Female family relationships were at the heart of social networks in Celtic society in Britain before the Roman invasion, a new analysis suggests.

Genetic evidence from Late Iron Age cemeteries suggests that women were closely related by blood, while unrelated men tended to enter the community from elsewhere, most likely after marriage.

An examination of ancient DNA found in 57 graves in Dorset, southwest England, showed that two-thirds of the people descended from a single maternal line. The cemetery was used from approximately 100 BC to 200 AD

"This is really jaw-dropping - it has never been observed before in European prehistory," said study co-author Lara Cassidy, a geneticist at Trinity College Dublin.

The findings, published Wednesday in the journal Nature, suggest that women stay in the same circles throughout their lives - maintaining social networks and possibly inheriting or managing land and property.

At the same time, "you have a husband who comes in as a relative stranger, dependent on the land and livelihood of his wife's family," Cassidy said.

This pattern, known as maternal residence, is historically rare.

The authors write: "This matrilineal pattern has not been described in European prehistory, but when we compared mitochondrial haplotype variation between European archaeological sites spanning six millennia, British Iron Age cemeteries were characterized by dominant matrilineal ” in an article accompanying the study.

Archaeologists studying British and European cemeteries have previously found the opposite pattern, in which women left home to join their husbands' family groups, only in other ancient periods, from the Neolithic to the early Middle Ages, said Max's Guido Gnecchi-Ruscone. Germany's Max Planck Institute was not involved in the study.

In studies of pre-industrial societies from around 1800 to the present, anthropologists found that men joined their wives' extended families only 8 percent of the time, Cassidy said.

But archaeologists already knew that women played some special roles in Iron Age Britain. Before the Roman invasion of AD 43, England was home to tribes (sometimes called Celts) made up of tribes closely related in language and artistic style. Celtic women were found buried with valuables, and Roman writers including Julius Caesar wrote disdainfully of their relative independence and fighting ability.

The researchers found that patterns of strong female kinship relationships did not necessarily imply that women also held formal positions of political power, i.e. matriarchy.

But it does suggest that women had some control over land and property, as well as strong social support, making Celtic society in Britain "more egalitarian than the Roman world," said study co-author and archaeologist at Bournemouth University Myles Russell said.

"When the Romans arrived, they were surprised to find women occupying positions of power," Russell said.

He told AFP that some were skeptical of the claims, arguing that "the Romans exaggerated the freedom of British women and painted a picture of an uncivilized society".

"But archeology and now genetics show that women were influential in many areas of Iron Age life," he said.

"Indeed, matrilineal descent may be the primary shaper of group identity."

AFP contributed to this report.