time it contributed to the formation of ''Ancestral South Indians'' (ASI) by admixture with hunter-gatherers further South having higher proportions of AASI-related ancestry. The proximity to West-Eurasian populations is based on the ''ANI-ASI'' gradient, also termed the ''Indian Cline'', with the groups harboring higher ANI-ancestry being closer to West Eurasians as compared to populations harboring higher ASI-ancestry. Tribal groups from southern India harbor mostly ASI ancestry and sits farthest from West-Eurasian groups on the PCA compared to other South Asians.

It has been found that the ancestral node of the phylogenetic tree of all the mtDNA types ( mitochondrial DNA haplogroups) typically found in Central Asia, the West Asia and Europe are also to be found in South Asia at relatively high frequencies. The inferred divergence of this common ancestral node is estimated to have occurred slightly less than 50,000 years ago. In India, the major maternal lineages are various M subclades, followed by R and U sublineages. These mitochondrial haplogroups' coalescence times have been approximated to date to 50,000 BP.

The major paternal lineages of South Asians, represented by Y chromosomes, are haplogroups R1a1, R2, H, L and J2, as well as O-M175. R1a1, J2 and L are mainly found among European and Middle Eastern populations, O-M175 is mainly restricted among Austroasiatic and Tibeto-Burmese speakers, and also common among East and Southeast Asians, while H is mostly restricted to South Asians. Some researchers have argued that Y-DNA Haplogroup R1a1 (M17) is of autochthonous South Asian origin. However, proposals for a Central Asian/Eurasian steppe origin for R1a1 are also quite common and supported by several more recent studies.

Genetic studies comparing eight X chromosome based STR markers using a multidimensional scaling plot (MDS plot), revealed that South Asians like Indians, Bangladeshis and Sinhalese people cluster close to each other, but also closer to Europeans. In contrast Southeast Asians, East Asians and Africans were placed at a distant positions, outside the main cluster.

mtDNA

The most frequent mtDNA haplogroups in South Asia are M, R and U (where U is a descendant of R).
Arguing for the longer term "rival Y-Chromosome model", Stephen Oppenheimer believes that it is highly suggestive that India is the origin of the Eurasian mtDNA haplogroups which he calls the "Eurasian Eves". According to Oppenheimer it is highly probable that nearly all human maternal lineages in Central Asia, the Middle East and Europe descended from only four mtDNA lines that originated in South Asia 50,000–100,000 years ago.

Macrohaplogroup M

The macrohaplogroup M, which is considered as a cluster of the proto-Asian maternal lineages, represents more than 60% of South Asian MtDNA.

The M macrohaplotype in India includes many subgroups that differ profoundly from other sublineages in East Asia especially Mongoloid populations. The deep roots of M phylogeny clearly ascertain the relic of South Asian lineages as compared to other M sublineages (in East Asia and elsewhere) suggesting 'in-situ' origin of these sub-haplogroups in South Asia, most likely in India. These deep-rooting lineages are not language specific and spread over all the language groups in India.

Virtually all modern Central Asian MtDNA M lineages seem to belong to the Eastern Eurasian ( Mongolian) rather than the South Asian subtypes of haplogroup M, which indicates that no large-scale migration from the present Turkic-speaking populations of Central Asia occurred to India. The absence of haplogroup M in Europeans, compared to its equally high frequency among South Asians, East Asians and in some Central Asian populations contrasts with the Western Eurasian leanings of South Asian paternal lineages.

Most of the extant mtDNA boundaries in South and Southwest Asia were likely shaped during the initial settlement of Eurasia by anatomically modern humans.

Macrohaplogroup R

The macrohaplogroup R (a very large and old subdivision of macrohaplogroup N) is also widely represented and accounts for the other 40% of South Asian MtDNA. A very old and most important subdivision of it is haplogroup U that, while also present in West Eurasia, has several subclades specific to South Asia.

Most important South Asian haplogroups within R:

Haplogroup U

Haplogroup U is a sub-haplogroup of macrohaplogroup R. The distribution of haplogroup U is a mirror image of that for haplogroup M: the former has not been described so far among eastern Asians but is frequent in European populations as well as among South Asians. South Asian U lineages differ substantially from those in Europe and their coalescence to a common ancestor also dates back to about 50,000 years.

