Stars Beyond Reach:The Process Of Births
Thematically, births are not natural, but instead are a controlled process with rapid-aging of the populace. The populace is also able to have new knowledge downloaded directly into their brains, ala The Matrix, making them pretty versatile. There are many other constraints, but parents of breeding age, time spent in childhood, and time learning new trades are not among them. Too complicated an un-fun! And doesn’t make sense thematically for our time scale, anyway.