What does it mean to be monogamous? Is it:
- Sexual exclusivity between two partners?
- A two-party partnership, characterized by cooperation where resources are shared and children are produced?
- A genetic commitment to producing offspring with a single partner?
- A social system in which only two people at a time are contracted by marriage ?
Or is it perhaps some combination of these four?
For some people, establishing yourself in an exclusively committed relationship where you wake up next to the same person day after day is the realization of a major social milestone. For others, it sounds like a prison sentence. Monogamy is a great socially sanctioning agent: it awards status, recognition, and offers commentary on one’s character. It’s a marker of adulthood and maturity. And by and large, we're taught by social standards, it is something to aspire to. But as countless people—from celebrities to our neighbors—have demonstrated, it’s not for everyone.
The societal definition of monogamy tends to equate it to monogamous marriage, which creates a rigid view of coupling. This perspective overlooks the variations that may exist in this state of partnership. You may certainly have a single spouse or mate over a lifetime with whom you share resources and appear to be socially and sexually committed, or you may have a series of sequential mates with whom you are exclusive. It’s estimated that only about 3% of mammals are monogamous—specifically meaning that they are sexually exclusive (1). Among primates about 10-15% have traditionally been categorized as monogamous. However, anthropologist Agustin Fuentes (1999) proposed revisions to the concept of primate monogamy that suggests only 3% of primate groups may be considered monogamous (2). He argues that as a social system, the term generates far too much ambiguity, and its standards are exacting. He relegates the social connotations of monogamy to pair-bonding, a term that has become widely accepted with reference to an exclusive relationship between partners. Monogamy, as defined by Fuentes is solely:
A prolonged association and essentially exclusive mating relationship between one male and one female (3).
As a social system, monogamy appears to place a great deal of stress on the individual. Why have we adhered so closely to social definitions of monogamy? Does the growing awareness of infidelity in the larger public indicate a potential shift in our acceptance of variations in previously defined monogamous relationships?
It’s Time to “Settle Down”
For the purposes of today’s discussion, we’ll use the social/systemic definitions of monogamy that moves it beyond just sexual exclusivity, with the understanding that there is a fair amount of fluidity in how monogamy may be defined by individuals. For example, an unmarried cohabiting couple may be monogamous, or a childless, unmarried pair who have been dating exclusively for some time may be monogamous, or you may choose to date only one person at a time—which are all examples of monogamy: a long-term partnership entered into by two adults where resources are shared to a mutual benefit, with or without the presence of children.
There are many examples in the natural world of multiple mate preferences, and examples within human society of polygamous social customs. So where did monogamy come from?
One popular theory about the evolutionary roots of monogamy traces this social arrangement back to parental care and the survival of offspring (4, 5). Human offspring remain in a dependent phase for an extended period of time, requiring parental involvement to ensure survival. There are other benefits to parental involvement. For example, when both parties are invested in the care of the offspring, the interbirth period can be shorter. That is, humans can wean their children much sooner than other primates, and can care for multiple dependents simultaneously. But parental involvement requires much from the parents themselves—they need to produce resources for their children, sometimes to the detriment of their own needs. It makes sense that parents would want to provide more care for offspring that are decidedly theirs. This yields the term paternity certainty, which is a factor that is believed to encourage male involvement in the rearing of children:
In mating systems in which only one male mates with several females, as in gorillas, paternity certainty is close to 100%, but any investment the male might provide will be divided among many offspring. Socially monogamous mating systems, in contrast, serve to increase a male’s paternity certainty, even when there is some level of sexual infidelity, while concentrating his parental efforts on fewer offspring (6).
Thus, adult pair bonding that results in birthing and raising children may be an exaptation—"a system that originally evolved for one reason [protection and care of offspring], but comes to serve another [establishment of a social system]" (7, 8).
For these sorts of relationship arrangements to persist beyond infant care suggests, however, that there may be other rewards as well. It is possible that participation in particular relationship arrangements may result in specific, pleasurable neurochemical events. Studies conducted on voles, which display a variety of life strategies and social behaviors—apparently, they’re quite complex rodents—demonstrate that pair bonding may be regulated by the release of certain neurochemicals. For example, when male voles are exposed to female voles, vasopressin, which influences behavior and cognition, is released in the region of the brain related to sexual dimorphism, allowing them to recognize potential mates (9). In female voles, it is believed that oxytocin—the widely recognized feel-good hormone—performs a similar function (10). Oxytocin has been widely linked to maternal bonds, but vole behavior suggests that one possible reason for the persistence of monogamy may be that both partners transfer the effects of oxytocin from the parent-child bond to the pair bond itself.
