It is believed that when the male Y and female X chromosomes split 200-300 million years ago, the degradation of the male began. A series of stratification events inhibit the exchange of genetic information between chromosomes. The termination of the exchange of information between the X and Y-chromosomes forms a specific section on the male. This results in the loss of genes and entire DNA fragments. Some of the genetic material of the male sex chromosome has been lost, making it less of a “female sex chromosome”. According to the scientists, from the five stratification events, the Y-chromosome lost about 3% of the genes that were originally the same between the two: the X and the Y-chromosome. This has given rise to the theory that the Y-chromosome will continue to degrade until its extinction. A team from the Whitehead Institute for Biomedical Research in Massachusetts, led by David Page, found that the degradation of the male sex chromosome stopped 30 million years ago. Scientists did not find any changes in the regions of the Y-chromosome, neither in rhesus macaque monkeys, with which our evolutionary paths diverged 25 million years ago, nor in chimpanzees, which took their own branch of development 6 million years ago. In their work, the team looked at 11 million nucleotide pairs on the Y-chromosome of rhesus macaques. They compared this sequence to an analogous section of the male (human) Y-chromosome and the Y-chromosome of chimpanzees. Only one “pragene” has been found to be missing from the human Y-chromosome. After only this reduction is established for 30 million years, according to scientists, the male Y-chromosome will not be lost. The research is presented in the journal Nature.