Monogamy Introduction

April 19th, 2009

Humans are among a short list of mammals that practice monogamy; others on that list of include certain rodents, bats and primates (Barash 2001).  In contrast, an estimated 90 percent of all bird species back fidelity.  However, even among birds, where monogamy is the standard, promiscuity is still rampant.  Thus, monogamy may not be the most natural choice for a species.  Nonetheless, humans and birds consider monogamy the preferred practice of choice.  Our culture is responsible for imposing monogamy upon us as the acceptable standard, though questions remain: if monogamy is not the most natural practice, then what is?  What evidences supports this claim, and how and why did monogamy emerge?

 According to the Merriam Webster online dictionary, monogamy is defined as the state of custom of being married to one person at a time or the condition or practice of having a single mate during a period of time.  The key feature of this system is an understood exclusiveness.  Two individuals in a relationship are therefore emotionally and sexually exclusive.  Among birds, monogamy is defined as the mating of a male and female that results in a “pair bond.”  The length of these bonds varies among the species, ranging from bonds that last for one nesting such as in House Wrens, or a lifetime, in the case of swans and geese (Ehrlich et. al. 1988).

Theories on the Emergence of Monogamy

April 19th, 2009

Theories have surfaced as to how and why monogamy emerged in our present day society, but no one theory is widely accepted.  Biologist Richard Alexander introduced the phrases ecologically imposed monogamy (EIM) and socially imposed monogamy (SIM).  He speculated that EIM arises under conditions in which individual males are unable to gain by trying to care for offspring of multiple mates.  Alexander proposed a Theory of SIM that states that monogamy represents social equality, a key feature of economically established societies.  When societies experience growth, it is necessary to enforce rules to ensure equal reproductive opportunities and maintain a balance of power.  Monogamy is therefore implemented, and it is such a system that will bring about cooperation and stability.  The restrictions of monogamy guarantee every member of society the right to bear children while limiting the amount of variation in reproduction in families.  Therefore SIM is a typical characteristic of democratic societies (Kanazawa et. al. 1999).

  Anthropologist Laura Betzig proposed a modified version of Alexander’s theory.  She suggested that wealthy and powerful males practice monogamy to gain necessary and invaluable services and cooperation from individuals.  Betzig cites that “industrialization gave rise to specialization and may have also brought on reproductive concessions,” (MacDonald 1995).  With the emergence of specialization and division of labor, political leaders relied on lower ranking officials.  As a reward for their efforts and cooperation, these leaders might have distributed their wives and mistresses.  Eventually lower ranking officials would take these females as their mates, entering into relationships within them and laying the groundwork for monogamy.  Betzig speculates that this exchange would yield long term gains-political leaders would be able to keep their positions of power.  Moreover, she draws a link between the presence of monogamy with greater economic development under democracy. 

Psychologist Kevin Macdonald outlined a general idea of SIM.  He theorized that the emergence of monogamy is due to internal political processes, mainly egalitarian ideas and social controls.  Ecological and environmental aspects could not significantly account for the development of monogamy in a given society.  In sum, the theories of Alexander, Betzig and MacDonald attribute the rise of monogamy to different mechanisms, though democracy is the common thread among them (Kanazawa et. al. 1999).

Widely regarded as a monogamous animal, birds still, partake in their fair share of “extra-curricular” activities.  With the emergence of DNA fingerprinting and other paternity analysis techniques in the last decade, ecologists have discovered that birds frequently engage in adulterous behavior commonly known as extra pair copulations (EPC).  Two different studies on two distinct species of socially monogamous bird populations found that their respective birds participated in EPCs in order to increase their offspring’s fitness.

Reasons, Risks & Rewards

April 19th, 2009

Reasons for engaging in EPCs in birds and extra- marital sex in humans vary among males and female.  From a biological standpoint, birds engage in EPCs to increase their fitness, produce genetically diverse offspring, seek potential future mates, and ensure against mate fertility (Tryjanowski et. al. 2006). The benefits of EPCs might be as immediate as being doted on by one’s lover or as prospective as producing an offspring with a sexually attractive trait.  For example, female swallows are inclined to seek EPCs with males who have deeply forked tales because such as tails are deemed sexually attractive.  In contrast, humans mainly engage in extra-marital affairs for reasons stemming from their desire to seek emotional and sexual satisfaction.  From a psychological perspective, men and women may engage in extra- marital sex to fulfill sexual curiosity, satisfy the need for a more active sex life, or simply for the “thrill of the chase” (Houston 2005). 

