Why doesn the idea that heritability accounts for IQ hold up?
Genetics influences IQ. People with genes for high IQ pass them on to their children. Their children will be smarter than other children on average. The question is: How much of the variation in IQ in a given population is accounted for by genes? Estimates have run as high as 80 percent. This is not the same thing as saying that your IQ is 80 percent determined by genes. That’s quite wrong. In any case, a number of errors of the kind I detail in my book have resulted in estimates of heritability that are too high. For example, identical twins reared apart are very similar with respect to IQ, and the conclusion was that this indicates that genes are tremendously important and environments are not very important because being raised in different environments doesn’t prevent IQs from being highly similar. But it turns out that identical twins reared apart aren’t really raised in very different environments, in general. They typically are raised in the same town and often by relatives. So
