In human specie, all the information necessary to generate a new person is contained in 46 chromosomes, or 23 pairs. One pair determines gender: XX in women and XY in men.
The female chromosome X has about 1100 pieces of information, or genes. The male chromosome Y has only 200 genes.
However, some experts are convinced that the chromosome Y eventually disappear. In the other hand, there are experts that do not think so.
The evidence is that approx. 200 – 300 million years, chromosome Y shared in common 600 genes with the female chromosome X. Currently, chromosome Y only share 19 genes with chromosome X. During the last 25 million years, chromosome Y has remained unchanged.
Given this evidence, this period can be interpreted as a definite stability, as David Page (Massachusetts Institute of Technology) or a break to the final reduction, as Jennifer Graves (Australia National University).