And if a society values intelligence, they should encourage smarter people to reproduce and offer as much birth control as possible to less smart people. Following this line of reasoning and policy is sure to ignite all kinds of flame wars ;-)
The problem is that smart people tend to earn more, thus the children tend to cost them more both in terms of opportunity cost (hours away from work) and actual cost (more likely to consider things like private school as essential). To incentive them you would need to start giving already wealthy people quite significant tax breaks etc.
This is the silliest argument for why intelligence would be negatively correlated with number of children. FWIW, the original article very much did not assert that assertion; reproductive success (meaning having any children at all survive the parents) in fact may be positively correlated because the social status of richer/more intelligent parents translates to higher survival rates for their offspring.
Regardless, while the absolute cost of raising children may be higher for high-income families, the share of their total income that represents is much lower. Someone earning minimum wage will struggle to support even one child's basic food, clothing, and shelter; their counterpart making $1M a year could easily afford private school, childcare, and the best possible opportunities for a family of 3-4 children.
My comment doesn't argue that intelligence is negatively correlated with having children, it argues that it is difficult to incentivise intelligent people to have children. Although looking at figures for 2010 it does seem that there is a negative correlation between income and number of births (at least in the US).
Survival rate is unlikely to be highly correlated with income in a first world country because even the poor have relatively good healthcare. The group most likely to have children are those earning $10,000 per year or less, probably because at that income level the state will pay most of the costs associated with child rearing. In fact in some cases having children might make a person better off financially due to higher priority for welfare or public housing etc.
There is an interesting and much-neglected corollary to the heritability of intelligence, which is that we are part of the least intelligent generation of humanity that has ever lived.
This follows from the two conditions:
1) intelligence is at least somewhat heritable (empirically true, according to the article)
and
2) intelligence is positively correlated with reproductive success (plausible give humans seem to have been selected for it)
The conclusion follows from the way world population has exploded in the past 250 years, increasing roughly ten-fold in twenty or twenty-five generations. That increase equates to "zero selective pressure": basically anybody could breed successfully, and they did (including my ancestors, some of whom occupied the more stagnant and brackish depths of the gene pool...)
So up until 1750 or so intelligence was being selected for, generation after generation. After that time, there was no pressure and the many small effects that this article documents as underlying the heritability of intelligence (with no single gene showing as much as a 1% effect on the overall outcome) would happily carry us all on a random walk across the landscape, creating engineers in some parts and political partisans in others.
This realization makes particularly funny the various organizations that have at times promoted Nobelists etc as pinnacles of intelligence (William Shockly, inventor of the transistor, was heavily involved in this kind of thing). Nobelists are certainly bright, but it seems more likely you'd find the most intelligent people amongst still-extant stone age tribes, whose pre-industrial life-style would still subject them to selective pressures long released in the more-developed world.
> Nobelists are certainly bright, but it seems more likely you'd find the most intelligent people amongst still-extant stone age tribes, whose pre-industrial life-style would still subject them to selective pressures long released in the more-developed world.
This conclusion is only justifiable if (1) the population of "stone age tribes" and the part of the world where those selective pressures have been released (because people are indivisible units beyond a certain point), and (2) if intelligence was fully determined by genetics rather than merely having some heritable component.
If there are important environmental factors in intelligence to which modern technology can positively contributed, and there are a lot more people living with modern technology, then its quite possible that the mean, median, and max realized intelligence would be higher in the modern part of the world than in "stone age tribes", even if the latter have more genetic benefit from pro-intelligence selective pressure and thus a higher mean/median genetic intelligence capacity.
Stone age tribes select for more than just intelligence, as a smart guy you might be an advisor to the tribe leader but the tribe leader was most probably a medium smart very bulky fellow.
It's called eugenics and it's very bad. At the very least it suffers from this self-referential craziness that nearly guarantees bad results.
People are economically unproductive because the economy slowly gets more and more hostile to more and more people. Tyler Cowan and others call this problem "Zero Marginal Product Workers".
And it sure did ignite flame wars and the topic is not openly pursued anymore in scientific circles, regardless of how objective it might be.
Luckily we don't have to go there. Technology is going to be the great equalizer, and might end up offering you off-the-shelf intelligence upgrade (I'm talking about a time-frame of next 30-80 years).
So long as people have to compete in the workplace, then the resulting equilibrium from everybody having an artificially extended intelligence will probably be ( according to Arnold Kling ) like the Vickies and Thetes in Neal Stephenson's "The Diamond Age".
Dr. Kling is using the book as a template/metaphor more than as a specific proscriptive. But I've seen this myself in the wind as various crises have held forth since 1973 ( when I was first old enough to ask questions about what was going on ).
I'm not sure IQ is really that great in the grand scheme of things. Don't get me wrong it's good, but IQ wouldn't help us much if managed to screw the environment beyond our ability to repair it.