Y chromosome

The major South Asian Y-chromosome DNA haplogroups are H, J2, L, R1a1, R2, which are commonly found among other West-Eurasian populations, such as Middle Easterners or Europeans. Their geographical origins are listed as follows, according to the latest scholarship:

Haplogroup H

Haplogroup H (Y-DNA) is found at a high frequency in South Asia and is considered to represent the major indigenous paternal lineage. H is today rarely found outside of South Asia, but is common among South Asian-descended populations, such as the Romanis, particularly the H-M82 subgroup. H was also found in some ancient samples of Europe and is still found today at a low frequency in certain southeastern Europeans and Arabs of the Levant. Haplogroup H is frequently found among populations of India, Sri Lanka, Nepal, Pakistan and the Maldives. All three branches of Haplogroup H (Y-DNA) are found in South Asia.

Haplogroup H is believed to have arisen in South Asia between 30,000 and 40,000 years ago. Its probable site of introduction is South Asia, since it is concentrated there. It seems to represent the main Y-Chromosome haplogroup of the paleolithic inhabitants of South Asia and Europe respectively. Some individuals in South Asia have also been shown to belong to the much rarer subclade H3 (Z5857). Haplogroup H is by no means restricted to specific populations. For example, H is possessed by about 28.8% of Indo-Aryan castes. and in tribals about 25–35%.

Haplogroup J2

Haplogroup J2 has been present in South Asia mostly as J2a-M410 and J2b-M102, since neolithic times (9500 YBP). J2 clades attain peak frequencies in the North-West and South India and is found at 19% within South Indian castes, 11% in North Indian castes and 12% in Pakistan. In South India, the presence of J2 is higher among middle castes at 21%, followed by upper castes at 18.6% and lower castes at 14%. Among caste groups, the highest frequency of J2-M172 is observed among Tamil Vellalars of South India, at 38.7%. J2 is present in tribals too and has a frequency of 11% in Austro-Asiatic tribals. Among the Austro-Asiatic tribals, the predominant J2 occurs in the Lodha (35%). J2 is also present in the South Indian hill tribe Toda at 38.46%, in the Andh tribe of Telangana at 35.19% and in the Kol tribe of Uttar Pradesh at a frequency of 33.34%. Haplogroup J-P209 was found to be more common in India's Shia Muslims, of which 28.7% belong to haplogroup J, with 13.7% in J-M410, 10.6% in J-M267 and 4.4% in J2b.

In Pakistan, the highest frequencies of J2-M172 were observed among the Parsis at 38.89%, the Dravidian-speaking Brahuis at 28.18% and the Makrani Balochs at 24%. It also occurs at 18.18% in Makrani Siddis and at 3% in Karnataka Siddis.

J2-M172 is found at an overall frequency of 10.3% among the Sinhalese people of Sri Lanka. In Maldives, 20.6% of Maldivian population were found to be haplogroup J2 positive.

Haplogroup L

According to Dr. Spencer Wells, L-M20 originated in the Pamir Knot region in Tajikistan and migrated into Pakistan and India ca. 30,000 years ago. However, most other studies have proposed a South Asian origin for L-M20 and associated its expansion with the Indus valley (~7,000 YBP). There are three subbranches of haplogroup L: L1-M76 (L1a1), L2-M317 (L1b) and L3-M357 (L1a2), found at varying levels in South Asia.

India

Haplogroup L shows time of neolithic expansion. The clade is present in the Indian population at an overall frequency of ca. 7–15%. Haplogroup L has a higher frequency among south Indian castes (ca. 17–19%) and reaches 68% in some castes in Karnataka but is somewhat rarer in northern Indian castes (ca. 5–6%). The presence of haplogroup L is quite rare among tribal groups (ca. 5,6–7%), however 14.6% has been observed among the Chenchus.

Among regional and social groups, moderate to high frequencies have been observed in Konkanastha Brahmins (18.6%), Punjabis (12.1%), Gujaratis (10.4%), Lambadis (17.1%), and Jats (36.8%).

Pakistan

In Pakistan, L1-M76 and L3-M357 subclades of L-M20 reach overall frequencies of 5.1% and 6.8%, respectively.
Haplogroup L3 (M357) is found frequently among Burusho (approx. 12%) and Pashtuns (approx. 7%). Its highest frequency can be found in south western Balochistan province along the Makran coast (28%) to Indus River delta. L3a (PK3) is found in approximately 23% of Nuristani in northwest Pakistan.

