but natural selection limits the survivors to well-adapted ones.
except when interfering humans keep dodgy foetusses alive in intensive care units.
(Often quite justifiably, of course, granting life to viable humans who would otherwise not make it - but there are some occasions when one feels that a little less iknterference would be better for all concerned. I speak from experience of teaching badly disabled young adults.)

and, just bye-the-bye. jheem said, "]and unwanted offspring outside of marriage.""
I would dispute that all - or even most - children born outside wedlick are unwanted.