Everyone claims it's the cost, but poor people used to have kids constantly. When I lived in Baltimore the guy on my block grew up there. They had 12 kids in a ~1100 sq foot row home with two bedrooms and 1 (or no?) bathroom. You can find similar stories everywhere.
Kids are cheap when you are poor because you aren’t seeking status. A home in a highly desirable suburban school district won’t support 12 kids in the lifestyle that people demand in those places.
Whoever has custody of the kids is fine. The social services benefits scale. They won’t get rich, but they’ll eat. People will be OK. The only people who lose are stupid men who have multiple children with multiple women.
Once you have a little cash, the formula changes completely.
You also have the state which pays for most of the top line expenses of having kids. Once you start making money, those benefits don't fade, they instantly disappear entirely.
Natural selection does not care one bit about the individual, to the question is completely meaningless. Add to that, that we share 99.9% of our DNA, so you passing it on, means I'm passing it on for free, while you sit there with all the cost. Who's the fool now?! ;)
But passing on genes is a pretty arbitrary goal. It's the one encoded in our genes, but (looks around at random object) passing on teacup design is encoded in a teacup. The most teacups are the ones that make people look at them and say "I want a copy of that cup". It's just statistics, not the ultimate meaning of the universe. The humans who think it's the ultimate meaning of the universe may be more likely to replicate - but that's a genetically inherited delusion, not a fact. You can pass on your editor choice just as well as you can pass on your genes.
