Princeton/Stanford Working Papers in Classics



Monogamy and polygyny in Greece, Rome, and world history

Version 1.0


June 2008


Walter Scheidel


Stanford University



Abstract: In what sense were the ancient Greeks and Romans monogamous, and why does it matter? This
paper summarizes the physical and anthropological record of polygyny, briefly sketches the historical
expansion of formal monogamy, considers complementary theories of mate choice, and situates Greco-
Roman practice on a spectrum from traditional polygamy to more recent forms of normative monogyny.


© Walter Scheidel. scheidel@stanford.edu

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A peculiar institution?

Greek and Roman men were not allowed to be married to more than one wife at a time
and not meant to cohabit with concubines during marriage, and not even rulers were exempt from
these norms. That these facts have generally received little attention and occasioned no surprise
among historians specializing in this period bespeaks a remarkable lack of cross-cultural
awareness.1 Greco-Roman monogamy may well appear unexceptional from a modern Western
perspective but was far from common at the time. My paper seeks to put this institution in
context.


Biology

Biologists distinguish between “genetic monogamy,” which refers to mutually exclusive
reproductive mating arrangements between two partners, and “social monogamy,” in which
mutually exclusive pair-bonding need not be matched by reproductive outcomes. While “genetic
monogamy” is fairly rare across animal species, “social monogamy” is common among birds but
atypical of mammals. Physiological evidence suggests that humans are unusual among mammals
– including primates – for being predominantly monogamous and only mildly polygynous in both
“genetic” and “social” terms.
A moderate degree of polygyny (a term preferable to “polygamy”2) may be extrapolated
from two observations. One is that in humans, adult males are on average bigger (i.e., taller as
well as heavier) than females. Male-biased sexual dimorphism is a correlate of polygyny: the
more polygynous a species, the bigger males are in relation to females. Species with female
harems consequently display extreme levels of dimorphism: male sea lions for example can be
three times as heavy as females. The human dimorphism index of 1.15 (based on weight and
height) indicates that humans are only mildly polygynous. This basic ratio has been traced back
as far as Australopithecus afarensis more than 3 million years ago.3 The other reason is that
whereas “Mitochondrial Eve” – our matrilineal most recent common ancestor – lived about
200,000 years ago, “Y-chromosomal Adam” – our patrilineal most recent common ancestor – is
considerably less distant, having lived only 90,000-60,000 years ago. This is a function of the

This paper was prepared for the conference “Cross-cultural approaches to family and household structures
in the ancient world,” Institute for the Study of the Ancient World, NYU, New York, May 9, 2008.
1 Erdmann 1934: 87-103 appears to be the most substantial discussion of Greek monogamy and polygyny.
Recent scholarship on the Greek and Roman families usually gives short shrift to or completely ignores this
issue: for rare exceptions, see Friedl 1996: esp. 25-39, 214-28, 380-94; Ogden 1999. Monogamy is not even
mentioned in the index of Krause 1992, a bibliography of 4,336 titles on the Roman family. Under the label
“monogamy,” Treggiari 1991: 229-319 focuses on spousal affection, perennial monogamy, and adultery.
Greco-Roman monogamy has mostly been problematized by scholars from outside the field of Ancient
History: see esp. MacDonald 1990: 204-27; Betzig 1992a, 1992b. I will address this deficit in Scheidel
forthcoming.
2 For the sake of clarity, in the following I apply the terms “monogamy” and “polygamy” only to marital
unions and use “monogyny” and “polygyny” more broadly to denote exclusive or parallel sexual and
reproductive relationships. “Polygynous polygamy” is meant to specify the nature of polygamous
arrangements, and “polygyny” may but need not include “polygynous polygamy.” Marital polyandry has
been extremely rare in world history and will not be considered here.
3 Reno et al. 2003.

