In the near future, there will be more news coming out about genetics and correlates of IQ.

So this might be a good time for me to ask some really dumb questions about the genetic causes of variance in IQ using my favorite cognitive tool of weird/homey analogies.

Consider the stereotypical reputations of three vehicles in the 4th quarter of the 20th Century:

– A 12 cylinder Jaguar luxury sports sedan

– A 4 cylinder Toyota Camry family sedan

– A 4-wheel drive Land Rover with a power winch for getting out of rivers, like in The Gods Must Be Crazy

The Jaguar was designed to have a high top speed. Less effort was put into actually manufacturing it well, so its actual top speed over the course of its lifespan was more than a few times zero because it was stuck in the repair shop.

The Camry was designed to have a moderate top speed, but much effort was put into building it well so that it wouldn’t very often have a effective speed of zero because it seldom was in need of repairs.

The Land Rover with a winch was slower than the other two vehicles on the racetrack or even on a winding highway, but you could winch it at 0.05 mph across a four foot deep river that would completely halt the two sedans.

Leaving aside environmental influences on IQ …

So, do smart people tend to be smart because theirs genes are like how the blueprints of a 12 cylinder Jaguar are designed to impart a high maximum speed?

Or do smart people tend to be smart less because they have rare patterns of high-performance genes that, if all worked well, would grant them unusually high IQs the way a Jaguar could go really fast, if all worked well … but instead, smart people tend to be smart because their brains were assembled with fewer glitches, the way a Camry built at the Nagoya factory in 1985 was likely to need fewer lifetime repairs than a Jaguar built at the English factory?

In the first case, some people tend to be more intelligent than other people because their ancestors evolved new and different genetic patterns to be more intelligent.

In the second case, people are pretty similar in terms of underlying genetic blueprints for intelligence, but smart people tend to be those whose blueprints happened to be executed best. For example, small deleterious mutations can build up over the generations, and smart people happen to have fewer of those.

Another dimension could be that different environments could select for different designs. For example, not too many motorists in the San Fernando Valley really need a winch on the front of their vehicles, but it appears to be pretty handy to have one in Botswana.