Scrutable

“When I say rapidly, I’m talking in the evolutionary sense. Sex chromosomes evolved in mammals roughly 180 million years ago. It has taken that long for the Y chromosome to erode to this level,” says Graves.

“It’s funny that people get so upset about the loss of the Y chromosome. My rough calculations are that we’ve got another six or seven million years until the chromosome is completely gone.”

Woodchopper wrote: Sun Nov 03, 2024 7:58 pm From the article

“When I say rapidly, I’m talking in the evolutionary sense. Sex chromosomes evolved in mammals roughly 180 million years ago. It has taken that long for the Y chromosome to erode to this level,” says Graves.

“It’s funny that people get so upset about the loss of the Y chromosome. My rough calculations are that we’ve got another six or seven million years until the chromosome is completely gone.”

IMHO any prediction based upon what'll happen in six million years time is pretty speculative. During such a long time it seems equally plausible that humans will either become extinct, or we'll be so advanced that we'll have stopped caring about chromosomes millions of years before.

Tessa K wrote: Sun Nov 03, 2024 8:00 pm

Woodchopper wrote: Sun Nov 03, 2024 7:58 pm From the article

“When I say rapidly, I’m talking in the evolutionary sense. Sex chromosomes evolved in mammals roughly 180 million years ago. It has taken that long for the Y chromosome to erode to this level,” says Graves.

“It’s funny that people get so upset about the loss of the Y chromosome. My rough calculations are that we’ve got another six or seven million years until the chromosome is completely gone.”

IMHO any prediction based upon what'll happen in six million years time is pretty speculative. During such a long time it seems equally plausible that humans will either become extinct, or we'll be so advanced that we'll have stopped caring about chromosomes millions of years before.

That was my thought based on instinct

Right now, this is all speculative. The Y chromosome is degrading, that much is clear. The future result, on the other hand, is less so. In millions of years, men could simply cease to exist. We could equally see an evolutionary change with an entirely new sex forming.

In fact, with so many humans around the world and the innate weirdness of the Y chromosome, Graves believes that somewhere there could already be a man born without a Y chromosome for the first time.

Lew Dolby wrote: Sun Nov 03, 2024 9:50 pm I hate this simplistic view of genetics. "All women are xx, all men are xy" stuff

Apart from the fact most people don't know what chromosomes they have, there are people walking around who are 47 XXX, 47 XXY, 47 XYY - Kleinfelter syndrome and the rest.

Allo V Psycho wrote: Mon Nov 04, 2024 5:08 pm No, the article is confused/ing.
The Y chromsome carries the SRY gene, which initiates male sexual development. This can already translocate to another chromosome, and you can get a 46 XX male
https://www.sciencedirect.com/science/a ... 2915323314
This individual is pretty much a normal male, but because there are a few other genes on the Y which support sperm development and were therefore absent, he sought help for infertility, which is how he was identified. This is a rare condition (but there may be other individuals like this, undetected). If the other genes on the Y also translocated (or the Y chromosome pretty much as a whole became part of another chromosome), then the 'Y chromosome' might disappear but we would still have male and female sexual development controlled by SRY but in a different place.
The article indicates that this has already happened in a vole and a rat, so no, it doesn't have to take millions of years. It COULD happen overnight.

Looking at all the direct quotes from Jenny Graves, they all seem fine. It's the journalist parts of it that are misleading. These say

Right now, this is all speculative. The Y chromosome is degrading, that much is clear. The future result, on the other hand, is less so. In millions of years, men could simply cease to exist. We could equally see an evolutionary change with an entirely new sex forming.

'Men wouldn't 'simply cease to exist - they would arise through a different deployment of genes on chromosome. And 'an entirely new sex'' is nonsensical.

In fact, with so many humans around the world and the innate weirdness of the Y chromosome, Graves believes that somewhere there could already be a man born without a Y chromosome for the first time.

As for "Graves believes there could already be a man born without a Y chromosome" that's not a direct quote and I'm pretty sure Graves knows that there are such individuals. It's the journalist who is confused.

El Pollo Diablo wrote: Tue Nov 05, 2024 12:41 pm Can I ask, if there is an X chromosome with all the male sexual characteristics on it, and the other three chromosomes involved in sexual reproduction are all standard X chromosomes - then functionally, what's the difference between the male X and a Y chromosome? Surely, if men are passing down the male X to their sons as now, won't that see the same slow generational deterioration in the male X chromosome quality over time?

El Pollo Diablo wrote: Tue Nov 05, 2024 12:41 pm Can I ask, if there is an X chromosome with all the male sexual characteristics on it, and the other three chromosomes involved in sexual reproduction are all standard X chromosomes - then functionally, what's the difference between the male X and a Y chromosome? Surely, if men are passing down the male X to their sons as now, won't that see the same slow generational deterioration in the male X chromosome quality over time?

El Pollo Diablo wrote: Tue Nov 05, 2024 2:16 pm Sorry, that was badly expressed. So in a couple engaging in a bit of productive how's-your-father, in a world where the Y chromosome has been upgraded to a shiny new X_m chromosome, the woman has XX, the man has XX_m.

Three of those four chromosomes are normal X, one is X_m. Obviously, only two of them are actually involved in any one baby-boffing, but regardless, the X_m remains the only chromosome that can produce males, and will be passed on in that instance. So what's stopping that X_m chromosome getting worse over time, like the current Y one does? Or is that not how it works?

Allo V Psycho wrote: Mon Nov 04, 2024 5:08 pm The Y chromsome carries the SRY gene, which initiates male sexual development. This can already translocate to another chromosome, and you can get a 46 XX male

El Pollo Diablo wrote: Tue Nov 05, 2024 2:16 pm Sorry, that was badly expressed. So in a couple engaging in a bit of productive how's-your-father, in a world where the Y chromosome has been upgraded to a shiny new X_m chromosome, the woman has XX, the man has XX_m.

Three of those four chromosomes are normal X, one is X_m. Obviously, only two of them are actually involved in any one baby-boffing, but regardless, the X_m remains the only chromosome that can produce males, and will be passed on in that instance. So what's stopping that X_m chromosome getting worse over time, like the current Y one does? Or is that not how it works?

Sciolus wrote: Tue Nov 05, 2024 2:42 pm

Allo V Psycho wrote: Mon Nov 04, 2024 5:08 pm The Y chromsome carries the SRY gene, which initiates male sexual development. This can already translocate to another chromosome, and you can get a 46 XX male

Thanks for your educational (to me) post.
At the moment, the XY system means that half of people have one copy of SRY and half of people have no copies (ignoring outliers). What would happen if SRY migrated to a different chromosome, population-wide? In the short term, I think you would find 25% with no copies, 50% with one copy and 25% with two copies, so presumably 25% female and 75% male. I'm not sure how evolutionarily stable that would be, and wonder if we would evolve some other sex-determining mechanism. Biology shows us there are plenty to choose from.