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generally well-documented fact that male reproductive success tends to be more variable than for
females, which is consistent with some degree of polygyny.4


Incidence

The notion of moderate polygyny is supported by the global anthropological record. We
find that most societies condoned social and genetic polygamy – almost always in the form of
polygynous polygamy – but also that most individual bonding and mating arrangements were
monogamous. Of 1,154 societies described in the Human Relations Area Files, 93% recognize
some degree of socially sanctioned polygyny, and in 70% of all cases polygyny is the preferred
choice (which does not mean that it is dominant in quantitative terms).5 However, precision is
difficult to attain due to the frequent failure to distinguish between rare, de facto absent, and
formally banned social polygamy, or between polygamy (as a form of marriage) and other forms
of polygyny (such as concurrent concubinage). This casts doubt on the finding that among 862
societies surveyed in George Peter Murdock’s Ethnographic Atlas, “monogamy” is observed in
16% of all cases (n=134).6 In a more recent study of 348 better-known societies, 20% (n=71) are
defined as monogamous whereas another 20% displayed limited polygyny and fully 60% more
frequent polygyny.7 However, these numbers are problematic in that the underlying coding places
each society in a single category. This raises the possibility that some or perhaps even many of
these putatively “monogamous” cultures allowed for a measure of polygyny, most notably among
rulers, or tolerated some form of formalized concurrent concubinage – a suspicion borne out by
the fact that ancient Egyptians and Babylonians are classified as “monogamous,” regardless of
well-documented resource polygyny amongst their rulers.8 This problem is well illustrated by the
Western North American Indian Data Set. In each of its 172 societies, monogamy is found to be
the dominant form of marriage, accounting for 60+% of all unions.9 At the same time, in only 28
cases, or 16%, is polygyny reported to be absent or very rare: once again, the failure to
distinguish between “very rare” and “no polygamy” is critical.10


Distribution

For all their deficiencies, these surveys convey the impression that largely monogamous
systems were not very common and that strict social monogamy was even rarer in world history.
Monogamy and polygamy are non-randomly distributed in both spatial and developmental
terms.11 One study draws on data from 351 societies to divide the world into nine macro-regions
defined by systematic variation in social structure. Most of Eurasia and North Africa consist of

4 For extreme genetic manifestations of this phenomenon, see Zerja et al. 2003 (8% of Central Asian men
may descend from Genghis Khan); Xue et al. 2005 (1.6 million Chinese and Mongolian men may descend
from the Qing dynasty).
5 Clark 1998: 1047.
6 Murdock 1967: 62-125. Murdock 1981 surveys the 563 best-known of 1,264 societies. In this sample,
independent monogamous families account for 11.7% of the total (n=66) (133 table 4).
7 Burton et al. 1996: 89 table 1.
8 Murdock 1967: 82, 86. In this schema Manchu and northern Chinese likewise count as “monogamous”
(86).
9 Jorgensen 1980, 1999: 235-6.
10 Jorgensen 1980: SO291; Borgerhoff Mulder, Nunn, and Towner 2006: 61.
11 For developmental differentiation, see below, at n.16.

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two regions labeled “North Eurasia & Circumpolar” and “Middle Old World.”12 These major
cultural entities broadly correspond to fundamental phylogenetic divisions.13 The North Eurasian
and Circumpolar region is the older of the two and associated with moderately patricentric
kinship systems. The Middle Old World region was a later development probably linked to the
rise of pastoralism and later farming, and defined by strong patricentrism and the political and
military dominance of patrilineal groups. Cross-culturally, matricentrism is strongly correlated
with monogamy and patricentrism with polygyny.14 Thus, the earliest evidence of what has been
called “Socially Imposed Monogamy” or “SIM” – in ancient Greece and Rome – hails from the
faultline between these two Afroeurasian macro-regions and more generally from a more or less
polygynous environment.


