Honing Fertility Fall Theories
Richard Hanania has done me the honor of carefully thinking through my & other fertility theories, finding consequences and data tests I didn't think of. If you have time, go read him first, then come back here.
He calls my status theory “Kings and Queens” (KAQ), and interprets it as suggesting a wealth threshold effects. Which he tests, finding favorably:
Overall, I think this is very strong evidence for an effect where the relationship between wealth and fertility starts out weak and negative, becomes strong and negative as more and more people feel that they and their children are potential kings and queens up to the $5K or $10K range, and then disappears as practically everyone is subject to this effect.
But he notices that the theory needs another assumption, which he finds somewhat ad hoc:
We have to imagine something in our evolutionary programming that says “limit fertility when you are close to becoming a king, but be fruitful when you actually become a king.” … One could argue that we use absolute living standards to decide we’re aristocrats, but then rely on signals of relative status to decide we’re kings, like if you hear trumpets playing before you walk into a room. When I pointed this out to Robin recently, he acknowledged that this was indeed an implication of KAQ in a postscript to his article. But this makes the theory somewhat ad hoc, relying on signals of absolute wealth in one situation and then conveniently switching to relative status in another.
I see two different possibilities here. First, the concept of royalty (kings and queens) just might equal that of the highest status folks around. In which case royals would need to carefully ensure no one else in their society showed anything like their levels of wealth and status signs. And foreign royalty would just not be allowed to show off their status signs to locals, for fear locals would accept them as their new royalty. In this case, the evolved heuristic would be to go wild on fertility when you joined this highest status group. Seems like this could work.
The second possibility is that the concept of royalty is not just equal to that of highest status, in which case we’d have to have had different markers we track to see who are our local royals. As this would be an important thing to get right, we’d be pretty good at it. In which case our evolved heuristic could be to go wild on fertility when those markers apply to us personally. Seems like this could also work.
Hanania also considered my more recent theory that we just copy high status fertility behavior, ignoring a key selection effect:
Recently, Hanson came up with another theory, which says that we evolved to imitate successful people, and due to selection effects, among elites the most successful around them tend to be those who had the fewest kids. …
As for why this limited fertility norm has only spread to the general population now, one has to “again postulate that humans encoded this behavior as something that mainly makes sense for parents who are relatively rich and high status, but not otherwise.” This strikes me as not very convincing, and perhaps not even internally consistent. The theory holds that evolution equips us with a feeling of where we are in a hierarchy based on absolute wealth, but that mechanism is at the same time maladaptive, because it causes elites to fall prey to selection effects. …
A simpler version of this imitation theory, one that doesn’t rely on threshold effects, might say that the most successful members of society were always those who came from families that limited their fertility. But most of the population usually did not have enough exposure to elites to notice. Under this theory, elites have always been behaving maladaptively and falling prey to selection effects, but not enough people have been elites for this to change our evolutionary trajectory. Now, with greater wealth and communications technology, more and more people are exposed to the ultra-successful. This would explain both decreasing fertility as wealth increases, and also decreasing fertility as time moves forward, given the spread of radio, TV, and the internet. …
We can call this “elite exposure theory.” I think that for it to work, one must in addition assume that at the level of a village or whatever, the most successful members of society didn’t actually limit their fertility that much, but once people expand their horizons, the true outliers in status and prestige disproportionately come from small families.
I agree that Hanania’s elite exposure version of the theory looks better; we have seen big historical effects of social communication on local fertility changes. So yes, fertility should fall when people notice that their local elites tend to have lower fertility. But I suspect that this selection effect should itself vary with context, and was previously overwhelmed by contrary effects. Which would then explain why everyone hasn’t always known about the correlation; it wasn’t always true or as strong.
For foragers, there was a big effect where higher status men attracted more and higher status women to have more kids with them. And higher status women attracted higher status men to have kids with them. Creating a positive correlation between status and fertility. Yes, it was also true than when choosing how much time to spend with each kid, parents with more kids could spend less time with each kid. But time spent on each kid was then only a modest fraction of the influence of parents on kid status.
In contrast, wealth and property passed on to each kid was a much larger fraction of the influence of farmer world elites on kid status. So in that world we should expect a larger selection effect, which would then be more quickly noticed and emulated. So as a society became larger and more unequal, and with better communication, we’d expect a transition from elites having higher fertility, to a selection effect of elites having lower fertility, which then gets amplified as people learn about this fact and start to copy elite fertility habits.
