08/12/2025
"...what is the probability that two randomly chosen African-Americans descended from enslaved Africans forcibly transported to North America share at least one such transported ancestor in common?...the probability is approximately 19-31% that two randomly chosen African-Americans born around 1960-1965 possess at least one shared African ancestor [who was trafficked to North America]."
Meaning that in a group of five older African Americans, it is more likely than not that at least one pair shares an ancestor in that genealogical timeframe.
All African Americans descended from enslaved Africans draw from a finite, bottlenecked, overlapping genealogical pool of transported African ancestors.
As genealogical trees expand backward, overlap becomes extremely likely even at modest sample sizes.
Agranat-Tamir, L., Agwamba, K. D., Mooney, J. A., & Rosenberg, N. A. (2025). Shared ancestors and the birthday problem. The American Statistician, (just-accepted), 1-18.