Definitions

“SIM” represents a cultural construct that prohibits concurrent marital relations with
more than one person regardless of socio-economic status. However, “Socially Imposed
Universal Monogamy” or “SIUM” would be a more precise term that captures the full meaning of
this principle by emphasizing the lack of exemptions even for rulers and elites. Social constraints
on monogamy differ from what is known as “Ecologically Imposed Monogamy” (EIM) which
occurs in an environment where polygamy is admissible in principle but certain men cannot
afford to support more than one wife or family or therefore limit themselves to one spouse at a
time.15 From a global perspective this used to be the dominant form of marriage or cohabitation:
EIM could take many forms, from instances where a sizeable proportion of all men in a given
population marry multiply while many others go without wives to de facto universal monogamy
in small groups confined to particularly unfavorable environments.
The wide range of quasi-marital and cognate arrangements indicates that the traditional
dichotomy of “polygamy” and “monogamy” fails to capture real-world differentiation among
marriage and mating practices. I would like to propose a trichotomy consisting of (1)
“polygamy,” defined by the overt presence of multiple ties of sexual access and “legitimate”
reproduction (whilst allowing for differentiation among female spouses, especially between a
principal wife and lower-ranking co-wives); (2) “monogamy/polygyny,” where marital
relationships and their attendant legal and social consequences are limited to single female
partner but the husband is – in terms of legal rules and social sanction – free to (or may formally
obtain his wife’s consent to) pursue additional non-casual sexual and reproductive relationships
that may (but need not) entail cohabitation, most notably with co-resident or altrilocal
concubines; and (3) “monogyny,” with – ideally – genuinely exclusive marital and sexual
relationships (where applicable excluding casual encounters provided by “affairs” or prostitution)
(Table 1). Given the degree of cultural variation in definitions of “marriage,” for example, these
ideal types are necessarily artificial and over-schematic and merely meant to delimit segments of
a continuous spectrum: thus, the intermediate “monogamy/polygyny” pattern is particularly
elastic, although the acceptance or rejection of co-residence might serve as a significant marker of
differentiation. Serial or perennial “monogyny,” needless to say, cannot be expected to prevail in
pure form but simply denotes one end of the spectrum.


12 Burton et al. 1996: 100-1, 103-4, with Jones 2003: 509-10. The “Middle Old World” encompasses North
Africa, the south Balkans, and most of Asia except for Siberia and South-East Asia, with most of Europe
and Sibera defined as “North Eurasia & Circumpolar.”
13 Jones 2003: 506, based on Cavalli-Sforza, Menozzi, and Piazza 1994.
14 Burton et al. 1996: 93-4, cf. 109 fig.13.
15 For the concepts of EIM and SIM, see Alexander et al. 1979: 418-20. SIUM is my own coinage.

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Table 1
Idealized configurations of marital and mating practices

Marriage type Mating type
Type of monogamy



Polygamy Polygyny Ecologically
Imposed
Monogamy
Monogamy
Polygyny
Socially Imposed Universal Monogamy
Monogamy
Monogyny
Socially Imposed Universal Monogamy


The matrix in Table 1 shows that in a society with socially condoned polygamy,
monogamous relationships may arise from ecological constraints (though not from social rules).
At the same time, SIUM accommodates a wide range of actual habitational and mating practices,
from intense polygyny with subordinates (e.g., slave harems) to (serial or perennial) monogyny.


History

This tabulation not only differentiates among different marriage and mating practices but
also provides a crude evolutionary sequence from top to bottom. Moderate – and ecologically
mediated – polygyny appears to have dominated for millions of years. Francois Nielsen’s analysis
of Murdock’s data shows that a weak trend away from polygamy was reversed in advanced
horticultural societies (where women’s labor was and still is generally critical in generating
resources) but subsequently resumed in agrarian systems: “monogamy” is attested for 10.5% of
the surveyed hunter-gatherer cultures (n=172), 24.8% of simple horticultural systems (n=157),
6.5% of advanced horticultural systems (n=261), and 41.5% of agrarian societies (n=135), as well
as for 12.1% of fishing cultures (n=58) and 21.6% of herders (n=74).16 This is consistent with the
observation that in the Standard Cross-Cultural Sample (n=186), “46% of larger states have
socially imposed monogamy, compared to 26% of smaller states, 10% of chiefdoms, and 11% of
bands and tribes.”17
While agrarianism curtailed polygamy, in many cases it also helped to intensify
reproductive inequality within polygynous systems.18 In a series of groundbreaking studies
informed by the insights of Darwinian evolutionary psychology, Laura Betzig has documented a
close relationship between stratification, despotism, and polygyny in early agrarian states.19 The
pertinent evidence is too massive to be summarized here even in the most superficial manner:
suffice it to say that it extends across thousands of years of Eurasian, African, and American
history. Imperial state formation was particularly conducive to the growth of harems for rulers
and often the ruling elites more generally, for example in Pharaonic Egypt, the pre-Islamic and
Islamic Middle East, India, China, South-East Asia, among the Aztecs and Inka, and in many
African polities up to the fairly recent past.20 Polygyny was normally much more limited in sub-
elite circles, reflected in references to bigamy in various Mesopotamian cultures and ambiguous
evidence for Pharaonic Egypt but better documentation from Zoroastrian Iran, to name just a few