In human societies, monogamy has come to carry with it a certain degree of status. Dubbed the Ideology of Marriage and Family by researchers, American definitions of success have been long linked to marriage and children:
With so many of life’s rewards presumably located in coupling, parenting, and nuclear family, Americans look ever more intently in those directions. Couples expect to find happiness and meaningfulness in each other and in their children. They invest their time, attention, emotions, and resources in their own marriage and family to an extent probably unprecedented in the nation’s history. Sources of joy, identity, and meaning that once loomed large in people’s lives—such as friends, community, and kin, as well as passion in the purcuit of great casuses—are now mostly asides (e.g., we’re “just” friends) or quaint bits of nostalgia (e.g., those of 1960s flower children). Even work, long a central domain for men, is now sometimes described as if it were of little significance relative to marriage and family, regardless of the place it actually has in [people’s] lives (11).
“Settling down,” for whatever reason, signifies for many happiness, less loneliness, maturity, meaning, and completeness. Researchers propose that relationship status can be informative about reproductive potential—if you’ve been in a long-term committed relationship, then others view you as having reproductive potential (12). It is a commentary on your mate quality:
In an environment in which unpartnered females are a distinct anomaly—as they are among all sexually reproducing species, including, until very recently, humans—finding an unpartnered woman of reproductive age probably indicated that she was of exceptionally low mate value (13).
Today, people may choose to be single and non-monogamous, but to do so carries with it a great social weight.
But One Is Far From the Loneliest Number
Researchers DePaulo and Morris (2005) have documented what they have termed singlism: negative stereotypes directed at people who are not “seriously” coupled (as denoted by marriage) (14). Research reveals that single targets were:
- consistently viewed as more self-centered and envious
- viewed as more likely have had a sexually transmitted disease
- seen as more promiscuous
- viewed as having riskier personality traits
In experimental settings, singles were more likely to be overlooked for apartments and jobs, and there is any number of civil benefits awarded to those in a sanctioned monogamous relationship. However, this doesn’t mean that people don’t stray, nor does it mean that singles are less capable of long-term relationships or demonstrating higher quality character traits in comparison to their married, monogamous fellows. One, it seems, is not the loneliest number after all (if you've made it this far, a comedic intermission is in order):
The demands placed on an individual in a monogamous relationship are immense: Adult couples seek companionship, sexual intimacy, “soul-matery,” coparenting, economic sharing, advice, and so much more from each other, and largely only from each other. Is it really feasible to think that a single person can meet of these needs? Individuals are capable of developing intense affections for persons other than their sexual and social partner, but these alliances are often viewed in a suspicious light and are frowned up by social groups. Does this set the stage for monogamous commitments to fail?
People enter into monogamous relationships with certain expectations, and those expectations may not mirror the reality of personality or circumstance. What happens when a partner doesn't can't meet the needs that are prescribed to monogamy? Increasingly it seems people are entering into what are viewed as illicit partnerships. The question of why people cheat is a complicated one, and the definition of cheating itself can be quite varied. Is it time to reexamine the nature of partnerships? Or at least the social standards applied to monogamy?
Ed Note: This article has been modified slightly from it's original posting to enhance clarity in certain places. No substantial changes to content or context have been made. 17 June 2010.
Curtis, J. Thomas, & Wang, Z (2003). The Neurochemistry of Pair Bonding Current Directions in Psychology, 12 (2), 49-53
DePaulo, Bella,, & Morris, Wendy (2005). Singles in Society and in Science. Psychological Inquiry, 16 (2/3), 57-83
Fuentes, A. (1998). Re-Evaluating Primate Monogamy American Anthropologist, 100 (4), 890-907 DOI: 10.1525/aa.1922.214.171.1240
Pillsworth, E., & Haselton, M. (2005). The Evolution of Coupling. Psychological Inquiry, 16 (2/3), 98-104
1. Curtis and Wang (2003): 49.
2. Fuentes (1999): 800, 900.
3. Fuentes (1999): 800.
4. Fuentes (1999) lists four potential explanatory models, including wide dispersal of females (so limited access to mates), defense against predators or resource competition, protecting against infanticide, and parental care (891).
5. Pillsworth and Haselton (2005): 98.
6. Pillsworth and Haselton (2005): 99.
7. Diamond (2004): 117.
8. Shared dynamics include heightened desire for proximity, resistance to separation, and use of the target as a source for comfort and security (Diamond 2004: 117-118).
9. Curtis and Wang (2003): 50.
10. For fairly extensive coverage on oxytocin, please visit the archives of Are You Scicurious?
11. DePaulo and Morris (2005): 58.
12. Pillsworth and Haselton (2005): 101.
13. Pillsworth and Haselton (2005): 101.
14. DePaulo and Morris (2005): 59, 60.