There is a theory that the Y chromosome could disappear in as little as 4.3 million years. This is well beyond our foreseeable future, but given the Earth is 4.5 billion years old, it is relatively close. How did this theory come to fruition? If we rewind the clock to 166m years ago, to the very first mammals, the story was completely different. The early “proto-Y” chromosome was originally the same size as the X chromosome and contained all the same genes. However, Y chromosomes have a fundamental flaw. Unlike all other chromosomes, which we have two copies of in each of our cells, Y chromosomes are only ever present as a single copy, passed from fathers to their sons.
This means that genes on the Y chromosome cannot undergo genetic recombination, the “shuffling” of genes that occurs in each generation which helps to eliminate damaging gene mutations. Deprived of the benefits of recombination, Y chromosomal genes degenerate over time and are eventually lost from the genome.
Is the human species doomed?
Even if the Y chromosome in humans does disappear, it does not necessarily mean that males themselves are on their way out. Even in the species that have actually lost their Y chromosomes completely, males and females are both still necessary for reproduction.
In these cases, the SRY “master switch” gene that determines genetic maleness has moved to a different chromosome, meaning that these species produce males without needing a Y chromosome. However, the new sex-determining chromosome – the one that SRY moves on to – should then start the process of degeneration all over again due to the same lack of recombination that doomed their previous Y chromosome.
Get real time update about this post categories directly on your device, subscribe now.