Henrich polygamy power point (draft)

Outline: BackgroundEvolved Mating PsychologiesFemale and male psychologies are different in ways that till us (humans) toward polygynous mating systemsGreater absolute wealth differences among males, the greater the polygyny.Substantial polygyny in societies with large absolute differences in male wealth.Cultural Evolution and Social NormsSelf-re-enforcing stable equilibriaInternalized motivationsCompetition among societies can favour group-beneficial normsMating vs. marriage systems1

OutlineAnthropological review of marriage systemsConsistent with evolutionary expectations?Frequencies of spousal # variationsShould we expect polyandry or group marriage to also spread?Historical origins of modern monogamyUnusual monogamyCultural practices evolved gradually 2

OutlinePolygynous vs. monogamous marriage—comparison crucialSocietal impacts—increases the size of pool of low status males with little prospect for finding a mateIncreases crime and substance abuseFamilies—drive down paternal investment and internal conflictYoung childrenPoorer health and greater mortality Results from less paternal investment and internal conflictWomen and girlsAge of first marriage age gap, and equalityPsycho-social stress3

Evolved mating psychologyWhy males and female are differentEggs are expensive, limited, max 400 in a lifetimeSperm are cheap and disposable.. can make 12 million in an hour.Creates an asymmetry in the initial investment in reproductionAsymmetry magnified through Gestation—weakness, pregnancy sickness Lactation—calorically intensive, suppresses fertility4Henrich Aff #1, pages 27-28

Female mating strategiesWomen are limited in number of children they can have in their lifetime (max 10 in ancestral environments), and must invest in all of them.The key to their fitness is choosing wisely among potential fathers. Find the highest quality male who is willing to invest in the long-run with her offspring. Good genes, and paternal investment (rich, capable, and willing).But, can improve this situation by getting high quality genetic material on the side (extra-pair copulation).Long-term and short-term strategies5Henrich Aff #1, pages 27-28

Male mating strategiesMen can have literally thousands of offspring, but are also much more likely to get entirely shut out of the mating game.High variance (0 to 1000)—polygyny increases variance.Most successful strategy is one that has sex with as many women as possible, and never invests in rearing offspring.Many males, however, won’t be able to pursue this strategy because not very many women will have sex with them. Alternative (most common) strategy: commit to investing in a woman to form a long-term pair-bond.Male commits assistance and resources while female commits some degree of paternity certainty.Forming additional long-term pair-bonds increases fitnessMale also still increases his fitness is each “extra-pair” copulation6Henrich Aff #1, pages 28-29

Mating systems are outcome of the two psychologiesA particular pair-bonding pattern resultsMales will be inclined to make additional pair-bonds, if they can, and seek extra-pair copulations.Females don’t benefit much from additional pair-bonds. Why?She can only get pregnant sequentiallyPaternity certainty  more investmentMale jealousy conflictLower rate of extra-pair copulations by females7

A cultural speciesUnlike other animals, humans heavily reliant on cultural learning, on learning from other group members.Humans adaptively learn all manner of social behavior from others in their social milieuHow others should be judged, and what affects a person’s reputation or standing in the community.Internalize local norms as intrinsic motivationSocial NormsSelf-re-enforcing social rules for behaviorWhen pair-bonds are regulated by social norms  marriage8

Marriage systemsSets of cultural evolved rules—called institutions—that regulate pair-bondingTransfer at marriage: brideprice or dowryDivision of labor, responsibilities to offspring and spouseRules about sex90%+ of societies emphasize norms regulating female sexualityResidence—who lives with whom: patrilocal or matrilocalInheritance9Henrich, Aff #1, page 26

Marriage systemsSets of cultural evolved rules—called institutions—that regulate pair-bondingCombinations of husbands and wivesPolygyny—norms that permit or favor one husband with 1+ wives.Polyandry—norms that permit or favor a wife with 1+ husbandsALL marriage systems culturally reinforce the pair-bonding aspect of human psychology.Not all human societies have marriage systems. The Na of Western China.10Henrich, Aff #1, page 31

