Deep inside an underground compound within the evil lair of the American Anthropological Association, Lord Skeletor summoned a scientist to spread falsehoods about the science of monoamine oxidase A, the warrior gene. That scientist was Christopher Irwin Smith, Associate Professor of Biology at Willamette University. Dr. Smith set about penning a diatribe full of errors and misleading innuendo. “I shall post this on the Internet and not allow better-informed people to comment on it,” he muttered before mustering an evil cackle that echoed through his dark private chamber.
Our investigators have uncovered the following especially telling response comment:
Dr. Smith,
Your impressive background prevents me from having any sympathy for you regarding the multiple egregious errors in this post. Probably the worst aspect of it is the timing because the last two years have produced two important meta-analyses confirming MAOA as an aggression and antisocial behavior gene. I’m guessing you have no awareness of either one.
“…Nielsen and Williamson’s studies were able to identify many regions in the genome that appear to have experienced recent natural selection, but MAO-A is not one of them.”
You neglected to mention that their study examined single-nucleotide polymorphisms, not repeat polymorphisms, like either of the functional MAOA-uVNTR promoters. The same is true for Voight et al.
“it is likely that these genetic variants are not –on their own– associated with violent or impulsive behavior… Simply carrying the ‘low expression’ allele in the MAO-A promoter does not have any effect at all on impulsivity or aggression.”
I doubt that you would have written this if you had been aware of the new meta-analysis by Ficks and Waldman, which came to the opposite conclusion.
“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).”
You are misrepresenting the findings of Caspi et al. It is MAOA-4R, not MAOA-3R that has the effect, which is a protective effect. According to Caspi et al, abuse could not affect those with MAOA-4R at all. Other studies have found the same protective effect against high testosterone levels and low IQ. Byrd and Manuck recently provided a meta-analysis verifying the abuse-MAOA interaction effect.
“Indeed, genetic variants associated with lower resilience to trauma are most common in Asian populations, not African ones (Sabol et al. 1998).”
Are you seriously saying that 61.0% is significantly higher than 59.1%? I think you must have been thinking about the copy-and-paste error by Lea and Chambers that claimed that 77% of Chinese men have MAOA-3R. I have labeled that the “idiot test” because it has caught many highly credentialed idiots who were trying to do the same thing that you are trying to do now: brush off decades of good research on MAOA. Ficks and Waldman only found a modest main effect of MAOA-3R, so you would need to argue not only that the gene is as common in Asians but also that the interacting factors (child abuse, high testosterone, an IQ less than 85) are as common in Asians, as well. Then, there is the issue of MAOA-2R….
“Note that Sabol study did not consider differences between populations in the frequencies of the ‘2-repeat’ alleles that Wade references…”
Did not consider? Gee, that is an interesting way of putting it. Of course, they tried to determine the allele frequency of each kind of allele in that VNTR, and they reported absolutely no instances of MAOA-2R in any group out of a total sample of over 2,000 X-chromosomes. MAOA-2R had not been discovered until the next year by Kunugi et al. Ever since, we have known that MAOA-2R is rare in whites but not that rare. Something is seriously wrong with the Sabol et al allele frequencies.
“To my knowledge, the frequency of the 2-repeat allele across populations has not been extensively measured; studies that have looked at its incidence appear to have focused on specific cohorts in the US as part of epidemiological studies.”
Is this your way of trying to cast doubt upon the allele frequencies reported in the literature for MAOA-2R in African-American men? Establishing an allele frequency does not require a 31-study meta-analysis. We have consistent findings from multiple studies that MAOA-2R is many times more common in African-American men than either white or Asian men. Would you like to read each study?
