Voles—like other mammals, including humans—exhibit the phenomenon of opportunistic infidelity. Some call it side-stepping, others cheating. And anthropologists have always known that monogamy is not the default condition in human cultures and civilization. The behavior of rejecting a recent and yearning for a new sex partner is dubbed the Coolidge Effect, based on an anecdotal story about John Calvin Coolidge, the 30th President of the United States, visiting a rooster & hen farm .
Interestingly, a lot of chemistry is behind how our (and the voles) bonding impulses are switched and wired: it has been found that natural variations in the DNA sequence of the vasopressin receptor gene determine the occurrence of neurochemical receptors in certain brain areas and thus the quality of monogamous or polygynous interaction [2,4]. Non-coding DNA, once misnamed “junk DNA,” plays a significant role in sexual programming.
Prairie vole studies demonstrate that brain chemicals are critical and effective communicators in regulating love, bonding and child care. The chemical messenger compound oxytocin—known as a hormone regulating social-cue perception, childbirth and maternal bonding—and the hormone vasopressin are such chemical candidates that trigger partner bonding :
When a female prairie vole received an oxytocin injection in her brain, she huddled with her partner more and formed stronger bonds. Another hormone, vasopressin, related to territoriality, has been found to promote pair-bonding in males. [...] If the hormones responsible for maternal behavior in females and territoriality in males were released during sex, they could foster this novel male-female bond. Prairie vole sex, for instance, involves an unusual amount of vaginal-cervical stimulation—probably an adapted behavior that triggers the oxytocin release normally associated with childbirth. Instead of bonding with a baby, the female bonds with her partner.Beyond love: oxytocin—the lack of it—has also been linked with autism-spectrum disorder (ASD) .
Keywords: molecular biology, neuroscience, neurochemistry, monogamy, partnership, wanderers, anthropology.
References and more to explore
 Bob Yirka: Researchers find epigenetic factor in monogamy for voles. June 3, 2013 [phys.org/news/2013-06-epigenetic-factor-monogamy-voles.html].
 Abigail Tucker: Love. What can rodents tell us about why humans love? Smithsonian February 2014, 44 (10), pp. 42-49 [www.smithsonianmag.com/science-nature/what-can-rodents-tell-us-about-why-humans-love-180949441/].
 Marnia: The Coolidge Effect. June 23, 2005 [www.reuniting.info/science/coolidge_effect].
 JUNKDNA [youdontevenknowme.wordpress.com/2013/05/23/human-brains-are-built-to-fall-in-love/].
 Christopher Bergland: The Neurobiology of the “Love Hormone” Revealed. Psychology Today August 5, 2013 [www.psychologytoday.com/blog/the-athletes-way/201308/the-neurobiology-the-love-hormone-revealed].