Irish researchers find evidence of 5,000-year-old incestuous 'ruling social elite'
DNA from ancient tomb suggests social class 'akin to similarly inbred Inca god-kings and Egyptian pharaohs'
Irish researchers have learned that a man who lived more than 5,000 years ago was born from incest, suggesting he was "among a ruling social elite akin to similarly inbred Inca god-kings and Egyptian pharaohs."
Lara Cassidy, a post-doctoral student in ancient genomics at Trinity College Dublin, has been studying DNA from a man whose remains were excavated in the 1960s from Newgrange, a monolithic Stone Age passage tomb in Ireland.
When her team finally sequenced the genome, she says the results were "quite shocking."
"We inherit two copies of the genome, one from our mother and one from our father. And this man's copies were remarkably similar, really long stretches of identical sequences," Cassidy told As It Happens host Carol Off.
"That's sort of the telltale signal of very close inbreeding. You can actually estimate and confirm it was first-degree relatives who were his parents. So either a brother and sister, or a parent and child."
The findings have been published in the journal Nature.
This form of first-degree incest has historically only been deemed socially acceptable among ruling classes, such as the Egyptian pharaohs, Cassidy said.
"A lot of work has been done in anthropology looking at first-degree incest, because it is so rare that it's socially accepted," she said. "It's a universal taboo for biological and cultural reasons."
Members of aristocracies engaged in this type of taboo behaviour because it helped to keep their kin or clan in power.
Breaking taboos also had a "shock value" and allowed for the ruling classes to separate themselves from the general population through a "we can do this, you can't" mentality, Cassidy said.
"When you look at all the documented cases we have of this behaviour and the elite or the leader are typically polygamists, they take many wives, and wives that are more closely related and have more privileges," Cassidy said.
"When that is pushed to the absolute extreme, what you get is sibling marriage."
The tomb — located about 50 kilometres north of Dublin — is made up of about 200,000 tonnes of earth and stone and constructed in such a way that on the winter solstice, the sun will shine through the entrance and illuminate the chambers encased within, Cassidy said.
The fact that this man was buried in not only "one of the most prestigious burial structures in prehistoric Europe, but actually the most prestigious place within that tomb," suggests it was likely his parents' incestuous relationship was "socially sanctioned by the society," she said.
The team also discovered a web of distant relations between this man and other individuals from sites of passage tomb tradition across the country.
"It seems what we have here is a powerful extended kin-group, who had access to elite burial sites in many regions of the island for at least half a millennium," Cassidy said in university press release.
Still, Cassidy told Off that researchers are limited in what they can glean from DNA evidence alone.
"DNA is providing us with a new way of looking at these social structure hierarchies in the deep past. But of course, we have to be conscious here that we don't have a written record," she said.
"We are working with populations from a very remote time period."
Written by Adam Jacobson. Produced by Katie Geleff.