As a lot of modern parents seem to think of having children as "buying a teddy bear" it is not clear why one is worse then the other. And the system did do reasonably well for several thousand years.

You're right, Kim: it IS depressing. If the only reason you want another kid is to have someone to take care of you in your old age, would we be pessimistic in assuming that child might feel no responsibility to you by that time in your life? We would have to assume, by Caplan's sentiments, that the child is seen as ONLY an economic asset to the parents' future. So, what does that do to the child as he/she grows up? With no love lost there, I can see a generous child deciding to throw his parents in a nursing home and pay the expenses the government won't cover, but never visiting. How very sad!