The clade is present in moderate distribution among the general Pakistani population (14% approx).

Sri Lanka

In one study, 16% of the Sinhalese were found to be Haplogroup L-M20 positive. In another study 18% were found to belong to L1.

Haplogroup R1a1

In South Asia, R1a1 has been observed often with high frequency in a number of demographic groups, as well as with highest STR diversity which lead some to see it as the locus of origin.
While R1a originated ca. 22,000 to 25,000 years ago, its subclade M417 (R1a1a1) diversified ca. 5,800 years ago. The distribution of M417-subclades R1-Z282 (including R1-Z280) in Central and Eastern Europe and R1-Z93 in Asia suggests that R1a1a diversified within the Eurasian Steppes or the Middle East and Caucasus region. The place of origin of these subclades plays a role in the debate about the origins of Indo-Europeans.

India

In India, a high percentage of this haplogroup is observed in West Bengal Brahmins (72%) to the east, Gujarat Lohanas (60%) to the west, Khatris (67%) in the north, and Iyengar Brahmins (31%) in the south. It has also been found in several South Indian Dravidian-speaking tribals including the Kotas (41%) of Tamil Nadu, Chenchu (26%) and Valmikis of Andhra Pradesh as well as the Yadav and Kallar of Tamil Nadu suggesting that M17 is widespread in these southern Indians tribes. Besides these, studies show high percentages in regionally diverse groups such as Manipuris (50%) to the extreme northeast and in among Punjabis (47%) to the extreme northwest.

Pakistan

In Pakistan, it is found at 71% among the Mohanna of Sindh Province to the south and 46% among the Baltis of Gilgit-Baltistan to the north.

Sri Lanka

23% of the Sinhalese people out of a sample of 87 subjects were found to be R1a1a (R-SRY1532) positive according to a 2003 research.

Maldives

In the Maldives, 23.8% of the Maldivian people were found to be R1a1a (M17) positive.

Nepal

People in Terai region, Nepal show R1a1a at 69%.

Haplogroup R2

In South Asia, the frequency of R2 and R2a lineage is around 10–15% in India and Sri Lanka and 7–8% in Pakistan. At least 90% of R-M124 individuals are located in South Asia. It is also reported in Caucasus and Central Asia at a lower frequency. A genetic study by Mondal et al. in 2017 concluded that Haplogroup R2 originated in northern India and was already present before the Steppe migration.

India

Among regional groups, it is found among West Bengalis (23%), New Delhi Hindus (20%), Punjabis (5%) and Gujaratis (3%). Among tribal groups, Karmalis of West Bengal showed highest at 100% followed by Lodhas (43%) to the east, while Bhil of Gujarat in the west were at 18%, Tharus of the north showed it at 17%, the Chenchu and Pallan of the south were at 20% and 14% respectively. Among caste groups, high percentages are shown by Jaunpur Kshatriyas (87%), Kamma (73%), Bihar Yadav (50%), Khandayat (46%)and Kallar (44%).

It is also significantly high in many Brahmin groups including Punjabi Brahmins (25%), Bengali Brahmins (22%), Konkanastha Brahmins (20%), Chaturvedis (32%), Bhargavas (32%), Kashmiri Pandits (14%) and Lingayat Brahmins (30%).

North Indian Muslims have a frequency of 19% (Sunni) and 13% (Shia), while Dawoodi Bohra Muslim in the western state of Gujarat have a frequency of 16% and Mappila Muslims of southern India have a frequency of 5%.

Pakistan

The R2 haplogroup is found in 14% of the Burusho people. Among the Hunza people it is found at 18% while the Parsis show it at 20%.

Sri Lanka

38% of the Sinhalese of Sri Lanka were found to be R2 positive according to a 2003 research.

Maldives

12% of the Maldivians are found to have R2.

Nepal

In Nepal, R2 percentages range from 2% to 26% within different groups under various studies. Newars show a significantly high frequency of 26% while people of Kathmandu show it at 10%.

Haplogroup O

Haplogroup O1 (O-F265) and O2 (O-M122), the primary branches of Haplogroup O-M175 are very common among the Austroasiatic and Tibeto-Burmese speaking populations of South Asia respectively.

