Doubtful. The pure altruist would concentrate all their efforts on the single activity with the highest marginal social return. Several times per day that activity would be eating, because eating prevents a socially beneficial organism from dying. Eating has poor substitutes, but there are excellent substitutes for personally having a child (e.g. convincing a less altruistic couple to have another child).
there are excellent substitutes for personally having a child (e.g. convincing a less altruistic couple to have another child).
Not all children are of equivalent social benefit. If a pure altruist could make a copy of themselves at age 20, twenty years from now, for the low price of 20% of their time-discounted total social benefit - well, depending on the time-discount of investing in the future, it seems like a no-brainer.
Well, unless the descendants also use similar reasoning to spend their time-discounted total social benefit in the same way. You have to cash out at some point, or else the entire thing is pointless.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.