Will men be wiped out from Earth? The case of disappearing Y chromosomes

Are we heading towards a future where only girls are born? If a recent study is to be believed, the answer is yes. The future is female.

What are we talking about? A recent study has revealed that the Y chromosome, which is crucial for determining male sex, is gradually shrinking and might eventually disappear. This could result in a world where only girls are born.

Here’s a deep dive into what the study has revealed and what this means for the human race.

What is the Y chromosome? How does it determine human sex?

The Y chromosome is one of the two sex chromosomes in humans — the other is the X chromosome. Humans and most other mammals have two sex chromosomes — X and Y — that in combination determine the sex of an individual. Females have two X chromosomes in their cells, while males have one X and one Y.

As The Conversation reports, the names have nothing to do with their shape; the X stands for “unknown”.

The X chromosome contains about 900 genes that do all sorts of jobs unrelated to sex. However, it is the Y chromosome, which contains around 55 genes, that carries the all-important SRY gene that triggers the development of male characteristics in embryos.

What’s this about the fading Y chromosome?

A study, which has recently been shared widely, has revealed that the Y chromosome is degenerating. Professor Jenny Graves, explained this concept through the lens of the platypus. “In platypus, the XY pair is just an ordinary chromosome with two equal members,” she said. “This suggests the mammal X and Y were an ordinary pair of chromosomes not that long ago.”

“In turn, this must mean the Y chromosome has lost 900 to 55 active genes over the 166 million years that humans and platypus have been evolving separately. That’s a loss of about five genes per million years. At this rate, the last 55 genes will be gone in 11 million years,” she explained.

But why is this occurring? A report published earlier in The Week stated that most of the Y is made of repetitive ‘junk DNA’. “With such an unstable composition, the Y chromosome is at risk of completely disappearing over the course of multiple generations,” said the report.

The report further explains that as males only have one copy of the chromosome, it does not have the opportunity to go through genetic recombination, which is the “shuffling of genes that occurs in each generation which helps to eliminate damaging gene mutations”. Without recombination, Y chromosomal genes degenerate over time.

Does this mean there will be no men in the future?

The possibility of the disappearance of the Y chromosome raises questions about the future of the human race. Would the loss of the Y chromosome lead to human extinction?

Professor Graves said, “When humans run out of Y chromosome, they might become extinct (if we haven’t already gone extinct ourselves long since), or they might evolve a new sex gene that defines new sex chromosomes."

She further explained that while a few lizards and snakes are female-only species, this can’t occur in the human race or among mammals because we have at least 30 crucial “imprinted” genes that work only if they come from the father via sperm.

Is there any hope for men?

But before you start mulling over the doom and gloom of the human race, pause. That’s because a research paper that was published in Proceedings of the National Academy of Science shows how the spiny rat has evolved a new male-determining gene.

The study shows the mole voles of eastern Europe and the spiny rats of Japan have lost their Y chromosome and the SRY gene but continue to survive. Researchers led by Asato Kuroiwa at Japan’s Hokkaido University found that most Y chromosome genes in spiny rats had relocated to other chromosomes. This discovery suggests that while the Y chromosome may disappear, a new mechanism for determining sex could evolve.

This finding is significant for the future of the human race. Scientists say that if someone visited Earth in 11 million years, they might find no humans — or several different human species, kept apart by their different sex-determination systems.

But until then, the human race is safe.

With inputs from agencies