Future fertility

I think that most models of the demographic transition have human fertility continuing to fall globally - for some time to come. Recently I read a prediction - posted by Jason Collins - that fertility would rise. Here is Jason's post linking to his article: Fertility is going to go up.

I am pretty sceptical. At one point Jason confesses that he might be wrong, writing:

I’m the first to admit we could be wrong in the prediction of a fertility increase. What other shocks are still to come? Will the continually changing environment drown out the underlying evolutionary dynamics? Our instinct is that most of the shocks that can affect fertility have played out in the developed world – increased incomes, effective contraception, female choice and so on. But what further shocks could reduce fertility?

Here's my attempt at a list of the big fertility-reducing factors that currently still lie largely in the future:

• More engaging games;
• More engaging pornography;
• Sex with robots;
• Economic competition with machines;
• Chemically-induced orgasms;

Basically, memes have run rings around genes, reducing human fertility. IMO, this process shows no sign of stopping - or even slowing down. The argument that parasites rarely kill their hosts doesn't help much here - parasites can kill their hosts if they have multiple host types and aren't dependent on one particular host type. That will be the situation with intelligent machines - memes won't be dependent on human hosts any more - so they won't be forced to keep them around.

Overall, based on our current understanding of cultural evolution, it seems quite reasonable to model future human fertility as falling to zero. Fertility is going to go down. Jason's argument for the opposite conclusion seems to be based on DNA evolution. However, this is slow - by comparison with cultural evolution. You have to model cultural evolution to have much hope of predicting future changes.