The Y chromosome is a male symbol, carrying the "SRY" gene - which determines whether the embryo develops into either male (XY) or female (XX). However, the Y chromosome contains only a few other genes and is the only one that is not required. In addition, the Y chromosome is rapidly degenerating. If the virus continues to degenerate at the current rate, the Y chromosome will disappear completely after 4.6 million years.
However, the Y chromosome is not always the case. 166 million years ago, in the first mammals, the Y and X chromosomes were about as long and carry the same genes. However, the Y chromosome has inherent defects. It exists as a single (rather than as a double) form, inherited from the father to the son. This means that genes on the Y chromosome can not undergo "genetic recombination" - gene recombination helps to eliminate deleterious genetic mutations. As a result, the Y chromosome is constantly degraded over time.
However, recent studies show that the Y chromosome develops certain mechanisms that slow the rate of gene loss and may eventually stop degenerating. For example, a Danish study showed that men's Y chromosomes are susceptible to massive structural rearrangements, leading to "gene amplification." In addition, the Y chromosome evolved some unusual "palindromes" that prevented further degradation. They found that the "gene transfer" rate of palindromic sequences on the Y chromosome is very high.
For other species, there is also growing evidence that the Y chromosome is undergoing gene amplification. These amplified genes are important in making sperm and controlling the sex ratio of offspring (at least in rats). Evidence shows that mouse gene amplification is the result of natural selection.
So, Y chromosome will disappear? Currently, the scientific community is divided into two camps: One believes that the Y-chromosome defense mechanism works to ultimately save the Y chromosome; the other believes that these defenses can only be delayed but do not prevent the disappearance of the Y-chromosome. In 2016, Jenny Graves, of La Trobe University in Australia, pointed out in his dissertation that Japanese echinops and echidna have completely lost the Y chromosome. She believes that the loss of Y chromosome will lead to fertility problems, and ultimately promote the formation of new species.
Will men be extinct?
Even if the Y chromosome eventually disappears, men may not be extinct. At present, the species missing the Y chromosome still needs both sexes to breed offspring. In them, the sex-determining SRY gene is transferred to another chromosome. In other words, they do not need the Y chromosome, but also reproduce the male. However, this new sex-determining chromosome will start to degenerate for the same reason.
Interestingly, reproductive technology can solve this problem, although the normal mating process requires the involvement of the Y chromosome. This means that genetic engineering may soon be able to replace the genetic function of the Y chromosome so that lesbian, infertile men can reproduce offspring. Of course, even if the technology is mature, it is unlikely that ordinary people will stop their natural reproduction.
This topic is very interesting, but we need not worry too much about it. Even though the Y chromosome will disappear, it will be 4.6 million years from now. Even if it really disappears, most of human reproduction still needs gender participation.