Anthropological TerminologyA marriage is long-term pair-bond between two people that is recognized and sanctioned by the couple’s community. Being married comes with economic, social, and sexual expectations, prescriptions, and prohibitions (norms) for both parties. Marriage may or may not be sanctioned by formal laws, and marriage existed long before formal laws or even writing. Public rituals usually mark the commencement of a marriage.The key to understanding marriage is recognizing the role of a community in defining, sanctioning, and enforcing it.11Henrich Aff #1, page 26, footnote 3

Key summary pointsWithin the context of marriage systems, male mating psychology strongly favours long-term pair-bonds with multiple partners. Their ability to attract long-term partners will depend on their resources and social status. Male psychology is generally highly averse to sexually sharing a long-term mate with another male. The evolutionary reasons for this involve paternity uncertainty. Female ovulation is largely concealed from malesMales should respond to a shortage of females by more fiercely guarding their mates.Sustain paternity certaintyFemales are not particularly advantaged by pair-bonding with multiple males. 12Henrich, Aff #1, page 32

Marriages systems reflect our evolved mating psychologyThe whole database13Henrich, Aff #1, page 33

Standard Cross Cultural Sample.Historically more independent societies14Henrich, Aff #1, page 33

Normative prescriptions15Henrich, Aff #1, page 34

Monogamous marriage may be even more unusual than it appears16Ecological monogamy

Historically connected societies (Irish, Rome)

Class-based monogamy (Egypt, Babylon)Henrich, Aff #1, page 33

Types of polygynyGeneral polygynyWives need not be, and general are not, sisters or classificatory sisters (cousins)Separate the wivesSororal polygynyWives should be sisters or classificatory sisters.Having related wives reduces intra-household co-wife conflictMuch more closely related households.17Henrich, Aff #1, page 35

Polygyny, status, and wealthSmall-scale hunter-gatherers are polygynous, mildly.In all polygynous societies, a man’s social status, prestige, hunting skill, nobility, and wealth lead to more. More absolute wealth differences, more variations in wife numbers (if permitted).18Henrich, Aff #1, page 35

Polygyny, status, and wealthBetzig (1982; 1993) puts a fine point on this observation by analyzing what the autocratic leaders of chiefdoms, empires, and early states did regarding wives and concubines. She reveals a strong pattern that, given the wherewithal to do so (no internalized social norms or laws to impede them), powerful men consistently assemble immense harems with 100 or more women. This ranges from High Chiefs in Tonga and Fiji to emperors in China and the Andes. Harems get bigger and bigger as the societies get larger and more complex. 19Henrich, Aff #1, page 35

Polyandrous marriages are quite rarePolyandry is usually fraternal polyandry, meaning brothers marry the same womantypically found intermixed with other marriage types in the same society, including both monogamy and polygynyconsidered to be somewhat unstable with the youngest husbands leaving the marriage, or taking additional wives themselves (giving rise to polygynandry)principally confined to the Himalayan and, to a lesser degree, Indian regions of Eurasia, though it has been observed elsewhere, including in the Americas (Levine and Silk 1997). Many researchers have argued that polyandry emerges when sustaining a household requires the input of multiple males (Levine and Silk 1997). 20

Group marriage?Scattered reports. Many of these reports are of dubious quality. Or, non-anthropological observers have confused marriage with the custom of wife sharing or loaning, which was common in both aboriginal North America and Australia. In these societies, which were numerous (and usually polygynous), husbands controlled sexual access to their wives, and it is considered polite and honourable for them to give those “services” to close friends or honoured guests for a night or period of time. Since these other men are also often married, it might appear as if some kind of complicated marital arrangement exists.Polygynandry—starts as polyandry, one of low status brothers marries polygynously. 21Henrich, Aff #1, page 38

Theoretical InterludeWhy look at history of modern monogamy?Is this history consistent with the theory?Is it rare?Is it associated with successfully spreading societies.Ancient GreeceRomeEuropeIt could be that monogamous marriage moved with plow agriculture, or that it’s a peculiarly Judeo-Christian idea.Not the case22

