I think this is a bit too reductive. Certainly contraceptives have played some role, but human evolution is not purely biological, it's also cultural. Modern ci

I think this is a bit too reductive. Certainly contraceptives have played some role, but human evolution is not purely biological, it's also cultural. Modern civilisation has a lot more ways to be successful without having children than middle age or older civilisation did. Most importantly for women, who previously had housewife, mother and certain low-status menial/sex jobs as their only culturally accepted roles. It's not surprising to me that as women were permitted higher education, voting rights, etc, cultural evolutionary pressures shiftes quite massively. And history seems to bear that out.