16 Nielsen 2004: 306 table 10, 309. The overall incidence is 17.9% (n=857).
17 Sanderson 2001: 332. See also below, at n.48, on state (population) size.
18 Nielsen’s claim (2004: 309-10) that maximum harem size was smaller in agrarian than in advanced
horticultural polygynous societies is invalidated by the exclusion from his sample of many of the most
egregious instances of harem polygyny in agrarian empires (cf. the dataset in Betzig 1986: 107-33).
19 Betzig 1986, 1992a, 1992b, 1993a, 1993b, 1995, 2005.
20 For this and the following, see now esp. Scheidel 2008, expanding on Betzig’s work.

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examples. At the same time, formal barriers to non-marital polygynous relations between men
and their slave women were normally lacking.
Moving on to the Greco-Roman world, elite polygyny looms large in the Homeric
tradition.21 By the historical period, by contrast, SIUM was firmly established as the only
legitimate marriage system: polygamy was considered a barbarian custom or a mark of tyranny
and monogamy was regarded as quintessentially “Greek.” However, SIUM co-existed with
concubinage even for married men: as far as we can tell, they were supposed to draw the line at
cohabitation, which was considered inappropriate.22 At the same time, married men’s sexual
congress with their own slave women or with prostitutes was free of social and legal sanction. As
several probable instances among both the Argead kings and later Hellenistic rulers show,
polygamy persisted in “hellenized” Macedonia.23 There is no sign of an early polygamous
tradition in Rome. Whether concubinage was feasible concurrently with marriage has been
debated in modern scholarship and the evidence is inconclusive: it was not until the sixth century
CE, after centuries of Christian influence, that the emperor Justinian claimed that “ancient law”
prohibited husbands from keeping wives and concubines at the same time.24 As in Greece, sexual
relations of married men with their own slave women were not unlawful, including relationships
that resulted in offspring. Formal recognition of the latter was optional but not unknown.
Moreover, ease of divorce underwrote a degree of effective polygyny: while men were unable to
have more than one wife at a time they could marry several in a row, thereby raising reproductive
inequality overall.25
Greco-Roman SIUM was preserved and gradually reinforced by the Christian church
which labored to suppress polygamy among Germans and Slavs at a time when the Arab
conquests lent ideological support to polygamy in parts of the Mediterranean and across the
Middle East. The Middle Ages, as SIUM spread as a by-product of Christianization, witnessed
the church’s struggle against divorce and elite concubinage, practices whose curtailment would
render monogamous precepts more effective.26 Ashkenazi Jewry followed this trend, highlighted
by Gershom ben Judah’s ban of polygamy at a synod around 1000 CE. In western Europe, a brief
spell of Anabaptist polygamy in Münster in 1535/6 (and, if true, a decree in Nürnberg in 1650
reacting to the lack of men after the Thirty Years War) was to be the final gasp of this practice,
whereas Mormonism subsequently briefly revived it in the United States in 1831.27 In the wake
of European overseas colonization, demic diffusion and imitation by non-European populations
finally elevated SIUM to a globally dominant principle. The spread of SIUM outside Europe was
slow and has yet to be systematically tracked and analyzed. In Japan, legislation against polygyny
commenced in 1880. Polygamy was banned in Thailand in 1935, in China in 1953, for Hindus in
India in 1955, and in Nepal in 1963. The main exceptions to this global trend have been the least
secularized Islamic countries of the Middle East and more generally sub-Saharan Africa. Despite
the Quran’s tolerance of up to four wives, countries such as Turkey (1926) and Tunisia (1956)
have formally outlawed polygamy and others have imposed judicial restrictions on this practice.

