The Return of "Commune-ism"
The most likely scenario by which world human fertility will rise again includes a big return to communism. It will be a small-scale religious “commune” form of “commune-ism”, not industrial state “communism”, but “communism” of a sort nonetheless. (Bryan Caplan prefers the word “communitarianism” here.)
To see why, note two big facts about fertility. The first big fact is that human fertility (kids per woman in her lifetime) has been robustly and consistently falling since it first started to do so in France ~250 years ago. Most of the world is now below replacement fertility, and the rest should soon follow, resulting in a world population peak in about thirty years, and a world economy peak not long after.
After “hovering” near that peak for a few to many decades, population will likely then fall by half every generation or two. (That’s my guess; UN predicts much a much slower fall.) The economy will fall a bit faster, due to shrinking innovation rates and scale economies. Extinction follows in ~800-1600 years unless we see a bigger change to fertility trends than we’ve seen in the last 250 years.
The most obvious correlate of this fertility fall is rising society income, but that income is correlated with many other things, some of which may contribute more directly than income to falling fertility. Such as longer lifespans, more birth control, weaker gender roles, weaker religion, more schooling, more urbanization, weaker families, more individualism, and more integration into world culture. Most of these correlates were visible in France ~200 years ago, and we can now see in detail many of the social pressures that line up to keep fertility down.
The second big fact to keep in mind about fertility is that we have seen many small but consistent exceptions to this global fertility fall, exceptions which have many distinctive features in common. For example, Orthodox Jews, Salafist Muslims, Mormons, Laestadian Lutherans, and especially Anabaptists such as Amish, Mennonites and Hutterites. Some of these have maintained their distinctive cultures and high fertility for very long periods. Amish, for example, have doubled roughly every twenty years for over a century.
These groups tend to be fertile, insular, religious, pacifist, rural, and family-oriented. They uphold traditional gender roles, discourage birth control, limit years of schooling, maintain internal censorship, limit tech to maintain social isolation, and are made of small laregly-independent communities of about a hundred which split when they get large. And they tend to be communal, with mostly shared property, collective choices of activities and roles, and strong norms governing behaviors which are quite egalitarian re differences in talk, dress, housing, etc.
Christianity was once such an insular family-oriented often-communal religious cult which started small but eventually came to dominate the Roman Empire 300 years later mainly due to its doubling in numbers roughly every forty years. Orthodox Jews started as a small fraction of Israel in 1948 but are now 13%, and should be a majority within a few decades. If they maintain past growth rates, Amish would number 300 million in two centuries, dominating the U.S. well before then.
Of course such groups may face new obstacles as they grow. For example, while Mormons started with many small insular fertile groups much like these other groups, a central Mormon organization reined in extremists to gain acceptance of outsiders. And now Mormon fertility falls as fast as non-religious comparables, just with a twenty year delay. Other possible obstacles include subgroups splitting off and adopting less fertility-friendly habits, pacifism making them vulnerable to war, troubles entering more urban complex economic sectors, and outsiders forcing changes due to moral indignation at their deviant practices.
Even so, with so many social forces blocking shared global culture from drifting toward high fertility, and so few examples of that drift happening in recent centuries, insular fertile subcultures seem a strong candidate for how fertility might rise. And as new stable versions don’t arise often, existing versions offer good guesses for what future versions might look like.
Can theory helps us organize this data? I’ve previously tried to explain our fertility fall as an evolutionary mistake. When ancestors started living in larger social groups with stronger status ladders, “kings and queens” arose who gained high reproductive success. Evolution (some combo of DNA and culture) then endowed us with the following heuristic: pay more for status markers, relative to number of kids, when we or kids have an unusually high chance to become king or queen. (This heuristic should trigger more on markers of dominance status, not prestige status, as prestige differences aren’t sufficient to create kings and queens.)
This heuristic should have triggered on having unusually high relative wealth, but as average society wealth rarely varied much back then across societies, evolution took a shortcut and actually triggered it on high absolute wealth. So once our whole world become rich, a crazy deviation from all prior history, our heuristic misfired; we all now implicitly and mistakenly guess that we have a good chance of being king or queen, and cut fertility in response. (All unconsciously of course.)
It makes sense for this heuristic to also check if one’s society is big enough, and has enough status inequality, to support kings and queens. No point in cutting fertility to invest in status markers if your world has no kings and queens. And these checks can explain why the exceptional subcultures that have maintained high fertility in our rich world are small isolated egalitarian communal ones. Isolation limits attention to the local group, where one sees a group too small and with too little (dominance) status inequality to support kings and queens. And so members of these exceptional subcultures don’t trigger the usual heuristic that induces rich folks to cut fertility to gain status markers to increase the chances they or their kids become kings or queens.
Can we explain the other observed correlates of recent insular fertile subcultures? Rural locations, censorship, and pacifism make social isolation easier; after all, soldiers often assimilate to comrade soldier cultures. Family orientation, traditional gender roles, low birth control, and limits on years of schooling all seem to more directly predict higher fertility. And strong religion increases conformity and makes it easier to control all these things while maintaining insularity and censorship. So it seems that we do have decent explanations for the insular fertile subculture package.
Note that to explain why recent state industrial communism failed to maintain high fertility under high wealth, we need to presume that those socities in fact had sufficient scale and dominance inequality to make it plausible to members that their society had kings and queens. And in fact such societies did in fact have leaders with much higher reproductive success, leaders chosen from among those with better status markers.
As this theory analysis seems to check out, that boosts my confidence in my main predictions here: world human fertility will long continue to fall, and the most likely identifiable scenario by which it rises again involves the rise of insular fertile subcultures like our current small examples. Cultures that in essence implement small-scale religious “commune-ism”. And if this is how the future plays out, then we seem to be in for a few centuries of pain and loss. This cultural displacement may involve a lot of conflict, and practices and techs that we now value may be lost and need to be rediscovered or recreated in later centuries.
Yes, it is possible that before this econ fall hits hard and ends innovation for a while, we may find ways to greatly extend the fertile human lifespan, or to create AIs or ems that can wholesale replace human labor. And yes, let’s aggressively pursue such possibilities. But such scenarios don’t obviously seem more likely to me than this insular fertile subculture scenario. And I’ve explained why I see nations funding fertility as unlikely.
In our world today these insular fertile subcultures suffer from being less open to new ideas and less able to innovate, and from limiting themselves to smaller scale economic organization. However, those disadvantages will weaken in the predicted shrunken-scale low-innovation future economy. The world may find it hard to rediscover how to innovate, and to promote innovation, once its economy becomes large enough compared to its prior peak for innovation to again be cost-effective.
Added 17Sep: Polls say US public is evenly divided between wanting US to have more vs fewer kids.