How many millennia ago was this?
Sorry but passing on genes has never been an issue; all it takes is hitting puberty and getting horny. I know it's doesn't fit your narrative but did you ever ask which segments of society tended to have more children even hundreds of years ago?
its about passing on the best genes. anybody can have kids, the government will take care of them. by the way if a kid is in care(government) statistically they are much higher probability of having problem.
not everyone had children way back when. 60% of women had children and 40% of men had them. people with resources(men) were more likely to pass on their genetics. women provided fertility and beauty. it was an exchange. women died during child birth, medical technology didnt exist, people died at a young age, etc. the average old age for people was previously much younger than todays 80. science
. its was survival of the fittest throughout mans evolution, until recently. technology enabled man and allowed man to improve his chances of survival and to prosper(breed). anyone can breed right now, doesnt mean they are the fittest of the genetics out there to further the species. people who are medically fragile, have mental health issues, low iq, etc are breeding which undoes on a genetic level natures way of improving the human animal.
100s of years ago people were dropping like flies. outbreaks that actually decimated populations, yet there were people who survive because genetically they had better immune systems. survival of the fittest. now anyone can pass on their genes, almost anyone.