Thursday, March 18, 2010

Should We Cure Bad Behavior?

Tough questions about crime and neuro-rehabilitation


Brain and genetic research is also beginning to illuminate some of the neurochemical sources of violence. For example, elevated levels of dopamine and norepinephrine are associated with impulsivity and violence. The gene for catechol-O-methyltransferase (COMT) comes in two varieties, one of which is four times slower in breaking down dopamine and norepinephrine. Studies indicate that people with the slow COMT variation are more prone to violence. Monoamine oxidase-A (MAOA) is another brain enzyme that inactivates dopamine, norepinephrine and serotonin. It too comes in two versions. A study in New Zealand found that men who carry the low activity version and who had been reared in abusive households are much more likely  to commit crimes and be violent. The researchers explicitly noted that "these findings could inform the development of future pharmacological treatments."

Monday, March 08, 2010

Human culture, an Evolutionary Force

by Nicholas Wade
New York Times
March 1, 2010

Genes enabling lactose tolerance, which probably resulted in more surviving 
offspring, were detected in cultures like this Kenyan shepherd’s.

As with any other species, human populations are shaped by the usual forces of natural selection, like famine, disease or climate. A new force is now coming into focus. It is one with a surprising implication — that for the last 20,000 years or so, people have inadvertently been shaping their own evolution.
The force is human culture, broadly defined as any learned behavior, including technology. The evidence of its activity is the more surprising because culture has long seemed to play just the opposite role. Biologists have seen it as a shield that protects people from the full force of other selective pressures, since clothes and shelter dull the bite of cold and farming helps build surpluses to ride out famine.
Because of this buffering action, culture was thought to have blunted the rate of human evolution, or even brought it to a halt, in the distant past. Many biologists are now seeing the role of culture in a quite different light.
Although it does shield people from other forces, culture itself seems to be a powerful force of natural selection. People adapt genetically to sustained cultural changes, like new diets. And this interaction works more quickly than other selective forces, “leading some practitioners to argue that gene-culture co-evolution could be the dominant mode of human evolution,” Kevin N. Laland and colleagues wrote in the February issue of Nature Reviews Genetics. Dr. Laland is an evolutionary biologist at the University of St. Andrews in Scotland....

Complete article here