Why do so many modern women choose not to reproduce - especially women of high intelligence?
The average woman in a modern society has considerably fewer than the replacement level of fertility, with only one-point-something children per woman.
Probably about a third or more of women college graduates have zero children - and among the most intelligent women (IQ in about the top couple of percent) the proportion is even higher, and average fertility is something like 0.5 children per woman.
The reason why so many women have zero children is essentially pathological, and related to things such as the secularization of society, decline of parental choice and influence concerning women's fertility, the high prevalence of contraception and abortion (allowing sex without fertility), Left wing ideology propagated in the mass media and so on.
But these are amplifiers - and amplifiers must have something to work-on - something to amplify; and if women were evolved towards 'reproduction at any price' then cultural and technological factors would not have had anything like so large an effect.
Therefore, it is probable that women have some baseline tendency not to reproduce at all under certain conditions; in particular not to reproduce when a suitable mate is not available.
In other words, it seems likely that women have to some extent and under some conditions been 'hard wired' by natural selection that it is better not to reproduce at all, than to reproduce with the wrong man or men.
And if this is true it implies some significant degree of group selection - in the sense that women may be safeguarding the integrity of the group gene pool rather than taking a chance on their own specific reproductive success.
In particular, I am suggesting that women have evolved such that (on average) they would rather not reproduce at all than have offspring with a man who has signs (cues) of carrying a heavy load of genetic mutations - which would correlate with very low attractiveness - which comes from very low status, evidence of significant chronic disease, evidence of developmental or congenital disorders, and even very advanced age - and so on.
All of these are correlated with a higher probability of a significant mutational load. This would, of course, reduce the probability of successfully rearing offspring - but for a women confronted with zero reproductive success, even the slimmest chance of bringing up one child would increase here genetic representation in the next generation more than voluntarily having no children whatsoever.
So, I conclude that the very high proportion of women who choose to have zero children in modern society is mostly a product of social pathology (facilitated by technology) - but that this has been amplified from an evolved tendency of women not to mate with men who are likely to introduce a significant mutation load into her lineage, or genetic grouping of relatives.
NOTE: An alternative strategy to not mating, is what might be termed deliberately sterile mating. It is possible, indeed likely - according to WD Hamilton (Narrow Roads to Gene Land, Vols 1-3), that group selection mechanisms would favour varieties of sexual behaviour that eliminate high loads of mutated genes from the relevant gene pool. This might favour self-willed death (passive or active suicide), self-chosen sterility (as described above), sterile matings (with infertile mates, elderly mates, same-sex mates, or non-human or non-living mates) or alternatively assortative mating in which low fitness/ high mutation load individuals are attracted to other low fitness/ high mutation load individuals - such that either no offspring or only unfit offspring - unfit, that is, under 'natural conditions' - will result; and the mutational load of both partners is eliminated in a single generation. Hamilton suggests that organisms can sense, internally, the problems due to a high load of deleterious mutations, and infer the high probability of group fitness damage from their own survival and/or reproduction - and adjust their motivation and behaviour accordingly. If correct, this would predict a higher mutational load among those members of the population who pursue sterile mating strategies, especially those who choose sterile mating strategies.)