But do you have evidence for the assertion that there is a negative correlation between intelligence and reproductive success? I read somewhere (can't find the source) that smart guys on average actually have more children than stupid ones, and that for women fertility is about the same.
I've seen multiple sources showing reduced fertility in high-IQ females (across multiple countries.)
The culprit, however, doesn't seem to be raw intelligence as such, but modern western education, which seems to have a dose dependent sterilizing effect on females. In that light, high IQ isn't fertility-reducing in itself, rather low IQ is protective against modern western education.
Would love to see some proper evidence for these claims.
One can easily see that clever ladies tend to focus much more on long education/career, rather than jumping straight on babies-making bandwagon. Also, finding good partner to have kids with seems much harder for them (well, for clever guys sadly too). Considering most university level education ends when people are around +-23 (not even going into PhD ones), and then they just become fully autonomous and step in working treadmill (earn->spend->earn-> cycle), I would name culture/work/environment situation or pressure for that.
Also generally, more clever people focus more on quality rather than quantity, and babies are no exception. Norm are 1-3 kids, not because women are not fertile anymore (unless climacterium is reached), rather time & resources are considered.
Even this is very simplistic & dumbed down view on these matters.
It's not just modern western education. Basic education for girls in third-world countries is associated with lower birth rates. Additionally, comparatively minor decreases in poverty in undeveloped countries correlate with declines in birth rates -- possibly because declining poverty usually goes hand in hand with declining infant mortality. The latter being one of the biggest reasons that the average birth rates in developed countries have dropped from 30-40 per thousand to 10-15 per thousand in just the past 150 years.
"modern western education, which seems to have a dose dependent sterilizing effect on females. In that light, high IQ isn't fertility-reducing in itself, rather low IQ is protective against modern western education"
I admire the way you phrased this.
The difference in size between educated and uneducated families might be very large in societies that are in transition on the development scale, but I wonder if the same is true in a society that is stable on that scale. Do uneducated families in the West have more kids than educated families, or do they just have their 2.1 children earlier in life?
