If this occurs in the sex chromosomes, this can cause differences such as delayed development or changes in height around puberty. Led by the Francis Crick Institute, the research team developed a new technique to measure the number of chromosomes in ancient genomes more precisely. They identified five people who had sex chromosomes which fell outside of the XX or XY categories. All were buried according to their society’s customs although no possessions were found with them to shed more light on their lives. Their syndrome was shown to be mosaic: some cells had one copy of chromosome X and some had two.