Human Male Karyotype
Y Chromosome Highlighted
https://en.wikipedia.org/wiki/Y_chromosome
Although the Y chromosome’s role in sex determination is clear, research has shown that it is undergoing rapid evolutionary deterioration. Many generations ago the Y chromosome was large, and contained as many genes as the X chromosome. Now it is a fraction of its past size and contains fewer than 80 functional genes. This has led to debates and concerns over the years regarding the Y chromosome’s eventual destiny. Many speculate that the Y chromosome has become superfluous and could completely decay within the next 10 million years. ___ Uncertain Fate of Y Chromosome
I need not paint in graphic detail the fate of the human race should the essential functions of Y chromosome genes continue to be degraded to a significant degree.
By one estimate, the human Y chromosome has lost 1,393 of its 1,438 original genes over the course of its existence, and linear extrapolation of this 1,393-gene loss over 300 million years gives a rate of genetic loss of 4.6 genes per million years.[21] Continued loss of genes at the rate of 4.6 genes per million years would result in a Y chromosome with no functional genes – that is the Y chromosome would lose complete function – within the next 10 million years, or half that time with the current age estimate of 160 million years.[16][22]
We have seen many reports describing a decline in human sperm quality and quantity across the world.
More:
Sperm counts — measured by sperm concentration or total sperm count — declined by 1.4% per year on average among men from North America, Europe and Australia between 1973 and 2011, a new study published in the journal Human Reproductive Health found. Overall, sperm counts fell between 50% and 60% over those 38 years, with no evidence of a leveling off in recent years. This significant decline in male reproductive health “has serious implications beyond fertility concerns,” it concluded. The researchers analyzed samples from nearly 43,000 men from 185 studies.
Similar scientific reports describing declines in male testosterone production have been filed.
(More:)
“This population-level decline in testosterone concentrations in men is not explained fully by the usual suspects: increasing BMI and prevalence of obesity, certain other co-morbid conditions or decreasing incidence of smoking. Although the analysis by Travison et al did reveal significant age-related increases in adiposity and medication use and a welcome decline in smoking, the age-matched decline in testosterone concentrations persisted even after adjusting for these variables,” Shalender Bhasin, MD, of the section of endocrinology, diabetes, and nutrition, Boston University School of Medicine, wrote in an accompanying editorial.
As more genes are lost from the Y chromosome over time, it is likely that some of these lost genes will have played a significant role in supporting traditional male behaviours and functions — without which the future of the human collective will be compromised.
Other Signs of Male Decline
If a young woman cares about the health and longevity of her prospective child, she may wish to bypass her contemporaries and seek out an older man — with longer telomeres — to father her child:
… an individual’s telomeres lengthened not only with their father’s age at their birth, but also with their paternal grandfather’s age at their father’s birth. This shows the effect is amplified over the generations – the paternal grandfather’s age is associated with longer telomeres in his grandchildren.
The increase per year of a man’s delay in reproduction roughly equalled the amount of annual telomere shortening observed in middle-age adults.
The findings published in Proceedings of the National Academy of Sciences suggest delayed paternal reproduction can lead to cumulative, multi-generational increases in telomere length in descendants – which could promote long life.
Telomeres have been called the “chromosomal clock” because they seem to be central to biological ageing. Longer telomeres are a sign of being biologically younger and healthier. __ https://www.telegraph.co.uk/news/science/science-news/9325945/Children-of-older-fathers-are-more-likely-to-live-longer.html
The above findings by Professor Christopher Kuzawa at Northwestern U. are interesting, and have many distinctly different possible explanations. But I suspect that one of the reasons that these older fathers (and older grandfathers) yielded children with longer telomeres, may be that these men were born earlier in the process of the long decline of the Y chromosome.
More in depth look at the phenomenon of older fathers and longer telomeres — this article helps to explain some of the mystery, and lays much of the blame at the feet of a female germline-controlled ongoing decline in human telomere length.
Without the ability to recombine during meiosis, the Y chromosome is unable to expose individual alleles to natural selection. Deleterious alleles are allowed to “hitchhike” with beneficial neighbors, thus propagating maladapted alleles in to the next generation. Conversely, advantageous alleles may be selected against if they are surrounded by harmful alleles (background selection). Due to this inability to sort through its gene content, the Y chromosome is particularly prone to the accumulation of “junk” DNA. Massive accumulations of retrotransposable elements are scattered throughout the Y.[16] The random insertion of DNA segments often disrupts encoded gene sequences and renders them nonfunctional. However, the Y chromosome has no way of weeding out these “jumping genes”. Without the ability to isolate alleles, selection cannot effectively act upon them. __ Wikipedia “Y Chromosome”
The Y chromosome is subject to damage from internal processes as well as from external processes — including environmental toxicity or nutritional deprivation. Since it has no good way to eliminate bad gene sequences, the damage is cumulative over time.
