Great—glad you wrote that post up on intergenerational dynamics (and remarkably quickly!). I haven’t read through the details in a while, but I think the best paper I’ve seen trying to estimate heritability at the family-level is this one by Tom Vogl, which you might find interesting to dig into. I believe his headline finding is that in low fertility settings that this composition effect accounts for fertility rates being ~4% higher in this generation than it would otherwise be (but that’s just a refresher from my quick skim just now).
My skepticism about evolution is skepticism about the existing variance in biological preferences for children. Obviously that’s not something we can easily get at, since outcomes are the product of environment + constraints + culture + preferences, etc. But (1) this preference isn’t currently common enough to push some economically developed countries above replacement rate and (2) once social/economic conditions that generate low-fertility stabilize, this sort of mental-model would always predict increasing fertility rates (since every generations composition becomes more favorable to high-fertility). I’m not sure there’s even a single country with moderate to low fertility that’s seen an increase over the last 10-20 years, even though the demographic transition occurred in some countries a few generations ago. (And we only have a few more, ~7-10, generations worth of time until we’re at pretty low population levels).
Though I’m happy to admit that this is hard to generate convincing evidence on, so maybe in a few more generations it could start to show up in aggregate numbers. But until there’s a country or two with consistent increases in fertility, through policy or evolution or whatever, I will remain very concerned that the decline will not be self-correcting.
Don’t have much to add on the other points you made :)
Great—glad you wrote that post up on intergenerational dynamics (and remarkably quickly!). I haven’t read through the details in a while, but I think the best paper I’ve seen trying to estimate heritability at the family-level is this one by Tom Vogl, which you might find interesting to dig into. I believe his headline finding is that in low fertility settings that this composition effect accounts for fertility rates being ~4% higher in this generation than it would otherwise be (but that’s just a refresher from my quick skim just now).
My skepticism about evolution is skepticism about the existing variance in biological preferences for children. Obviously that’s not something we can easily get at, since outcomes are the product of environment + constraints + culture + preferences, etc. But (1) this preference isn’t currently common enough to push some economically developed countries above replacement rate and (2) once social/economic conditions that generate low-fertility stabilize, this sort of mental-model would always predict increasing fertility rates (since every generations composition becomes more favorable to high-fertility). I’m not sure there’s even a single country with moderate to low fertility that’s seen an increase over the last 10-20 years, even though the demographic transition occurred in some countries a few generations ago. (And we only have a few more, ~7-10, generations worth of time until we’re at pretty low population levels).
Though I’m happy to admit that this is hard to generate convincing evidence on, so maybe in a few more generations it could start to show up in aggregate numbers. But until there’s a country or two with consistent increases in fertility, through policy or evolution or whatever, I will remain very concerned that the decline will not be self-correcting.
Don’t have much to add on the other points you made :)
Thanks! Published the post.