Haplogroup O-M95, a subclade of O1-F265, is mainly restricted in Austroasiatic-speaking groups in South Asia. According to Kumar ''et al'' 2007, M95 averages at 55% in Munda and 41% of Khasi-Khmuic speakers of from Northeast India, while Reddy et al. 2007 found an average frequency 53% among Mundari and 31% among Khasi speakers. Zhang et al. 2015, found a higher average of 67.53% and 74,00% among Munda and Khasi-speaking groups respectively. Abundant in the Andaman and Nicobar Islands (averaging ~45%), it is fixed (100%) in some populations like Shompen, Onge and Nicobarese. A migration of O-M95 from Southeast Asia into India has been suggested with an expansion time of 5.2 ± 0.6 KYA in Northeast India.

Haplogroup O2-M122 is primarily found among the males of Tibeto-Burmese ancestry in the Himalayas and Northeast India. Haplogroup O-M122, believed to have originated in Southern China shows very high percentages. It is found at 86.6% among Tamangs of Nepal, with similarly high frequencies, 75% to 85%, among the northeastern Indian Tibeto-Burman groups, including Adi, Naga, Apatani, Nyishi, Kachari and Rabha. In Northeast India, Baric speakers display a high frequency and homogeneity of O-M134, indicating a population bottleneck effect that occurred during a westward and then southward migration of the founding population of Tibeto-Burmans during its branching from the parental population. It has a significant presence among the Khasis (29%), despite being generally absent in other Austroasiatics of India, and it shows up at 55% among neighbouring Garos, a Tibeto-Burman group.

Reconstructing South Asian population history

The , divides the population of South Asia into four ethnolinguistic (not genetic) groups: Indo-European, Dravidian, Tibeto-Burman and Austro-Asiatic. The molecular anthropology studies use three different type of markers: Mitochondrial DNA (mtDNA) variation which is maternally inherited and highly polymorphic, Y Chromosome variation which involves uniparental transmission along the male lines, and Autosomal DNA variation.

mtDNA variation

Most of the studies based on mtDNA variation have reported genetic unity of South Asian populations across language, caste and tribal groups.
It is likely that haplogroup M was brought to Asia from East Africa along the southern route by earliest migration wave 78,000 years ago.

According to Kivisild et al. (1999), "Minor overlaps with lineages described in other Eurasian populations clearly demonstrate that recent immigrations have had very little impact on the innate structure of the maternal gene pool of South Asians. Despite the variations found within India, these populations stem from a limited number of founder lineages. These lineages were most likely introduced to South Asia during the Middle Palaeolithic, before the peopling of Europe 48,000 years ago and perhaps the Old World in general." Basu et al. (2003) also emphasises underlying unity of female lineages in India.

Y Chromosome variation

Conclusions based on Y Chromosome variation have been more varied than those based on mtDNA variation. While Kivisild et al. proposes an ancient and shared genetic heritage of male lineages in South Asia, Bamshad et al. (2001) suggests an affinity between South Asian male lineages and modern west Eurasians proportionate to upper-caste rank and places upper-caste populations of southern Indian states closer to East Europeans.

Basu et al. (2003) concludes that Austro–Asiatic tribal populations entered India first from the Northwest corridor and much later some of them through Northeastern corridor. Whereas, Kumar et al. (2007) analysed 25 South Asian Austro-Asiatic tribes and found a strong paternal genetic link among the sub-linguistic groups of the South Asian Austro-Asiatic populations. Mukherjee et al. (2001) places Pakistanis and North Indians between west Asian and Central Asian populations, whereas Cordaux et al. (2004) argues that the Indian caste populations are closer to Central Asian populations. Sahoo et al. (2006) and Sengupta et al. (2006) suggest that Indian caste populations have not been subject to any recent admixtures. Sanghamitra Sahoo concludes his study with:

Closest-neighbor analysis done by Mondal et al. in 2017 concluded that Indian Y-lineages are close to southern European populations and the time of divergence between the two predated Steppe migration:

