The Future of Fertility

Demographers are reporting that the U.S. birth rate is "bottom[ing] out" -- after years of decline, it didn't change from 2011 to 2012.

This is largely the result of the economic recovery. But it's worth thinking about the long term, too, and so I'd like to draw attention to this study, which we ran in our White Papers & Research section last month. The thesis is that evolution will throw off our predictions about entitlement spending.

We usually assume that evolution happens at a glacial pace, but it doesn't always. Certainly, the slow rate of genetic mutation limits the speed at which a species can add entirely new features, but evolution can act quickly when it has existing variation to work with. For example, some wolves are tamer than others; if you breed the tamest wolves together for a few generations, they become noticeably more like dogs. Even in the natural world, a sudden shock to the environment can create incredibly rapid changes.

Humans have experienced an environmental shock in the form of modernity, including contraception and the temptations of high personal consumption. We are facing options that evolution has not equipped us to evaluate.

Most Americans artificially limit their fertility, and some choose not to reproduce at all. Obviously, people with fewer children can invest more time and money in ensuring each child's survival, but there's no evidence that this strategy is at work here -- in the U.S., few people die before reaching reproductive age, and the rich folks who could afford the most kids are having the fewest. It's pretty clear that, going forward, a desire to have more children will be a strong evolutionary advantage.

As the new paper demonstrates, there's a significant correlation between the fertility of parents and that of their children, and much of this correlation is likely attributable to genetics. Depending on numerous variables, evolution might increase the fertility rate significantly in as little as two generations. And we shouldn't ignore culture -- like genes, it can influence fertility and is transmitted to some degree from parent to child.

Thus, we shouldn't assume that the current trend toward lower birth rates will continue. The future of Medicare and Social Security might not be as grim as we expect, and we might need to spend more on schools than we think we will.

Robert VerBruggen is editor of RealClearPolicy. Twitter: @RAVerBruggen

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