21 Wickert-Micknat 1982: 83-4; Mauritsch 1992: 92-8; Scheidel 2008, section 3.3.1; Hunt forthcoming.
22 Scheidel 2008, section 3.3. For temporary emergency authorization of bigamy in Athens following
massive male casulties in the Peloponnesian War in the late fifth century BCE, see Ogden 1996: 72-5.
23 Ogden 1999.
24 Scheidel 2008, section 3.5. Quote from the Codex Iustinianus 7.15.3.2.
25 On the serial aspect of monogamy see esp. Fischer 1989.
26 E.g., Goody 1983; Brundage 1987; MacDonald 1995: 7-18. Cf. also very briefly Herlihy 1995: 579-80.
27 Anabaptists: Cairncross 1974: 1-53; and cf. 74-89 on the Christian monogamy-polygamy debate
engendered by the Thirty Years War. Mormons: e.g., Kern 1981: 135-204; Foster 1984: 123-225; Van
Wagoner 1989. The church leadership renounced plural marriage in 1890 and more forcefully in 1904. For
contemporary Mormon polygamy, see, e.g., Altman and Ginat 1996.

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In what has been termed the “polygyny belt” from Senegal in the west to Tanzania in the east, 20-
30% of married men tend to be in polygynous unions.28
In the very long run, the trajectory of historical change reaches from habitual resource
polygyny at low levels of overall development to formal monogamy coupled with various forms
of concubinage in early agrarian states and on to SIUM in parts of the first-millennium BCE
Mediterranean that co-existed with de facto polygyny with slave women, a practice that
subsequently declined together with the institution of chattel slavery and evolved into church-
backed monogamy accompanied by more casual relations with servants or other subordinates that
were gradually curtailed by modernization. At this latest stage, European dominance underwrote
the spread of this principle across much of the world.


Causation

This rough model of cultural change raises questions of causation. Two distinct but
related issues are at stake: the reasons for variation in the incidence of polygynous polygamy and
monogamy, and the motivation for the social imposition of universal monogamy regardless of
status and resources.

Female choice

The overall incidence of polygyny may be explained as a function of female mate choice.
Economists have long argued that polgyny is beneficial to most women if there is substantial
inequality among men in terms of resources or other properties that are relevant to reproductive
success.29 Simply put, a woman may be better off sharing a resource-rich husband with other
women than to monopolize access to a resource-poor husband. In this context, moreover,
polygyny not only benefits multiply married women but also monogamously married women in
the same population by allowing them to avoid unions with the least desirable males.30
Conversely, this custom benefits male polygynists but harms other men to varying degrees, the
more so the more unequally resources are distributed and this inequality is correlated with
polygynous preferences. Hence polygyny tends to reinforce male inequality by matching
reproductive inequality with resource inequality.31
Based on these observations, Satoshi Kanazawa and Mary Still hypothesize that the
degree of resource inequality among men should have a positive effect on the incidence of
polygyny.32 Furthermore, women’s ability to choose a marriage partner is expected to increase

