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Monogamy and marriage may suit men after all
MEYER/TENDANCE FLOUE
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Monogamy and marriage may suit men after all intense, because men would risk diluting the value of their property by dividing it up among too many offspring and heirs. “Having a plot of land that is not big enough to support your family is not clever,” says Fortunato. The pair modelled the behaviour of populations incorporating monogamous and polygynous men over two generations. They made the assumption that women in early agrarian cultures did not provide much in the way of material resources. Monogamy won out over polygyny, in terms of reliably passing resources to the most genetically related family members, so long as property remained precious, women mostly faithful and men shrewd – that is, they transferred property exclusively to the children of faithful wives (Journal of Evolution Biology, vol 23, p 149). So far, real-world support for this model is anecdotal. Fortunato suggests that the advent and spread of agriculture about 10,000 years ago played an integral role in the emergence of monogamy, since until then owning specific land was largely pointless. Population growth and technological advances allowed farmers to grow crops more effectively, increasing the value of land to future generations. Fortunato also reckons that
“Men and women will tend to form exclusive pairs when land is scarce and its cultivation intense” cultures adopt religions that fit their monogamous or polygamous values, rather than the other way around. “I think the evidence must come from archaeology and changes in marriage systems,” she says. Anthropologist Sarah Blaffer Hrdy at the University of California, Davis, says humans are flexible and opportunistic in other aspects of their lives, “so why shouldn’t their marriage customs reflect this?” Ewen Callaway ■
–Trust me, I’m your wife–
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SOME couples come together for love, others for money, pregnancy or because they’re told to. Whatever the reason, socially prescribed monogamy and its ultimate cultural expression, marriage, may have emerged because of the evolutionary benefits that both offer. By providing men with increased assurance that their wives’ children are their true heirs and women with the confidence that their kids will benefit from a decent inheritance, monogamous marriage is a win-win situation, argue Laura Fortunato at University College London and Marco Archetti at Harvard University. Their view challenges theories of marriage that emphasise the role of religion and the societal benefits of keeping men from fighting over women. Such theories also contend that by giving up multiple wives or partners, men sacrifice their interests for those of the group. “But there are actually some situations where monogamous marriage is a better strategy for men as well as for women,” says Fortunato, who created a mathematical model to find out how such scenarios might work. The emergence of social monogamy – where monogamy is socially enforced and polygamy is forbidden – is a mystery. The Babylonian king Hammurabi prescribed it in his ancient law code around 1790 BC, though the practice probably stretches back thousands of years further. Fortunato distinguishes this from pair bonding and sexual monogamy, which was practiced by early humans and their ancient ancestors. She says the fact that many populations around the world practice some form of polygyny is a clear indication that social monogamy is not inevitable and therefore needs explaining. Fortunato and Archetti conclude that men and women will tend to form socially monogamous pairs when land is scarce and its cultivation
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9 January 2010 | NewScientist | 13
For daily news stories, visit www.NewScientist.com/news
Monogamy and marriage may suit men after all intense, because men would risk diluting the value of their property by dividing it up among too many offspring and heirs. “Having a plot of land that is not big enough to support your family is not clever,” says Fortunato. The pair modelled the behaviour of populations incorporating monogamous and polygynous men over two generations. They made the assumption that women in early agrarian cultures did not provide much in the way of material resources. Monogamy won out over polygyny, in terms of reliably passing resources to the most genetically related family members, so long as property remained precious, women mostly faithful and men shrewd – that is, they transferred property exclusively to the children of faithful wives (Journal of Evolution Biology, vol 23, p 149). So far, real-world support for this model is anecdotal. Fortunato suggests that the advent and spread of agriculture about 10,000 years ago played an integral role in the emergence of monogamy, since until then owning specific land was largely pointless. Population growth and technological advances allowed farmers to grow crops more effectively, increasing the value of land to future generations. Fortunato also reckons that
“Men and women will tend to form exclusive pairs when land is scarce and its cultivation intense” cultures adopt religions that fit their monogamous or polygamous values, rather than the other way around. “I think the evidence must come from archaeology and changes in marriage systems,” she says. Anthropologist Sarah Blaffer Hrdy at the University of California, Davis, says humans are flexible and opportunistic in other aspects of their lives, “so why shouldn’t their marriage customs reflect this?” Ewen Callaway ■
–Trust me, I’m your wife–
Ε#0/.∀#∃#:%Φ&∋∃/∀,%Γ−%ΗΙϑΙΚΛ<%=5∋0#Μ%Β&#% ∃#)/8−%Β#(#.)−7#4%)−+∃∀#.,%−!%Γ ≅
SOME couples come together for love, others for money, pregnancy or because they’re told to. Whatever the reason, socially prescribed monogamy and its ultimate cultural expression, marriage, may have emerged because of the evolutionary benefits that both offer. By providing men with increased assurance that their wives’ children are their true heirs and women with the confidence that their kids will benefit from a decent inheritance, monogamous marriage is a win-win situation, argue Laura Fortunato at University College London and Marco Archetti at Harvard University. Their view challenges theories of marriage that emphasise the role of religion and the societal benefits of keeping men from fighting over women. Such theories also contend that by giving up multiple wives or partners, men sacrifice their interests for those of the group. “But there are actually some situations where monogamous marriage is a better strategy for men as well as for women,” says Fortunato, who created a mathematical model to find out how such scenarios might work. The emergence of social monogamy – where monogamy is socially enforced and polygamy is forbidden – is a mystery. The Babylonian king Hammurabi prescribed it in his ancient law code around 1790 BC, though the practice probably stretches back thousands of years further. Fortunato distinguishes this from pair bonding and sexual monogamy, which was practiced by early humans and their ancient ancestors. She says the fact that many populations around the world practice some form of polygyny is a clear indication that social monogamy is not inevitable and therefore needs explaining. Fortunato and Archetti conclude that men and women will tend to form socially monogamous pairs when land is scarce and its cultivation
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9 January 2010 | NewScientist | 13