JOIN USA study by the city-based CCMB has shown eight generations (200 years) of unidirectional gene flow into the Siddis from neighbouring Indian populations.
Disclosing the results of the study today, CCMB Director Mohan Rao and Senior Scientist K Thangaraj said their research was aimed at looking at the part of Africa they have originated from, the likely founder population of Indian Siddis, the admix with neighbouring Indian populations and the medical and social implications of admixture.
Siddis are mainly found in Gujarat, Karnataka and Andhra Pradesh. They have typical African features like dark skin, curly hair and broad nose, Rao said.
Rao said historically, Siddis had been brought by Portuguese traders during 17th and 19th centuries and sold to Nawabs and Sultans in India to serve as soldiers and slaves.
Scientists at CCMB screened the Siddi populations from Junagarh district of Gujarat and Uttara Kannad district of Karnataka with hundreds of thousands of genetic markers.
Finally, they selected three different sets of markers, Y-chromosome markers, which are paternally inherited, mitochondrial DNA markers, which are maternally inherited and the autosomal markers that are inherited from both parents.
Along with Siddis, CCMB also analysed six populations, who are inhabited in the close vicinity of Siddis, to establish their gene inflow, Rao explained. The statistical evidence show the Siddi population has a combination of ancestries (ie 70% Africans and 30% Indians and Europeans), according to the study.
The scientists further estimated that Siddis might have admixed with the neighbouring Indian populations for about 200 years (8 generations) ago.
"Our genetic finding coincides with the historical record of the arrival of Siddis in India. We also observed 10 per cent of the African-specific genetic signatures in Siddis, which gives protection against malaria," Rao added.
Further investigation revealed that among the sub- Saharan African populations, Siddis are the direct descendants of the Bantu-speakers. Scientists found the presence of the Indian-specific genetic signature in Siddis but not vice versa, suggesting the unidirectional gene flow from the Indian populations to Siddis.
The admixture of Siddis with the neighbouring populations has remarkable medical and social implications. A genetic variant, which originated in Africa about 5,000 years back to protect against malaria, has been found only in 10 per cent of the Siddi population, the CCMB Director said.
"This low frequency is mainly due to their admixture with the neighbouring Indian populations, which ultimately makes Indian Siddis more susceptible to malaria than their African ancestors," Rao added