History is rife with famous married cousins: Charles Darwin, Albert Einstein, Edgar Allan Poe, and H.G. Wells all married their cousins. One estimate suggests that nearly 80 percent of all marriages in history have been between first or second cousins.
Now, the largest study of its kind to date links consanguineous marriage—marriage between blood relatives—with a 2-fold increase in the risk of birth defects, such as heart and lung problems and Down syndrome. A similar increased risk was found for mothers over the age of 34.
Read the full article here: Married Cousins Boost Birth Defects
