The gender of a child at birth largely depends on the genetic preponderance of the chromosome combination. Whether it will be two X chromosomes, and then such reproductive organs as ovaries will develop in the fetus and it means that a girl will be born. And if there are two different chromosomes, X and Y, then such a combination will allow a boy to be born. The genetic material is formed by a certain number of genes, among that the Y chromosome is considered as the negligible.
But that's not all. The scientists' studies led to the conclusion that gradually the Y-chromosome will not only decrease over time, but may even disappear altogether that predicts the death of humanity as a species.
Now the researchers asked if the Y chromosome is really dying out and what it means for the humanity? Melissa Wilson, who is an evolutionary biologist at Arizona State University, says that the X- and Y-chromosomes did not always determine the sex of the child. The first mammals on our planet appeared between 100 and 200 million years ago.
And they didn't have any sex chromosomes at all. Jennifer Graves, a geneticist from La Trobe University in Melbourne, confirms that fact: the truth is that animals do not need sex chromosomes, it was million years ago and it still remain. All the chromosomes are a special mixture of genes, and they are both related and not related to gender.
But the only feature of the Y-chromosome is one gene, SRY, that acts as a switch for testicular development. At some point in evolutionary development, a gene with such a switch appeared on a simple chromosome. And thus, the Y-chromosome became responsible for the development of the male reproductive organs.
But since its inception, it began to decline sharply. Dangerous mutations began to develop in genes, and the chromosomes can avoid the transmission of mutations by recombining with each other. During a so-called bad mutation, the chromosomes can swap places with each other.
But the Y-chromosome cannot do that on its own and therefore it is eliminated by natural selection. If 166 million years ago there were 1669 genes on the Y-chromosome, then after 10 million years only 45 will remain, and the entire Y will disappear in 4.5 million years.