History of Western MonogamyTraces back through Rome to the Greek city statesAdopted recently in much of the world1880 in Japan, 1926 in Turkey, 1956 in Tunisia, 1953 in China, 1955 in India (except Muslims), and 1963 in Nepal. Greek city states first legally instituted monogamy as part of many different reforms, including elements of democratic governance, which were meant to build egalitarian social solidarity among their citizenries.Prior to this, all accounts suggest polygynous marriage was common, at least among the nobility, and monogamy was a strange “Greek idea” Instituted legally in the early sixth century BCE in Athens. 23Henrich, Aff #1, page 36-37

History of Western MonogamyWhile Greek monogamy limited each male citizen to a single wife, it was considered acceptable to import sex slaves, which wealthy men did. This approach is interesting because it addresses one of the fundamental social dilemmas posed by marriage systems: by keeping local women available to low status men for marriage this avoiding the problems created by poor unmarried males, while at the same time allowing rich men broad sexual access to “imported” women.This reduces opposition from wealthy and nobility24Henrich, Aff #1, page 36-37

History of Western MonogamyRomans likely inherited and further developed the monogamy of the Greeks, though Etruscan marriage norms and relative sexual equality likely had some influence. Rome outlawed polygamy and regulated this with laws about sexual behaviour, birth legitimacy, and inheritance. Bigamists could be prosecuted, and married women had to be accompanied in public (Herlihy 1995; Macdonald 1995). 25Henrich, Aff #1, page 37

History of Western MonogamyAugustus felt Roman morality was declining and weakening his empire, so he instituted a series of reforms in an effort to get every man from age 25 to 60 to be married. A series of Roman emperors after Augustus continued to reinforce these legal principles and adapt the law. Historians: the evolution of this aspect of the Roman legal system is intimately intertwined with the emergence of greater sexual equality under the law (Macdonald 1990; Herlihy 1995; Scheidel 2009).26Henrich, Aff #1, page 37

Into EuropeEarly Christian ideas about monogamy and sexual purity are a combination of the evolving Roman ideals and notions drawn from Greek stoicism. Christian ideals solidified and eventually spread throughout Europe, which was highly polygynous in the pre-Christian era and during the early days of Christianity. European aristocracies were highly polygynous in the 5th century. All sought alliances with the Catholic Church, which worked vigorously to impose monogamous marriage on the aristocracy. 27Henrich, Aff #1, page 37

Into EuropeAs European kings gradually converted to Christianity the Church increasingly controlled their marriages, and thus their legitimate heirs (that is, they controlled who had rights to political power). Since the lower strata of these societies, who were rapidly adopting Christianity, were economically limited to monogamous marriage anyway, the main line of resistance came from the nobility. Once the nobility began to accept monogamous marriage (declining the harems of their peers elsewhere in the world), general monogamy and associated laws followed (Macdonald 1995). Historians argue that monogamous marriage in Europe meant that for the first time kings were subject to the same rules as peasants.28Henrich, Aff #1, page 38

History of Western MonogamyThese ideas do not come from Judaism (which permitted polygynous marriage until at least the 11th century), or the Christian Gospels. In the Old Testament, the prophets and kings are all polygynous.At best, the New Testament offers some vague recommendations for monogamy among church leaders in the Pastoral Letters (Scheidel 2009).29Henrich, Aff #1, page 37

Summary points so farPolygynous marriage has been widespread, and emerges in an immense variety of social contexts.Wealthy, high status men tend to marry polygynously, if they are permitted.Polyandry is quite rare, in a manner consistent with evolutionary theory.Imposed universal monogamous marriage is uncommon too, and seems to have evolved culturally to increase solidarity, foster an egalitarian spirit, and stabilize society. 30Henrich, Aff #1, page 38

Polygynous marriageMonogamous marriageMinimizes the pool of low-status unmarried men.Unmarried low status men have a fighting chance of obtaining a mate without big risksReduces rates of murder, robbery, rape, and drug abuse.Decreased competition reduces male effort at controlling females.Fertile conditions for gender equalityExpands pool of low-status unmarried men.Facing genetic extinction, these men are motivated to engage in risky behaviors.Increases rates of murder, robbery, rape, and drug abuse.Increased competition drives age of first marriage for females down, expands age gap.causes males to seek to tighten control of wives, daughters, and spouses. 31

