incest
DNA analysis of 5,000-year-old Irish remains reveals an incestuous elite social class
[Researchers found] an adult male buried at the 5,000-year-old Newgrange monument; his DNA revealed that his parents were first-degree relatives, ...
Sex and genetics: We’re looking for someone who isn’t an exact match of ourselves
We know that both men and woman are attracted to each other's shapes. But human sexual desire, and partner preference, ...