Modern analysis of a 1,000-year-old grave in Finland challenges long-held beliefs about gender roles in ancient societies, and may suggest non-binary people were not only accepted but respected members of their communities, researchers have said.

According to a peer-reviewed study in the European Journal of Archaeology, DNA analysis of remains in a late iron age grave at Suontaka Vesitorninmäki in Hattula, southern Finland, may have belonged to a high-status non-binary person.

First discovered in 1968 during building work, the grave contained jewellery in the form of oval brooches as well as fragments of woollen clothing suggesting the dead person was dressed in “a typical feminine costume of the era”, the researchers said.

But unusually, the grave also held a hiltless sword placed on the person’s left side, with another sword, probably deposited at a later date, buried above the original grave – accoutrements more often associated with masculinity.

For decades, the researchers said, archaeologists had assumed either that two bodies, a man and a woman, had been buried in the Suontaka grave, or that it was evidence strong female leaders, even woman warriors, existed in early medieval Finland.

“The buried individual seems to have been a highly respected member of their community,” said the study’s lead author, Ulla Moilanen, an archaeologist from the University of Turku. “They were laid in the grave on a soft feather blanket with valuable furs and objects.”

DNA analysis, however, showed the grave held the remains of only one person – and that they had Klinefelter syndrome. Usually, a female has two X chromosomes (XX) and a male has one X and one Y (XY). In Klinefelter syndrome, a male is born with an extra copy of the X chromosome (XXY).

Males with the syndrome, which affects about one in 660 men, are still genetically male and often do not realise they have the extra chromosome, but the condition can cause enlarged breasts, a small penis and testicles, a low sex drive and infertility.

The Finnish researchers warned that the DNA results were based on a small sample and only a relatively small number of genetic sequences could be read, meaning they had to rely to some extent on modelling.

But they said that based on their data, it was likely that the body in the Suontaka grave had the chromosomes XXY. The high-status burial led them to conclude the person may have identified as outside the traditional gender divisions.