Social Construction of Behaviour
Group A: Polygamy &
Polyandry
With gay marriage now legal nationwide, many (like William Baude in the New York Times)
are now wondering if legalised polygamy may be next, and some (like Fredrik Deboer
in Politico) are suggesting that it should be. Should it? As Baude points out in his
op-ed, polygamy should remain illegal because it would increase gender inequality and
social instability:
‘Judge Richard A. Posner of the United States Court of Appeals for the Seventh Circuit
rejected a right to plural marriage because it would lead to gender imbalances if ‘the five
wealthiest men have a total of 50 wives.’ Similarly, the same-sex marriage advocate
Jonathan Rauch has argued that polygamy allows ‘high-status men to hoard wives’ and
destabilise society."
Note that Posner and Rauch are assuming that the most common type of legal polygamous
marriage would be one husband with multiple wives (polygyny), as opposed to one wife
with multiple husbands (polyandry). They’re also not considering more complex types of
plural marriage (e.g. multi-male multi-female), or homosexual plural marriage. Is it safe to
assume that most polygamous heterosexual marriages would indeed involve one husband
with multiple wives? Probably, as this chimes with the evidence about how people tend to
mate cross-culturally. Historically, polygamy was permitted in the vast majority of cultures; in
these cultures, polygyny was far more common than polyandry. Still, even within cultures
that permit polygyny, it is much less common than monogamous marriage, in part because it
can be difficult to attract more than one spouse, even if you'd want to.
Why is polygyny more common than other forms of plural marriage? Because of how
humans are psychologically adapted for mating. The evolutionary reproductive benefits of
having more than one spouse were higher for men than women. In 1972, biologist Robert
Trivers outlined the foundational reason for this: For men more than women, reproductive
success is limited by the number of mates. A man with many wives can produce many
children per nine months, whereas a woman can usually produce only one, whether she has
one husband or 100. Females certainly may obtain other kinds of reproductive benefits (like
resources for their own children) from mating with multiple males, but these benefits are
less straightforward than actual additional offspring. Relatedly, the reproductive costs of
having more than one spouse are lower for women than for men. If a man's wife
becomes pregnant by his co-husband, he'll have to wait a long time—nine months plus an
inter-birth interval that in hunter-gatherer societies averages 3.25 years for his turn to
reproduce. If a woman's husband impregnates her co-wife, he can immediately impregnate
her, too. She may suffer other reproductive costs from having to share a husband (like
Group A: Polygamy &
Polyandry
With gay marriage now legal nationwide, many (like William Baude in the New York Times)
are now wondering if legalised polygamy may be next, and some (like Fredrik Deboer
in Politico) are suggesting that it should be. Should it? As Baude points out in his
op-ed, polygamy should remain illegal because it would increase gender inequality and
social instability:
‘Judge Richard A. Posner of the United States Court of Appeals for the Seventh Circuit
rejected a right to plural marriage because it would lead to gender imbalances if ‘the five
wealthiest men have a total of 50 wives.’ Similarly, the same-sex marriage advocate
Jonathan Rauch has argued that polygamy allows ‘high-status men to hoard wives’ and
destabilise society."
Note that Posner and Rauch are assuming that the most common type of legal polygamous
marriage would be one husband with multiple wives (polygyny), as opposed to one wife
with multiple husbands (polyandry). They’re also not considering more complex types of
plural marriage (e.g. multi-male multi-female), or homosexual plural marriage. Is it safe to
assume that most polygamous heterosexual marriages would indeed involve one husband
with multiple wives? Probably, as this chimes with the evidence about how people tend to
mate cross-culturally. Historically, polygamy was permitted in the vast majority of cultures; in
these cultures, polygyny was far more common than polyandry. Still, even within cultures
that permit polygyny, it is much less common than monogamous marriage, in part because it
can be difficult to attract more than one spouse, even if you'd want to.
Why is polygyny more common than other forms of plural marriage? Because of how
humans are psychologically adapted for mating. The evolutionary reproductive benefits of
having more than one spouse were higher for men than women. In 1972, biologist Robert
Trivers outlined the foundational reason for this: For men more than women, reproductive
success is limited by the number of mates. A man with many wives can produce many
children per nine months, whereas a woman can usually produce only one, whether she has
one husband or 100. Females certainly may obtain other kinds of reproductive benefits (like
resources for their own children) from mating with multiple males, but these benefits are
less straightforward than actual additional offspring. Relatedly, the reproductive costs of
having more than one spouse are lower for women than for men. If a man's wife
becomes pregnant by his co-husband, he'll have to wait a long time—nine months plus an
inter-birth interval that in hunter-gatherer societies averages 3.25 years for his turn to
reproduce. If a woman's husband impregnates her co-wife, he can immediately impregnate
her, too. She may suffer other reproductive costs from having to share a husband (like
