Religious following: The Y chromosome in India 1/12/06. By Chrissie Giles Research has revealed that the spread of Islam in southern India was down more to culture than to genes.

The Y chromosome is a useful bit of DNA. Studies of this chromosome - which is passed down from father to son - can tell us a great deal about our history, from measuring the relatedness of men with the same surnames to tracking the spread of the first humans out of Africa.

A group from the Wellcome Trust Sanger Institute, led by Dr Chris Tyler-Smith, has been using the Y chromosome DNA sequence to look at the relationship between the spread of language and the spread of genes in the Himalayas; as a side project to this study, the researchers decided to examine the way another cultural phenomenon - religion - had spread through India.

One of the most significant religious changes in India was the arrival of Muslims from central Asia, which began in the 8th century. Marriage between Muslim men and Hindu women, and the resulting birth of Muslim offspring, was a key part of this Islamisation.

As such, the team investigated the extent to which this cultural change was reflected in the Y chromosomes of Indian Muslims today.

Previous studies of the genetic background of Indian Muslims have produced mixed results. However, given evidence from Islamisation in other parts of Asia, it seemed likely that some kind of genetic mark would have been left by these religious changes.

The team typed the Y chromosomes of nearly 250 unrelated men from Andhra Pradesh in southern India and compared them to those of over 4000 Muslim and non-Muslim men from other parts of the world, including North India, Central Asia and the Middle East.

Surprisingly, the Y chromosomes of the Andrha Pradesh Muslims were genetically more alike to those of geographically close non-Muslims than those of Muslims elsewhere in India. So, in terms of the Y chromosome at least, religion and genetics are not closely related here, but geography and genetics are.

These findings may indicate that inter-religious marriage was not enough to replace the Y-chromosome heritage of Hindus, built up over thousands of years before. Unlike in other parts of Asia, the spread of Islam in southern India seems to have been more cultural than genetic.

Further reading

Gutala R et al. A shared Y-chromosome heritage between Muslims and Hindus in India. Hum Genet 2006;120(4):543-51. Abstract