Everyone on Earth is related to everyone else, DNA shows

The history of Europe is written in its people's DNA.

The Huns and the Slavs made incursions into Eastern Europe about 1,500 years ago. Migrants moved from Ireland to England in recent centuries. Populations in Italy and Spain have been comparatively stable.

None of this is breaking news. But scientists were able to see it anew by examining the patterns of genes in 2,257 people now living in 40 countries on the continent.

It's surprising "how much past history was still evident in the patterns we've seen," said Peter Ralph, a computational biologist at USC who reported the findings Tuesday in the journal PLOS Biology.

Ralph and his former postdoctoral advisor, Graham Coop, a geneticist at UC Davis, conducted their analysis by looking at the Population Reference Sample data. The data include language and country-of-origin information for several thousand European people, along with DNA sequences covering 500,000 locations on the genome that are known to vary from person to person.

Coop and Ralph used computer programs to ferret out sequences that were identical or nearly identical and used the matches to figure out who was related to whom.

Following the DNA trails they encountered, the researchers were able to confirm that Europeans living near one another were more closely related than Europeans living farther apart.

They were also able to put a time frame on the genetic relatedness they saw, by examining the length of the DNA segments the people shared.

The DNA sequences you have in common with each of your parents are quite long, the chunks you share with each of your four grandparents are half as long, and the bits you share with each of your eight great-grandparents are half as long again.

"The longer ago an ancestor is, the shorter the chunk is likely to be," Ralph said.

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Everyone on Earth is related to everyone else, DNA shows