What do prairie voles, water pipits, and humans have in common? Individuals of each species forge monogamous pairings.

While they might have very little else in common, at least two of these animals share a bunch of genes that encourage this form of romantic bonding. That is according to a study recently published in the Proceedings of the National Academy of Sciences.

Researchers from the University of Texas (UT) at Austin came to this conclusion after analyzing the male brains of 10 different species, five that are monogamous and five that are not. Each animal defined as monogamous was compared to a close cousin who enjoys a more freewheeling lifestyle, and so loved-up prairie voles were compared to meadow voles, water pipits to dunnocks, etc.

"Our study spans 450 million years of evolution, which is how long ago all these species shared a common ancestor," first author Rebecca Young, research associate in UT Austin's Department of Integrative Biology, said in a statement.

Interestingly, the definition of monogamy adopted by the researchers might not quite fit with what we have all come to expect with the concept – namely, your respective other will remain faithful. Extra-pair liaisons were permitted provided the species met the following criteria: