The end of human fathers?

The disappearance of the Y-chromosome has raised some alarms

Photo by Isaac Quesada on Unsplash

We fear that human existence might be threatened by the final pandemic with a new exotic disease or alternatively with our political mutual destruction in a final, catastrophic world war. Instead, it could be something more subtle, yet just as destructive, like the disappearance of human males, sending the human species reeling toward extinction.

Father’s Day seems a good time to reflect on this relatively recent discovery.

Starting with the basics of biological sex determination:

In mammals, with a few notable exceptions, female are homogametic (XX) and males have a single X and a small, heterochromatic and gene poor Y that bears a male dominant sex determining gene SRY.¹

So it is this sex determining gene, SRY, that is especially important to preserve to ensure the production of human males.

But evolution over the past 166 million years has crept toward the Y-chromosome’s almost certain disappearance.² In 2013, an article was published noting the disappearing Y-chromosome,³ due to the fact that it has been losing genes over time because of various movements of genes such as insertions, deletions, and transposons. In 2020, a research team also found that while the Y-chromosome was losing genes, but that it is not unique to the Y-chromosome;⁴ however, the Y-chromosome is the one most likely at risk of disappearance because it has the fewest number of genes to lose.

In 2022, a genetic research scientist team at La Trobe University in Australia⁵ discovered that the Y-chromosome in male humans had been loosing genes over millions of years at a rate that predicted its ultimate demise in anywhere from a few thousand years to a couple million years.

Vole moles

At least one mammalian species has survived the disappearance of its y-chromosome in males. Initially it was not clear how the species continued to perpetuate itself. It seems that two things happened: one, some of the y-chromosome genes had not disappeared but migrated to other chromosomes; and two, another gene had taken the role of the triggering gene (SYR) that set in motion the gene that manufactured sperm.⁶

This process was repeated in different communities of voles with slight differences but enough to create different species, making breeding impossible between other communities. If this process happened in the human species, different communities that could not interbreed would destroy one of the first diplomatic strategies in the history of the world — marrying into the neighboring community to bring peace (or steal property, depending on the political expediency needed). So even if new mechanisms for determining sex in humans evolve, there will likely be different processes that create humans so different they cannot mate, thus factions of humans would almost certainly be at war with each other. Not a peaceful future.

Parthenogenesis?

Parthenogenesis or the ability for a female to reproduce on her own, involves the spontaneous division of the egg to begin embryonic growth. However, this was thought not possible in humans, because of a number of actions that are present in frogs, for example, that are not present in humans. However, recent theories suggest it happens in humans.⁷ But this lack of genetic diversity spells trouble down the line in a few generations.

Other X-Y anomalies

We have known for some time of other anomalies with the X-Y genes, like Klinefelter’s Syndrome, where individuals receive one or more X chromosomes in combination with a Y-chromosome. These combinations (aneuplody) typically result in sterility, but it was possible to extract sperm according to some research.⁸ These occur at a surprisingly frequent rate: one in 500 males. For each additional X that is added (XXXY for example), the negative effects increase.⁹ So maybe there is more flexibility in preserving sex determination that has yet to emerge that might save us.

Survival Strategy

We can take some comfort in knowing that the vole and the rat have continued to exist without a Y-chromosome, having lost it over eons.

Despite the degeneration, the Y-chromosome may protect itself from extinction through mechanisms that maintain its essential functions in sex determination and sperm production. Perhaps taking up the genes as they are lost from the Y-chromosome or different genes adopting the functions of the lost genes in order to continue to determine gender and induce sperm production, like the vole might naturally occur.¹⁰

Further, an opinion paper published August 6, 2020 in the journal Trends in Genetics proposed a new theory on how the Y-chromosome may be more resilient than it may appear, called the "persistent Y hypothesis". It is believed that due to its self-regulation that it might conserve itself when faced with elimination by terminating the meiotic or cell division process.¹¹

But should we be doing more? We prepare for nuclear war, even asteroid destruction of the earth by creating a United Nations committee to decide on a strategy with a worldwide common goal of defense.

It is fairly straightforward as to which Departments in the U.S. government would lead each of those efforts — the Department of Defense for nuclear war, and NASA for asteroid defense. Yet, it is not so clear who is responsible for the genetic future of America? Genetics have been regulated to protect privacy and to avoid discrimination, but not for survival. The Department most likely to be assigned this task is probably the Department of Health and Human Services, and its agency, the National Human Genomic Research Institute (NHGRI), although their mission is research, and not regulation or strategy.¹² They would still be most likely to take the lead on this kind of task, much like NIAID/NIH took the lead on the COVID-19 Pandemic, although it’s mission is research not public management of a pandemic. (That is actually CDC’s mission, but that’s another story.) FDA regulates fertility treatments, so they would be another possible lead agency for developing a survival strategy.¹³

And what would such a strategy look like? Maybe like a scene out of Gattaca?¹⁴ Will Fertility Clinics become a government funded network of clinics? Should we even plan for an event that is perhaps millenia away, but also 99% certain?

Like climate change and other plans for catastrophic events in the future, it is probably more likely that we will encounter a catastrophic event we haven’t yet contemplated before we meet that disaster, so for the foreseeable future you can probably rest (relatively) easy on this Father’s Day.

My expectation is best summed up by this quote from Dr. Ian Malcolm of Jurassic Park (a 1993 movie and book by Michael Crichton),¹⁵ one of my favorite movies: "Because the history of evolution is that life escapes all barriers. Life breaks free. Life expands to new territories. Painfully, perhaps even dangerously. But life finds a way". 

1. https://pubmed.ncbi.nlm.nih.gov/17400006/

2. https://www.sciencedaily.com/releases/2020/08/200806111839.htm

3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4120474/

4. https://www.nature.com/articles/s41598-020-58997-2

5. I have actually been there and taught a course in their law school—totally unrelated to this issue. It was in the spring and I remember being warned when I asked where the park was located, that I should watch for Brown snakes that were everywhere with zillions of babies this time of year. Since Brown snakes are highly poisonous as well as the many other venomous snakes in Australia I imagined I could also meet, I opted not to go to the park.

6. https://www.pnas.org/doi/10.1073/pnas.2211574119

7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10227352

8. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1634840/?_ga=2.54197032.1299068029.1718281886-310519376.1718281885

9. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1634840/?_ga=2.54197032.1299068029.1718281886-310519376.1718281885

10. https://www.sciencedaily.com/releases/2020/08/200806111839.htm

11. https://www.cell.com/trends/genetics/abstract/S0168-9525(20)30154-2?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0168952520301542%3Fshowall%3Dtrue

12. https://www.genome.gov/about-nhgri/NHGRI-Vision-and-Mission

13. https://www.genome.gov/10003899/other-federal-agencies-involved-in-genomics

14. https://en.wikipedia.org/wiki/Gattaca

15. https://en.wikipedia.org/wiki/Jurassic_Park_(novel)