Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, Oxford University, and University College London have published an interactive map to show how genes from different population groups around the world have mixed as historical events occurred, the journal Science reports.
When different population groups interbreed, their offspring’s DNA is a mixture of the DNA from each group. Pieces of this DNA are then passed along through subsequent generations, carrying on all the way to today.
Modern genetic data combined with appropriate statistical methods have the potential to contribute substantially to our understanding of human history. We have developed an approach that exploits the genomic structure of admixed populations to date and characterize historical mixture events at fine scales. We used this to produce an atlas of worldwide human admixture history, constructed by using genetic data alone and encompassing over 100 [historical] events occurring over the past 4000 years. We identified events whose dates and participants suggest they describe genetic impacts of the Mongol empire, Arab slave trade, Bantu expansion, first millennium CE migrations in Eastern Europe, and European colonialism, as well as unrecorded events, revealing admixture to be an almost universal force shaping human populations.
Resources on the Internet
A release by the Max Planck Institute for Evolutionary Anthropology is available here. The map itself, along with the accompanying article, is available from the project’s site, here.
Playing with the map is fairly straightforward. For example, key events in the history of Cambodia can be mapped genetically by selecting “Cambodian” from the “Historical Event” menu. When you do that, you see the paths people took as they flooded into Cambodia in the 1200s–1500s, and can read about the proportions in which they did the flooding.
“We infer a ~19% contribution from a source that is related to modern-day Central, South and East Asians, and an ~81% contribution from a source related specifically to modern-day Han and Dai, the latter a branch of the Tai people who entered the region in historical times,” we read below the map. “This event, with similar proportions to those inferred is dated to 1362CE (1194–1502 CE), a period spanning the end of the Indianized Khmer empire (802–1431 AD), one of the most powerful empires in Southeast Asia whose fall was hypothesized to relate to a Tai influx.”
Oh, how easy it is
“What amazes me most is simply how well our technique works,” Garrett Hellenthal, professor at the University College London’s Genetics Institute and lead author of the study, said. “Although individual mutations carry only weak signals about where a person is from, by adding information across the whole genome we can reconstruct these mixing events.
“Sometimes individuals sampled from nearby regions can have surprisingly different sources of mixing. For example, we identify distinct events happening at different times among groups other than the Hazara sampled within Pakistan, with some inheriting DNA from sub-Saharan Africa, perhaps related to the Arab Slave Trade, another from East Asia, and yet another from ancient Europe.
“Nearly all our populations show mixing events, so they are very common throughout recent history and often involve people migrating over large distances.”
Some gene painting from North America
The map also shows two population groups in North America, including the Mayan people.
“If you were to paint the genomes of people in modern-day Maya, for example, you would use a mixed palette with colors from Spanish-like, West African and Native American DNA,” said Daniel Falush of the Max Planck Institute, co-senior author of the study. “This mix dates back to around 1670 AD, consistent with historical accounts describing Spanish and West African people entering the Americas around that time.
“Though we can’t directly sample DNA from the groups that mixed in the past, we can capture much of the DNA of these original groups as persisting within a mixed palette of modern-day groups.”