A recent study has unveiled significant insights into the family connections among African Americans, suggesting that the term “cousin” might often indicate a genuine familial relationship. Published on February 7, 2026, in the journal The American Statistician, the research employs a mathematical model to explore the genealogical ties that exist among African Americans, particularly in the context of the historical impact of slavery.
The study, led by Noah Rosenberg, a professor of biology at Stanford University, reveals that individuals born between 1960 and 1965 have a probability ranging from 19% to 31% of sharing at least one ancestor who was forcibly brought to North America during the Transatlantic Slave Trade. This probability increases to over 50% for those born between 1985 and 1990, indicating a significant likelihood that these individuals share a common lineage.
Exploring Ancestry Through Mathematical Modeling
The research highlights the challenges faced by African Americans in tracing their ancestry due to inadequate record-keeping during the era of slavery. The lack of documentation means many individuals are unaware of their genealogical roots prior to the 1870 census. By applying a mathematical framework, Rosenberg and his team aimed to provide insights into the shared heritage of African Americans, despite the historical loss of genealogical information.
The study draws on concepts from a well-known statistical problem called “the birthday problem,” which illustrates the probability of shared birthdays among a group. For instance, in a group of 23 people, there is over a 50% chance that at least two individuals share the same birthday. The researchers adapted this principle to analyze the likelihood of individuals sharing ancestors who experienced the same historical events, such as the Transatlantic Slave Trade.
Rosenberg explained, “We used a mathematical model of genealogies to see what might be found in families where the precise story is not known. We found that there is a surprisingly high probability that two people share an ancestor who arrived as an enslaved person during the Transatlantic Slave Trade.” This research not only sheds light on the relatedness of the African American population but also contributes to understanding broader American demographic history.
Filling Historical Gaps
The findings suggest that African Americans born in the early 1960s each have approximately 300 ancestors among the estimated 400,000 to 500,000 Africans brought to North America from the early 1600s to 1860. As the generations progress, the number of ancestors increases, thereby enhancing the probability of shared lineage among individuals of the same generation.
Previous research has sought to fill gaps in African American ancestry using genetic methods. While this study does not aim to establish connections between specific descendants and ancestors, it offers valuable insights into shared heritage. Rosenberg stated, “In most cases, the question of whether two specific people have a shared transported ancestor cannot be directly answered because many aspects of the history of slavery led to profound loss of genealogical information. A mathematical model therefore has potential to make a meaningful contribution.”
The study serves as a significant step toward understanding the complexities of African American genealogy and the lasting impact of historical events on familial connections. As researchers continue to explore these themes, the implications for African American identity and heritage remain profound, highlighting the importance of historical awareness in the ongoing discourse about ancestry and family ties.