For females specifically, the risks associated with getting caught seem to outweigh the benefits, yet males have less to lose as their costs are lower. Adoption of a purely promiscuous or mixed mating strategy would be in a male’s best interest as such.  Because males do not bear offspring or nurse young, they have a high reproductive potential.  Therefore, men are less selective in choosing additional mates with whom they reproduce with and pass on their favorable genes.  In addition, males produce sperm in abundance which is far less costly than females who produce eggs.  On the flipside, females bear the children and are responsible for nursing them, which is a huge investment of time and energy (Diamond 2005).  Thus, they are more likely to adopt fidelity as their mating strategy.

The risks of getting caught “cheating” can result in heavy repercussions for males and females, birds and humans alike.  If caught, males run the risk of sperm depletion, cuckoldry, reduction of parental assistance and possible divorce.  Females too, risk a reduction of parental care, divorce, retaliation, spousal abuse and in the case of birds, harassment from extra-pair males (Tryjanowski et. al. 2006).  With so many risks involved for both parties of getting caught, it is imperative that the unfaithful offender keep their extra-curricular affairs private.  For humans, this often means spinning a web of lies to cover for suspicious behavior.  In birds, this means copulating in less conspicuous places, which is exactly what one study found among great grey shrikes.

Bird Studies

April 19th, 2009

Widely regarded as a monogamous animal, birds still, partake in their fair share of “extra-curricular” activities.  With the emergence of DNA fingerprinting and other paternity analysis techniques in the last decade, ecologists have discovered that birds frequently engage in adulterous behavior commonly known as extra pair copulations (EPC).  Two different studies on two distinct species of socially monogamous bird populations found that their respective birds participated in EPCs in order to increase their offspring’s fitness. 

The first study was by a team of scientists of the MAX Planck Society who studied the songbird, the blue tit. The team spent four years in the Viennese forest monitoring and analyzing social bonds and genetic paternity in a population of blue tits.  Using microsatellite markers, scientists observed that nestlings sired through EPCs were more genetically different than their half siblings sired by the social father.  These extra-pair young were fathered by distantly breeding males which led to more heterozygous young.  The scientists found over several years that the young that survived the harsh first winter and bred, were more heterozygous than those nestlings that did not.  This was a crucial find in that in an average clutch of eleven, one or two nestlings are expected to survive to see spring.  In general, EPCs produced genetically diverse offspring that were more reproductively successful and robust than offspring sired by closely related males (Kempenaers 2003). 

The second study analyzed a population of splendid fairy wren in Australia from 1992-1996.  Blood samples were taken for genetic analysis and all of the birds were tagged for identification.  The results showed that there was a strong correlation between reproductive promiscuity and the opportunity for sexual selection.  The findings also revealed that the number of offspring males sired was related to the number of mates.  As a result, the average annual reproductive success of males who had offspring from EPCs was nearly three times greater of males that did not (Webster et. al. 2007).

A team of scientists studied the copulations of these territorial and socially monogamous birds in Western Poland.  Data was collected from fertile females from 184 territories during the breeding seasons of 2001-2005.  Each female’s copulations were observed a maximum of three times.  The data collected revealed that all 26 within- pair copulations occurred in open areas, which included electrical fences, electrical lines and tree tops.  However, only two of 13 EPCs occurred in open spaces, the rest took place in more secluded areas such inside bushes and in tree branches.  It was noted that male shrikes ventured more often into extra territorial affairs, thus EPCs occurred in the female’s territory.  Both males and females exhibited incredibly surreptitious behavior when seeking and maintaining EPCs.  The study also concluded that engaging in EPCs brought greater rewards for female strikes than within-pair copulations.  Great gray shrike males invested more in EPCs than in within- copulations.  Furthermore, a male’s ability to maintain his secrecy when seeking out and engaging in EPCs may be an attractive quality to fickle females.  This behavior trait could in turn be heritable and passed down to offspring (Tryjanowski et. al. 2006).

