The Breeder's Equation
From a didactic perspective, I think he goes off the rails by immediately focusing on something as abstract and hard to measure as intelligence, and where there&#x27;s a long history of  people talking about whether it&#x27;s even a single trait. In terms of just explaining the breeder&#x27;s equation, I think he could have been more effective talking about, IDK, tall Dutch people.<p>The other thing that&#x27;s annoying here is that although this is an &#x27;equation&#x27;, as I understand it it&#x27;s typically not predictive because that heritability term is so fuzzy. It&#x27;s not that you know the heritability term in advance and predict the response to selection; measuring the response to selection also updates your information about the heritability.<p>His examples have a cherry-picking feel for this reason. Take the &quot;national merit finalists&quot; thing he mentions multiple times. Note that he doesn&#x27;t mention the IQ distribution of the college professors (surely it&#x27;s logistically impractical to get any large number of busy faculty to spend time taking such tests) or of the college towns (which might not be the same as the overall population mean), or the degree to which being a professor is correlated with IQ or the degree to which being a national merit finalists is correlated to IQ. Had the data come out differently (and I suspect he mentions _finalist_ multiple times because there wasn&#x27;t as distinct a signal among _winners_), this perspective leaves plenty of room to declare that (a) maybe heritability of intelligence is lower than initially thought or assortative mating along IQ lines is weaker than expected (b) maybe professor-ness is less correlated to IQ than assumed or (c) maybe national merit finalist status isn&#x27;t especially correlated to IQ (semifinalists have to submit a bunch of info other than test results).