28 Jacoby 1995: 939. See more generally Lesthaeghe, Kaufmann, and Meekers 1989.
29 Becker 1974 = Febrero and Schwartz 1995: 316-7; Grossbard 1980: esp. 324; Becker 1991: esp. 87, 89.
Becker 1991: 80-107 provides the fullest formal analysis of the economics of polygyny. Cf. also Bergstrom
1994.
30 For simple illustrations of the main point, see Wright 1994: 97, repeated by Kanazawa and Still 1999: 27-
8.
31 This observation is distinct from the notion that polygyny favors male polygynists if women produce
gains other than children, especially by contributing to subsistence. This is held to be important in
horticultural systems where women do much of the farm work (e.g., Boserup 1970: 50; Goody 1976: 34,
129; cf. also Sanderson 2001: 331). However, Bretschneider 1995: 177-9 finds little support for the concept
of “wealth-increasing polygyny” (cf. White 1988: 549-50). Jacoby 1995: 965 observes that while women in
Cote d’Ivoire prefer wealthy men as spouses, they more specifically favor men on whose farms their (i.e.
the women’s) labor is more productive. In this scenario, male polygynists gain both in terms of production
and reproduction.
32 Kanazawa and Still 1999: 32-5. Sellen and Hruschka 2004 observe that the principle that “marital unions
are more commonly and more highly polygynous when men differentially control access to material

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the incidence of polygyny if men’s resource inequality is high, and vice versa. In their view, “the
extent of resource inequality among men and the level of women’s power have a positive
interaction effect on the level of polygyny in society.”33 In this scenario, the spread of monogamy
is a function of decreasing resource inequality among men. These assumptions are borne out by
simulation models and successfully tested against indices of resource inequality and women’s
power in 127 modern countries. These data show that greater resource inequality significantly
increases the incidence of polygyny and also indicate positive interaction effects of inequality and
women’s power on polygyny.34 Economic development is found to be negatively correlated with
polygyny, suggesting that male resource inequality diminished with economic development.
Whilst this argument has stood up well to preliminary criticism,35 the apparent
significance of “women’s power” is hard to explain given that female choice cannot be limited to
a prospective wife’s own decision-making: if polygynous unions with resource-rich men are
advantageous, a woman’s kin can reasonably be expected to arrange a marriage pursuant to the
same calculus of rational choice.36 This suggests that women’s power per se ought to be
irrelevant to observed outcomes. Moreover, a separate model by Eric Gould and associates
maintains that the composition of resource inequality is as important as its overall level: their
simulation indicates that while resource inequality based on non-labor income (such as control of
land and physical capital) favors polygyny, the marriage market equilibrium becomes more
monogamous if inequality is determined by disparities in labor income, which tends to be a
function of human capital.37 More importantly, however, neither one of these models is capable
of accounting for the existence of SIUM.38 In principle, they would readily allow for a moderate
degree of polygyny even in the most developed countries today, at the very least among the very
wealthy. I conclude that female choice theory is necessary but insufficient to explain SIUM and
that we need to take account of male choice to make sense of this institution.

Male choice

A “male choice” approach to polygynous polygamy and monogamy is likewise
predicated on the observation that in the context of male resource inequality, polygyny tends to
favor many women and disadvantage many men. This situation, in turn, is inherently conducive
to inter-male conflict and competition and thereby impedes cooperation.39 The negative effects of

resources, particularly where those resources are valuable, renewable, and heritable” (707) mutatis
mutandis also extends to foraging populations, with control of access to hunting and fishing sites serving as
the critical variable.
33 Kanazawa and Still 1999: 33.
34 Ibid. 34-5 (simulations), 35-41 (empirical tests). By contrast, the evidence does not show a negative
correlation between democracy and polygyny; cf. below.
35 See Sanderson 2001 and MacDonald 2001, with Kanazawa 2001a, 2001b.
36 Kanazawa 2001a: 338-40 defends the concept of female mate choice against the assumption that males
made the decisions but does not consider female choice mediated by kin.
37 Gould, Moav, and Simhon 2004.
38 As already noted by Sanderson 2001: 330. It makes little sense for Kanazawa and Still 1999 to present
their female choice model as an alternative what they call the “male compromise theory” of monogamy,
described below under the rubric of “male choice” (i.e., men banning polygamy as an intra-group
bargaining strategy), which ultimately seeks to account for normative monogamy rather than the relative
incidence of monogamy and polygamy. In my view there is no direct conflict between these approaches:
“male choice” theory is an auxiliary hypothesis that must be joined to “female choice” theory in order to
explain the phenomenon of SIUM.
39 For the correlation between sexual dimorphism (a proxy of polygyny, see above) and the intensity of
male-male conflict in other species, see esp. Alexander et al. 1979; Mitani, Gros-Louis, and Richards 1996;
Weckerly 1998.

