Fertility (= kids per adult) has been falling worldwide for centuries. It seems to be correlated strongly with societal (not individual) wealth, and mediated by norms transmitted via mass media. World elite culture supports falling fertility by celebrating professional more than parenting accomplishment. Among many rich world elites, fertility has fallen below replacement level, and is still falling further. More others should join them as the world gets richer and more culturally integrated.

With seven billion humans today, if the population were to fall in half every two generations it would take roughly 1600 years for humanity to go extinct. So the risk isn’t immediate, and lots of things might change before then. (E.g., see my book Age of Em.) But as this trend has been consistent for centuries, it’s hardly crazy to think that it may continue for many more centuries.

Yes, extinction isn’t that likely, as a more likely scenario has selection stepping in to promote higher fertility. However, on reflection I think it also makes sense to worry about that better scenario, as the most likely way for selection to promote fertility is by promoting insular subcultures, especially re gender/mating/fertility. Let me explain.

Today the cultures associated with higher fertility tend to be more “traditional”, and less integrated with the dominant world elite culture. And a few small subcultures, like Mennonites and Amish, or Mormons and Orthodox Jews, even manage to maintain high fertility while staying closely connected to the dominant culture. However, as a big fraction of the youth of such subcultures leave them, it isn’t obvious that these subcultures can long sustain net growth.

But this does point to the plausibly winning strategy: subcultures that are both highly fertile and highly insular, keeping enough youth from wanting to defect from their subculture to join the dominant low fertility culture. Through some combination of genes, culture, and tech, they find a way isolate their members more from outside cultural influence, and thereby to support sustained population growth (or at least less rapid decline).

That scenario is a win relative to human extinction, but it should worry those who see much value embodied in the dominant culture, and much harm that could come from more cultural isolation, or from the religions or ideologies that might be used to sustain such insularity. For example, as traditional cultures are the main source today of insular fertile cultures, they seem likely to also be the main source of such winning subcultures in a few centuries. Maybe we’ll get a traditional culture who happens to take a lot from the dominant culture. But also maybe not.

What other options do we have? We could hope that genetic evolution will turn out to be faster than we fear, that global culture will change its mind and switch to promoting fertility, or that cheap nurturing robot parents will appear in time. But these seem faint hopes. The dominant culture may well seek to repress divergent insular fertile subcultures, but that would raise the risk of human extinction.

One possible fix that comes to mind here is for the dominant culture to tolerate and even encourage mating and gender variance among new cultural descendants of that dominant culture. That is, encourage the creation of new subcultures that inherit most of their cultural elements from the dominant culture, but that explore different approaches to mating, gender , and parenting within each subculture. Swinging, polyamory, and home schooling subcultures of today show that such cultural descendants are at least possible. Hopefully such subcultures would mainly be more culturally insular only regarding their mating, gender, and parenting aspects.

With enough such experiments, we might find new subcultures that promote much higher fertility, and yet which also inherit many aspects of dominant culture. And these might have a fighting chance against insular subcultures descended from more traditional cultures. Alas, this fix requires that the dominant culture become much more tolerant of local variations in gender, mating, and parenting, which may not be much more likely than their just coming to see the wisdom of promoting fertility. After all we are currently in an increasingly Puritan era of more not less conformity on such things.

I’m afraid I really don’t see a good solution here yet. But I at least want to flag the problem for consideration.