For example, in general, West Africans have wider faces than Europeans and Europeans have longer faces than West Africans. Researchers have used these facts to help determine the admixture percentages of a combined sample of African Americans with West African and European ancestry whose genetic makeup was known through DNA testing. The scientists found that there was a very strong statistical correlation between the amounts of admixture and the facial traits.
Genes predict the ancestry of African-Americans
Am I that predictable? Genetic variation and Jewish ancestry