Historian Henry Louis Gates Jr. On DNA Testing And Finding His Own Roots

GATES: The average African-American is 24 percent European. Now think about that. And most DNA companies in the United States will tell you that they have never tested an African-American who is 100 percent from sub-Saharan Africa. This is called an admixture test. It measures your ancestry back 500 years approximately. So what that means is that it's the percent of - if you had a perfect family tree, what percent would be from sub-Saharan Africa? What percent would be from Europe? What percent would be Native American?

African-American - I love to joke about this. African-Americans all think that they're a descendant from a Native American. And the average African-American has less than 1 percent Native American ancestry, but they have 24 percent European ancestry. So where does that come from? It comes from slavery. Was this an equal sexual relationship? Of course not. So obviously rape or, at best, cajoled sexuality was the cause, but there are exceptions. When I did Morgan Freeman's family tree, it was obvious through his DNA that he was descended from a white man who was an overseer on a plantation in Mississippi. And we knew the name of his great-great-grandmother and the name of this white man. So overseer, slave plantation - rape, right? Except in the next scene, I showed him their headstones. They were buried next to each other. As soon as the Civil War ended, they became common law husband and wife...