Robin Hanson:

The clearest proof of biologically maladaptive culture drift is fertility. Children per woman per lifetime has been declining worldwide for centuries, and is now below replacement levels almost everywhere. Earth passed peak births in 2016, and in a few decades, we’ll pass peak population. Absent huge AI advances, innovation rates will then fall even faster than the population, causing a many-centuries-long innovation pause, and then less liberal governance, perhaps including even the return of slavery.

This fertility fall is driven by many strong and beloved cultural trends, including more gender equality, more intensive parenting, longer inflexible career paths, less religion, more urbanity, capstone replacing cornerstone marriage, and less grandparent involvement. On the whole, these look more like non-adaptive value drifts than adaptive learning or context-dependence. And having fertility fall below replacement during times of plenty seems clearly maladaptive. While policy solutions exist, like big payouts to parents, they seem unlikely to be adopted, as they need us to care enough, and to allow the reversal of beloved trends.

How exactly did culture drift to hurt fertility? Maybe many independent trends just added up to that. But another possibility is that high-status folks had wealth to invest in kids and widespread status markers that could be improved by wealth. Then our general cultural habit of copying high-status behavior could have combined with a selection effect: having fewer kids causes each to have higher status. This pattern was widely reported in history, at least among elites.

Just as our cultural drift story predicts, the main fertility exceptions we see are in fragmented, very insular cultures like Mennonites, Amish, and Haredim. By doubling every two decades, they look on track to replace our mainline civilization in a few centuries, just as Christians once took over Romewith similar growth rates over a similar timescale. And just as Christians discarded many things they didn’t like about Roman civilization, these new groups may discard many aspects of our liberal civilization that we now treasure.

In fact, many ancient civilizations like Greece and Rome plausibly fell due to low fertility. And humanity may repeat this pattern: innovation causing wealth causing fewer richer cultures, which drift, fall, and fragment. Culture selection then heals drifts, letting civilizations rise again.

Is There a Fix?

Eventually, when our descendants spread across the stars, long communication delays will ensure cultural fragmentation, and thus more selection. (Fast or easily copied minds might also work, as in my book Age of Em.) Before then, I see only three fixes: conservative, totalitarian, and multicultural. And none seems likely to work (though we should try).

The conservative fix is to revert culture back to a point when cultural selection was strong, and then stop it from changing. If these cultural values are shallow, this would forgo gains from adapting deep values to changing conditions since then. But agreeing on deeper underlying conservative values seems hard.