John Novembre, a population geneticist at the University of California, Los Angeles, has discovered that it is possible to tell a Finn from a Dane and a German from a Brit by reading single-letter DNA differences in the genomes of thousands of Europeans.
"It tells us that geography matters," New Scientist magazine quoted Novembre as saying.
The researchers say that despite language, immigration and intermarriage, genetic differences between Europeans are almost entirely related to where they were born.
They, however, insist that this fact should not be taken to mean that the citizens of each European nation represent miniature races.
"The genetic diversity in Europe is very low. There isn't really much," says Manfred Kayser, a geneticist at Erasmus University Rotterdam in the Netherlands.
Research teams led by Kayser and Novembre identified the gene-geography pattern only by analysing hundreds of thousands of common gene variants called single nucleotide polymorphisms (SNPs) across the genomes of people from about two-dozen countries.
The researchers describe SNPs as places in the genome where a person's DNA may read A, while another's T.
Although the two teams worked separately, they used some of the same DNA samples that were gathered by the pharmaceutical company GlaxoSmithKline to help hunt for genes linked to drug side effects.
The researchers recorded the results alongside the country of origin for each subject as well as that of their parents and grandparents when possible.
Half a million SNPs were decoded for each subject, but to get an overall assessment of the difference between any two genomes, the researchers used a mathematical trick that scrunched the hundreds of thousands of SNPs into two coordinates, with each person's genome represented by a point.
The greater the distance between two points, the greater the difference in their genomes.
A striking map of Europe emerged when the two teams plotted thousands of genomes on a single graph along with their country of origin.
While Spanish and Portuguese genomes clustered "south-west" of French genomes, Italian genomes jutted "south-east" of Swiss.
The researcher said that though the cardinal directions were artificial, the spatial relationships between genomes were not.
The closer together two people lived, they added, the more similar their DNA.
Telling about the accuracy of the map, Novembre revealed that when a geopolitical map was placed over it, half of the genomes landed within 310 kilometres of their country of origin, while 90 per cent fell within 700 km.
Both teams found that southern Europeans boast more overall genetic diversity than Scandinavians, British and Irish.
"That makes perfect sense with the major migration waves that went into Europe," says Kayser, noting Homo sapien's European debut 35,000 years ago, post-ice age expansions 20,000 years ago, and movements propelled by the advent of farming 10,000 years ago.
In each case, members of established southern populations struck north.
"A pattern in which genes mirror geography is essentially what you would expect from a history in which people moved slowly and mated mainly with their close neighbours," says Noah Rosenberg, a geneticist at the University of Michigan in Ann Arbor.
The studies have been published in the journals Nature and Current Biology.