Why is polygamy declining? - Matt Ridley

Human monogamy is an enduring puzzle. Among mammals we are the
exception: just 3 per cent of mammals form pair bonds. Our closest
relatives, chimpanzees, bonobos, orangutans and gorillas, are
promiscuous, very promiscuous, territorial-polygamous and
harem-polygamous respectively. Only gibbons among the apes practise
monogamy and they don’t try to do it within a gregarious
species.

Yet we are clearly monogamous by instinct as well as by
tradition. Even in societies that allow polygamy, most people are
in one-partner couples. Free-love communes always, without
exception, collapse because people will insist on falling in love
with particular individuals. This pairing tendency would baffle a
bonobo, where sexual jealousy is apparently unknown.

We are like birds. Penguins and parrots, like us, practise
monogamy within large “urban” colonies. One likely evolutionary
reason is that when it takes two to raise a baby, a male is more
likely to have grandchildren if he puts a lot of effort into one
brood, rather than loving and leaving lots of females. In the
Pleistocene, the long helpless childhood of human beings probably
rewarded diligent fathers with more offspring than callous
philanderers.

You could achieve both if you were cunning. Monogamy and
fidelity are not quite the same thing. Female birds generally like
to stick to one mate to help them bring up the babies, but often —
DNA studies reveal — sneak off and get the babies’ genes supplied
by another, genetically superior male with better plumage or a more
varied song. Successful hunters in human foraging societies tend to
get the same result.

In primates, the threat of infanticide also seems to play a role
in deciding female strategy. In many monkeys and apes, when a new
male takes over a troop, the first thing he does is kill any babies
to bring females back into oestrus quickly. Female gorillas, which
live in small harems, suffer this fate frequently. Chimpanzees
avoid the problem by a system of maximised promiscuity — where
every female does her utmost to mate with every male in the group,
the better to confuse paternity and thereby prevent infanticide by
a new alpha male. In human beings, a horror of step-parents may go
deep.

So at some point in the distant past, we developed the habit of
monogamous pair bonding. Intellectuals, from Rousseau to Engels to
Margaret Mead, have been tempted to speculate about a promiscuous
human past not so long ago, from which marriage crystallised.
Initial encounters with other civilisations based around
agriculture and full of polygamy, such as in Mexico or Tahiti, at
first seemed to confirm this idea, but when in the 20th century
anthropologists began getting to know hunter-gatherers (supposedly
the most primitive level of society), they were startled to find
that monogamous marriage predominated in them. In human beings,
monogamy probably goes back hundreds of thousands if not millions
of years.

Polygamy, in this reading, was mainly an aberration of the last
10,000 years caused by agriculture, which allowed the accumulation
of huge surpluses, which powerful men translated into prodigious
sexual rewards. Herding societies in particular became highly
polygamous, causing people with names such as Attila, Ghenghis or
Tamerlane to conquer other lands so as to supply women to their
sex-starved followers: polygamy and violence tend to go
together.

However, the winners from a polygamous system are not just the
high-status men, but also the low-status women. The peasant girl
who joined the palace harem achieved safety, plentiful food and
access to luxuries, while her brother languished in celibate
poverty. The losers are the low-status men and the high-status
women.

It makes evolutionary sense that high-status males are
attractive to women, because they were in the past likely to be
able to ensure the success of any children they fathered, and that
men are attracted to what Amazonian Indians call “moko dude” women.
(The phrase means “ripe” when used of fruit and, when used of
women: “of the right age, health, genetic quality and
unencumberedness likely to make them capable of producing many
healthy children and grandchildren”, or, more pithily,
“phwoar”.)

So how come the president of France, with the status of a
monarch, cannot even get away with two women at a time? Inch by
inch, from Odysseus to Figaro to Bill Clinton, Western mores have
insisted on monogamy even for the powerful. Clearly the interests
of high-status men and low-status women have lost out to the
interests of high-status women and low-status men.

Interestingly, this trend continues, even as disapproval of
divorce and cohabitation has diminished. Nobody minds much that
François Hollande has never married his three “wives”. Yet that
does not mean that Valérie Trierweiler is prepared to share.

The spread of Christianity, with its teachings on monogamy and
female virtue, could hardly have been better designed to appeal to
poor men, polygamy’s big losers. Democracy, too, seems to insist on
monogamy. Between The Iliad and The
Odyssey (as William Tucker points out in a fine forthcoming
book called Marriage and Civilization), democracy
arrives and there is a sea change from the polygamy of Agamemnon to
the lovelorn fidelity of Odysseus and Penelope.

In a recent paper entitled “The puzzle of
monogamous marriage”, three American anthropologists argue that
this trend is partly explained by competition between societies. To
be economically successful, modern nations had to suppress violence
within themselves.

This was incompatible with rulers grabbing all the best girls:
“In suppressing intrasexual competition and reducing the size of
the pool of unmarried men, normative monogamy reduces crime rates,
including rape, murder, assault, robbery and fraud, as well as
decreasing personal abuses . . . By shifting male efforts from
seeking wives to paternal investment, normative monogamy increases
savings, child investment and economic productivity.”

Which leads to the delightful thought that Mr Hollande’s amorous
proclivities contribute to France’s economic stagnation.