On Aug. 29, 2022, a group of international researchers, coordinated by Dr Joao Teixeira at The Australian National University, announced they had uncovered evidence of a super rare genetic condition that gives men an extra X chromosome, reporting the oldest clinical case of Klinefelter Syndrome to date. The evidence comes from a 1,000-year-old skeleton from Portugal.

Klinefelter Syndrome is a rare genetic condition where individuals are born with an extra copy of the X chromosome, occurring in approximately one in 1,000 genetic-male births.

The study coordinated by Dr João Teixeira, an ARC DECRA Fellow at The Australian National University (ANU), brought together a multidisciplinary team that combined genetic, statistical, archaeological and anthropological information to establish a definitive diagnosis.

The team began by analysing genetic information obtained from a skeleton found in northeastern Portugal that had been radiocarbon dated to the 11th century by researchers from the University of Coimbra in Portugal.

The researchers say the findings will help establish a historic record for Klinefelter Syndrome, as well as enhance understanding of its prevalence throughout human history.