For ten years, Genographic Project scientists have explored and explained how patterns in our DNA show evidence of migration out of Africa and across the globe. But new research shows that eventually some of our ancient ancestors also moved back. (Nat Geo Explorers Journal)
- To uncover evidence of an ancient migration pattern, scientists studied the DNA of a specific haplogroup (O2a1). What is a haplogroup?
- A haplogroup is a group that shares a set of similar DNA sequences (called haplotypes). Haplogroups are used to understand genetic lineages. Learn more about haplogroups here.
- According to the Genographic Project, “Your haplogroup is your branch on the human family tree. All people alive today belong to distinct haplogroups based on the sequence of genetic markers carried in their cells. People belonging to the same haplogroup can trace their descent to a common ancestor and even a specific place where that ancestor may have lived.”
- The map above shows some dominant haplogroups around the world.
- Geneticists who conducted the new research say they studied the O2a1 haplogroup because “it accounts for almost 15 percent of Indian male lineages and 58 percent of male lineages from Southeast Asia,” among other reasons. What about the women? What percentage of Southeast Asian women belong to the O2a1 haplogroup?
- They don’t. Like all the haplogroups shown on the map above, O2a1 is a Y-chromosome haplogroup. That means the DNA sequences (haplotypes) that link this specific group are found on the Y chromosome. And only men have Y chromosomes. (Men also have X chromosomes. Women only have Xs. There are, of course, significant exceptions.)
- Read through the terrific Explorers Journal blog post, then take a look at the map at the top of this post or the more simplified map of the “Global Human Journey” above. The migration pattern described in the blog post is a little different than what geneticists may have expected. What is the typical migration pattern in Southeast Asia? How is the new pattern different?
- DNA has shown that genetically modern humans left Africa around 60,000 years ago and went eastward into Asia.
- The new study shows that a population (the O2a1 haplogroup) migrated from what is now Laos and Southeast Asia westward—back to the Indian subcontinent.
- Take a look at the map at the top of this post. What type of migration routes do you think the ancient O2a1 population used in order to move from Southeast Asia to the Indian subcontinent?
- They could have followed overland routes, trekking through the lowland plains and forests of what are today Laos, Thailand, Myanmar, Bangladesh, and India.
- They could have followed rivers and their tributaries, such as the Mekong, Irawaddy, and Ganges-Brahmaputra.
- They could have followed coastal migration routes, navigating the northern shore of the Bay of Bengal, including the mighty Ganges-Brahmaputra delta.
Nat Geo: The Global Human Journey video
Nat Geo: Genographic Project Education
Nat Geo: The Genographic Project (Celebrating 10 years of mapping the human story!)
(extra credit) Journal of Systematics and Evolution: A late Neolithic expansion of Y chromosomal haplogroup O2a1-M95 from east to west