Peopling of India
The peopling of India refers to the migration of Homo sapiens into the Indian subcontinent. Anatomically modern humans settled India in multiple waves of early migrations, over tens of millennia. The first migrants came with the Southern Coastal dispersal, ca. 65,000 years ago, whereafter complex migrations within south and southeast Asia took place. West Eurasian hunter-gatherers migrated to South Asia after the latest Ice Age, but before the onset of farming. Together with a minor number of ancient South Asian hunter-gatherers they formed the population of the Indus Valley Civilisation.
With the decline of the IVC, and the migration of Indo-Europeans, the IVC-people contributed to the formation of both the Ancestral North Indians, who were closely related to west Eurasians, and the Ancestral South Indians, who were predominantly descended from ancient South Asian hunter-gatherers who were distantly related to the Andamanese. These two ancestral populations mixed extensively between 1,900-4,200 years ago and created the peoples inhabiting the Indian subcontinent today, while the migrations of the Munda people and the Tibeto-Burmese speaking people from East Asia also added new elements.
First modern human settlers
Pre- or post-Toba
The dating of the earliest successful migration modern humans out of Africa is a matter of dispute. It may have pre- or post-dated the Toba catastrophe, a volcanic super eruption that took place between 69,000 and 77,000 years ago at the site of present-day Lake Toba. According to Michael Petraglia, stone tools discovered below the layers of ash deposits in India at Jwalapuram, Andhra Pradesh point to a pre-Toba dispersal. The population who created these tools is not known with certainty as no human remains were found. An indication for post-Toba is haplogroup L3, that originated before the dispersal of humans out of Africa, and can be dated to 60,000–70,000 years ago, "suggesting that humanity left Africa a few thousand years after Toba."Impact
It has been hypothesized that the Toba supereruption about 74,000 years ago destroyed much of India's central forests, covering it with a layer of volcanic ash, and may have brought humans worldwide to a state of near-extinction by suddenly plunging the planet into an ice-age that could have lasted for up to 1,800 years. If true, this may "explain the apparent bottleneck in human populations that geneticists believe occurred between 50,000 and 100,000 years ago" and the relative "lack of genetic diversity among humans alive today."Since the Toba event is believed to have had such a harsh impact and "specifically blanketed the Indian subcontinent in a deep layer of ash," it was "difficult to see how India's first colonists could have survived this greatest of all disasters." Therefore, it was believed that all humans previously present in India went extinct during, or shortly after, this event and these first Indians left "no trace of their DNA in present-day humans" – a theory seemingly backed by genetic studies.
Pre-Toba tools
Research published in 2009 by a team led by Michael Petraglia of the University of Oxford suggested that some humans may have survived the hypothesized catastrophe on the Indian mainland. Undertaking "Pompeii-like excavations" under the layer of Toba ash, the team discovered tools and human habitations from both before and after the eruption. However, human fossils have not been found from this period, and nothing is known of the ethnicity of these early humans in India. Recent research also by Macauly et al. and Posth et al., also argue for a post-Toba dispersal.Early Stone Age hominin fossils have been found in the Narmada valley of Madhya Pradesh. Some have been dated to 200- 700,000 BP. It is uncertain what species they represent.
Post-Toba Southern Coastal dispersal
By some 70-50,000 years ago, only a small group, possibly as few as 150 to 1,000 people, crossed the Red Sea. The group that crossed the Red Sea travelled along the coastal route around the coast of Arabia and Persia until reaching India, which appears to be the first major settling point. Geneticist Spencer Wells says that the early travellers followed the southern coastline of Asia, crossed about of sea, and colonized Australia by around 50,000 years ago. The Aborigines of Australia, Wells says, are the descendants of the first wave of migrations.The oldest definitively identified Homo sapiens fossils yet found in South Asia are Balangoda man. Named for the location in Sri Lanka where they were discovered, they are at least 28,000 years old.
AASI
Narashimhan et al.introduced the term AASI for these oldest human habitants, "Ancient Ancestral South Indian," which were related to the East Asian, Onge and Aboriginal Australian ancestors. It is distantly related to Andaman islanders. According to Narashimhan et al., "essentially all the ancestry of present-day eastern and 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."