Thus in forager worlds, and in simple relatively-egalitarian farming worlds, the correlation between fertility and status would be positive or near zero; it would only get substantially negative when there were enough elites for whom inherited property formed a large enough fraction of how parents effected kid status.
I offered two fertility theories, Hanania refined and critiqued them, and now I’ve try to refined them further. Who will take the next step?
Added Nov 18: Ruxandra Teslo criticizes the Kings and Queens story here.
I'm not sure whether you mentioned this in one of your posts on the topic, as I haven't read all, so I apologize if I'm restating something covered before, but it's interesting to note a few ancient societies had a straightforward way to allow for high fertility among elites coupled with status/wealth preservation: limiting inheritance to the first child of the main wife. That one child inherited everything, the others inherited nothing, and thus extraordinarily rich and/or powerful men had dozens, sometimes hundreds, and, on a few instances, even thousands of children (e.g., Genghis Khan).
Nowadays that'd be considered deeply immoral by most to all societies, thus not an option, but it fits with the KAQ hypothesis, after all, no matter how many children a King has, only one will be king. It'd therefore be interesting to check whether the low fertility "mid-range" of "elites-but-not-kings" correlates with fair inheritance laws benefiting all children, thus incentivizing those families to have fewer ones.
Do we need new fertility theories? I feel like the ones we have are much simpler and do a great job explaining things:
(1) Education strongly explains what's going on. Education increases income and decreases fertility. That is extremely well documented I think.
How education increases income needs no explanation I think. How it decreases fertility is straightforward:
(a) People almost totally avoid having children during education, and the more years in education, the more of the fertile years are spent almost totally avoiding children.
(b) Education gives people, and especially women, something else to do besides raising a family.
(c) At a basic level (literacy vs. illiteracy), those who are more educated can better control their fertility.
(2) Having more choices also strongly explains what is going on. As income increases, people simply have more choices of things to do besides having children.
(a) Opportunity costs are much higher when you have many alternative options for your time. The lost alternatives (both economic and not) are much greater when a woman has many more choices of what to do with her time, and a richer society affords her many more choices.
(b) We can easily see that when TV or Internet reaches a place, its fertility goes way down. Very simply, people can watch TV or browse the Internet rather than do **the thing.** ;-) It is well documented that fertility increases during blackouts.
These two very old and widely supported 'theories' -- education and having more choices -- nicely explain why increasing income and wealth are associated with lower fertility. We have great theories that are simply and almost certainly true.
Why do we need complicate theories that defy Occams razor? Is it because there is that slight U-shape? That (ever so slight) recovery at the very highest incomes?
I think that slight recovery at high incomes is easy to explain: At the high end of the income spectrum, folks are all about self actualization, and having children is going to part of that for most people. If you are an A-type trying to meet every definition of success, where you check all the boxes, of course you will want kids. For the strivers conquering Maslow's Hierarchy of Needs, skipping kids would be a big oversight. Top politicians, the ultimate strivers in our society, almost always have children.
These are the simplest, Occams-Razor type explanations. Why do we need further theories beyond this when these theories are pretty robustly supported and very convincing?
We aren't very likely to do away with either education or fun alternatives entertainments beyond sex. So what is the solution? How do we get to higher fertility?
The easiest answer is just to value children really highly. You can just decide children are really important, and that should override everything else. That is what worked for Israel. They are extremely educated and full of entertainments. But they just decided, 'we've gotta have a lot of kids or our people are f$cked' and so they do.
Just deciding that children are super important probably seems like too simple of a solution, but it probably really is that simple. The elite strivers (of which politicians are my example) are busier than anyone, and more educated than most. But they have decent fertility just by deciding that is an important part of their complete life. Plus being good strivers, they are great at attaining marriage, which is key to fertility.
The fertility of the religious is due to the same thing. It isn't a mystery. They have a worldview where having children is a key part of a fulfilled life. But anyone can have that worldview. The problem right now is that culture doesn't value parenthood (and its usual precursor) that highly.
Summary: Now that fertility has crashed in high income places, for very mundane causes that we understand well, the solution is not to try to undo those causes, but overcome them by just valuing children more than ever before, the way Israel does.