The Y Chromosome, which determines the sex of human and other mammal babies, is slowly shrinking and may disappear in male species in a few million years.
While the shrinking of the Y chromosome raises concerns regarding the process of evolution, a study has stated that this may pave the way for a new era of sex determination.
The Y Chromosome, which determines the sex of human and other mammal babies, is slowly shrinking and may disappear in male species in a few million years.
While the shrinking of the Y chromosome raises concerns regarding the process of evolution, a study has stated that this may pave the way for a new era of sex determination.
In most mammals, including human beings, male species typically have one X and one Y chromosome, whereas female species have both X chromosomes.
The Y Chromosome is responsible for the development of male reproductive tissues as it carries the SRY gene. The SRY gene in turn triggers SOX9, a gene crucial for male determination across all vertebrates and is essential for male development.
Based on a study published in the 'Proceedings of the National Academy of Sciences' in 2022, the Y chromosome has lost 97 percent of its gene content and is now less than one-third the size of the X chromosome.
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As per Jennifer Graves, a distinguished Professor of Genetics and Vice Chancellor's Fellow, has stated that the Y chromosome in human males is shrinking. As per Graves, the human Y chromosome has lost 1393 of its original 1438 genes, and if it continues to reduce at this rate, it will lose the last 45 in another 10 to 11 million years.
However, despite the rapid shrinking of the Y chromosome, the study published in 'Proceedings of the National Academy of Sciences' reveals that all hope is not lost.
In 2022, scientists and researchers from Hokkaido University in Japan have stated that spiny rats, which lost their Y chromosome genes years ago, have evolved to develop a new sex-determining gene.
As per the study, most Y chromosome genes in spiny rats had relocated to other chromosomes. However, the researchers, led by Asator Kuroiwa, could not locate the SRY gene or any other potential replacement.
Despite no detection of SRY, the researchers found a small duplication near the SOX9 gene on chromosome 3 in spiny rats. This duplication was present in all males, not females.
With this, the duplication contains the switch with activates the SOX9 gene in a similar manner to its response to SRY, meaning that the gene can operate without the Y chromosome.
A similar observation was made in a 2008 study on mole voles or the " Transcaucasian mole vole". Based on the study, the Transcaucasian mole vole have no SRY gene or Y chromosomes. Both the sexes - amle and female have a set of XO chromosomes.
Hence, with the evolution in spiny rats and mole voles, the study shows that mammals can evolve different sex-determining mechanisms even if the Y chromosome is gone.
The 2022 study goes on to point out that the loss in the Y chromosome continues to pose an evolutionary concern. However, there may just be a chance that the human males also evolve to create another sex-determining gene which will continue the reproduction of male offspring.
However, scientists have also cautioned that such evolutionary changes could also led to the formation of a completely new species due to the emergence of various sex-determining systems.