Capitalism has been around for a couple of hundred years. During most of that time fertility rates were high in pretty much every capitalist society. This changed within a generation of contraceptives becoming widely available, even in those capitalist societies most strongly influenced by socialism, with low poverty rates and where generally everyone can easily afford to have children. I think we can make a fair guess which factor was more important, between capitalism and contraception.

Humans, and mammals in general, never developed an innate desire to reproduce. It was never necessary in an evolutionary sense, since fucking led to reproduction. There hasn't been enough time for humans as a species to adapt to the new reality, and we can probably develop new contraceptive technology faster than any resistance to them can evolve (one would expect, for example, allergies to the contraceptive pill or condoms to start appearing and/or increasing in frequency among the population).

The more impactful evolution might be of a sociological nature. Cultures and subcultures that encourage large families should be expected to begin proliferating globally. We have seen some beginnings of this happening, such as the Haredim in Israel and ultraconservative communities elsewhere.