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January 24, 2005

The Genetics of Selflessness

A group of Israeli researchers have a very interesting paper available as an advance online publication from Molecular Psychiatry. Noting that two dopaminergic genes (DRD4 and the microsatellite variant DRD5) have been implicated in ADHD and antisocial behavior, the authors hypothesized that "if one variant contributes to antisocial traits, then conversely the absence of this variant or the presence of other variants might contribute to altruistic behavior."

Together with the insulin-like growth factor 2 gene (IGF2), they find significant associations between scores on the

Selflessness Scale and the DRD4 exon III (D4.4), the IGF2 Apa I (‘G’) and DRD5 (146 and 148 bp repeat) polymorphisms. Univariate analysis also showed significant associations with the most common D4.4 allele, the IGF2 ApaI (‘G’ allele) and DRD5 (148 bp repeat, negatively associated) for all three factors (KIN, NON-KIN and NON-CARING). We also found a significant association (P¼0.002) between the D4 4/4 genotype and TPQ reward [Cloninger’s TPQ4 subscale related to empathy]

This association with the "feel good" chemical dopamine would appear to provide the sort of proximate mechanism necessary to compel people to act contrary to their fitness. Also of interest, all three of the genes were associated with altruistic behaviors toward both kin and non-kin.

Addendum from Razib: A few years ago Greg Cochran & Henry Harpending pointed out that the DRD4 alleles vary widely in frequency, and suggest that the 7R allele has been under positive selection (possibly frequency dependent, that is, multiple "morphs") in some populations. You can find a comparison chart here for the particular class of polymorphisms Greg & Henry are talking about (4 repeat is ancestral, 7 repeat is the selected variant, these are on exon III, just as above).

Money quote:


It is probably no accident that two of the best known ethnographies of the twentieth century are titled "The Harmless People," about the !Kung who have few or no 7R alleles, and "The Fierce People," about the Yanomamo with a high frequency of 7R.

Reference

Bachner-Melman, R. et al. 2005. Dopaminergic polymorphisms associated with self-report measures of human altruism: a fresh phenotype for the dopamine D4 receptor. Molecular Psychiatry: advance online publication 18 January 2005.

Posted by God Fearing Atheist at 05:40 PM