Polygynous marriageMonogamous marriageMarried low status males shift into long-term investment mode. Married high status males impeded from investing in seeking additional long-term mates.Both now motivated to focus on current wife and her offspring. Invest and maximize quality of offspring.Monogamous familiesMaximizes genetic relatednessIncreases paternity certainty, which reduce domestic violence.Married men reduce investment in current wife and offspringRemain on mating market: married men continue to seek additional wivesFocus energies, attention & resources on obtaining additional wives.Polygynous familiesCreate families loaded with non-relatives (step moms), which increase potential for abuse and violenceDecrease paternity certainty32

33Even sex ratioIllustrative exampleOf course, there is always a pool of unmarried menNot yet married

Not marriageable Male StatusSize of unmarried pool0%Henrich, Aff #1, page 40

34Even sex ratioMale StatusMale Status33% polygynous 67% monogamousMost wives anyone has is 4Size of unmarried pool40% unmarriedPool of low status males0%

35Why will the low status guys take greater risks?Male StatusHow much does he have to improve his status to have a shot at a pair-bond?Now, he’s got to be in the top 60%In the monogamous world, this guy was marriedHe was in the bottom 10%

36Why will the low status guys take greater risks?Male StatusHow much does he have to improve his status to have a shot at a pair-bond?Now, he’s got to be in the top 60%And, he’s got to fight it out with all the rest of these guys who are shooting for the same minimumHe was in the bottom 10%

Predictions and Empirical EvidencePolygyny increase the size of the pool of low-status men and motivates them to engage in risky behaviours.Evidence suggests that such unmarried, low status malesn engage in crime, social disruption, and personal abuses at higher rates. Competition for mates and access to sex created by the pool of unmarried men increases kidnapping of women (as sex slaves), rape, and prostitution. Greater polygyny is strongly associated with higher rates of rape. 37Henrich, Aff #1, page 39

Marriage on CrimeMarried men are less likely to commit crimes and abuse substances compared to unmarried men.Substantial correlational evidence. Is it causal?Longitude studies tracking males from age 17 to 70 show that the same men are less likely to commit crimes during the married periods of their lives (Sampson et. al. 2006). Massachusetts reform school.For all crimes, it reduce a man’s chances of committing a crime by 35%.For property and violent crimes, marriage cuts the probability of committing a crime by half. When men divorce or are widowed, their crime rates go up.It’s not the men, it’s the marriage.38Henrich, Aff #1, page 40-41

Marriage on CrimeHorney et. al. (1995) working with Nebraska inmates (recall data).Moving in with a wife reduces the probability of a man committing a crime by roughly half, controlling for employment, drug abuse, etc. Effect is strongest for assault and weakest for property crimes. Marriage effect is similar to entering school.Cohabitating with a girlfriend (as opposed to a wife) either increases or does not impact individuals’ crime rates. The positive effect on crime of living with a wife is larger than the negative effect created by heavy drinking.Taking drugs had the biggest effect on increasing crime rates. Horney et. al. may underestimate the total impact of marriage because marriage also reduces binge drinking and drug use. Same story in London, Farrington and West.39Henrich, Aff #1, page 41

Polygyny and CrimeDo these individual-level effects aggregate up to the societal level?Analytical challenge: polygynous marriage isn’t randomly distributed across different societies. Tends to co-occur with low GDP per capita, low female equality, little democracy, etc.Run cross-national regressions using a polygyny variable to predict different crimes, controlling for Economic Development, Economic Inequality, Population Density, and Democracy.Replace polygyny variable with % of unmarried males. If our causal story is corrected, this will be at least as strong.Look within countries and longitudinally using sex ratios as a proxy for polygyny in different regions.40Henrich, Aff #1, page 42

Cross-national analysesVery conservative analysis since Economic Development, Economic Inequality, and Democracy are controlled for.Monogamous marriage may cause economic development, greater equality, and democracy.Polygyny variable is vary noisy. Kanazawa and Still coded all of the cultures in the Encyclopaedia of World Cultures on a four point scale (from 0 = monogamy is the rule and is widespread, to 3 = polygyny is the rule and is widespread), and then developed a country-level value by aggregating all of the cultures within a country.41Henrich, Aff #1, page 42-43

