Latest research shows that the presence of the genetic mutation for lighter skin - found in "almost 100 percent" of Europeans - broadly conforms to many cultural and linguistic differences, as well as ancestral, in the wider Indian population. (Agencies)
The genetic mutation in SLC24A5 is known to be pivotal in the evolution of light skin, and is responsible for a significant part of the skin colour differences between Europeans and Africans.
Now, a new study has examined for the first time a large, uniform genetic sample collected directly in south India, and suggests that natural selection is not the sole factor in skin tone variation across the Indian sub-continent, and that cultural and linguistic traits still delineate this skin pigment genetic mutation.
The results show that the gene is found with much higher frequency in Indo-European speaking groups that are more prevalent in the north-west of the country.
But the mutation is also high in populations groups known to have migrated north to south, such as the Saurashtrians, who - while native to Gujarat - are now predominantly found in the Madurai district.
Researchers say that the study, published in the journal PLoS Genetics, shows that the genetic mutation in SLC24A5 has a common origin between Europeans and Indians.
But while the complete dominance of the gene in Europeans is likely to be solely down to natural selection, they say, the rich diversity of this genetic variant in India - high in some populations while non-existent in others, even neighbouring ones - has some correlation with factors of language, ancestral migration and distinct social practices such as limiting marriage partners to those with specific criteria.
The researchers say the findings display an "intriguing interplay" between natural selection and the "unique history and structure" of populations inhabiting the Indian subcontinent.
"In India, this genetic variant doesn't just follow a 'classical' theory of natural selection - that it's lower in the south where darker skin protects against fiercer sunlight," said study co-author Mircea Iliescu from Cambridge University's Biological Anthropology Division.
"The distribution of the SLC24A5 genetic variant in India follows patterns very much influenced by population. Understanding the genetic architecture behind the remarkable skin colour variation found today in the populations of India has the potential to shed light on the wider mechanisms responsible for creating diversity throughout human evolution," Iliescu said.
Latest research shows that the presence of the genetic mutation for lighter skin - found in "almost 100 percent" of Europeans - broadly conforms to many cultural and linguistic differences, as well as ancestral, in the wider Indian population.