An Evolutionary and Ethical Evaluation of Polygamy

Presently, the normative and legal understanding of marriage is, if little else, monogamous in nature. Historically, most cultures and peoples considered polygamy completely acceptable, if not outright desirable. The difference between our norms and historical ones is due to more than random chance or changing tastes alone. The monogamous arrangement of married people, for an assortment of reasons, ethical, economic, and evolutionary, has taken root in a majority of the world’s most economically developed and educated nations.

Over the course of human history, sundry institutions and arrangements cropped up and some of them proved evolutionarily advantageous. Some of these “successful” arrangements and institutions include things like cities, religions, and arguably – monogamous marriage. Yet there is more to the rhyme and reason of marriage than evolution, after all, for obvious reasons other than survival, the institution persists which means that there are probably moral or at the very least, economic reasons for people to continually engage in it generation after generation.

Following from these premises, the related questions of ‘whether or not the normalization or stigmatization of polygamy would be a good or bad thing?’ and ‘how arguments for either relate to humanity’s evolutionary past and contemporary psychology?’ come to the fore.

Prior to answering these questions, there are a few basic definitions of key terms that I ought to provide. Throughout this article, I will use the term ‘polygamy’ to mean a marital relationship between one man and multiple woman and the term ‘monogamy’ to mean a marital relationship between one man and one woman. Lastly, a marital relationship will be defined here as an arrangement between people which involves procreation and a substantive degree of parental investment on the part of all those involved which is given legitimization by an authoritative body such as the church, state, or more loosely, social norms. Though there are many who might characterize monogamy or polygamy as more inclusive terms capable of describing homosexual or polyandrous relationships, such arrangements are in the extreme minority which is why the focus of the discussion to follow will instead be on the understanding of monogamy and polygamy set out above.

David Buss and David Schmidtt argue in their paper, “Sexual Strategies Theory: An Evolutionary Perspective on Human Mating,” that due to the difference in basic biological investments required of both genders during the mating process, women are the “limiting resource” during mating. This is the case according to Buss and Schmidt, because a man’s investment consists of but a few droplets of abundant fluid  intermingled with a few minutes’ labor whereas a woman’s investment requires a comparatively expensive egg, of which there are only a finite number available during a very fixed biological window, coupled with nine months of gestation (each of which reduces a woman’s independent survivability), in addition to lactation costs which can extend for years (Buss and Schmidtt 206-207).

Out of this investment imbalance, they argue that an innate preference for short term procreative relationships has been evolutionarily selected for in men to a greater degree than in women. This notion is bolstered by cross-cultural survey data which confirms that men do indeed intuitively prefer a multitude of short-term relationships when that option is made available, though it should be noted that they retain these preferences in addition to preferences for longer relationships (Buss & Schmidtt 210). In contrast, women responded to the same survey expressing a marked preference for longer and fewer relationships. Whereas surveyed men usually responded that they would prefer over eighteen partners over the course of their lifetime, women typically responded with a desire for no more than four or five.

If it is the case that men disproportionately prefer a bevy of short-term sexual relationships compared to women who prefer fewer total and longer relationships, then the prevalence of long-term marital unions, monogamous or polygamous, necessitates explanation.

Buss and Schmidtt advance several arguments for why this is the case which generally fall into two categories: the first, related to reductions in the costs associated with finding a reproductive partner and the second, in the benefits involved in bringing in an economic partner which allows for division of labor and increases in spare time which could be allotted towards skill refinement or resource acquisition (Buss & Schmidtt 214-217).

Simply put, marriage seems to work as an efficient mechanism for men to achieve their reproductive goals while simultaneously mitigating high reproductive costs incurred by women.

In “The Puzzle of Monogamous Marriage,” Joseph Henrich , Robert Boyd , and Peter J. Richerson contend that as far as monogamous and polygamous marriages are concerned, the reason a society may normalize one versus the other is related to prudential variables. In some undeveloped societies where resource accumulation is rare, it is effectively impossible for one male to support more than one mate while in more developed societies, resource accumulation allows those males with more resources to take on surplus wives and provide for them either at the same level which they would find when attached to an average man or at an even higher level (Heinrich et al 659-670). In more complex and stratified societies, where a handful of fortunate members enjoy a level of affluence many times that of the ordinary man, polygamy can reach astounding heights. In the distant past, this sort of harem building behavior was prevalent among the wealthy in many peoples, yet nowadays even among the world’s most illustrious billionaires, harems are virtually nonexistent.

If it is the case that some men can afford to take multiple wives and in doing so offer them a standard of living either at or above the mean, then it should follow that in modern economically advanced societies which feature multitudes of people far richer than the poorest, that there be an abundance of polygamous arrangements, yet there are virtually none. Furthermore, many of these selfsame developed societies counterintuitively typically possess laws and norms which expressly forbid polygamy.

