Genes loosen iron casts of Indian castes

Pure castes are a myth.

How old is India's caste system? How many ancestries have made up the mosaic of Indian civilisation?

It was believed that two kinds of people - Ancestral North Indian ( ANI ) and Ancestral South Indian ( ASI ) - entered India at different times. These two groups intermingled, but over time, reduced their interaction and then stratified. Thus caste was born

A study - published in last week's Proceedings of the National Academy of Sciences - finds that this story isn't so neat. There, authors proffer evidence for two more groups - Ancestral Austro Asiatic (

AAA ) and Ancestral Tibeto-Burman (

ATB ) that currently constitute much of India's tribes.

In the graphic below, nine caste/ethnic tribe groups of 20, studied by the scientists, are depicted with their rough, geographical location. The four circles represent the four ancestries that have made up mainland India -

ANI, ASI, AAA and ATB - and the coloured arches in the chart show the proportion of genes from these ancestries that make them.

Pure castes, thus, are a myth.

Social and cultural characterists of nine population groups

Name	Description	Sample Size
Khatri (KSH)	Upper caste/ North/ Indo-European/ Traditionally warrior	19
Maratha (MRT)	Upper caste/ West/ Indo-European/ Traditionally warrior	7
Iyer (IYR)	Upper caste/ South/ Dravidian/ Traditionally priest	20
Gond (GND)	Tribe/ Central/ Dravidian/ Austro-Asiatic/ Agriculturist	20
Paniya (PNY)	Tribe/ South/ Dravidian/ Austro-Asiatic/ Hunter-Gatherer	18
Birhor (BIR)	Tribe/ Central/ Austro-Asiatic/ Hunter-Gatherer	16
Kadar (KDR)	Tribe/ South/ Dravidian/ Hunter-Gatherer	20
Ho (HO)	Tribe/ Central & East/ Austro-Asiatic/ Agriculturist	18
Jarawa (JRW)	Tribe/ Andaman and Nicobar/ Ongan/ Hunter-Gatherer	19

Mainland India's four ancestral components

The genes that make up castes

The following numbers show approximately the number of generations before which caste groups became endogamous. For instance, 70 generations (22 years for a generation) ago, the Iyers had genes from both AAA and ASI whereas around the same time the HO had genes from three ancestries.

Castes thus began to harden and the upper castes became endogamous only around 1500 years ago.

Key:

Khatri KSH | Gujarati Brahmin GBR | West Bengal Brahmin WBR | Maratha MRT | Iyer IYR | Kadar KDR | Irula IRL | Paniya PNY | Gond GND | Ho HO | Santal SAN | Korwa KOR | Birhor BIR | Manipuri Brahmin MPB | Tharu THR | Tripuri TRI | Jamatia JAM | Jarawa JRW | Onge ONG | Pallan PLN

(Authors: Analabha Basu, Neeta Sarkar-Roy, Partha P. Majumdar. Text: Mohit Rao)

(Graphics: Deepak Harichandran and L Balamurugan)