DNA reveals megalithic tombs were family graves

A new international study confirmed for the first time through genetic analysis that megalithic tombs, which have always been shrouded in mystery, contain many closely related individuals.

Scientists analysed teeth and bones from tombs in Ireland, Scotland, on the Swedish island of Gotland and in the Czech Republic as part of the new genetic study of Stone Age funeral practices.

They found 12 Irish individuals from 16 different teeth dated from 3,790 and 3,360 BC.

The study reported than some of the family members were "separated in time by at least one generation and possibly up to 12 generations" which meant the tombs could have been used over hundreds of years by one family line.

The scientists suggest that the tombs could contain chieftains or village chiefs and mostly their male relatives.

The international research team examined the remains of 24 individuals - 11 people from the Primrose Grange tomb and one from the Listoghil tomb at Carrowmore site in Co Sligo. Bones and other remains from the tombs in other countries were included in the study.

The megalithic tombs built from 4,500BC along the Atlantic have long attracted speculation, but until now scientists could never determine if they were graves used by societies or by families.

The findings show the megalithic tombs held mostly family members and were also heavily male-dominated.

"Our results show kin relations among the buried individuals and an over representation of males, suggesting that at least some of these funerary monuments were used by patrilineal societies," said the authors.

Researchers, led by Uppsala University in Sweden, radio carbon-dated the human remains to between 3,800 and 2,600BC. DNA was extracted from both bones and teeth for genome sequencing.

In the two Irish tombs, there were five close family relationships. Two were first degree (which were categorised as offspring or a parent, or a full sibling) and three were second degree (defined as an aunt, uncle, niece, nephew, grandparent, grandchild, cousin or half-sibling).

In the Primrose Grange tomb, they found what was predicted to be a father-daughter relationship, along with a second-degree relationship between another two remains thought to be half-siblings or cousins, with a less likely possibility of a grandfather-grandson or uncle-nephew relationship.

The male in the nearby Carrowmore grave and one of the Primrose males were thought to be at least second-degree related - which shows family members were buried close by in neighbouring graves.

They also found another of the Irish females had family ties to the males buried in her tomb.

It is thought one of the main functions of the tomb was to house the remains of the male line of the family. "This would explain the inclusion of more males than females in the tombs," said the study.

But even though there were only two females compared to nine males in the tomb, they both had strong family ties to the men or boys. "The finding that three of the five kinship relationships in these megaliths involved females indicates that female kindred members were not excluded."

The findings have just been published in the Proceedings of the National Academy of Sciences. The paper, headed by co-first authors Dr Federico Sanchez-Quinto and Dr Helena Malmstrom, explained that starting around 4,500BC, a new phenomenon of constructing megalithic monuments - particularly for funerary practices - emerged along the Atlantic.

The researchers compared their gene pool to other Stone Age groups and found they were closely related to Neolithic farmers in northern and western Europe, and also to some groups in Iberia, but less related to farmer groups in central Europe.