Cross-national analysesProng (1) polygyny and crimePositive relationship between polygyny and murder, rape, assault, and robbery.Murder and rape are significant at conventional levels, and marginal on robbery.Coefficient on assault is large but not well estimated.Being fully polygynous increases murders and rapes by 12 per 100,000.Being fully polygynous increases robberies by 64 per 100,000.42Henrich, Aff #1, page 43

Cross-national analysesProng (2): Replace polygyny with % unmarried men over 15.Now the % of unmarried men is positively related to murder, rape, robbery, and assault.Murder, rape, and robbery now are all significant at conventional levels.An increase of 40 in the % of unmarried men predicts an increase of 11 per 100,000 in murders.22 per 100,000 in rapes180 per 100,000 robberiesAssault is marginally significant 108 per 100,000 assaults43Minimum effect sizes, since we are controlling for GDP per capita, equality, and democracyHenrich, Aff #1, page 43-44

Cross-national analysesProng (3): Within country analysesBy themselves, cross-national analyses don’t permit any assessment of causality.Use sex ratio as a proxy for effects of polygyny—could create the same kinds of effects for crime.India—son preference create sex ratio favoring males. Varies across districts in India.Because it is within one country it deals with many of the problems of cross-national analysis.China—son preference plus one child policy enacted at different times allows us to get closer to causality.U.S.—could this work in the a Western democracy?44Henrich, Aff #1, page 44

IndiaRising murder rate in India (Dreze and Khera 2000)319 districts, 90% of populationMurder avoids reporting biasesControlling for economic and demographic differences, more males to females predicts higher murder rates.Showed that it’s not just more males. Highersex ratios make the males more murderous.The effect is large: going from a male to female ratio (in Uttar Pradesh) of 1.12 to one (in Kerala) of 0.97 cuts the murder rate in half.Literacy is also an important independent predictor of murder rates across districts, though poverty and urbanization are not. 45Henrich, Aff #1, page 45

ChinaCrucial natural experiment In China, sex ratios (males to females) rose markedly from 1.053 to 1.095 between 1988 and 2004, nearly doubling the unmarried or “surplus” men (Edlund et al. 2007). At the same time, crime rates nearly doubled—90% of which were committed by men. The increase in sex ratio was created by the gradual implementation of China’s one-child policy. Each province implemented the policy at different times for idiosyncratic reasons (unrelated to crime rates or sex ratios)Excellent opportunity for statistical analyses of the impacts of the policy and the alterations in sex ratio it created. 46Henrich, Aff #1, page 44

ChinaIdeal natural experiment for two reasons: Limiting child number through potent family planning led to preferences for male children. That means that male children are exceptionally valued.They would benefit from heavy parental investment, and one should expect, if anything, that such children would be less likely to commit crimes than the boys of previous generations. Limiting family size means the population began to shrink, a demographic shift that opens up opportunities in the labour market and ought to decrease people’s likelihood of committing crimes. So it is significant that, despite these downward forces, crime still went up.47Henrich, Aff #1, page 44

ChinaControlling for many other economic and social variables, a 0.01 increase in sex ratio is associated with a 3% increase in property and violent crimes. Inequality, unemployment, and urbanization also show positive effects on crime rates, but the effect of sex ratio is independent of these effects. These analyses also indicate that the effect arises from an increase in the size of the pool of low-status unmarried men, and not from an increase in men in general. 48Henrich, Aff #1, page 44

ChinaCausalityThe authors show that the year of implementation of the one-child policy predicts sex ratio, and this predicts crime rates across provinces.The sex ratio decades later cannot be causing the implementation of the one-child policy (in the past).The one-child policy caused families to strongly favour males, creating a pool of unmarried low status men.This pool generates massive increases in crime rates despite economic growth, and a shrinking population.49Henrich, Aff #1, page 44

