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Dr. Thomas R. Insel Shares Research Findings on Mammals & Monogamy at Herndon Lecture

"Are we by nature monogamous?" That question was one addressed in the J. Emmett Herndon lecture given by Thomas R. Insel, M.D., director of Yerkes Primate Research Center, to a packed Winship Ballroom audience on 27 October. And the answer? Well, yes and no.

What began for Insel, a psychiatrist and neuroscientist, as a special interest in developing treatments for diseases characterized by attachment disorders, such as autism and schizophrenia, has led to research that lies at the intersection of science and the humanities. Insel related how his research "started from a hard-core scientific perspective and...gradually moved into a much more social-behavioral aspect. Are humans monogamous? Are our brains coded for monogamous behavior? What is the nature of love and attachment?"

"Most of twentieth-century biology is based on paradigms originated by Charles Darwin." In the course of evolution, reproductive success and survival of the young produced by pair bonds is the goal. According to Insel, social monogamy is described as male/female pairs who share both nests and investment in protecting and rearing their young. Social monogamy is important in the survival of species when raising young requires two individuals, where females couldn't succeed on their own because of "dangerous territory, risk of predation or starvation." However, in these pair-bond relationships there are still numerous extra-pair copulations. For most of what scientists consider monogamous social organization, it has been shown by examination of DNA that "molecular biology genotypes don't show exclusivity." Biologists find it very rare for reproductive pairs of any species to be truly sexually exclusive.

In a study done by ethnographer G.P. Murdock (1949) of 849 human societies, 83% were found to be polygynous; 16% monogamous (serially); and 1% polyandrous. The implication is that humans are most likely to be monogamous in a serial way (not mate for life).

The most striking examples of social monogamy in mammals are canids wolves, coyotes, foxes, and dogs. In examining the nature of pair-bond relationships in our closest relatives, the primates, Insel found the information "remarkably uninstructive" for providing answers to whether humans are monogamous, for none of these primate societies were found to be good models of human social organization. But, as he search for a neural basis for monogamous attachment, Insel found surprising answers by using a species of rodents, prairie voles, as laboratory models.

Prairie voles are rodents found in the American midwest who live in monogamous, multigenerational colonies where males are invested in sharing in the rearing of their young with their female partners. Most mate for life. Prairie voles have several genetically close relatives, including montane voles, who look very much like them but are different in important ways. Unlike prairie voles, montane voles live in isolated burrows, don't share nests, display no evidence of social bonding, and males are not invested in caring for their offspring (they may even eat them).

Designing experiments with voles in the laboratory, Insel focused on two hormones released by sexual activity, oxytocin (OT) and vasopressin (VP). He hypothesized that it was possible that the release of these hormones with mating leads to pair bonding. Insel found that if he allowed female prairie voles to mate but blocked OT, the female didn't form a preference for her partner. This suggested that the release of OT is necessary for the female to form a monogamous pair bon. For male prairie voles, treatment with the antagonist to the other hormone, VP, produced the same results.

If this principle was operating to produce attachment bonds in prairie voles, what would happen if the same were done with their emotionally detached cousins, the montane voles? When the hormones OT and VP were administered to the montane voles, there was no change in their attachment behavior. Why? Here Insel theorizes that the difference may be related to where receptors for OT and VP are placed in the brain; they are located in quite different areas of the brains in prairie and montane voles. In prairie voles, these receptors are associated with the same circuits attuned to conditioned stimuli - are located in reward pathways. With montane voles, they are not.

Saying that he is "accused of being hopelessly reductive when talking about the gene sequences that are the molecular basis of monogamy," Insel goes on to say that research is "at the point of identifying specific genes that seem to direct certain species to monogamous behavior, and that if we move them around, we can change the social behavior...." This is what drives Insel's research. Understanding the nature of monogamy by uncovering the normal bases for social attachment behavior holds the promise of someday opening the way to development of medical treatment for those disabling and socially devastating attachment disorders.

After quoting William Blake's Auguries of Innocence (1803), "To See a World in a grain of Sand / And a Heaven in a Wild Flower / Hold Infinity in the palm of your hand / And Eternity in an hour," Insel closed the closed the lecture with, "One of the wonderful things about science is that as we get more and more so-called reductionistic, rather than coming up with more answers, it all just gets more and more mysterious....for every discovery raises more and more questions. There are beautiful, beautiful mechanisms for directing social behavior and for guiding and maintaing the path of evolution."

[ Posted by Donna Price at September 1, 1998 07:52 AM | More Public Events articles ]

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