Though they may speak different languages and eat distinct foods, people from far-flung geographical locations are genetically very similar, researchers say. A report published today in the journal Science suggests that 93 to 95 percent of human genetic variation exists among individuals within populations, while differences among major groups make up less than 5 percent of the variation. But the findings also reveal that even these tiny differences alone can provide enough information to group people by population.

Marcus W. Feldman of Stanford University and his colleagues analyzed samples from 1,056 people belonging to 52 populations. Specifically, they looked at 377 so-called microsatellites, short segments of DNA that occur in specific patterns. "Each microsatellite had between four and 32 distinct types," Feldman says. "Most were found in people from several continents, suggesting that only a tiny fraction of genetic traits are distinctive to specific populations. This means that visible differences between human groups--such as skin color and skull shape--result from differences in a very small proportion of genetic traits."