Darwin, Reproduction and Religion
The theoretical argument is simple and persuasive. Humans vary in, among other things, their taste for having children. It seems likely that some of that variation is genetic. We are now in an environment where reproductive success is limited mainly by parental choice, not by resource constraints; most people in developed societies could afford to rear many more children than they do. So people with more of a taste for having children, those who are more phyloprogenitive, will out-reproduce those who are less, increasing the share of their descendants in the population and, eventually, bringing average birth rates back up. While the author does not carry the argument all the way, the logical implication is that the process will continue until reproductive success is again constrained by resources—a Darwinian version of Malthus' old argument for why a society rich enough so that the cost of children was low could not be in long term equilibrium.
The second half of the argument, and the one the post centers on, is the relation between religion and fertility. FuturePundit quotes various authorites to the effect that, on a world wide basis, more religious people are also more fertile, not only across societies but within societies. By his account, while the decline in fertility has not yet reversed itself, the decline in religious belief has, due largely to the greater fertility of believers.
It is a persuasive argument, but I have one problem with it. Human generations are long, so human evolution is slow. I can well believe that if we maintained the world more or less as it is for five or ten generations, FuturePundit's predictions would come true; fertility rates would begin to rise and religious belief continue to become more common.
We are not going to maintain the world more or less as it is for that long. We live in a time of very rapid change, driven by technological progress. That makes all long term predictions highly uncertain—the main reason I am opposed to expensive precautions intended to prevent long term consequences of global warming.
Here is a short list of possible technological changes that might—or might not—reverse one element or another of the equation:
1. Artificial wombs, to convert the cost of childbearing from time and pain to money, thus giving a reproductive advantage to higher income couples and richer (and, on average, less religious) societies.
2. Uploading—the ability to reproduce oneself by copying the brain's software to a computer.
3. Advanced virtual reality or very good recreational drugs, providing the illusion of a heaven on earth to compete with religion's (I think illusory) promise of a future heaven, leaving the more active parts of life, including reproduction, to people with a strong preference for reality over fantasy.
Readers are invited to contribute more items for the list.