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intra-group conflict and the benefits of cooperation supply an incentive for males to engage in
bargaining in order to reduce polygyny and thus overall reproductive inequality within a given
group. As Richard Alexander and associates put it, “the net effect of rules prescribing monogamy
is almost certainly a significant depression in the variance of male reproductive success relative to
that in stratified societies which do not prescribe monogamy.”40 Since this form of compromise
bargaining erodes the reproductive advantages customarily enjoyed by resource-rich elites, it is
unlikely to occur in the absence of powerful incentives. The drive for competitiveness mediated
by inter-group conflict has been identified as a plausible factor. All other things being equal,
restrictions on polygynous polygamy (e.g., its limitation to bigamy) and even more so its
prohibition in the context of SIUM can be expected to reduce competition within the group and
increase cohesion and cooperation and inter-group competitiveness.41 In the most basic terms,
reducing reproductive inequality is thought to promote collective action, which must be
considered a vital element of successful state formation.42
This hypothesis is susceptible to empirical testing. What we might call a “weak” version
of this hypothesis – that monogamy is positively correlated with social cohesion and
competitiveness that are in turn positively correlated with advances in development such as
agarianism and large-scale state formation – is partly borne out by the observation that polygamy
is less common in agrarian societies than in other systems.43 At the same time, however, imperial
state formation in particular can be shown to be associated with sometimes extreme levels of
resource polygyny.44 It would therefore be impossible to claim that monogamy is a necessary
precondition of social up-scaling.45 A “strong” version of the hypothesis holds that although
polygamy is insufficiently divisive to prevent up-scaling per se, it is nevertheless relatively less
competitive than monogamy: in consequence, once SIUM has emerged, it is expected to out-
compete polygynous systems for human and material assets. In Alexander’s view, the rise of
stable large states (loosely if not entirely accurately labeled “nations”) is intimately linked to this
institution: “It is almost as if no nation can become both quite large and quite unified except
under socially imposed monogamy.”46
Michael Price argues that this assumption is consistent with both historical and
contemporary evidence. He represents the spread of SIUM from highly localized beginnings to a
global phenomenon as a function of the expansion of European powers at the expense of other
(non-SIUM) competitors and the eventual imitation of Western practices by other societies.47 In
addition, he investigates the relationship between SIUM and state success by comparing
contemporary monogamous and polygynous societies with the help of standardized measures of
cooperativeness. Using population size, use of the death penalty, democratization, corruption, and
per-capita GDP as proxies, he shows that in a sample of 156 states, monogamous ones are more
populous, less likely to use the death penalty, less authoritarian, less corrupt, and richer than
polygynous ones.48

40 Alexander et al. 1979: 420.
41 Alexander 1987: 71. For a formal model in which polygyny is constrained by a ruler’s need to discourage
rivals, see now Lagerlöf 2007. This scenario could easily be expanded to cover elites more generally.
42 See most recently Blanton and Fargher 2008.
43 See above, at n.16.
44 See esp. Betzig 1993a; Scheidel 2008. White and Burton 1988 maintain that the incidence of warfare for
plunder and capture of women is positively correlated with the incidence of polygyny, and Bretschneider
1995 finds that in the 186 societies of the Standard Cross-Cultural Sample polygyny is a positive correlate
of successful inter-group warfare.
45 Cf. also MacDonald 1990: 198, 204.
46 Alexander et al. 1979: 432-3. In a somewhat different vein, cf. Nielsen 2004: 312 for the possibility of a
connection between increasing freedom and SIUM. But cf. below, n.63.
47 Price 1999: 33-45. I am greatly indebted to Dr Michael Price for sharing his unpublished paper with me.
48 Price 1999: 45-52. See also Sanderson 2001: 332.

