What Made the Y Chromosome So Tiny?

The Y chromosome, a chunk of genetic code that is unique to male animals, isn’t just physically smaller than the X. It also contains far fewer genes. The X has more than 1000 genes, while the Y has fewer than 200 —and most of them don’t even work. Why do men have this odd, stunted chromosome in their genomes?

Source: What Made the Y Chromosome So Tiny?

Some animals already have lost the Y for good. And yet, they keep having male offspring. How? Nob0dy knows yet.