Autosomal DNA variation

AASI-ANI-ASI

Results of studies based upon autosomal DNA variation have also been varied. In a major study (2009) using over 500,000 biallelic autosomal markers, Reich hypothesized that the modern South Asian population was the result of admixture between two genetically divergent ancestral populations dating from the post-Holocene era. These two "reconstructed" ancient populations he termed "Ancestral South Indians" (ASI) and "Ancestral North Indians" (ANI). According to Reich: "ANI ancestry is significantly higher in Indo-European than Dravidian speakers, suggesting that the ancestral ASI may have spoken a Dravidian language before mixing with the ANI." While the ANI is genetically close to Middle Easterners, Central Asians and Europeans, the ASI is not closely related to groups outside of the subcontinent. As no "ASI" ancient DNA is available, the indigenous Andamanese Onge are used as an (imperfect) proxy of ASI (according to Reich et al., the Andamanese, though distinct from them, are the closest living population to the ASI). According to Reich et al., both ANI and ASI ancestry are found all over the subcontinent (in both northern and southern India) in varying proportions, and that "ANI ancestry ranges from 39-71% in India, and is higher in traditionally upper caste and Indo-European speakers."

Moorjani et al. 2013 state that the ASI, though not closely related to any living group, are "related (distantly) to indigenous Andaman Islanders." Moorjani et al. however suggest possible gene flow into the Andamanese from a population related to the ASI, causing the modeled relationship. The study concluded that "almost all groups speaking Indo-European or Dravidian languages lie along a gradient of varying relatedness to West-Eurasians in PCA (referred to as "Indian cline")".

A 2013 study by Chaubey using the single-nucleotide polymorphism (SNP), shows that the genome of Andamanese people (Onge) is closer to those of other Oceanic Negrito groups than to that of South Asians.

According to Basu et al. 2016, further analysis revealed that the genomic structure of mainland Indian populations is best explained by contributions from four ancestral components. In addition to the ANI and ASI, Basu et al. (2016) identified two East Asian ancestral components in mainland India that are major for the Austro-Asiatic-speaking tribals and the Tibeto-Burman speakers, which they denoted as AAA (for "Ancestral Austro-Asiatic") and ATB (for "Ancestral Tibeto-Burman") respectively. The study also infers that the populations of the Andaman Islands archipelago form a distinct ancestry, which "was found to be coancestral to Oceanic populations" but more distant from South Asians.

The cline of admixture between the ANI and ASI lineages is dated to the period of c. 4.2–1.9 kya by Moorjani et al. (2013), corresponding to the Indian Bronze Age, and associated by the authors with the process of deurbanisation of the Indus Valley civilization and the population shift to the Gangetic system in the incipient Indian Iron Age. Basu et al. (2003) suggests that "Dravidian speakers were possibly widespread throughout India before the arrival of the Indo-European-speaking nomads" and that "formation of populations by fission that resulted in founder and drift effects have left their imprints on the genetic structures of contemporary populations". The geneticist PP Majumder (2010) has recently argued that the findings of Reich et al. (2009) are in remarkable concordance with previous research using mtDNA and Y-DNA:

Chaubey et al. 2015 detected a distinctive East Asian ancestral component, mainly restricted to specific populations in the foothills of Himalaya and northeastern part of India. Highest frequency of the component is observed among the Tibeto-Burmese speaking groups of northeast India and was also detected in Andamanese populations at 32%, with substantial presence also among Austroasiatic speakers. It is found to be largely absent in Indo-European and Dravidian speakers, except in some specific ethnic groups living in the Himalayan foothills and central-south India. The researchers however suggested that the East Asian ancestry (represented by the Han) measured in the studied Andamanese groups may actually reflect the capture of the affinity of the Andamanese with Melanesians and Malaysian Negritos (rather than true East Asian admixture), as a previous study by Chaubey et al. suggested "a deep common ancestry" between Andamanese, Melanesians and other Negrito groups, and an affinity between Southeast Asian Negritos and Melanesians (as well as the Andamanese) with East Asians.

Lazaridis et al. (2016) notes "The demographic impact of steppe related populations on South Asia was substantial, as the Mala, a south Indian Dalit population with minimal ANI (Ancestral North Indian) along the 'Indian Cline' of such ancestry is inferred to have ~ 18% steppe-related ancestry, while the Kalash of Pakistan are inferred to have ~ 50%, similar to present-day northern Europeans." The study estimated (6.5–50.2%) steppe-related admixture in South Asians. Lazaridis et al. further notes that "A useful direction of future research is a more comprehensive sampling of ancient DNA from steppe populations, as well as populations of central Asia (east of Iran and south of the steppe), which may reveal more proximate sources of the ANI than the ones considered here, and of South Asia to determine the trajectory of population change in the area directly.