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This raises the question whether the success of SIUM-bearing societies is causally related
to SIUM or whether SIUM is a coincidental and neutral side effect that has been transmitted
alongside other features that were in fact responsible for Western dominance.49 I believe that this
question cannot be answered on the basis of the data that have been marshaled to date.50 The
notion that SIUM tends to be positively correlated with state success and human well-being is
consistent with the observation that polygyny currently retards development in sub-Saharan
Africa:51 yet this does not show that development and competitiveness are necessarily predicated
upon SIUM. The fact that the causes of the “rise of the West” continue to be fiercely contested in
modern scholarship makes it seem a priori unlikely that it was causally tied to a single variable.52
Ultimately, the proposed relationship between state success and SIUM may turn out to be
inherently untestable or at the very least to require more sophisticated coding and multivariate
regression analysis. The most we can say at this point is that inasmuch as SIUM is likely to foster
cooperation and constrain conflict and inequality it is a plausible contributing factor to state
success and general human development rather than merely a neutral feature. However, the
burden of proof rests on anyone wishing to maintain that it was a necessary precondition or
driving force.
Laura Betzig’s version of “male choice / compromise theory” views effective monogamy
as a fairly recent development brought about by the increased division of labor associated with
industrialization which impelled bargaining processes between subordinates and dominants.53
Betzig’s approach cannot be criticized for disregarding earlier instances of monogamy or even
SIUM since she defines Greco-Roman, medieval, and early modern Europe as effectively
polygynous.54 However, Betzig’s emphasis on polygynous practices in earlier historical periods
makes it difficult to posit any kind of critical break with the past: from this perspective, current
conditions are merely the latest phase of ongoing cultural evolution. In a sense Betzig is both
right and wrong: right about the slow rate of change and the severe limitations of historical forms
of monogamy yet also mistaken in ignoring the potential impact of SIUM on actual behavior and
in arbitrarily identifying a shift to more genuine monogamy in the recent past. What we are
dealing with is a wide range of preferences and practices that leaves little room for a dichotomy
of polygamy/polygny and monogamy/monogyny but requires us to situate any given society
along this spectrum and to ascertain what, if anything, it contributed to the overarching trend
toward more effective monogyny.55

49 Emphasized by Wilson 1995: 37. Cf. also Price 1999: 29-30, 55.
50 None of the six reasons invoked by Price 1999: 56-7 seem to me particularly compelling; however,
detailed discussion of his unpublished arguments would be out of place here. It is also unwarranted to
suppose (ibid. 44) that non-colonized countries eventually embraced SIUM not just “because they began
recognizing Western economic and political dominance” but more specifically “in order to remain
competitive with traditionally Christian nations.” Westernization entailed the adoption of whole bundles of
European institutions and there is nothing to suggest that for these “late adopters” SIUM per se was – or
was thought of as being – imbued with competitiveness-enhancing properties. Cf. however Lagerlöf 2007:
22 for the observation that according to his own model population growth endogenously reduces polygyny.
51 See esp. Tertilt 2005 for a model predicting that banning polygyny in sub-Saharan Africa would reduce
fertility and greatly increase savings and per capita output. Cf. also Schoellman and Tertilt 2006; Tertilt
2006.
52 The same is necessarily true of the analogous argument by Hartmann 2004 that seeks to trace “Western”
progress to the north-western European pattern of late marriage. Recent scholarship on the putative causes
of the “rise of the West” is too rich to reference here even selectively.
53 Betzig 1986: 103-6; 1993b. Note that her emphasis on recent economic development is consistent with
the premise of Gould, Moav, and Simhon 2004.
54 Contra Herlihy 1995: 578; MacDonald 1995: 4. Effective polygyny: Betzig 1992a, 1992b, 1995, 2002.
Cf. also Price 1999: 18-22 for discussion.
55 I therefore agree with Price that Betzig’s approach elides the significance of SI(U)M, regardless of how
effective it was in practice.

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