In today’s Wall Street Journal, “The Fertility Gap” between Democrats and Republicans is analyzed:

According to the 2004 General Social Survey, if you picked 100 unrelated, politically liberal adults at random, you would find that they had, between them, 147 children. If you picked 100 conservatives, you would find 208 kids. That’s a “fertility gap” of 41%. Given the fact that about 80% of people with an identifiable party preference grow up to vote the same way as their parents, this gap translates into lots more little Republicans than little Democrats to vote in future elections.

For a less politically correct treatment, here’s an earlier article with stark graphs (that’s free):

The white people in Republican-voting regions consistently have more children than the white people in Democratic-voting regions.

But that’s just the facts. The philosophy question is more interesting.

If the adults have less than 200+ children by the time they die, their philosophy will have to spread faster than their progeny because at less than replacement rate the base of supporters will shrink. In mathematical terms, a stochastic series with an average geometric mean less than one will converge at 0.

In population terms, subpopulations with less fertility than replacement values will die out.

Religions with an admonishment to be fruitful and multiply will last longer than competing ones. Philosophies that call for zero or negative population growth will commit suicide in a whisp of finite time. It doesn’t take many generations for a philosophy to die out. A philosophy that garners 3/4 of the previous generation’s adherents will go from 150 million adherents to 1,500 aherents in 40 generations.

Optimism about the human condition is selected for. People who believe in Julian Simon’s theory of plentiful commodities and bountiful technology (The Ultimate Resource 2) will be more fertile than the worriers about carbon pollution and the population problem du jour. The former ideas have positive probability of being eternal.