Pathak et al. 2018 concluded that the Indo-European speakers of the Gangetic Plains and the Dravidian speakers have significant Yamnaya Early-Middle Bronze Age (Steppe_EMBA) ancestry but no Middle-Late Bronze Age Steppe (Steppe_MLBA) ancestry. On the other hand, the "North-Western Indian and Pakistani" populations (PNWI) showed significant Steppe_MLBA ancestry along with Yamnaya (Steppe_EMBA) ancestry. The study also noted that ancient South Asian samples had significantly higher Steppe_MLBA than Steppe_EMBA (or Yamnaya). The study also suggested that the Rors could be used as a proxy for the ANI.

David Reich in his 2018 book ''Who We Are and How We Got Here'' states that the 2016 analyses found the ASI to have significant amounts of an ancestry component deriving from Iranian farmers (about 25% of their ancestry), with the remaining 75% of their ancestry deriving from native South Asian hunter-gatherers. He adds that ASI were unlikely the local hunter-gatherers of South Asia as previously established, but a population responsible for spreading agriculture throughout South Asia. In the case of the ANI, the Iranian farmer ancestry is 50%, with the rest being from steppe groups related to the Yamnaya.

, similarly, conclude that ANI and ASI were formed in the 2nd millennium BCE. They were preceded by a mixture of AASI (ancient ancestral south Indian, i.e. hunter-gatherers sharing a distant root with the Andamanese, Australian Aboriginals, and East Asians); and Iranian agriculturalists who arrived in India ca. 4700–3000 BCE, and "must have reached the Indus Valley by the 4th millennium BCE". According to Narasimhan et al., this mixed population, which probably was native to the Indus Valley Civilisation, "contributed in large proportions to both the ANI and ASI", which took shape during the 2nd millennium BCE. ANI formed out of a mixture of "''Indus Periphery''-related groups" and migrants from the steppe, while ASI was formed out of "''Indus Periphery''-related groups" who moved south and mixed further with local hunter-gatherers. The ancestry of the ASI population is suggested to have averaged about 73% from the AASI and 27% from Iranian-related farmers. Narasimhan et al. observe that samples from the Indus periphery group are always mixes of the same two proximal sources of AASI and Iranian agriculturalist-related ancestry; with "one of the Indus Periphery individuals having ~42% AASI ancestry and the other two individuals having ~14-18% AASI ancestry" (with the remainder of their ancestry being from the Iranian agriculturalist-related population). The authors propose that the AASI indigenous hunter-gatherers represent a divergent branch that split off around the same time that East Asian, Onge (Andamanese) and Australian Aboriginal ancestors separated from each other. It inferred, "essentially all the ancestry of present-day eastern and southern Asians (prior to West Eurasian-related admixture in southern Asians) derives from a single eastward spread, which gave rise in a short span of time to the lineages leading to AASI, East Asians, Onge, and Australians."

A genetic study by Yelmen et al. (2019) argue that the native South Asian genetic component is rather distinct from the Andamanese, and that the Andamanese are thus an imperfect proxy. This component (when represented by the Andamanese Onge) was not detected in the northern Indian Gujarati, and thus it is suggested that the South Indian tribal Paniya people (a group of predominantly ASI ancestry) would serve as a better proxy than the Andamanese (Onge) for the "native South Asian" component in modern South Asians, as the Paniya are directly derived from the natives of South Asia (rather than distantly related to them as the Onge are).

Two genetic studies analysing remains from the Indus Valley civilisation (of parts of Bronze Age Northwest India and East Pakistan), found them to have a mixture of ancestry, both from native South Asian hunter-gatherers sharing a distant root with the Andamanese, and from a group related to Iranian farmers. The samples analyzed by Shinde derived about 50-98% of their genome fom Iranian-related peoples and from 2-50% from native South Asian hunter-gatherers. The samples analyzed by Narasimhan et al. had 45–82% of Iranian farmer-related ancestry and 11–50% of South Asian hunter-gatherer origin. The analysed samples of both studies have little to none of the " Steppe ancestry" component associated with later Indo-European migrations into India. The authors found that the respective amounts of those ancestries varied significantly between individuals, and concluded that more samples are needed to get the full picture of Indian population history.