Historical sourcesCourtwright in his book, Violent Land, indicates that pools of unmarried men have created similar effects (high crime, violence, drug abuse, etc.) in a variety of circumstances. The violent character of the American West arose principally from the large pool of unmarried men who migrated there. Variation in crime rates, including murders, in America corresponds to the spatial distribution of sex ratios in the 19th century. As sex ratios move toward 1 in regions, crime rates drop.Similar cases in New South Wales in Australia in the late 1700s and the Argentinean Pampas in the gaucho era.50Henrich, Aff #1, page 45

Polygynous marriageMonogamous marriageMinimizes the pool of low-status unmarried men.Unmarried low status men have a fighting chance of obtaining a mate without big risksReduces rates of murder, robbery, rape, and drug abuse.Decreased competition reduces male effort at controlling females.Fertile conditions for increasing or sustaining gender equalityExpands pool of low-status unmarried men.Facing genetic extinction, these men are motivated to engage in risky behaviors.Increases rates of murder, robbery, rape, and drug abuse.Increased competition drives age of first marriage for females down, expands age gap.causes males to seek to tighten control of wives, daughters, and spouses. 51

Polygyny, Age of Marriage, Age Gaps & Gender EqualityPolygynous marriage ignites a competitive process for wives among men that increases males’ efforts to control femalesdrives down the age of first marriage for females while increasing the age gap between spouses Seeking out the only available females for both first and subsequent wives, men of all ages pursue younger females.This is necessarily true of men choosing to strictly adhere to monogamous marriage. Competition drives men to use whatever connections, advantages, and alliances they have in order to obtain wives.Once girls become wives, older husbands will strive to “protect” their young wives from other males dampen women’s freedoms & exacerbate inequality.This effect is further exacerbated by age gaps. 52Henrich, Aff #1, page 49

Three lines of evidence Macro-level data: examine macro level (country level) data, comparing highly polygynous countries with less polygynous countriesmonogamously marrying countries from between 20 degree south latitude and 20 degrees north latitude (i.e., tropical non-African nations). Micro-level data: examine four case studies and compare the age of first marriage for women and age gap between married people in polygynous and monogamous marriages.Sex ratio as a proxy for the effects of polygyny on women and gender equality. 53Henrich, Aff #1, page 49

54Macro-level DataHenrich, Aff #1, page 50

Micro-level Data55Further polygynously marrying men are seeking out younger first wivesHenrich, Aff #1, page 53

Gender Equity?UNDP’s Gender Empowerment IndexMale/female income ratiosFemale representation in high status jobsCanada ranked 4th in 2009 (0.83).57Henrich, Aff #1, page 51

Effects of polygyny on gender equalityUse sex ratio as a proxy to determine the effects of polygyny on women.High sex ratio will increase competition for women. Age of marriage will go down and age gap expands

Men will tighten their control on wives, sisters and daughters. Higher sex ratio mean less gender equality58

Effects of polygyny on marriage age and age gapAn analysis of 117 countries found that in countries with a high ratio of males to females, females married younger (South and Trent 1988). The rising sex ratio in China has caused rich families to acquire infant girls to guarantee their sons have wives (Hudson and den Boer 2004). NOTE the typo ( “declining sex ratio”, pg. 55).Similarly, in some regions of India more than half of females in some regions are married before age 15 (Burns 1998). In the American frontier where females were in short supply, brides were reported as young as 12 and 13 (Courtwright 1996).This converges with our findings above, indicating that competition for scarce females drives the age of first marriage down.59

Cross-national analysis: sex ratio and gender empowermentSouth and Trent analyzed data from 117 countries around the world. The sample included countries from the full spectrum of development, but with a bias towards more developed countries.The sex ratios based on number of males and females between the ages of 15 and 49 from any year between 1973 and 1982Analyses controlled for the reliability of the sex ratio data for each countrythe socioeconomic development of each country an index composed of variables including GDP per capita, infant mortality, percentage of population living in urban areas, and life expectancy.60

Cross-national analysis: sex ratio and gender empowermentHigher sex ratios (i.e., more males than females) predict lower participation of women in the labour forcelower illegitimacy rates (women more frequently have babies outside of marriage when they have more power)lower divorce rates (women can divorce)61Henrich, Aff #1, page 55-56

