As I understand it, birth defects are like 99.999% of the time unhelpful. But that 0.0001% of the time the genetic freak is a huge advantage and that gets passed down in the gene pool and thus, over many many generations, evolution.
Alcohol, which is known to increase birth defects, should increase the speed at which that happens. Right? Like playing the lottery with more tickets.
I have a hard time believing that not having enough sex was ever the reason that prehistoric people had too few children.
Oh they HAD enough children. The majority just died early. Disease, fire, cliffs, dinosaurs eating them. It was rough.
The only “dinosaurs” that were around at the same time anything vaguely human was, was chickens and such other theropod descendants.
We, uh, ate them.