There must be an explanation for why polygamy is not the norm in highly developed countries, if all the premises above follow. Most likely, the explanation involves the various social detriments and ills consequent to a communal adoption, normalization, or legitimization of polygamy. Surely, polygamy cannot be all detriment and ill. Upon even a rudimentary analysis there seem to be some benefits, yet most societies seem to have arrived at the conclusion that the detractions of polygamy are greater than the benefits offered.

The philosopher, John Rawls, a modern contractarian, set out in his book, Justice as Fairness, to describe a system where people could arrive at a Just social arrangement. A basic version of his theory goes as follows: a fair society is one designed behind a “veil of ignorance,” or more plainly put, a fair and just society could be arrived at if the designers pretended that they did not know who they would be, or even what mental or physical faculties they would possess once the “veil” had been lifted. In this way, the designers would theoretically create a society where arrangements are fair to everyone involved, wherein even the ‘worst off’ person occupies a position acceptable to all the designers were they to occupy it.

This particular construction of the concept of fairness is, in the most general terms, shared by a number of social contract theorists ranging from the likes of Immanuel Kant to Thomas Jefferson. Though each of the aforementioned differs in respect to what they understand a rational man behind the “veil” would consider “acceptable,” they all generally agree that societies should be structured in such a way that those who are least well off are in a state that no one finds categorically appalling. It is for this reason that I have chosen the latter theory of justice as a barometer for fairness and it is using this very simplistic construct of fairness, that I will try to tackle the question of polygamy, the exact phrasing of that question being: ‘Is institutionalized polygamy a just arrangement?’

Richerson, Boyd, and Heinrich describe in their argument for monogamy and against polygamy, societies of Mormons in America, central Africa, and in Asia wherein men and women enter into binding marriage more or less freely (at least in regards to first marriages, remarrying for men and women is subject to more variation) (Heinrich et al 661). In these societies, like ours, there are some people with much wealth and some unfortunates with little to none, while most people are of about average wealth.

Men of average wealth can support one wife at the average standard of living while the poor can support no wives at the average standard and the rich can support many at or above the average living standard. If polygamy were legal then it stands to reason that women would generally marry the average and rich men while the poor men, especially the exceedingly destitute, will be mate-less with the exception of the sporadic endearingly romantic couple. Before considering the ills consequent to this social arrangement, let us consider the gains.

Firstly, most of the women in this scenario enjoy an average or higher standard living. Secondly, those men who have surplus wives – and therefore disproportionally more offspring – are also the most successful, which may mean that if the basis of their success is at least partially to do with their genes, then more children will possess those same success engendering genes in the next generation. Thirdly, there is more marital choice and therefore personal freedom in this scenario than in others. If monogamy were institutionalized, those women who would inevitably have married higher on the socioeconomic scale under a polygamous regime would be forced to marry someone who provides less.

These three points represent the most clear and obvious rewards of institutionalizing polygamy and so it will be these benefits which will be compared against its detriments.

Two arguments are presented by Heinrich, Boyd and Richerson against polygamy and in favor of normative monogamy. The first is that “Monogamous marriage reduces the intensity of intrasexual competition”(Heinrich et al 660). Polygamy, because it raises the bar for marriageability among males, results in an increased fierceness in competition for wives among low status men. Because of the sizeable benefits accrued by having a wife to manage a household, produce and care for children, and relieve carnal urges, men will in theory, if faced by a scarcity of women, increase their participation in status aggrandizing behavior. This conclusion is borne out by a study of Mormon communities between 1830 and 1890 which showed that as the government stamped out polygamy, intrasexual conflict decreased by eight times its original levels (Moorad et al 7-8). Furthermore, not only are unmarried men more likely to engage in risky status related behavior, but Heinrich, Boyd and Richerson  additionally found that undesirable behaviors such as murder, robbery, rape, gambling, and alcohol abuse are more likely to be present in those who do not marry then those who do (this statement takes into account a study of each individual’s history with the above mentioned activities which diminishes the probability that the unmarried wastrels were simply the sort indisposed to marriage in the first place).

Another interesting effect of increased intrasexual competition related to polygamy discussed by Heinrich, Boyd and Richerson is that it widens the marital age gap. When women enter the marriage market, high status males begin snatching up women who are not quickly partnered. Since the high status males are older and newly marriageable wives younger, the age gap is greater. This effect becomes exacerbated when average and lower status males are forced to ‘wait out’ their turn at the marriage market during the introduction of each new ‘class’ of marriageable woman.