Apply to developed countries?Limit sample to developed countries ONLYsex ratio had a greater effect on indicators of women’s roles than in less developed countries, with the exception of participation in the labour force. In more developed countries, higher sex ratios predict for women a (a) lower age at first marriage, (b) higher fertility rate, and (c) lower literacy62Henrich, Aff #1, page 56

The Role of Sexual Jealousy and Age DisparityBreitman and Shackelford (2004) show that in Chicago, controlling for a wide range of other factors, the age gap between husbands and wives is strongly related to homicide rates. The larger the age gap, the more likely it is that a husband will kill his wife, and vice-versa (the young wife murders her husband). The effect is highly non-linear: in moving from spouses being the same age to husbands being between 13 and 15 years older, the rate increases from 5 per 100,000 to 8 per 100,000. Then, it spikes to almost five times the same-age rate. Domestic violence will be worse in polygynous societies because of the age gap.

FLDS age gaps of 16 years are not uncommon63Henrich, Aff #2, page 7-8

North America?A 15 year long ethnographic study in the FLDS community in Colorado City/Centennial Park in the U.S. reveals similar dynamics. Anthropologist William Jankowiak writes (p.171): There is a shortage of eligible women to marry in every polygynous society, and this is a primary factor responsible for intergenerational conflict in Colorado City/Centennial Park. Senior males are always on the marriage market and thus compete with younger men for mates in a limited pool of eligible women…in the 1960s a local policeman, without approval of the religious leadership, would threaten to arrest unmarried males who did not leave the community…The competition for mates is acute…Young men know…that if they do not find a girlfriend before they graduate from high school, they probably never will have one. Without a girlfriend, they will leave the community to find a wife (p. 172-173).64Henrich, Aff #2, page 9

North AmericaFor those possessing contemporary Western values regarding gender equality it may be difficult to imagine how educated, modern North Americans could ever come to “compete” for women, or treat them as “resources” to be divided up. In this setting, fathers often exchanged daughters in order to marry them…men wanted to marry off their daughter before they could decide to select from within their age cohort. By the 1990’s Second Ward fathers began to negotiate marital exchanges not for themselves but for a favorite son, or in some cases a grandson (p. 171).Within the First Ward, families also gave/give daughters as a kind of patronage to the prophet. Jankowiak writes:The prophet’s age does not restrict families from offering their daughters to him…the reason why fathers give their daughter to the prophet (often with a wife’s encouragement) are to gain prestige and to obtain material and spiritual benefits (p. 171). 65Henrich, Aff #2, page 9

A “What If” Economic Model of Imposing MonogamyTertilt developed an economic decision-making model using standard modeling tools from economics to examine what gives rise to polygyny, how it affects an economy, and what impact, if any, imposed monogamy has (2005).Her model assumes both men and women care about both having children and “consuming,” but that men can continue to reproduce their entire lives while women are limited to only a portion of their lives She also assumes that men tend to prefer younger women.She shows that her model produces polygynous mating patterns under a wide range of conditions, and that it can produce results that match real-world patterns related to age-gaps, fertility, and saving rates for polygynous countries.66Henrich, Aff #1, page 32

Imposing MonogamyShe then calibrates the model to the Highly Polygynous data shown above (and other related data) and then asks the question of what happens when she imposes monogamy on everyone (in the model). The result is that the fertility rate goes downthe age gap goes downsaving rates go up, bride prices disappearand GDP per capita goes way up. This occurs because men (in the model) can’t invest in obtaining wives or selling daughters (which they do massively, otherwise), and instead they save and invest in production and consumption. 67Henrich, Aff #1, page 33

What about empowering women?Tertilt (2006) uses the same model to compare the effects of imposing monogamy legally to the effect of increasing the power of women. Tertilt alters her model to shift reproductive decision-making from men to women, but leaves polygyny legal.In this female-choice model, The #of wives per husband declines a little bit, as does fertility.GDP per capita also goes up someSavings rates go up substantially. Overall, however, empowering women does not have nearly the impact on GDP per capita and fertility as imposing monogamy.This underlines the point made above that giving women free choice does not necessarily yield monogamy, low fertility, or economic growth, though it does yield less intensive polygyny. 68Henrich, Aff #1, page 33