Biology Favors Polygamy

April 19th, 2009

In our culture, monogamy is the standard; however, our biology simply favors polygamy.  In general, males are built larger than females which are typically observed among polygamous species, in example primates.  Larger stature is essential for males who are in competition for potential mates, and strength and brawn are viewed as favorable traits.  Additionally, females mature earlier than males which backs polygamy because competition among males carries an evolutionary payoff to them to continue to grow and develop to increase their chances of mate success (Barash 2001).

Monogamy– An Unrealistic System?

April 19th, 2009

 Every girl dreams of one day finding her prince charming and living happily ever after, though the alarmingly high divorce rate deflates this illusion.  According to the National Center for Health Statistics, 3.6 divorces per 1,000 total population occurred in the U.S. (44 states) from March 2007- March 2008.  With such a high divorce rate, and infidelity as the leading cause of the demise of a marriage, monogamy could be considered an unrealistic system.  In species with bi-parental investment and care, a male has many opportunities to increase his reproductive success by engaging in EPCs.  This will inevitably lead to conflict with his mate if it infringes on the time and energy he spends with their shared offspring.  From a female’s point of view, she could potentially increase her number of offspring by mating with multiple males, though conflict arises with previous mates fearing dilution of their paternity success.  Both scenarios are likely to lead one partner to control the mating activities of the other.  In essence, monogamy gives rise to sexual conflicts and creates tension (Hosken et. al 2008).

The Importance of Culture

April 19th, 2009

Monogamy is the shiny ideal only because our dominant culture tells us that it is acceptable and appropriate.  Monogamy in our culture is a social norm.  With time, our attitudes change, as our societies evolve and reflect our differing styles, opinions and beliefs.  Presently, monogamy is here to stay, though prior to Western colonialism, more than 75 percent of all human societies were polygamous (Barash 2001).

It is important to understand that individual cultures strongly influence the accepted mating practice.  For example, there are several polygynous and polygamous Mormon communities that reside in the U.S. today.  Mormons are a distinct religious community in that it has its own unique history, teachings and values.  In that particular community, polygamy and polygyny is deemed acceptable by the culture.  This also holds true for non-religious communities such as the Tre-ba of Tibet, a polyandrous society.  As strange and unconventional as it might seem to us, the culture of the Tre-ba of Tibet dictate that it is normal for one woman to have several husbands (Diamond 2005). These examples serve to emphasize that there are a few exceptional societies in which monogamy is not the norm.

In Conclusion–

April 19th, 2009

Monogamy is the not the most natural practice nor is it the most beneficial from a biological standpoint.  This is not to say that monogamy is wrong, but that it is artificially impressed on us by culture.  Humans and birds identify themselves as monogamous because that is the traditional practice among the majority of the population.  And ultimately, this idea defines our sexual identification.

Works Cited

April 19th, 2009

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Barash, David. “Deflating the Myth of Monogamy.”   2001 Web.14 Apr 2009.



Webster, Michael, Tarvin, Tuttle, and Pruett-Jones. “Prosmiscuity Drives Sexual Selection in a

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“Unfaithful Songbirds Increase Offspring Fitness.” Max Planck Society. 15 OCT 2003. Max

Planck Society. 14 Apr 2009



Hosken, D.J., Stockley, Tregenza, and Wedell. “Monogamy and the Battle of Sexes.” Annual

Review of Entomology 15 SEP 2008 362-363. Web.12 APR 2009.


Houston, Ruth. “Cheating Husbands and Cheating Wives Give Different Reasons for Having

Affairs.” 2005 27 Mar 2009>.


Ehrlich, Paul, Dobkin, and Wheye. “Monogamy.” 1988 1. Web.12 APR 2009.


“Births, Marriages, Divorces, and Deaths:.” National Vital Statisticss Report. 21 AUG 2008.

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“monogamy.” Merriam-Webster Online Dictionary. 2009.

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