Evolution is not our friend. Evolution favours reproductive fitness, not happiness. Happiness is just one of many tools in the toolbox for getting us to reproduce.

The current situation with low birth rates due to the availability of contraceptives is a temporary blip. Right now you can witness a wide range of forces arrayed against that status quo. Note that for humans, evolution operates not only at the genetic level but also at the cultural level since parents can pass their culture on to their children.

We’re witnessing a major backlash and reaction against secular liberalism, a return to authoritarianism and a revival of religious membership. Religion has always been one of the most powerful of evolution’s cultural weapons for increasing reproductive fitness.