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What they actually found was that a variation in a gene called AVPR1a influences how much money students give to others in the “dictator game,” an experiment where subjects make unilateral decisions about how to divide money between themselves and another player.
A part of the gene that comes ahead of the protein-coding portion of AVPR1a can come in a range of sizes, which can be roughly grouped as long or short. Students with the long form gave the other player significantly more than those with the short form. Students with the long form also rated themselves as more altruistic than those with the short form.
AVPR1a actually has a long history of being linked to behaviors in humans. The same variation associated with altruism has been linked with propensity to be involved in creative dance, dieting behavior, and conflict between siblings. Other variations in the AVPR1a gene were recently associated with age of first sexual encounter and reproduction.
According to the researchers who have carried out these studies (and it should be mentioned that all but the sexuality study came out of the same lab), the common thread between all of these associations between behavioral traits and AVPR1a is social interaction.
But what on earth is AVPR1a?
AVPR1a encodes a protein called the arginine vasopressin receptor, which sits on cells and senses the presence of a hormone called vasopressin that controls a bunch of body processes including blood pressure and circadian rhythms. Why would it be involved in differences in social behavior? Nobody knows (yet!).
A length variation in AVPR1a much like the one found in humans is found in an animal called the vole. In these animals, AVPR1a is also associated with aspects of social behavior, including (at least to some extent), monogamy.
The vole looks like a portly mouse. There are more than 25 species. Some (like the prairie vole) are monogamous and the males spend a lot of time helping to raise their pups. Others (like the meadow vole) are a little more frisky – the males have multiple mates and don’t spend a lot of time helping to raise the kids.
Scientists found that the prairie vole had a longer form of the AVPR1a variation, while the meadow vole had short version. In a crucial experiment to show the importance of AVPR1a, researchers showed that if they put the long version (from the prairie voles) into the meadow voles (who normally have the short version), the meadow voles abandoned their wandering ways.
Propensity for monogamy and dancing ability may seem like frivolous things to study, but research on AVPR1a isn’t all fun and games. Variations in the gene have also been associated with autism in several studies. If AVPR1a is really controlling social behavior in some way, this makes sense: problems with social interaction are one of the symptoms of autism.
None of the associations between AVPR1a and human behavior have been replicated, so the results have to be taken with a grain of salt. And AVPR1a can’t be the only gene involved in monogamy. In voles, research has shown that there are some species with the long form of the gene that are not model husbands. And in humans, research has shown that even though female infidelity may have a genetic component, AVPR1a isn’t to blame.