DNA from a 5,200-year-old Irish tomb hints at ancient royal incest

A man buried in a huge, roughly 5,200-year-old Irish stone tomb was the product of incest, a new study finds.

DNA extracted from the ancient man’s remains displays an unusually large number of identical versions of the same genes. That pattern indicates that his parents were either a brother and sister or a parent and child, a team led by geneticists Lara Cassidy and Daniel Bradley of Trinity College Dublin reports June 17 in Nature.

That new DNA discovery combined with the monumental tomb suggests that ruling families who wielded enough power to direct big building projects emerged among some early European farming communities, the researchers contend.

The man’s bones had previously been found in the Newgrange passage tomb, an earthen mound covering more than 4,000 square meters near the River Boyne. A rooftop opening in a 19-meter-long stone passage allows sunlight to reach deep into a chamber inside the mound on the shortest days of the year, suggesting the structure held astrological and religious significance (SN: 6/29/74). It may have been built this way to mark a new year in dramatic fashion, perhaps while winter solstice ceremonies were conducted.

Cassidy and Bradley’s team studied DNA from 44 individuals buried in various Irish tombs and graves dating to between roughly 6,600 and 4,500 years ago. Only the Newgrange man, who was interred in the largest and most impressive structure, had inherited genetic markers of incest.

Socially sanctioned incest tends to be rare throughout history but is known from instances of royal inbreeding. Mating between brothers and sisters, for example, occurred in some ancient societies with ruling families headed by men regarded as gods not subject to human incest taboos. Ancient Egypt’s King Tutankhamun, whose rule began 3,352 years ago, was the son of a brother and sister. So finding the offspring of inbreeding in such an impressive stone structure is highly suggestive of a practice of inbreeding among elites, even if not conclusive, the researchers say.