Scientists have shown that they can use genomic analysis to pinpoint a person's geographical origins to within just a few hundred kilometers. Besides offering possibilities for the testing of genetic ancestry, the research could also have important implications for understanding the role of genes in complex diseases and other genomic-based health studies.

By plotting the differences between genetic variations of 3,000 Europeans in a two-dimensional grid, the researchers were able to reveal a pattern that looks remarkably like Europe. The scientists included researchers from Cornell University; the University of California, Los Angeles (UCLA); the University of Chicago; and the University of Lausanne, in Switzerland. The findings appear in this week's issue of Nature.

Others have recently published similar research, in Current Biology, says John Novembre, a coauthor of the Nature paper and an assistant professor at UCLA. But the latest study goes further, by using algorithms to try to predict a person's geographical origin based purely on his or her genetic variations, with a high degree of accuracy. The scientists were even able to reveal patterns of origin distinguishing French-, German-, and Italian-speaking groups within Switzerland.

In many respects, the results are not at all surprising, says Michael Krawczak of the Institute for Medical Informatics and Statistics at the Christian-Albrechts University of Kiel, in Germany, who took part in the Current Biology study. It was well established that the farther apart two people's origins, the more different their genes will be, he says. "But it had never been shown before at a genome-wide level."

One of the reasons that this is now possible is the plummeting cost of genotyping, says Novembre. The Affymetrix GeneChip measures 500,000 single nucleotide polymorphisms (SNPs)--variations at a single point in the genome--for just a few hundred dollars, he says.

Genetic samples were chosen to include individuals whose geographic ancestry could be determined, based on having all four grandparents coming from the same country.

The researchers then created a two-dimensional map with individuals positioned according to how similar or how different they are from all the others. When color-coded to show where each of their grandparents is from, the results are compelling, clearly showing the shape and boundaries of Europe.