Relation to Andaman Islanders
Several genetic studies have found evidence of a distant common ancestry between native Andaman Islanders and the AASI/ASI ancestral component found in South Asians. Modern South Asians have not been found to carry the paternal lineages common in the Andamanese, which has been suggested to indicate that certain paternal lineages may have become extinct in India, or that they may be very rare and have not yet been sampled. Chaubey and Endicott further noted that "Overall, the Andamanese are more closely related to Southeast Asians than they are to present-day South Asians."Shinde et al. 2019 found either Andamanese or East Siberian hunter-gatherers fit as proxy for AASI "due to shared ancestry deeply in time." According to Yelmen et al. the native South Asian genetic component is distinct from the Andamanese and not closely related, and that the Andamanese are thus an imperfect and imprecise proxy for ASI. According to Yelmen et al, the Andamanese component was not detected in the northern Indian Gujarati, and thus it is suggested that the South Indian tribal Paniya people would serve as a better proxy than the Andamanese for the "native South Asian" component in modern South Asians. According to Narashimhan et al., the "AASI" component in South Asians shares a common root with the Andamanese and is distantly related to the Onge, East Asians, and Aboriginal Australians.
Relation to "Negritos"
The present-day Andamese are considered to be part of the "Negritos," several diverse ethnic groups who inhabit isolated parts of southeast Asia. Based on their physical similarities, Negritos were once considered a single population of related people, but the appropriateness of using the label 'Negrito' to bundle together peoples of different ethnicity based on similarities in stature and complexion has been challenged. Recent research suggests that the Negritos include several separate groups, as well as demonstrating that they are not closely related to the Pygmies of Africa.According to Vishwanathan et al., the typical "negrito" features could also have been developed by convergent evolution. According to Gyaneshwer Chaubey and Endicott, "At the current level of genetic resolution, however, there is no evidence of a single ancestral population for the different groups traditionally defined as 'negritos." Basu et al. 2016 concluded that the Andamanese have a distinct ancestry and are not closely related to other South Asians, but are closer to Southeast Asian Negritos, indicating that South Asian peoples do not descend directly from "Negritos" as such.
Sri Lankan Vedda
Groups ancestral to the modern Veddas were probably the earliest inhabitants of Sri Lanka. Their arrival is dated tentatively to about 40,000–35,000 years ago. They are genetically distinguishable from the other peoples of Sri Lanka, and they show a high degree of intra-group diversity. This is consistent with a long history of existing as small subgroups undergoing significant genetic drift.Latest Glacial Maximum
Holocene
After the last glacial maximum, human populations started to grow and migrate. With the invention of agriculture, the so-called Neolithic revolution, larger numbers of people could be sustained. The use of metals further changed human ways of life, giving an initial advance to early users, and aiding further migrations, and admixture.According to Silva et al., multiple waves of migration from western Eurasia took place after the last Ice Age, both before and after the advent of farming in South Asia. According to Narasimhan et al., people related to Iranian hunter-gatherers were present in South Asia before the advent of farming. They mixed with Ancestral Ancient South Asians to form the Indus Valley population. With the decline of the IVC after 1900 BCE and the arrival of the Indo-Aryans, IVC-people mixed with incoming Indo-Aryans, forming the Ancestral North Indians. Other IVC-people mixed with AASI forming the Ancestral South Indians.
These two ancestral groups mixed in India between 4,200 and 1,900 years ago, whereafter a shift to endogamy took place, possibly by the enforcement of "social values and norms" during the Hindu Gupta rule. Reich et al. stated that “ANI ancestry ranges from 39-71% in India, and is higher in traditionally upper caste and Indo-European speakers”.
Basu et al. note that mainland India harbors two additional distinct ancestral components which have contributed to the gene pools of the Indian subcontinent, namely Ancestral Austro-Asiatic and Ancestral Tibeto-Burman.
West Eurasian ancestry
Pre-farming Iranian hunter-gatherers
Narasimhan et al. and Shinde et al. conclude that west Eurasian ancestry was already present before the advent of farming in South Asia.Metspalu et al. detected a genetic component in India, k5, which "distributed across the Indus Valley, Central Asia, and the Caucasus". According to Metspalu et al., k5 "might represent the genetic vestige of the ANI", though they also note that the geographic cline of this component within India "is very weak, which is unexpected under the ASI-ANI model", explaining that the ASI-ANI model implies an ANI contribution which decreases toward southern India. According to Metspalu et al., "regardless of where this component was from, its spread to other regions must have occurred well before our detection limits at 12,500 years."
