The biggest message, though, is that these differences are the details, not the main message, of human diversity. About 90 percent of the full catalogue of human genetic diversity exists in every human population. Individuals are likely to have almost as many differences with people we consider to be “like us” as with strangers on the other side of the world.

“What this says is that we are all extremely related to each other,” said Richard Myers, a geneticist at Stanford University School of Medicine, who helped lead one of the studies in the journal Science. “Most genetic variation is shared worldwide. It is only a small part of human genetic variation that is private to particular continents,” said Noah Rosenberg, of the University of Michigan. His group’s findings were published in the journal Nature.

All three studies examined single “letter” changes in the 3-billion letter transcript that makes up each person’s genome. Every individual carries tens of thousands of these variations. Some don’t change the “words” that are the genes; some change a word but not its meaning; and some change the meaning in a way that can be beneficial or harmful. Each person’s collection of these changes (called “single nucleotide polymorphisms, or SNPs) contributes to his or her individuality. People with a common ancestry, however, tend to have somewhat similar collections of SNPs.

“There is no single gene, no single DNA marker, that would distinguish one population from another,” Myers said. Instead, he said, “it is a pattern, like a bar code with thousands of lines on it,” that allows researchers to tease apart the fine points of relatedness between populations.

... contd.