Which part is the "bottleneck"? Is it the idea that at one point nearly all mammals were nocturnal and that it became advantageous for some to transition to diurnal since there was less competition for resources during the day?
the bottleneck was a global ecosystem level of selection.
dinosaurs pressured the mammals to stay small, hide in burrows, and roam at night.
dinosaurs, and a lot of other things came to an abrupt end, the basal mammals survived in thier bunkers with hoards of seed, and were relieved of selective pressure, thus diversified in thier traits this is when mammalian diurnalism made a big comeback so they could now compete among fellow mammals radiate and expand niche into the estate of the late dinosaurs
What a wild thought that our ancestor was a mousey thing that hid in a hole, terrified of the giant dinosaurs and falling asteroids, and survived only because it had the Jurassic mouse equivalent of a Costco habit while completely failing to suspect that its distant children will one day rule the planet.
I think it's a genetic trait diversity bottleneck? Mammals almost all went in the direction of nocturnal adaption and a lot of adaptions useful during the day were lost over time.
Animals in the wild don't typically die of cancer, so that's probably not much of an adaptation evolutionarily. Even if they did die of cancer, it would likely be after they've reproduced, which means there's no selective pressure to develop the adaptation.
> Animals in the wild don't typically die of cancer, so that's probably not much of an adaptation evolutionarily.
There's lots and lots of adaptations that repair damage to DNA and that deal with damaged cells. So there must have been lots of evolutionary pressure to keep them in place and keep them working.
Animals in the wild probably don't typically die of cancer, because those adaptations are in place.
But you are right, that even mammals active during the daytime have not (re)gained that specific photolyase DNA mechanism that their ancestors lost.
Mammalians being mostly nocturnal for most of their evolution... burrowing lifestyle. This explains people like me spending too much time in front of their computer in darkened rooms. I blame nature.
