This is not true. Intelligence is polygenic. The average human is no Von Neumann. At the very least genetic engineering could raise average IQ to Von Neumann’s level. We know that phenotype is possible with no ill effects. It will likely take us much further.
You haven't addressed my point. No one disputes that intelligence is partly genetic. However if it was possible to raise intelligence through genetic engineering with no ill effects then why hasn't evolution increased the incidence of that phenotype already?
Not my area of expertise, but I think the intuition for why evolution didn't make us all Einstein's comes in two parts:
(1) IQ is very polygenetic - a big IQ gene might be 0.1 IQ, and there aren't a lot even that large, if I recall the large genome wide association studies done on this. As GWAS studies get larger we find more, but they're all super small effects.
(2) Having an extra 0.1 IQ point is easy to lose in the noise of other effects on having offspring.
So even if we assumed IQ was perfectly correlated with more surviving offspring in modern societies, it might take an extremely long time (even longer than a whole planet and a thousand years) to make a detectable difference.
Why aren't all birds as smart as crows? Because the Blind Idiot God of Evolution doesn't care that you think increased intelligence is an obvious 'win'.
> the intervention may be simple, give major enhancements, but result in a net loss of reproductive fitness
The famous Ashkenazi theory of intelligence comes to mind. According to this theory, the Ashkenazi were forced into occupations demanding intelligence, and micro-selected for high intelligence. Except the high IQ genes were not previously prevalent among either Jews or gentiles because - like sickle-cell anemia - when they became too prevalent, they result in horrible diseases like Tay-Sachs. In 2007, a unique mutation in a Scottish family was found to increase verbal IQ in afflicted family members vs non by something like 25 points; this would be great for them - except for how that mutation starts causing blindness in one’s 20s or later. (In general, it’s much easier to find mutations or other genetic changes breaking intelligence than helping in cases of retardation26 and autism27.)
It's worth noting that the Ashkenazi theory remains unproven. No one has actually found any variants which would increase intelligence markedly. At some point that starts to look suspicious - maybe they don't exist after all.
Based on all the GWASes and additional studies which have been done since 2007 and a continued absence of confirmed examples of IQ-boosting variants with negative pleiotropic effects, I now would explain the lack of optimization of intelligence as being an example of 'too complex for evolution because too many little changes to do simultaneously', that is, mutation load: essentially, there are too many little effects (which sum up to make us far stupider than we have to be), which have been created & maintained by too many demographic bottlenecks and genetic drift and other effects, too much background selection, and too much selection on other traits (plus some level of dysgenics), for the various harmful variants to have been meaningfully selected against over the past 50kya. And that's why we could boost intelligence a lot with few harmful and many beneficial side effects.
Historrically inteligence has been a trait that had to be balanced with other factors in natural selection, traits such as having lower energy consumption, lower reaction time were important in the past in a way they simply aren't today. Sacrificing in other less relevent areas could easily lead to intelligence gains.
(Note I am not advocating for gene editing)
Also I don't think we have reached a local maximum, human society kind of fucks with natural selection so I imagine there is room for improvement.
Most likely because it seems to be a phenotype that does not reproduce itself. None of Von Neumann’s children had kids if I recall correctly. This environment does not select for IQ past a certain point; this does not imply we cannot engineer people to be more intelligent any more than it implies we cannot engineer people to be dwarfs.
Right so you're getting into deeper questions of what intelligence really means, and whether our measurements are meaningful in practical terms. Even if it was possible to genetically engineer humans with much higher IQs (and that is yet to be proven), there's still no evidence that those hypothetical supermen would end up ruling over us or having more children or whatever.
