Y Chromosome from Wikipedia ... SamKat

From: Y chromosome Wikipedia:

Shrinking theory

By one estimate, the human Y chromosome has lost 1,393 of its 1,438 original genes over the course of its existence, and linear extrapolation of this 1,393 gene loss over 300 million years gives a rate of genetic loss of 4.6 genes per million years.^[14] Continued loss of genes at the 4.6 genes per million year rate would result in a Y chromosome with no functional genes --- that is the Y chromosome would lose complete function --- within the next 10 million years. Comparative genomic analysis, however, reveals that many mammalian species are experiencing a similar loss of function in their heterozygous sex chromosome. Degeneration may simply be the fate of all nonrecombining sex chromosomes due to three common evolutionary forces: high mutation rate, inefficient selection and genetic drift.^[10] Furthermore, comparisons of the human and chimpanzee Y chromosomes (first published in 2005) show that the human Y chromosome has not lost any genes since the divergence of humans and chimpanzees between 6–7 million years ago,^[15] and a scientific report in 2012 stated that only one gene had been lost since humans diverged from the rhesus macaque 25 million years ago.^[16] These facts provide direct evidence that the linear extrapolation model is flawed and suggest that the current human Y chromosome is either no longer shrinking or is shrinking at a much slower rate than 4.6 genes per million years estimated by the linear extrapolation model.

The Y chromosome makes the male and double X chromosomes make the female.