I met plenty of ppl who talk about the climate or cost of housing as the reason for other ppl but I never knew of anyone making a decision this way. You know someone?
The point is that "I don't want to have children because I'm worried about the impact of climate change" (social) or "I don't want to have children because I think it'll be too expensive" (economic) is not caused by biology and thus there is no selecting such concerns out of the gene pool.
Not even mentioning that evolution doesn't even meaningfully work at these short timescales. Modern humans are essentially identical to ~40,000 years ago, simply not enough time and pressure for evolution to do its thing.
Parents who fail to instill love and desire of family into their kids won’t get to be grandparents. A few decades ago maybe you could take it for granted “everyone ends up having kids” now it obviously is a dead end unless you really help your kids through it. It feels to me like the next generation will have parents who will be intentional about this value. Others won’t bother having kids to begin with.
It'd take regression back to a society where women are considered to have no value outside of being child factories, for parents to be able to indoctrinate their kids into reproducing with no concern for how good of a life they can actually give those kids.
It could also simply be lead poisoning
How do you know that? Are those really the reasons, or is the underlying reason "I don't really feel an urge to want kids, so I'm using this reason to justify it"?
Evolution works slowly, but that's because most traits have fairly minimal benefits. Marginally better eyesight might mean a 2% better chance of procreating. Assuming there's some genetic factor for "emotional desire to have children regardless of the circumstances", the chance of procreation rate for that is rapidly approaching 100%.
It's obviously far more complicated than that - it will be an interesting question for future biologists - if there are any!
I think we should also recognize the the generation in question might have difficulty with relationships. Having kids means finding a partner bought into the idea too and taking the leap. It seems people aren't figuring that out until much later.