The Genetic History of South Asia (India, Pakistan, etc.)

Contents:

1. Introduction
2. Indigenous South Asians
3. Iranian Hunter-Gatherers
4. East Eurasians
5. European Pastoralists
6. Admixture Analysis
7. Sources

1. Introduction

South Asia is one of the most heterogeneous regions on earth. It is a true “melting pot” where all Eurasian races have steadily converged over thousands of years, if not tens of thousands. As such, the region exhibits a wide array of phenotypic diversity. Some of its native inhabitants could even be mistaken for Sub-Saharan Africans, by the untrained eye.

Untangling the genetic history of South Asia sounds like a monumentally complex task but it can be summarized quite simply by breaking things down into their basic components. South Asians descend from a handful of ‘basal’ populations and a few major migrations, which are covered in detail below.

2. Indigenous South Asians

India and the surrounding regions were originally inhabited by dark-skinned hunter-gatherers, named “Ancient Ancestral South Indians” (AASI) by geneticists. They were most similar to modern populations identified as ‘Australo-Melanesians’ by pre-21st-Century anthropologists, which include the “Negrito” Andamanese Islanders (e.g. Onge and Jarawa), Semangs and Bateks of Malaysia, Aetas of the Philippines, Vedda of Sri Lanka, and tribal populations of India, including the Munda, Gondi, and Irula. These groups have genetic affinities with Australian Aboriginals and Melanesians (hence the name).

The exact origin of this ‘Australo-Melanesian’ (or “South Eurasian”) population is currently unknown. Some scientists theorize that they belonged to an earlier Out of Africa expansion, distinct from that which gave rise to East and West Eurasians (i.e. East Asians and Caucasoids), while others believe that they represent an early ‘basal’ East Eurasian population that predates the East Asian “Mongoloid” phenotype.

“AASI” related ancestry forms the “base layer” of all South Asian genetics and is universal throughout the region. It can even be found in some populations of Southern East Asia, like the Yi, Naxi, and Tibetans. However, this ancestry peaks in South India, Sri Lanka, and among the aforementioned tribal populations.

“Negritos,” such as the Onge (below), can be genetically modeled as a mix of Papuan and East Eurasian-related ancestries or as an early split from East Eurasians.

The Paniya are probably the best proxy for “AASI” genetics, as they have limited admixture from East and West Eurasians.

3. Iranian Hunter-Gatherers

Hunter-gatherers from ancient Iran made significant contributions to the South Asian gene pool. They migrated into the region during the Neolithic, around 5500 BC, intermixing with the native South Asian hunter-gatherers to varying degrees. This mixed population formed the Indus Valley or Harappan Civilization in northwest India, which may be the origin of the Dravidian languages.

Iranian hunter-gatherers closest living relatives are the Brahuis and Balochis of Iran, Afghanistan, and Pakistan, who trace almost half of their ancestry to this ancient population. They were genetically distinct from the later farming populations of Iran, who had additional ancestry from Anatolian Neolithic Farmers.

Although Iranian hunter-gatherer ancestry is common throughout South Asia, it is notably absent from some smaller, tribal populations, such as the Munda, as well as the East Eurasian peoples who inhabit the region’s peripheries.

Balochis:

4. East Eurasians

East Eurasian-related ancestry arrived in South Asia during the Neolithic with the migration of Austroasiatic and Tibeto-Burmese speaking peoples from East and Southeast Asia respectively. Austroasiatic peoples were among the first East Eurasians to migrate into Southeast Asia, where they displaced the native Haobinhian hunter-gatherers, who were more closely related to the Onge than to modern Southeast Asians.

Recent genetic studies have found that the Sino-Tibetan language family likely originated in Northern China among the Yellow River millet farmers, while the Austric languages likely originated among the Yangtze River rice farmers of Southern China. These ancient populations were most similar to modern people from Northern China and Taiwan, respectively.

East Eurasian ancestry is mainly concentrated in the northern and eastern fringes of South Asia. The populations of Tibet, Burma, and Bhutan are almost entirely of East Eurasian descent, while Nepal is significantly more heterogeneous. East Eurasian ancestry is almost non-existent in India and Pakistan but can be found among the Austroasiatic-speaking tribal populations, like the Munda, who seem to be distributed quite randomly across the northeast of India.

Tibetan kids wearing fancy hats:

A Munda woman with subtle East Eurasian features:

5. European Pastoralists

The final major contribution to South Asian ancestry occurred during the Bronze Age. The Indus Valley Civilization began to decline around 1900 BC and by 1700 BC many Indus cities had been completely abandoned. Meanwhile, the Northern European population was exploding. European steppe pastoralists migrated into Central Asia from Eastern Europe around 2000 BC and expanded southwards via the Inner Asia Mountain Corridor. By 1500 BC, Europeans of the Andronovo Culture had entered South Asia via the Hindu Kush and began to conquer the collapsing Indus Valley Civilization, gradually intermixing with its native inhabitants. They introduced Indo-European languages and culture to the region and recorded their conquest via the world’s oldest religious text, the Rigveda.

The European origin of the Indo-Aryans and the migration itself was conclusively proven by genetic evidence in 2018. Leading Harvard geneticist David Reich stated that “the population that contributed genetic material to South Asia was (roughly) ~60% Yamnaya, ~30% European farmer-like ancestry, and ~10% Central Steppe hunter-gatherer ancestry” (which refers to West Siberian Hunter-Gatherers, a population similar to modern Udmurts).

Today, this European component accounts for ~0-30% of South Asian ancestry, peaking in the northwestern regions and among the upper classes of India.

Northern European phenotypes can be found among the mountain-dwelling Indo-Iranians of northern South Asia. They are not representative of the average Indo-Iranian phenotype (which is stereotypically “Middle Eastern”) and their tribes are often phenotypically diverse. Some of the earliest Indo-Aryans may have looked similar, but not identical, to the people below.

The closest modern populations to Indo-Aryans from Uzbekistan, Tajikistan, and Kazakhstan:

6. Admixture Analysis

Below is a simplified admixture analysis featuring various South Asian populations. Do not take this as gospel, it is simply a rough guide. The source populations are:

1. Andronovo from the Fergana Valley in Uzbekistan
2. Neolithic Iranian Hunter-Gatherers
3. Paniya used as a proxy for indigenous South Asian hunter-gatherers (AASI)
4. West Siberian Hunter-Gatherers from the Tarim Basin
5. Anatolian Neolithic Farmers
6. Levantine Hunter-Gatherers
7. Caucasus Hunter-Gatherers
8. Three East Asian populations:
   – Amur / Siberian
   – Yellow River / North China
   – Fujian / South China

7. Sources

Iranian ancestry:

• An Ancient Harappan Genome Lacks Ancestry from Steppe Pastoralists or Iranian Farmers
• The genetics of an early Neolithic pastoralist from the Zagros, Iran
• Genomic insights into the origin of farming in the ancient Near East

Asian ancestry:

• Peopling History of the Tibetan Plateau and Multiple Waves of Admixture of Tibetans Inferred From Both Ancient and Modern Genome-Wide Data
• A genetic history of migration, diversification, and admixture in Asia
• Unravelling the distinct strains of Tharu ancestry
• East Asian Ancestry in India
• Extensive ethnolinguistic diversity in Vietnam reflects multiple sources of genetic diversity

European ancestry

• The Genomic Formation of South and Central Asia
• The genomic origins of the Bronze Age Tarim Basin mummies