I occasionally read your blog and it sometimes gets me thinking in politically incorrect directions. I was just looking at your genomics slides. You are interested in the tails of the intelligence distribution, and seem to think there is a qualitative difference between +3 SD (1 in 1000) and +4 SD (1 in 30,000) ability. I suppose I share your view on this but I thought I'd check by doing a back of the envelope calculation. How many really impressive brains do I think there are in the world? By really impressive I mean capable of doing breakthrough work in a cognitively hard area like physics or math or computer science. Someone who, if I talk to them at a meeting, I can see they're doing really nontrivial things and have something to tell me. Such people are spread out over many different fields, including private industry, but let's see if we can estimate how many there are.There are about 100k Ultra-High Net Worth (UHNW) individuals in the world, defined as having investible assets of at least $30 million USD. So it would appear that most of these brainy types fail to capture the economic returns from their contributions to society -- Zuckerberg, Brin, Page, Gates, Allen, etc. excluded ;-) Would you rather be +4 SD in brainpower, or +4 SD in net worth?
Let me start with physics, which is what I know best. I'd guess the top 100 departments/labs in the world each have on average 10-20 such people. The next 200 places, maybe 5-10, and so on. So maybe 5k such people in physics worldwide. If I include other departments like math, engineering, biology, etc. I'd increase this by a factor of 5 across an entire university. Adding in private industry, military research, burn outs, etc. perhaps doubles the number again. So I'd say maybe 50k in the world. Definitely not more than 100k. I might be biased, but if I set the cutoff a little higher the concentration starts to peak much more strongly in areas like physics (theory) and math departments. But let's stick with this population of 100k, who are drawn from a world population of maybe 1-2 billion people depending on what you think of the educational systems in China and India. Interestingly, this makes the population I identified right around the +4 SD level you are talking about.
I'm not so sure these people can be identified through testing early in their lives, although it's an interesting question. I'm not even sure the people identified as +4 SD on g are the same as the ones I described above, but there is probably a lot of overlap.
I do think that if these 100k people were to disappear, there would be a strongly negative effect on scientific and, eventually, technological progress worldwide. Are there another 100k people of equivalent value to the human race? [italics mine]
See also Out on the tail, g genomics slides.