I haven't read your book yet, so forgive me if you discuss this there. But I’ve been wondering:
Simple traits (such as an organism's height) are probably relatively easy to alter via genetic mutations, without needing to combine many different genes chosen from huge populations. So, e.g., dog breeding altered dogs’ size relatively easily.
Complex adaptations aren’t nearly so easy to come by.
If intelligence is a conceptually simple thing, there might be simple mutations that create “more intelligence” -- it might be possible to make smarter people/mice/etc. by tuning a setting on an adaptation we already have. (E.g., “make more brain cells”).
If intelligence is instead something that requires many information-theoretic bits to specify, e.g. because “intelligence” is a matter of fit between an organism’s biases and the details of its environment, it shouldn’t be easy to create much more intelligence from a single mutation. (Just as if the target was a long arbitrary string in binary, and the genetic code specified that string digit by digit, simple mutations would increase fit by at most one digit.)
From the manner in which modern human intelligence evolved, what’s your guess at how simple human (or animal) intelligence is?
It must be simple in some way since it is so heritable. People with IQs of 90 and IQs of 140 both prosper and do fine. although there are lots of statistical differences between two such groups.
Other other hand if we take a trait like "propensity to learn language in childhood" this seems to me to be relatively invariable and fixed and so probably very complex.
Certainly one could breed for IQ and raise the population mean a lot. But what would we be doing to our children? People with 140 IQ seem to do all right but I would worry a lot about the kind of life a kid with an IQ of 220 would have.
Edit: Q&A is now closed. Thanks to everyone for participating, and thanks very much to Harpending and Cochran for their responses.
In response to Kaj's review, Henry Harpending and Gregory Cochran, the authors of the The 10,000 Year Explosion, have agreed to a Q&A session with the Less Wrong community.
If you have any questions for either Harpending or Cochran, please reply to this post with a question addressed to one or both of them. Material for questions might be derived from their blog for the book which includes stories about hunting animals in Africa with an eye towards evolutionary implications (which rose to Jennifer's attention based on Steve Sailer's prior attention).
Please do not kibitz in this Q&A... instead go to the kibitzing area to talk about the Q&A session itself. Eventually, this post will be edited to note that the process has been closed, at which time there should be no new questions.