[allemagne]

Baseless wild speculation time: I don't think the timing quite matches up, but the Neolithic Y-chromosome bottleneck is a little close to this.

What if radiation from the sun actually sterilized something like 90% of neolithic men? Is that possible?

This creates a selection pressure for men whose sperm just happens to be resistent to the sun's radiation to get with as many women as possible. So any groups that don't practice patriarchal polygyny are at a sudden and catastrophic disadvantage for not utilizing their men who are still fertile and get outcompeted in a generation.

Thousands of years later we're still unwinding the social ramifications of this.

[Terr_]

How could that worldwide event affect just humans and not any of our close relatives?

[DrFalkyn]

Most other primate species, indeed most other mammalian species, polygyny is the norm

[allemagne]

Sure, but assuming humans are just "naturally" polygynous doesn't explain the actual observed range of human behavior or the Y-chromasome bottleneck I just mentioned.

[nonameiguess]

I'd never even heard of this until today, but from looking it up, it seems speculated this happened nearer to the dawn of civilization, like 5000-7000 BCE at worst, nowhere near 12000 BCE.

[snowwrestler]

How would some sperm be resistant to radiation? Like what is the physical difference in that sperm that resists radiation? Your entire supposition rests on this being possible.

[bongodongobob]

Being inside a cave or underwater maybe.

[Terr_]

I assume you mean that some humans happened to be in a protected place during a critical period... rather than some weird practice of (effective!) delayed artificial insemination using miraculous pottery.