: Throughout much of human history, marrying cousins was common to preserve wealth, maintain social status, or secure political alliances. An estimated 80% of all historical marriages were between first or second cousins.
: Children of unrelated parents have a 3% risk of congenital defects. Kissin' Cousins
: Significant genetic issues, such as those seen in the "Habsburg jaw," typically result from centuries of continuous intermarrying within a small, closed gene pool rather than a single generation. Pop Culture and Media Representations : Throughout much of human history, marrying cousins
: For first cousins, the risk increases to roughly 6%. While this is a doubling of the baseline, some researchers argue it is not as high as public stigma suggests. : Throughout much of human history