A genetic link between Indians and two Aeta populations were unveiled in a study whose proponents include Frederick Delfin, university research associate at the DNA Analysis Laboratory in the University of the Philippines, Diliman.
According to Delfin, it is commonly accepted that the Asia-Pacific—including the Philippines—was peopled by human migration that passed through the coast of South Asia.
But the mitochondrial DNA (mtDNA) Indian-Philippine genetic link that Delfin and his team found “can be a signal of shared ancestry that actually originated from India”.
Two mtDNA sets, M52'58 and M52a, that both originate from Indian populations were found in the Aetas of Zambales and the Agtas of Iriga in the Philippines.
These shared common haplogroups show a link between the populations of India and the Philippines that is about 5,000 to 20,000 years old. This suggests that these migratory groups from India arrived before the Austronesian people landed in Philippine shores and populated the prehistoric Philippine archipelago.
Link found in female lineage
Mitochondrial DNA or mtDNA are the parts of a person's genome passed on by mothers to their children; only women pass them from generation to generation.
Common mtDNA haplogroups or specific lineages were found in some Philippine and Indian populations which suggest common origins between the two.
Since mtDNA ancestry is matrilineal and not a combination of genetic material from both parents, tracing someone's lineage through the mtDNA is a somewhat straightforward process.
Indian origins not found in other Southeast Asian groups
science blogger Nathaniel Hermosa said, is noteworthy because it is unique to the Philippines.
Established genetic studies showed that no such link has been found in other Southeast Asian groups.
“We also studied about 1,700 other mtDNA genomes (samples or individuals) across the Asia-Pacific region and did not find these two haplogroups anywhere else,” Delfin said in an email interview with GMA News Online.
Hermosa posed the question: “How did the people from South Asia travel to the Philippines without passing through the rest of Southeast Asia?”
Other regions in Southeast Asia might have been undersampled in this study, he added.
Delfin acknowledged this possibility, stating that, in reality, not all populations in the Asia-Pacific region have been studied. So other Southeast Asian haplogroups that could also share links to the Indian populations may not have been sampled yet.
Another possibility, he says, is a phenomenon called “genetic drift” in which historical accidents—natural disasters, for example, like earthquakes or floods—wipeout entire populations, leaving lucky survivors. This means that the survivors pass on their genes largely as a result of chance rather than natural selection.
Over time, the haplogroups that originated from India in other Asia-Pacific populations may have been eliminated, leaving only the ones observed between India and the Philippines.
Arrival of migratory groups from India
The same study also suggest “a genetic signal of a possible migration event that happened after the initial peopling of the Asia-Pacific region.”
Somewhere between the initial peopling of Asia and Pacific regions and the Austronesian expansion, those migratory groups from India came to the Philippines.
“This estimated age (5,000 to 20,000 years ago) is somewhat in between the estimated ages of the initial peopling of the Asia and Pacific regions (50,000 to 70,000 years ago) and the Austronesian expansion (5,000 to 7,000 years ago),” said Delfin.
The latter are thought to be the two major peopling events of the Philippines.
“Somehow after the ancestors of Asia-Pacific peoples first settled the region, there were subsequent population movements around the Asia-Pacific, that could have brought such Indian specific mtDNA haplogroups to the Philippines' prehistoric archipelago,” Delfin explained.
Calls for further study
Further investigation of this data will be done through an on-going project that focuses on different Negrito groups using autosomal single nucleotide polymorphism (aSNP) data, which unlike mtDNA data, is not limited to the female lineage and represents more the entirety of a person's genome.
This project is funded by Department of Science and Technology, Philippine Council for Health Research and Development (DOST-PCHRD).
The main proponent of this project is the Institute of Human Genetics, National Institutes of Health, UP Manila, (UP-NIH-IHG) headed by Dr. Eva Cutiongco-de la Paz, and is done in collaboration with the University of the Philippines Natural Sciences Research Institute DNA Analysis Laboratory (UP-NSRI-DAL) are collaborators in this project.— TJD, GMA News