The earliest known cases of sex-chromosome syndromes, identified by researchers, suggest that people with extra or missing chromosomes existed 5,000 years ago.

According to a study published in Communications Biology, people with genetic syndromes have existed throughout human history and have been a part of human societies. 

They often have distinct looks and demeanours compared to the rest of the population. Researchers can learn more about how ancient societies treated people with these differences by finding out about prehistoric people who had such genetic syndromes. 

Kyriaki Anastasiadou of the Francis Crick Institute in London, the co-author of the study, and his team used DNA sequencing to find that ancient people with an atypical number of chromosomes, including an infant with Down syndrome (caused by an extra copy of chromosome 21), lived around 5,000 years ago. 

The research team also discovered the first prehistoric person to have Turner syndrome was a female, who had only one complete copy of the X chromosome instead of two copies, generally found in females. She lived in Somerset in the United Kingdom during the Iron Age, roughly around 2,500 years ago. 

Anastasiadou and the team also found a male with an extra Y chromosome, called Jacob's syndrome. While a person with Turner's syndrome is shorter and has infertility problems, people with Jacob's syndrome are taller than average. The identified male live during the early Medieval Period, around 1,100 years ago. 

Furthermore, researchers identified three ancient males from different periods with an extra X chromosome, a condition called Klinefelter syndrome, linked to growing taller than average and having broader hips and larger breasts. 

According to Anastasiadou, no evidence indicated that these people experienced different treatment. "There didn't seem to be anything different about how they died or how they were buried at first glance," she said. 

The authors derived DNA samples from the teeth, skull, jaw and ear bones for the study. They used a computation tool for each individual to calculate the number of DNA fragments derived from the X and Y sex chromosomes. Then, they compared it to the amount of DNA fragments derived from non-sex chromosomes. With the help of this, they deduced the presence and ratio of X and Y chromosomes in each person.