Here's another one. Gerald Crabtree, an idiot scientist from Stanford, has a paper in which he argues that human intelligence has declined from its peak. His argument, as I understand it, is two-fold:
--Intelligence is a matter of survival. As survival, of the not-getting-eaten-by-a-bear type, gets easier and easier, there is not as much natural selection (stupider people getting eaten) for intelligence.
--The rate of mutation, which can be calculated, means that harmful brain mutations have resulted in an overall decay of human intelligence, over thousands of years. With no way of selecting out those mutations, there is no counterbalancing force to maintain the original level of intelligence.
The critical thinking exercise is to poke holes in this argument, which I hope I have not stated too facetiously (right).
1. First of all, the conclusion seems a bit trivial if it does not state by how much, exactly, intelligence has fallen. In other words, the decline might be real, but so negligible that nothing really follows from it. Is it .001%? Or .01%? Then the variability of intelligence within the human race will basically negate its effects. In other words, the smartest people around today will still be as smart as anyone 6,000 years ago. It would have to be a fairly large effect to be significant in the least. How much of an effect would be necessary? I have no idea, but does Crabtree? Does he make any argument about that?
2. Is the ability to avoid bears what we mainly mean by "intelligence"? Presumably our closest genetic ancestors also developed ways of not getting eaten, with much less of what we mean by "intelligence" than we do. In fact, any ape living today is better than we are at wilderness survival. In other words, there seems to be an unexamined disconnect between definitions of intelligence. High-level cognitive abilities, like those involved in solving complex mathematical equations, are not necessary at all for basic survival. In fact, often the smart guy will be the first to be eaten by the bear.
3. Intelligence is not selected just by survival, but also, presumably, by sexual selection. That kind of selection is probably more in play in modern, technologically advanced societies.
4. Any mutation harmful enough to do real harm to the overall intelligence of the species might have been weeded out (selected against) by a variety of means in more recent times. For example, it might have been as hard to survive to reproductive age as a serf in Tsarist Russia than on the savannah. We could also argue more complex the society, the more cognitive ability comes into play for survival, since many cognitive abilities like abstract reasoning aren't even relevant to hunter-gatherer conditions.
5. The whole thesis lacks any kind of corroboration. For example, we know ancient civilizations did great things requiring prodigious brain power. We know that modern peoples from 1500 on have also done similar things. There is no decline in intelligence that has to be explained in some way. Without any kind of corroboration, the argument boils down to idle speculation. Idle, in the sense that the thinking does not get us anywhere, like a car with the engine on and idling. In this, it resembles the worst of evolutionary psychology, a field comprised by "just so stories."
6. The science behind the calculations of mutations is something I have not the expertise to question. Note, however, that this scientific evidence is mustered to support an argument that raises many other questions of interpretation.
Please, no comments about the decline of intelligence as manifested by "kids today" or reality shows. GC is not arguing that the results are visible or detectible in any way. In fact, he is hiding behind the weakness of his own claims.
Media coverage of this will be terrible, I predict. First of all, it will call forth declensionist narratives of human decline. Headlines like "Yes, we really are stupider, scientist discovers." But his actual argument is for a decline that can hardly be detected at all, over many millennia. He is not arguing for a decline that is palpable over the course of a few generations, but the media spin will all go in that direction.