This suggests that society may wish to begin banking human sperm from suitable males, on a significant scale. More research on long-term human sperm storage is needed to assure viability over a long time scale. While the use of donor sperm from an earlier stage in the decline of the Y chromosome cannot possibly erase damage that has already occurred — in both the male and female germlines — it can sidestep some of the problems and allow more time for better solutions.
Fortunately, we do have some time. If only we could step away from the die-off tendencies of our leftist overlords and face the future objectively without all the PC censorship and postmodernist nonsense.
More:
Why young women should seek out older men to father their children — for the good of the species!
al fin next level 
Yes, according to this article: https://www.scientificamerican.com/article/reprieve-for-men-y-chromosome-is-not-vanishing/ the Y chromosome has won a reprieve for the past several million years, perhaps due to roughly 12 “core genes” present on the Y which are needed for vital functions beyond sex determination. A reprieve is often only temporary, however.
Important evolutionary changes often occur in fits and starts, with long pauses between. Because of the unique nature of Y selection and recombination, it is more vulnerable to degeneration than the other genes (see sources in article).
Consider the difference between the human and the chimp Y chromosome:
When such degeneration occurs in humans, it would not occur uniformly across all the human male populations of the planet. Particular populations — perhaps older populations — might display signs of Y degeneration earlier than newer populations, if the ticking time bomb hypothesis of genetic load and decay is correct. Even if it occurs in a punctuated equilibrium.
An interesting article describing Y chromosome influences on the brain can be found here:
https://europepmc.org/articles/PMC2854822
Much more.
Finally, this article: http://www.genetics.org/content/genetics/early/2017/10/10/genetics.117.300382.full.pdf
While somewhat technical, it provides much needed caution to anyone who thinks he has figured out what is happening with the human Y chromosomes. Everything is in flux.
You linked to an article using rats (a far less complex set of species than great apes, including humans) for having apparently lost their Y chromosomes. The evidence that life as complex as humanity can be possible after losing the Y chromosome is lacking.
See previous comment showing the alarming decay of the Y chromosome in chimps. Scientists are trying to reassure everyone that everything is fine with the human Y chromosome. But given the punctuated nature of chromosomal evolution, we can only watch and wait.
>See previous comment showing the alarming decay of the Y chromosome in chimps.
Chimps have more genetic diversity than humans. Even then, to claim they’re losing their Y chromosome is rather absurd.
>Scientists are trying to reassure everyone that everything is fine with the human Y chromosome
In the sense that there’s no reliable evidence of its upcoming removal, they’re correct.
Please keep in mind that evolutionary change in a species does not occur in unison at a specific time on a specific day. The crucial genes on the Y chromosome — the ones that are left and still functioning — are more vulnerable to loss than genes on other chromosomes. The pattern of loss will be noted slowly on a species level, if it is ever noted at all. Without the male of the species, humans are living far beyond the carrying capacity of many highly populated areas of the planet.
Science is changing, becoming more politicised. Some areas of study may well be abandoned as too politically sensitive.
As mentioned, older populations with older Y chromosomes may be farther along the path of decline.
The process cannot be predicted or timed. Timing evolutionary change is like timing the stock market. A fool’s game. It is not clear whether tools such as CRISPR will allow humans to compensate for this built-in weakness and chromosomal booby-trap.
But taking note of trends in evolution over millions of years is de rigueur for careful observors.
Be sure, Maldo, that convincing other people of the veracity of the speculations on this blog is the farthest thing from my mind. The science may be as clear as it can be at this stage, but that is still pretty damned murky! 😉
We know there is risk over time. We just do not yet know how much risk or over what time.
How are you sure that the male-determining chromosome wouldn’t change over from the fragile y-chromosome? Many other species are able to have males without the y-chromosome.
Over millions of years there is no certainty over the fate of the human Y chromosome. Past evolutionary history is no guarantee of future results, particularly given the exceptional fragility of the Y chromosome to loss of genes. If humans cannot deal with the chromosomal changes over that time scale, then perhaps they do not deserve to build an abundant and expansive human future.
Today’s growing dominance of political whims and fashions over scientific research is a threat to the future of the entire scientific enterprise. Some things are considered too politically offensive to study objectively. That is a far greater immediate threat to the human future than the decay of the Y chromosome. But at the same time, it is clear that many aspects of masculinity are under threat, as manifested by lower sperm counts, lower testosterone levels, the failure of men to achieve levels of competency and confidence that allow most of them to raise families, etc. etc.
Culture is largely to blame, but we would be mistaken not to simultaneously look for biological causes for the ongoing decline of males.
10 million years? I am quite sure there will be no humans in 10 millions years.
The male is nature’s petri dish. Females are significantly more similar to each-other than males are to each-other. This manifests even in regards to what the sexes find attractive (males have more agreement among themselvse what constitues a good looking woman than female do). There’s nothing remotely surprising about what you’re on about if you’re properly familiar with sex differences.