Henry Louis Gates writes in the NYT:
"I have been studying the family trees of 20 successful African-Americans, people in fields ranging from entertainment and sports (Oprah Winfrey, the track star Jackie Joyner-Kersee) to space travel and medicine (the astronaut Mae Jemison and Ben Carson, a pediatric neurosurgeon). And I’ve seen an astonishing pattern: 15 of the 20 descend from at least one line of former slaves who managed to obtain property by 1920 — a time when only 25 percent of all African-American families owned property.
"Ten years after slavery ended, Constantine Winfrey, Oprah’s great-grandfather, bartered eight bales of cleaned cotton (4,000 pounds) that he picked on his own time for 80 acres of prime bottomland in Mississippi. (He also learned to read and write while picking all that cotton.)"
Of course, he needs a control group of unsuccessful African-Americans to see if they are significantly less likely to be descended from black property owners (not to mention white property owners, who often tended to be the original source of wealth for their mulatto offspring who disproportionately made up the African-American middle class), but I would hardly be surprised that black people who make something of themselves today tend to be descended from black people who made something of themselves in the past. Similarly, economic historian Gregory Clark found that today's English tend to be descended from successful landowning farmers of the past, rather than from the propertyless poor who worked for them.
In summary, a lesson I've often pointed out is that we aren't self-made Ayn Rand heroes. Who your relatives are matters.