Over at Nothing in Biology Makes Sense, Chris Smith has been writing a series of posts digging deep into the evolutionary claims made in Nicholas Wade’s book A Troublesome Inheritance. Last week, Chris debunked the claim that human population genetics naturally sorts into “races”—this week, he’s taking on Wade’s claim that variation at a particular gene has made some human populations more prone to violence than others:

Although some studies have found genetic variants in the MAO-A promoter region that are more common in some ethnic groups than in others (Sabol et al. 1998; Widom & Brzustowicz 2006; Reti et al. 2011) it is likely that these genetic variants are not –on their own– associated with violent or impulsive behavior (Caspi et al. 2002; Widom & Brzustowicz 2006). Instead, genetic variation in the MAO-A promoter seems to make some children less able to recover from abuse and childhood trauma, and therefore more likely to act out later in life (Caspi et al. 2002; Widom & Brzustowicz 2006). Simply carrying the ‘low expression’ allele in the MAO-A promoter does not have any effect at all on impulsivity or aggression.

Chris co-teaches a class on exactly the topics covered in A Troublesome Inheritance, so I highly recommend you read the whole thing, and follow the series to its conclusion.