The Brain

If smart is the norm, stupidity gets more interesting

Few of us are smart as we’d like to be. The human intelligence varies, and this matter because smarter people generally earn money, enjoy better health, raise smarter children, feel happier and may be live longer.

But where does intelligence comes from? How is it built? Researchers have tried to find this out in our genes. 

With the rise of inexpensive genome sequencing, they’ve analysed the genomes of thousands of people, looking for gene variants that clearly affect intelligence, and have found a ground total of two. 


One determines the risk of Alzheimer`s and affects the IQ only late in life; the other seems to build a bigger brain, but on average it raises IQ by all of 1.29 points.

Other genetic factors may be at work: a report last year concluded that several 100 gene variants taken together seem to account for 40% to 50% of the difference in intelligence among the 3,500 of subjects in the study. 

But the doctors couldn’t find out which of these genes created any significant effect. And when they tried to predict the difference in intelligence, they could account for only 1% of the difference in IQ.

Once natural selection generated the set of genes that build our big, smart human brains, those genes became “fixed” in the human population; virtually everyone receives the same set, and precious few variants affect intelligence. 

This could account for the researchers’ failure to find many variants of measurable effect.

But in some other genetic realms, we do differ widely, for example, mutational load-the number of mutations we carry. This tends to run in the families, which means some of us generate and retain more mutations than others do. Among our 23,000 genes, you may carry 500 mutations and i carry 1,000.

Most mutations have no effect. But those that do are more likely to bring harm than good, a researcher said in an interview, because there are “simply many more ways of screwing something up than of improving it.”

Mutations that change the brain normal development or operation will probably slow it down. There is also an inheritance through genes yet to be identified, of course a trait known to be developmental stability. This is essentially the accuracy with which the genetic blueprint is built. 

Developmental keeps the project on track. It reveals itself most obviously in physical symmetry. The two sides of our brains and bodies are constructed separately but from the same 23,000-gene blueprint. 

If you have a high developmental stability, you will turn out highly symmetrical. Your feet will be the same shoe size, and the two sides of your face will be identical.
 

Symmetry and intelligence tend to run together, because both run with developmental stability. Symmetrical faces can be seen as attractive because they imply the steadiness of genetic development, which creates valuable assets for choosing a mate, like better general fitness and, of course intelligence or as a researcher says “a relatively stupidity”