Researchers at the Francis Crick Institute, in collaboration with the University of Oxford, the University of York and Oxford Archaeology, have developed a new technique to measure the number of chromosomes in ancient genomes more precisely, using it to identify the first prehistoric person with mosaic Turner syndrome. characterized by one X chromosome instead of two [XX]), who lived about 2500 years ago.
As part of their research published today in Communication Biologythey also identified the earliest known individual with Jacob syndrome (characterized by an extra Y — XYY chromosome) in the Early Medieval Period, three individuals with Klinefelter syndrome (characterized by an extra X — XXY chromosome) across a range of time periods, and an infant with Down syndrome since the Iron Age.
Most cells in the human body have 23 pairs of DNA molecules called chromosomes, and the sex chromosomes are usually XX (female) or XY (male), although there are differences in sexual development. “Aneuploidy” occurs when a person’s cells have an extra or missing chromosome. If this occurs on the race chromosomes, some differences, such as delayed growth or changes in height, can be seen during puberty.
Ancient DNA samples can corrode over time and can be contaminated with DNA from other ancient samples or from people who handle them. This makes it difficult to accurately record the differences in the number of racial chromosomes.
The team at Crick developed a computational method that aims to identify more variation in racial chromosomes. For race chromosomes, it involves counting the number of copies of the X and Y chromosomes and comparing the result to a predicted baseline (what one would expect to see).
The team used the new method to analyze ancient DNA from a large dataset of individuals collected as part of the Thousand Ancient British Genomes project on British history, identifying six individuals with aneuploidies across five sites in Somerset, Yorkshire, Oxford and Lincoln.2. Humans lived in a range of time periods, from the Iron Age (2500 years ago) to the Post-Medieval Period (about 250 years ago).
They identified five individuals who had race chromosomes that did not fall into the XX or XY categories. All were buried according to the customs of their society, although no possessions were found with them to shed more light on their lives.
The three people with Klinefelter syndrome lived at very different times, but shared some similarities — all were slightly taller than average and showed signs of delayed growth in adolescence.
By examining details of the bones, the research team was able to see that it was unlikely that the person with Turner syndrome had gone through puberty and started menstruating, despite their estimated age of 18-22. Their syndrome turned out to be mosaic – some cells had one copy of the X chromosome and some had two.
Kakia Anastasiadou, a PhD student in the Ancient Genomics Laboratory at the Crick, and first author of the study, said: “Through precise measurement of race chromosomes, we have been able to show the earliest prehistoric evidence of Turner syndrome from 2500 years ago, and the earliest known incidence of Jacob syndrome about 1200 years ago. It is difficult to get a full picture of how these individuals lived and interacted with their society, as they were not found with possessions or in unusual graves, but it may allow some insight into how their perceptions of gender identity have evolved over time. time”.
Pontus Skoglund, team leader in the Ancient Genomics Laboratory at the Crick, said: “Our method is also able to sort out DNA contamination in many cases and can help analyze incomplete ancient DNA so that it can be applied to archaeological residues that are difficult to analyze.
“Combining this data with the funerary context and possessions can allow for a historical perspective on how sex, gender and diversity were understood in earlier societies. I hope that this type of approach will be implemented as the shared resource of ancient data DNA continues to grow.”
The team worked with archaeologists from the University of Oxford, the Wells and Mendip Museum, University of York, University of Bradford, Oxford Archaeology, York Osteoarchaeology and Network Archaeology, acknowledging support from Lincolnshire County Council, Magdalen College and Balfour Beatty for National Highways.
Rick Schulting, Professor of Scientific and Prehistoric Archeology at the University of Oxford, said: “The results of this study open up exciting new possibilities for the study of sex in the past, moving beyond binary categories in a way that would have been impossible without advances that are done in ancient DNA analysis’.