Royal families today are like inbreeding

5000 year old DNA from royal tombs analyzed : Incest was common among Ireland's primeval elite

Huge graves and incest between closest relatives of the elite - 5000 years ago, dynasties apparently ruled on the Irish island as known from the Egyptian pharaohs and god kings of the Inca.

A genetic study is now reconstructing how these power structures came about - and that an Irish myth could actually be based on events that are thousands of years old.

Ireland has hundreds of “passage tombs” - grave complexes, where long corridors lead into burial chambers under large mounds of earth set in curb stones. The facilities date from the 4th millennium BC and are therefore older than, for example, the Egyptian pyramids of Giza.

The most famous is Newgrange, built between 3200 and 3000 BC in the east of the island north of Dublin, which is a Unesco World Heritage Site. The tomb with a diameter of around 90 meters is aligned so that the light at the winter solstice at sunrise falls through the 20-meter long corridor to the inner chamber vault with the altar. Newgrange is about 500 years older than the English Stonehenge.

The genetic material from 42 royal tombs confirms an ancient Irish myth

Little was known about the builders of the facilities. Now the team around the geneticist Daniel Bradley from Trinity College Dublin analyzed the genomes of 42 people from this time from different graves as well as from two inhabitants of the island before that epoch.

The results, published in the journal "Nature", show that related people are buried in various large graves from different regions of the island - in addition to Newgrange also in Carrowkeel and Carrowmore in the northwest.

"That looks like a powerful, ramified family group who had access to elite graves in many regions of the island for at least half a millennium," first author Lara Cassidy is quoted in a statement from Trinity College. In the case of a member of this group buried in Newgrange it turned out that his parents were first-degree relatives - that is, either siblings or mother and son or father and daughter.

Such incest connections are taboo almost worldwide - except in some ruling dynasties, which thus secured their family claim to power. There are similar examples from ancient Egypt and the Incas.

"The prestige of this form of burial speaks for an extreme hierarchy in which the only worthy partners of the elite were family members," says study director Bradley. Isotope analyzes of the human relics show that the people buried in these graves ate a lot of meat and animal products - evidence of their prosperity.

The incest findings from Newgrange fit a myth handed down from the 11th century: According to this, the royal builder of the neighboring Dowth grave complex secured the daily solar cycle through incest with his sister. This parallel to the study results raises the question of whether oral traditions could survive four millennia, writes the team.

Chance discovery: oldest evidence of trisomy 21

The research suggests that the island's original hunting and gathering population was displaced by a farming population that arrived about 6,000 years ago. These newcomers created the hierarchical form of society that the great tombs testify and for which the winter solstice was a crucial date, writes Alison Sheridan of the National Museums Scotland in Edinburgh in a "Nature" comment. Islanders probably traveled from far and wide to celebrate the winter solstice 5000 years ago.

During their analyzes, the researchers made a chance discovery: they discovered Down's syndrome in a boy from the megalithic tomb Poulnabrone in the west of Ireland. The grave is about 5500 years old and thus about 4000 years older than the earliest evidence of trisomy 21 to date.

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