JUN 03, 2014 12:00 AM PDT

Geographic Population Structure tool or "GPS"

WRITTEN BY: Peter Micheli
Throughout history it has been very common for previously separated gene pools to mix, especially during migrations and invasions. For example, the Vikings invaded Britain and paired up with the local population to form a new Viking-Anglo-Saxon gene pool, causing what is known as "genetic admixture". As this process continues it becomes very difficult to pinpoint where an individual's DNA was formed. Some traditional tools, such as Spatial Ancestry Analysis (SPA) have an accuracy level of less than two percent.

But, groundbreaking research from Dr. Eran Elhaik of the University of Sheffield's Department of Animal and Plant Sciences and Dr. Tatiana Tatarinova of the University of Southern California models the admixture processes, making it possible to locate the exact village a person's ancestors came from going back up to 1,000 years. Before this breakthrough it was only possible to identify where DNA was formed within 435 miles. The new tool is cleverly named the Geographic Population Structure tool or "GPS."

The complexity of genetic admixture is explained by Elhaik using different colored soups as an example. "If we think of our world as being made up of different colors of soup - representing different populations - it is easy to visualize how genetic admixture occurs. If a population from the blue soup region mixes with the population from the red soup region their offspring would appear as a purple soup." As this process continues, with more and more admixture taking place, it is easy to see how difficult it can be to pinpoint an individual's DNA's ancestry.

The GPS tool was modeled using more than 100,000 DNA signatures called AIMs (ancestry-informative markers). Those are often linked to certain geographic regions, allowing researchers to pinpoint where subjects came from, even if they later moved. Dr. Tatarinova said, "We were surprised at the simplicity and precision of this method. People in a given geographical area are more likely to have similar genetics. When they also have genetic traits found in other, distant regions, the geographical origin of those traits is generally the closest location where those traits can be found."

The new method can be extremely accurate as Dr. Elhaik and his associates proved by analyzing data from 10 villages in Sardinia and over 20 islands in Oceania. In the Sardinian study, for example, a quarter of the test subjects were located to their exact villages and the rest to within 31 miles. The Oceania results were similar, with about a 90% success rate of tracing the participants to their exact island.

This revolutionary technique can help develop life-saving personalized medicine approaches, advance forensic science, and provide insight for groups whose ancestral origin is uncertain, such as African Americans, Roma gypsies, and European Jews. It could also allow adoptees to hone in on their ancestral homes. And, it has great appeal to the growing numbers of people who study their genealogy as a hobby.

It has social implications as well because it muddies racial and ethnic distinctions. Dr. Elhaik explains, "This technique also means we can no longer easily classify people's ethnic identities with one single label. It is impossible for any of us to tick one box on a form such as White British or African as we are much complex models with our own unique identities. The notion of races is simply not plausible."

Where are you from? You might be surprised to find out.
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