Yang 2022 summarized that the indigenous South Asian (AASI) lineage gave rise to two groups, the proper AASI within South Asia, and the Andamanese peoples. Both populations are closer to each other than to any other population, while ultimately having trifurcated from an "eastern population" which gave also rise to Australasians (AA lineage) and East/Southeast Asians (ESEA lineage). According to her, the "''Comparison with ancient individuals from South Asia showed that all present-day Indians have a mixture of ancestry related to the AASI lineage, basal Iranian ancestry, and Steppe ancestry. Northern and southern Indians are both associated with Indus Periphery ancestry observed in populations near and in the Indus Valley older than 4,000 years. Southern Indian populations possess additional ancestry related to the AASI lineage beyond that found in the ancient Indus Valley individuals, which suggests that ancient individuals representing the AASI lineage, who have yet to be sampled, likely lived in southern India. Northern Indians show genetic patterns similar to those found in ancient populations near the Indus Valley younger than 4,000 years; all show admixture with populations associated with Steppe ancestry. These patterns illustrate that in South Asia, the formation of ancestries associated with northern and southern Indians likely post-dated 4,000 years ago, where northern Indian populations associated with the Indus Periphery cline mixed with populations of Steppe ancestry and southern Indian populations in the Indus Periphery cline primarily mixed with populations of the AASI lineage. Just as in other regions of Asia, admixture played a key role in the formation of present-day Indian populations''".

Genetic distance between caste groups and tribes

Studies by Watkins et al. (2005) and Kivisild et al. (2003) based on autosomal markers conclude that Indian caste and tribal populations have a common ancestry. Reddy et al. (2005) found fairly uniform allele frequency distributions across caste groups of southern Andhra Pradesh, but significantly larger genetic distance between caste groups and tribes indicating genetic isolation of the tribes and castes.

Viswanathan et al. (2004) in a study on genetic structure and affinities among tribal populations of southern India concludes, "''Genetic differentiation was high and genetic distances were not significantly correlated with geographic distances. Genetic drift therefore probably played a significant role in shaping the patterns of genetic variation observed in southern Indian tribal populations.'' Otherwise, analyses of population relationships showed that all Indian and South Asian populations are still similar to one another, regardless of phenotypic characteristics, and do not show any particular affinities to Africans. We conclude that the phenotypic similarities of some Indian groups to Africans ''do not'' reflect a close relationship between these groups, but are better explained by ''convergence''."

A 2011 study published in the American Journal of Human Genetics indicates that Indian ancestral components are the result of a more complex demographic history than was previously thought. According to the researchers, South Asia harbours two major ancestral components, one of which is spread at comparable frequency and genetic diversity in populations of Central Asia, West Asia and Europe; the other component is more restricted to South Asia. However, if one were to rule out the possibility of a large-scale Indo-Aryan migration, these findings suggest that the genetic affinities of both Indian ancestral components are the result of multiple gene flows over the course of thousands of years.

Narasimhan et al. 2019 found Austroasiatic-speaking Munda tribals could not be modeled simply as mixture of ASI, AASI, or ANI ancestry unlike other South Asians but required additional ancestry component from Southeast Asia. They were modeled as mixture of 64% AASI, and 36% East Asian-related ancestry, samplified by the Nicobarese, thus the ancestry profile of the Mundas provides an independent line of ancestry from Southeast Asia around the 3rd millennium BCE. Lipson et al. 2018 found similar admixture results in regard to Munda tribals stating ''"we obtained a good fit with three ancestry components: one western Eurasian, one deep eastern Eurasian (interpreted as an indigenous South Asian lineage), and one from the Austroasiatic clade"''. Lipson et al. 2018 further found that the Austroasiatic source clad (proportion 35%) in Munda tribals was inferred to be closest to Mlabri. Singh et al. 2020 similarly found Austroasiatic speakers in South Asia fall out of the South Asian cline due to their Southeast Asian genetic affinity.

See also

*Archaeogenetics
* Ethnic groups of South Asia
*List of ethnolinguistic regions of South Asia
*Peopling of India
*Y-DNA haplogroups in populations of South Asia
* Genetic studies on Gujarati people
* Genetic history of Europe
* Genetic history of the Middle East
* Genetic history of Southeast Asia

References

Further reading

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External links

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