The Atlantic

What Can You Do With the World's Largest Family Tree?

Scientists are beginning to find out.
Source: Daniel Maurer / AP

Your family tree might contain a few curious revelations. It might alert you to the existence of long-lost third cousins. It might tell you your 10-times-great-grandfather once bought a chunk of Brooklyn. It might reveal that you have royal blood. But when family trees includes millions of people—maybe even tens of millions of people—then we’re beyond the realm of individual stories.

When genealogies get so big, they’re not just the story of a family anymore; they contain the stories of whole countries and, at the risk of sounding grandiose, even all of humanity.

Last week, scientists using data from and each unveiled papers analyzing the genealogies. The team first analyzed the DNA tests to find clusters of closely related people in the present. Then, they matched up the people in those clusters with genealogy records containing 20 million people, which included the birthplaces of several generations of ancestors. With that, they could march backwards in time to see how those ancestors migrated across the U.S.

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