Scientists studying human Swedish twins and voles have discovered a gene variant involved in producing a hormone that affects monogamy in animals whereby men with two copies of the variant were twice as likely to have had a relationship crisis with their spouse or partner in the last 12 months than men who did not carry the variant.

The study was the work of lead author Hasse Walum, from Karolinska Institutet, Stockholm, Sweden and colleagues in Sweden and the US, and was published online on 2nd September in the Proceedings of the National Academy of Sciences (PNAS).

Experts suggest that pair-bonding is an important step in the evolutionary development of the social brain, wrote the authors. Studies on voles show that the hormone and neurotransmitter arginine vasopressin (AVP) plays an important role in this process, and that there is a strong link between a genetic sequence that codes for a subtype of the AVP receptor and the tendency for male voles to remain monogamous.

In this study, Walum and colleagues found that a similar mechanism exists in humans.

552 twins and their marital spouses or partners (82 per cent of the pairs were married, while 18 per cent lived together but were not married) who were taking part in the Twin and Offspring Study in Sweden filled in questionnaires on bonding and underwent DNA tests.

The researchers found that men with a particular variant of the AVPR1A gene (that codes for vasopressin in humans) scored lower on the bonding questions and were less likely to be married compared to men who did not have the variant.

Also, men with two copies of the gene variant were twice as likely to report having had a relationship crisis with their marital spouse or partner in the last 12 months as men without the variant.

Walum and colleagues concluded that:

“These results suggest an association between a single gene and pair-bonding behavior in humans, and indicate that the well characterized influence of AVP on pair-bonding in voles may be of relevance also for humans.”

“Genetic variation in the vasopressin receptor 1a gene ( AVPR1A ) associates with pair-bonding behavior in humans.”
Hasse Walum, Lars Westberg, Susanne Henningsson, Jenae M Neiderhiser, David Reiss, Wilmar Igl, Jody M Ganiban, Erica L Spotts, Nancy L Pedersen, Elias Eriksson, and Paul Lichtenstein.
PNAS published September 2, 2008.

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Sources: Journal article.

Written by: Catharine Paddock, PhD