Bangalore: A pan-Asian effort to study the genetic diversity of the region has found evidence that, to a large extent, settles a long-standing debate about how the continent was populated.
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Genetic data suggests that the initial settlement in Asia took place with a single entry of modern humans along the southern coastal route of what constitutes present-day India.
When exactly this event took place is yet to be determined.
Reporting in Friday’s issue of Science, a team of scientists from 40 institutions in 11 countries say it came to the conclusion after examining genetic data from about 2,000 people representing 73 populations across Asia.
For long, scholars have debated whether people migrated in two waves—to South-east Asia and later to Central and North-east Asia—or in a single wave of south-to-north movement. The new study, scientists say, sets the human genetic history straight.
“When we found out that all of humanity was derived from a migration out of Africa, it reversed centuries of Eurocentrism. That all Asians probably came through South-east Asia and migrated northward, once again brings us closer together, conceptually, as one people,” says co-author Edison Liu, executive director of the Genome Institute of Singapore and one of the key organizers of the HUGO Pan Asian SNP Consortium, which has been studying genetic diversity in Asian populations.
“I am delighted to see that this paper confirms our earlier hypothesis on early human migration,” says Kumarasamy Thangaraj, a scientist at the Centre for Cellular and Molecular Biology in Hyderabad.
Studying populations on the other side of the Indian Ocean, in Andaman Islands, his team reported in Science in 2005 that the southern route of migration was more plausible.
“Using a large sample size, the consortium has established the genetic affinities between East and Southeast Asian population. I wish they would make the data available for the scientists for comparative studies, which is useful for addressing several issues related to affinities of populations,” adds Thangaraj.
Evidently, that seems to be the purpose of the consortium. In India, it collaborates with the Council of Scientific and Industrial Research (CSIR) initiative called the Indian Genome Variation (IGV) consortium, which has supplied data from nine Indian populations for the latest study.
Samir K. Brahmachari, director general of CSIR, says it’s just the beginning—the significant amount of genetic differences within Asian populations can be a goldmine for discovery as scientists study disease and drug response.
In fact, the collaboration has already begun, says Shuhua Xu of the Chinese Academy of Sciences-Max Planck Society Partner Institute for Computational Biology in Shanghai, a consortium member.
Xu is currently in Delhi to sign a research pact to study the “copy number variations” in the Indian and Chinese populations. It was traditionally believed that there are two copies of a gene in a genome, but recent discovery shows that copies could vary in number, from one to three or more.
If people have multiple copies of the gene then drugs don’t work, said Brahmachari. Certain drugs have failed in China and Japan; a joint study will give us a lot of insight on drug responses, he added.
According to an IGV member in Delhi, Mitali Mukherjee, Indian researchers are gearing up to extend the IGV data to the larger world population data to study relatedness.
The present study, as well as IGV’s earlier study, shows that genetic ancestry is strongly correlated with linguistic affiliations as well as geography. Most populations show relatedness within ethnic/linguistic groups.
The immediate impact of this, says Liu, is the knowledge that there is greater diversity from North Asia to South-east Asia and South Asia. As scientists conduct genetic association studies to uncover genetic causes of disease, they will have to take into account this geographical diversity in the matching of subjects and controls.
However, there’s a derivative benefit from this, says Liu; and that is “fostering of genetic pride”.
“That any nation can boast of genetic uniqueness either because of singularity or of diversity is gratifying.”
Graphics by Ahmed Raza Khan / Mint