Human experimentation, one way or the other.

https://lemmy.world/post/44414566

Sadly, the stupid tend to breed prolifically, and anti-vax idiots often have a gaggle of spawn, and are keen to whelp more litters as the others die from perfectly preventable diseases

Of course they have many kids. They need to in order to survive their genes.

Many of their kids never reach adulthood.

Not that many of them die in Western countries although they may have shorter overall lifespans. Doesn’t help that they add generations in 15-22 years instead of 25-40.