These predictions are demonstrated in comparisons that Heinrich, Boyd and Richerson make in their analysis between highly polygonous, less polygonous and comparatively monogamous countries using data from Michèle Tertilt’s study, “Polygyny, Women’s Rights, and Development.” In that same study, Tertilt constructs an economic model that measures the effects of imposing monogamy on a highly polygonous countries (HPC), which assumes that both men and women are interested in having children and that while women have finite reproductive capabilities over their lifetime, men’s stretch across their entire lifespan.

The results of Tertilt’s model show that fertility rates decrease, saving rates rise, the age gaps between spouses declines, and GDP per capita surges upward substantially (Tertilt 1363). In summary, intrasexual conflict birthed by polygamy gives rise to increased violent crime rates, increased age gaps between spouses, and lower per capita economic performance.

The second claim that Heinrich, Boyd and Richerson make is that “Normative monogamy reduces intra-household conflict” (Heinrich et al 664). What exactly does this mean? Since in more polygamous populations, the age gap between spouses is larger and within polygamous marriages there is more competition for affection and higher degrees of unrelatedness between members of the household, it follows intuitively that conflict and tension within the household increases. This intuition is evidenced by ethnographic data from W. Jankowiak’s article, “Co-wives, husband, and the Mormon Polygynous family.” Similarly Heinrich, Boyd and Richerson found in the works of Daly and Wilson: “Discriminative Parental Solicitude: a Biological Perspective” and The Truth About Cinderella: a Darwinian View of Parental Love, that higher degrees of unrelatedness within a family correlates strongly with increased abuse, neglect and even homicide (Heinrich et al 665).

Now that some of the more obvious and apparent costs and benefits of polygamy have been made clear, an evaluation can be carried out. Stepping behind the “veil,” some particulars are apparent. Under polygamy, more woman are likely to be better off than under strict monogamy, furthermore greater freedom is had by the average person interested in entering into marriage. For a woman this means that she may marry a man regardless of whether or not he has other wives and for a man it means that he may ask another woman to marry him if he is already married.

On the flipside, a variety of social ills follow the normalization of polygamy such as widespread increases in relative crime rates, drug abuse, spousal and child neglect, and most importantly, the virtual guarantee that many men will go their entire lives without finding a partner with whom they could be romantically and biologically fulfilled.

While the litany of reasons mentioned before, aside from the last, balance the debate and guide it towards that area dominated by the pernicious dilemma of greater comfort versus greater freedom, it is the last point which seem to shift the scale against polygamy. As discussed above, behind the “veil,” none of the designers know who they will be once it is lifted and therefore, they will endeavor to make the choice that puts those who are worst off in a position that all agree is, at the very least, acceptable.

Knowing that humans by their very nature are, by and large, driven towards carnal, social, and romantic fulfillment and that lacking such fulfillment, commonly encounter great insurmountable sorrow, the designers behind the veil would rationally choose against the institutionalization of polygamy because its investiture would necessarily thrust a sizeable portion of the population into an arrangement where their measure of fundamental social goods would be lacking to such an extent so as to make such an arrangement unacceptable.

Polygamy, while in accord with humankind’s biological and psychosocial nature, as well as compatible with modern society, is an arrangement of affairs which, according to at least one reading of fairness, ought not to be institutionalized. Of course, this is not tantamount to an uncontroversial condemnation of polygamy. Certainly, under other moral and theological frameworks, the institution is entirely acceptable. However, what ought to be taken from the analysis above is not that polygamy does not work or that it is an atavistic vestige of long-dead ancestors, but that it is an arrangement which should not be condoned by people who care deeply about those who are least well off.



Works Cited:

Buss, David, and David Schmidtt. “Sexual Strategies Theory: An Evolutionary Perspective on Human Mating,” The American Psychological Association. Vol.100 No.2. 1993. Web. 4/18/15

Daly, M. & Wilson, M. “Discriminative Parental Solicitude: a biological perspective.” Journal of Marriage and Family. Vol. 42, No. 2. 1980. 11/20/15

Daly, M. & Wilson, M. The Truth About Cinderella: a Darwinian view of parental love. Yale University Press.1999. Web.11/20/15

Heinrich, J, Boyd, R, & Richerson, P. “The Puzzle of Monogamous Marriage.” Philosophical Transactions of the Royal Society. 2011. Web. 4/20/15

Moorad, J. A., Promislow, D. E. L., Smith, K. R. & Wade, M. J. “Mating system change reduces the strength of sexual selection in an American frontier population of the 19th century. Evolution and Human Behavior. 2010. Web. 11/19/15

Rawls, John. Justice as Fairness. Belknap Press; 2nd edition. 2001.Print.

Tertilt , Michèle. “Polygyny, Women’s Rights, and Development.” Journal of the European Economic Association. Vol.4, Issue 2-3. 2006. Web. 11/19/15