Darwin's theory that inbreeding could negatively affect plant health and number of offspring bore unpleasant fruit in his own family. Marriage to his first cousin produced 10 children. Three died before age 10, two from infectious diseases; three who survived and had long-term marriages did not have children.

It is probable that these problems may have plagued the Darwins because of their lineage. Studies show that susceptibility to infectious diseases and unexplained fertility are risk factors in marriages of people who are closely related.

Read more at: researchnews.osu.edu