Here is an idea for a science fiction short story, available gratis to whoever would like to run with it. It was stimulated by the post below, the developed world's falling fertility, and the recent UFO report that didn't offer much hope for ETs visiting.
Perhaps the reason we have not been contacted by some spacefaring intelligent species is because, as technology progresses, intelligent species get control of their fertility and eventually die out from individual unwillingness to reproduce. This happens before multi-lightyear spacefaring becomes a practical reality.
You'd think they'd invent uterine replicators and techno-creches to produce the needed replacement individuals. Perhaps that avenue is esthetically or ethically distasteful, not biologically feasible or, if bio-feasible, does not produce successful individuals.
