> 1000 years ago some subset of people chose not to have children, and humanity did just fine, and that same group of so-called "non-breeders" still exists today.
There have always been, and always will be, people who don’t have kids, for a whole host of reasons.
But that’s not the argument (or at least, not the steelman version of it, as opposed to the strawman one) - the argument is that if there are certain heritable traits that discourage people from having children, then all else being equal, natural selection will cause the frequency of those traits to decline over time, albeit often not to zero.
The all else being equal part is very important. In a society with strong social pressure to reproduce, a trait which makes people less likely to want children may not be strongly selected against - because the social pressure to reproduce means desire to have children only has a small impact on the odds of actually having them - whereas in a society which is much more individualist, it may have much more of an impact, so the selective pressure against that trait may be much stronger. And of course, a trait which produces less desire for children might nonetheless be selected for because it produces some other countervailing advantage
Still, I think the argument does have some weight - that in contemporary Western society where reproduction is far more of a voluntary choice than it once was, biological and cultural factors which encourage reproduction are going to be selected for to a much greater degree than they were in the less individualist societies of decades and centuries past, where less such encouragement was needed
There have always been, and always will be, people who don’t have kids, for a whole host of reasons.
But that’s not the argument (or at least, not the steelman version of it, as opposed to the strawman one) - the argument is that if there are certain heritable traits that discourage people from having children, then all else being equal, natural selection will cause the frequency of those traits to decline over time, albeit often not to zero.
The all else being equal part is very important. In a society with strong social pressure to reproduce, a trait which makes people less likely to want children may not be strongly selected against - because the social pressure to reproduce means desire to have children only has a small impact on the odds of actually having them - whereas in a society which is much more individualist, it may have much more of an impact, so the selective pressure against that trait may be much stronger. And of course, a trait which produces less desire for children might nonetheless be selected for because it produces some other countervailing advantage
Still, I think the argument does have some weight - that in contemporary Western society where reproduction is far more of a voluntary choice than it once was, biological and cultural factors which encourage reproduction are going to be selected for to a much greater degree than they were in the less individualist societies of decades and centuries past, where less such encouragement was needed