Credit: SpiffyJ
According to Jenny Graves, an Australian geneticist, the Y chromosome in humans is in a gradual state of degeneration—about five genes are lost every million years. If this continues, the Y chromosome will be gone in about 11 million years, taking the SRY gene essential for male development with it. In that event, natural human reproduction would be impossible.
This may seem far in the future, but the degradation of the Y chromosome also leads to more urgent questions. Sperm counts are already plummeting around the world and, long before the Y goes away, we have quit having enough sperm for male fertility.
But evolution might save us. Some mammals, like the Amami spiny rat and the Eastern European mole voles, have already lost their Y chromosomes and created other pathways for male development—by moving genes around, and upregulating SOX9. In one study, researchers identified male-specific DNA sequence neighboring SOX9 on chromosome 3 that provided an alternative for the lost SRY function.
Graves still warns that the creation of alternative sex determining systems in different populations or regions could lead to speciation, and humans could become many different genetically distinct species.
The degeneration of the Y chromosome is not just a curiosity, but possibly a slow-motion biological collapse underway.
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