A Genetic ‘GPS’ Can Track Your Origins 1,000 Years Back

It works by disregarding the entire concept of race.

May 2 2014, 3:04pm
A new method for DNA tracking can pinpoint your ancestry with impressive accuracy. Image: Wikimedia

A new “GPS” for your DNA can track your where your ancestors lived a millennium ago, and much more accurately than previous methods—down to the exact village in some cases.

The GPS method stands for Geographic Population Structure, and is a play on words as it helps you find your way home, just not the home you currently live in, explain the researchers behind the method, Ehran Elhaik of Sheffield University and Tatiana Tatarinova of the University of Southern California.

According to their study published this week in Nature, the tool has traced DNA origins with 98 percent accuracy, while previous methods were often off by 700 km, which is a whole different country in some parts of the world. But when researchers applied their GPS-based approach to over 200 Sardinian villagers, they were able to place a quarter of them in their villages of genetic origin, and the rest within 50 km.

The increased accuracy of the new model is based on a simple, if controversial, assumption made by the study authors: that race doesn’t exist.

“The model of races is incorrect and should be dismissed," Elhaik told me in an email.

Up until now, tracing genetic origins assumed that people could be typified as a mix of two to three defined races, presupposing a homogenous “European” identity, Elhaik said. “By contrast, GPS represents a paradigm shift in population genetics whereby all populations are considered admixed to various degrees.”

Admixing occurs when one gene pool mixes with another to create a whole new one. You can think of it like how primary colours mix to create new palettes and shades—“red” people from region A breed with “blue” people from region B, creating a new group of “purple” people, genetically speaking.

What the study assumed, if you’ll forgive the analogy a moment longer, is that there aren’t purely “red,” “yellow,” or “blue” people in terms of genetic makeup; we’re all somewhere in between, and every population worldwide displays a certain amount of admixing.

“We developed this paradigm because, looking back at human history, populations have never set foot and ‘evolved’ from one another as some geneticists believe. Rather, they constantly moved and when they arrived to a new place, they mixed with the local population,” Elhaik said. “A realistic model of human genetic diversity should assume mixture in all human populations, rather than succumb to simplistic assumptions.”

A color-coded depiction of the genetically mixed human population. Image: Nature

The researchers take this admixture data and use it as a reference point to calculate the exact relationships between specific admixtures and geographic locations. A DNA sample of unknown origin is broken down into its unique admixture—what Elhaik refers to as a kind of genetic fingerprint—which is derived from different gene pools. GPS then matches this “fingerprint” to a population that has a similar genetic admixture, and using a powerful algorithm developed by the team, matches the source DNA to a specific geographic location.  

Some populations, however, are so genetically mixed that their unique regional admixture is difficult to calculate, even with GPS. “Places like New York, Israel, London, and Kuwait have a large number of immigrants that create genetic diversity,” Elhaik explained. “It is very difficult to create a genetic signature for London that would allow us to place all the residents in London as accurately as we did with Sardinian villagers.”

The tool is a ground-breaking innovation for DNA tracking, which has applications for forensics, genetics research, and personalized medicine.

But even more interesting, it starts to blow up the very idea of race—an evolution theory proposed as far back as 1871 by Charles Darwin. He wrote in The Descent of Man and Selection in Relation to Sex that “it may be doubted whether any character can be named which is distinctive of a race and is constant.” 

A century and a half later, geneticists are working to back that theory up.

“I hope that our paper would help convince people that what we call human ‘populations,’ or ‘races,’ or ‘ethnicities,’ are essentially very similar groups of people,” Elhaik said. “Although their genomes were shaped by uneven demographic processes such as migrations and slavery, alongside random processes, we are still all very much alike.”