IQ is a particularly ugly aspect of science because the IQ literature reveals that which no one would wish to be the case. Which is that there are profound and virtually irremediable differences between people’s cognitive performances and that these differences have a very solid biological and heritable basis. 

No one wants to hear that it’s biological, no one wants to hear that it’s heritable, no one wants to hear that it’s permanent, and no one wants to hear that it has practical consequences on life outcomes. 

The armed forces determined after approximately a hundred years of study that a person with an IQ of 83 or less, couldn’t be trained to do anything that wasn’t counterproductive in the armed forces. And that should send a shudder of terror through everyone’s hearts. Because that is around 1.5 in ten people in the world. And we’re building a very complex and cognitively complex society. And in this complex society, there is less and less room for the gainful employment of individuals that don’t have the capacity to contend with cognitive complexity.