Polygynous marriageMonogamous marriageMarried men reduce investment in current wife and offspringRemain on mating market: married men continue to seek additional wivesFocus energies, attention & resources on obtaining additional wives.Polygynous familiesCreate families loaded with non-relatives (step moms), which increase potential for abuse and violenceDecrease paternity certaintyMarried low status males shift into long-term investment mode. Married high status males impeded from investing in seeking additional wives/matesBoth now motivated to focus on current wife and her offspring. Invest and maximize quality of offspring.Monogamous familiesMaximizes genetic relatednessIncreases paternity certainty, which reduce domestic violence.69

Predictions of family impactsRelative to monogamy, polygyny also impacts male parental investment by (1) eliminating opportunities for low-status males to establish pair-bonds (and invest in offspring), (2) diluting the per-child investment in larger and larger families, and (3) shifting investment by high status males from offspring into obtaining more long-term mates. Polygynous families also create situations for Co-wife conflict, half-siblings conflict, and jealouslyLots of stepparents and unrelated adult pairs70Henrich, Aff #1, page 46Henrich, Aff #2, pages 2-7

Predictions of family impactsEmpirical PredictionsPolygynous households, even relatively wealthier ones, have higher child mortality and poorer child health compared to monogamous families.

Cowives in polygynous households often/sometimes show greater psycho-social stress.71

Child mortality: North AmericaLow male parental investment, low relatedness, and high internal conflict mean influence the health of children.19th century Mormon communities in Utah (Heath and Hadley 1998)Compare the family composition and child survival data from 90 households consisting of 45 headed by wealthy men (top 2% of wealth in that community) and 45 headed by poor, but still married, men (from the bottom 16%). 72Henrich, Aff #1, page 47

Child Mortality: North AmericaThe first thing these data show is that wealthy males had on average 3.2 wives compared to 1.4 among the poor. All but five of the wealthy men had more than one wife. One rich man had 11 wives. Overall, the wealthy men controlled 120 women while the poor men controlled 63. This means that 90 husbands had 183 wives, which implies roughly 93 missing men had no wives. Ergo, the pool of unmarried low status men.73

Child Mortality: North AmericaWealthy men had more total offspring and longer reproductive careers (33 years for wealthy men compared to 22 years for poor men)The children of poor men had better survival rates to age 15. For poor men, 6.9 of their offspring (per wife) survived on average to age 15.For wealthy men, only 5.5 of their offspring survived. This is amazing, given that the poor men had less than 10% of the wealth of the rich men, and the rich men had significantly more total offspring (including those that did not make it to 15).74Henrich, Aff #1, page 47

It’s not the dilution effect aloneCompare the poor men with one or two wives with the rich men with one or two wives. Among men with one or two wives, For these poor men 6.9 children per wife survivedFor these rich men 5.7 children survived per wifeThis supports the idea that poor men with limited resources for another wife tend to invest more in their existing offspring while rich men with the same number of wives invest less in offspring because they are busy seeking additional wives.75Henrich, Aff #1, page 47

Cross-culturallyChild Health and Mortality These historical North American patterns are similar to those observed in recent studies of contemporary polygynous African societies. Children from polygynous families have an increased risk of diminished nutritional status, poor health outcomes, and higher mortality. Quantitative studies in Tanzania and Chad found that children in polygynous households had poorer nutritional status than their counterparts in monogamous households, as indicated by the children’s height and weight measurements (Begin et al. 1999; Sellen 1999; Hadley 2005). 76Henrich, Aff #1, page 48

Cross-culturally: Child Health and Mortality In Hadley’s (2005) Tanzanian study, despite these favourable conditions, the children of polygynously married mothers were more likely to be underweight, and were relatively shorter and gained less weight and height during the study than children of monogamously married mothers. In Sellen’s (1999) Tanzanian study, children of polygynous mothers had lower weight for age scores (WAZ) and height for age scores (HAZ) than children of monogamous mothers. The analyses controlled for wealth and child and maternal characteristics.77Henrich, Aff #1, page 48

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