[steve-b]

Which is why I mentioned childbearing as self-protection on the part of the parents. The focus here is on the parents' survival and welfare. Wouldn't you say that this point is independent of the two?

No. The reason for parents to have enough children to guarantee that a few survive, in an environment where mortality is high, is to provide themselves with old-age insurance. That's why your "third" point is simply a restatement of the original first point.

[TopQuark]

OK, now it's clear. We appear to disagree on something: the reason for many children is the continuation of the species in general; it is present even among animals, where no parental-protection issues even arise.