Speaking to Fountain Ink, Metspalu said, "the West Eurasian component in Indians appears to come from a population that diverged genetically from people actually living in Eurasia, and this separation happened at least 12,500 years ago." Moorjani et al. refer to Metspalu as "fail to find any evidence for shared ancestry between the ANI and groups in West Eurasia within the past 12,500 years". CCMB researcher Thangaraj believes that "it was much longer ago", and that "the ANI came to India in a second wave of migration that happened perhaps 40,000 years ago."
Possible migration of Iranian neolithic farmers
According to Gallego Romero et al., their research on lactose tolerance in India suggests that "the west Eurasian genetic contribution identified by Reich et al. principally reflects gene flow from Iran and the Middle East." Gallego Romero notes that Indians who are lactose-tolerant show a genetic pattern regarding this tolerance which is "characteristic of the common European mutation." According to Romero, this suggests that "the most common lactose tolerance mutation made a two-way migration out of the Middle East less than 10,000 years ago. While the mutation spread across Europe, another explorer must have brought the mutation eastward to India – likely traveling along the coast of the Persian Gulf where other pockets of the same mutation have been found."Mehrgarh, to the west of the Indus River valley, is a precursor of the Indus Valley Civilisation, whose inhabitants migrated into the Indus Valley and became the Indus Valley Civilisation. It is one of the earliest sites with evidence of farming and herding in South Asia. According to Lukacs and Hemphill, while there is a strong continuity between the neolithic and chalcolithic cultures of Mehrgarh, dental evidence shows that the chalcolithic population did not descend from the neolithic population of Mehrgarh, which "suggests moderate levels of gene flow." They further noted that "the direct lineal descendents of the Neolithic inhabitants of Mehrgarh are to be found to the south and the east of Mehrgarh, in northwestern India and the western edge of the Deccan plateau," with neolithic Mehrgarh showing greater affinity with chalcolithic Inamgaon, south of Mehrgarh, than with chalcolithic Mehrgarh.
Elamite-Dravidian hypothesis
While the IVC has been linked to the early Dravidian peoples, some scholars have suggested that their neolithic farmer predecessors may have migrated from the Zagros mountains to northern South Asia some 10,000 years ago. According to David McAlpin, the Dravidian languages were brought to India by immigration into India from Elam. Franklin Southworth also states that the Dravidian Languages originated in western Iran and that publications and research are "further evidence of viability". According to Renfrew and Cavalli-Sforza, proto-Dravidian was brought to India by farmers from the Iranian part of the Fertile Crescent, but more recently Heggerty and Renfrew noted that "McAlpin's analysis of the language data, and thus his claims, remain far from orthodoxy", adding that Fuller finds no relation of Dravidian language with other languages, and thus assumes it to be native to India. Renfrew and Bahn conclude that several scenarios are compatible with the data, and that "the linguistic jury is still very much out."According to another study in 2016, evidence support that the neolithic farmers ancestry component forms the main ancestry of modern South Asians. These neolithic farmers migrated from the fertile crescent, most likely from a region near the Zagros mountains in modern day Iran, to South Asia some 10,000 years ago.
Indus Valley Civilisation
Shinde et al. and Narasimhan et al., analysing remains from the Indus Valley civilisation, conclude that the IVC-population was a mixture people related to Iranians and AASI:According to Shinde et al. about 50-98% of the IVC-genome came from people related to early Iranian farmers, and from 2-50% of the IVC-genome came from native South Asian hunter-gatherers sharing a common ancestry with the Andamanese. According to Narasimhan et al. found 45–82% Iranian farmer-related ancestry and 11–50% AASI. 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.
Indo-Aryans
In the second millennium BCE people from the Sintashta culture migrated through Bactria-Margiana Culture and into the northern Indian subcontinent. The Indo-Aryan migrations started in approximately 1,800 BCE, after the invention of the war chariot, and also brought Indo-Aryan languages into the Levant and possibly Inner Asia.The Proto-Indo-Iranians, from which the Indo-Aryans developed, are identified with the Sintashta culture, and the Andronovo culture, which flourished ca. 1800–1400 BCE in the steppes around the Aral sea, present-day Kazakhstan, Uzbekistan and Turkmenistan. The proto-Indo-Iranians were influenced by the Bactria-Margiana Culture, south of the Andronovo culture, from which they borrowed their distinctive religious beliefs and practices. The Indo-Aryans split off around 1800–1600 BCE from the Iranians, whereafter the Indo-Aryans migrated into the Levant and north-western India.
