A new study shows that African-Americans are more genetically diverse than scientists had previously believed.

The study, in Science, showed that 16 percent of African-Americans retain advantageous gene variations (like resistance to malaria) from indigenous hunter-gatherers in southern Africa who mixed with migrating Bantu-speakers. That's a higher percentage of gene-mixing than was previously known.

How they did it: Researchers analyzed genetic variations in more than 2,000 living individuals in 57 populations across Africa. They showed that Bantu-speakers migrated south through rainforests and then east over an 800-year period (which is also different than what researchers had believed previously). They then compared specific immune-related gene variations to estimate the African ancestry of more than 5,000 African-Americans in different locations in the U.S.