White Americans share broad European roots—but their regional ancestry patterns tell different migration stories.

In this 2015 study, 148,789 self-identified European American 23andMe customers average 98.6% European ancestry. This is a sample average, not a rule for every White American.

British/Irish ancestry averages over 20% in every state analyzed. In Mississippi, Arkansas and Tennessee, it exceeds 50%. The authors suggest that less later immigration from other European regions may help explain the strong Southern signal.

Further north, Scandinavian ancestry reaches 10% or more on average in Minnesota and the Dakotas, while most states show only trace averages. Eastern European ancestry peaks in Illinois, Michigan and Pennsylvania, consistent with immigration into the Midwest and Northeast in the late 1800s and early 1900s.

Smaller Iberian signals also appear in Florida, Louisiana, California and Nevada. Spanish colonial history is one possible explanation, not a genetically proven route.

European ancestry is not the whole story for everyone. In Louisiana, as many as 8% of participants meet a 1% Native American ancestry threshold. About 5% in Louisiana and South Carolina meet a 2% African ancestry threshold. Those are shares of people—not average ancestry percentages.

A simplified model suggests roughly ten times as many female as male Native American ancestral contributions. This is inferred sex bias, not a literal count of ancestors. The authors place the detected non-European mixing mainly in the Americas within the last 500 years relative to the study.

The regional analysis includes 45,783 European Americans with location data. These customers are not a representative census, and the ancestry labels measure reference affinities—not exact national origins or personal identity.

📚 Source: Bryc et al. (2015), The American Journal of Human Genetics
The Genetic Ancestry of African Americans, Latinos, and European Americans across the United States

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