Humans have an instinctive drive to optimize genetic survival. Without it, we would not exist. One of the control mechanisms for this is our instinct for reproduction. We constantly access future availability of resources, attractiveness to high quality mates, and probability of a new child surviving to bear children of their own with high quality mates. The industrial revolution, with its massive increase in productivity and technological advancement, dramatically altered the survival cost function that humans must now optimize. A measly 200 years has not been enough time for our instinctual optimization algorithm to adapt. As a result, I believe we are seeing over-compensation for higher resources and lower mortality, which is most apparent in countries with the highest per-capita GDP (see https://en.wikipedia.org/wiki/Total_fertility_rate#/media/Fi...) where parents are over-delaying childbirth because they perceive an opportunity to improve their economic standing, improve their mate selection, and take better care of a smaller number of children. We even see this happening with immigrants from low-GDP countries who move to high-GDP countries and converge towards the lower fertility rate of their new country. I expect we will eventually adapt, but it will likely require a conscious override of instinct if we want to avoid a massive population decline in the process.