Lazaridis et al. notes that the demographic impact of steppe related populations on South Asia was substantial and forms a major component in northern India. Lazaridis et al.'s 2016 study estimates 6.5–50.2 % steppe related admixture in all modern South Asians with higher caste and Indo-Aryan speaking groups having more steppe admixture than others.
Post-IVC: ANI and ASI ancestral components in the Indian population
A series of studies since 2009-2019 have shown that the Indian subcontinent harbours two major ancestral components, formed in the 2nd milllennium BCE, namely the Ancestral North Indians, which is broadly related to West Eurasians, and the Ancestral South Indians which is clearly distinct from ANI. 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.ASI formed as mixture of "Indus Periphery-related" group who moved south and mixed further with AASI-related ancestry. "Indus Periphery-related" group did not carry steppe admixture and were instead mixture of Neolithic Iran-related ancestry and hypothesized AASI-related ancestry. According Narasimhan et al. 2018, the genetic makeup of the ASI population consisted of about 73% AASI and about 27% from Iranian-related peoples. This estimate is similar to that of Reich et al. in their more recent analysis, who in 2018 note that the ASI have a West-Eurasian ancestry component which Reich estimates at about 25% of their ancestry, with the remaining 75% of the ancestry of the ASI deriving from native South Asian hunter-gatherers.
ANI formed out of a mixture of "Indus Periphery-related groups" and migrants from Bronze age steppe. Lazaridis et al. notes that the demographic impact of steppe related populations on South Asia was substantial. According to the results, the Mala, a south Indian Dalit population with minimal Ancestral North Indian along the 'Indian Cline' have nevertheless ~ 18 % steppe-related ancestry, showing the strong influence of ANI ancestry in all populations of India. The Kalash of Pakistan are inferred to have ~ 50 % steppe-related ancestry, with the rest being of Iranian farmers ancestry. Reich et al. stated that “ANI ancestry ranges from 39-71% in India, and is higher in traditionally upper caste and Indo-Aryan speakers”.
Austroasiatic
According to Ness, there are three broad theories on the origins of the Austroasiatic speakers, namely northeastern India, central or southern China, or southeast Asia. Multiple researches indicate that the Austroasiatic populations in India are derived from migrations from southeast Asia during the Holocene. According to Van Driem,According to Chaubey et al., "AA speakers in India today are derived from dispersal from Southeast Asia, followed by extensive sex-specific admixture with local Indian populations." According to Zhang et al., Austroasiatic migrations from southeast Asia into India took place after the lates Glacial maximum, circa 10,000 years ago. According to Arunkumar et al., Y-chromosomal haplogroup O2a1-M95, which is typical for Austrosiatic speaking peoples, clearly decreases from Laos to east India, with "a serial decrease in expansion time from east to west," namely "5.7 ± 0.3 Kya in Laos, 5.2 ± 0.6 in Northeast India, and 4.3 ± 0.2 in East India." This suggests "a late Neolithic east to west spread of the lineage O2a1-M95 from Laos."
According to Riccio et al., the Munda people are likely descended from Austroasiatic migrants from southeast Asia. According to Ness, the Khasi probably migrated into India in the first millennium BCE.
According to a genetic research including linguistic analyses, suggests an East Asian origin for proto-Austroasiatic groups, which first migrated to Southeast Asia and later into India.
Tibeto-Burmese
According to Cordaux et al., the Tibeto-Burmans possibly came from the Himalayan and north-eastern borders of the subcontinent within the past 4,200 years.A wide variety of Tibeto-Burman languages are spoken on the southern slopes of the Himalayas. Sizable groups that have been identified are the West Himalayish languages of Himachal Pradesh and western Nepal, the Tamangic languages of western Nepal, including Tamang with one million speakers, and the Kiranti languages of eastern Nepal. The remaining groups are small, with several isolates.
The Newar language of central Nepal has a million speakers and a literature dating from the 12th century, and nearly a million people speak Magaric languages, but the rest have small speech communities. Other isolates and small groups in Nepal are Dura, Raji–Raute, Chepangic and Dhimalish. Lepcha is spoken in an area from eastern Nepal to western Bhutan. Most of the languages of Bhutan are Bodish, but it also has three small isolates, 'Ole, Lhokpu and Gongduk and a larger community of speakers of Tshangla.