“It's Ok, We're Not Cousins by Blood”: The Cousin Marriage Controversy in Historical Perspective

In February, 2008, British environment minister Phil Woolas sparked a major row in the United Kingdom when he attributed the high rate of birth defects in the Pakistani community to the practice of marriages between first cousins. “If you have a child with your cousin, the likelihood is there’ll be a genetic problem,” he told the Sunday Times [1]. Although a Muslim activist group demanded that Woolas be fired, he was instead promoted in October to the racially sensitive post of immigration minister. Most of his constituents would surely have shared Woolas’ view that the risk to offspring from first-cousin marriage is unacceptably high—as would many Americans. Indeed, in the United States, similar assumptions about the high level of genetic risk associated with cousin marriage are reflected in the 31 state laws that either bar the practice outright or permit it only where the couple obtains genetic counseling, is beyond reproductive age, or if one partner is sterile. When and why did such laws become popular, and is the sentiment that informs them grounded in scientific fact? US prohibitions on cousin marriage date to the Civil War and its immediate aftermath. The first ban was enacted by Kansas in 1858, with Nevada, North Dakota, South Dakota, Washington, New Hampshire, Ohio, and Wyoming following suit in the 1860s. Subsequently, the rate of increase in the number of laws was nearly constant until the mid-1920s; only Kentucky (1946), Maine (1985), and Texas (2005) have since banned cousins from marrying. (Several other efforts ultimately failed when bills were either vetoed by a governor or passed by only one house of a legislature; e.g., in 2000, the Maryland House of Delegates approved a ban by a vote of 82 to 46, but the bill died in the Senate.) The accompanying map (Figure 1) illustrates both the extent and the progress of legislation. It demonstrates that western states are disproportionately represented, reflecting the fact that either as territories or newly admitted states, they were writing their marriage codes from scratch and hence prompted to explicitly confront the issue. For the same reason, these states tended to be the first to prohibit cousin marriage. Perhaps surprisingly, these bans are not attributable to the rise of eugenics. Popular assumptions about hereditary risk and an associated need to control reproduction were widespread before the emergence of an organized eugenics movement around the turn of the 20th century. Indeed, most prominent American eugenists were, at best, lukewarm about the laws, which they thought both indiscriminate in their effects and difficult to enforce “It’s Ok, We’re Not Cousins by Blood”: The Cousin Marriage Controversy in Historical Perspective