Written by Petar Todorov, Tufts University
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Services to trace our ancestry have been around for quite some time. If you’re curious enough (and are willing to spring about $100), a genotyping test will tie your molecular blueprint to a specific region on the planet. Last week a technique to determine when geographically different populations met in time was published by a team of European scientists in the journal Science.
This particular method is based on understanding the mechanics of human reproduction on the molecular level. In the case of a child formed between a Roman soldier and a Gallic woman, this would mean that one chromosome comes from the mother and one from the father. However, chromosomes break and remix. As a result, the child will not end up with only Roman or Gallic chromosomes in its eggs or sperm. For example, some of these sex cells could carry a chromosome that will be 20% from dad and 80% for mom. With each subsequent generation, the fragments from the foreign population continue becoming smaller and more intermixed within the local DNA.
By comparing the fragmentation of foreign DNA within local populations around the globe the bioinformaticians have identified several historical events in which different groups of people came together. For example, the Kalash of Pakistan, who claim they are descendants of Alexander the Great’s army, bear genetic evidence of encountering Europeans around 900-200BCE. Genghis Khan, another conqueror active in the thirteenth century left his mark not only on history but on genetics as well. The populations in his path bear evidence of intermixing with the Mongol people in an event that happened 22 generations ago, or around 1306CE. Other admixture events detected by the scientists are the colonization of the Americas by the Spanish or less violent encounters among the Silk Road such evidence of Greeks coming in contact with the Tu people of China around 1100CE.
These new methods will hopefully lend greater evidence for history or eventually gain the ability to inform new avenues of research about events which are forgotten by man but recorded in genes. For the curious, the results of the study are available with this interactive map.
Petar Todorov is a guest contributor to Project Lever Magazine. Petar is an undergraduate student at Tufts University and very involved in research as well as the Tufts iGEM team.