Yeah, there are examples of the male chromosome being eliminated (some types of stick insects) but it's way more complex than that. Not only are chromosome degradation processes pretty fast in evolutionary time, highly conserved genes tend to be pretty resistant, sometimes even jumping chromosome if there's a degradation event.
"given the average rate of gene loss over geological time, we're several billion years overdue for ATPase disappearing" is my next pop-sci take.
It depends (there's a lot more than X and Y in the animal kingdom), but broadly and loosely yes. It tends to be long periods of relative stability punctuated by rapid gene loss/transfer, followed by stabilisation of the smaller chromosome. The suppression of recombination that allows for a strong and stable sex division to develop also kind of makes that chromosome less stable. Y and X were probably, originally, hermaphoditic chromosomes that then had one develop a dominant male allele and then to stabilise it developed the SRY gene to regulate it.
Yeah, there are examples of the male chromosome being eliminated (some types of stick insects) but it's way more complex than that. Not only are chromosome degradation processes pretty fast in evolutionary time, highly conserved genes tend to be pretty resistant, sometimes even jumping chromosome if there's a degradation event.
"given the average rate of gene loss over geological time, we're several billion years overdue for ATPase disappearing" is my next pop-sci take.
Ooooooo ty
Also, wouldn't Y-chromosome shrinkage most likely follow an exponential decay curve?
It depends (there's a lot more than X and Y in the animal kingdom), but broadly and loosely yes. It tends to be long periods of relative stability punctuated by rapid gene loss/transfer, followed by stabilisation of the smaller chromosome. The suppression of recombination that allows for a strong and stable sex division to develop also kind of makes that chromosome less stable. Y and X were probably, originally, hermaphoditic chromosomes that then had one develop a dominant male allele and then to stabilise it developed the SRY gene to regulate it.