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By David Barash
Jan. 23, 2001 |
or most biologists, the fact that the Rev. Jesse Jackson
had an illegitimate child by one of his staffers is neither
surprising nor a revelation. We've known for a long time that males
from many species tend to be interested in sexual variety,
particularly in having more than one partner.
Consider, for instance, this story: A missionary visited
a Maori village in 19th century New Zealand and there was a feast in
his honor. After the feast, the Maori chief called out, "A woman for
the bishop." Noting the scowl on the prelate's face, the obliging
chief roared again, even louder: "Two women for the
bishop!"
Given the choice, most men would rather have
two women than one (although not necessarily at the same time). And
they'd rather have three than two. As Margaret Mead once pointed
out, monogamy is the most difficult of all marital arrangements. For
some time, biologists have had a good idea why. Men are sperm
makers. Sperm are cheap and easily replaced. Unlike eggs, they do
not require that the guy doing the fertilizing become pregnant, give
birth and then nurse his young.
For women -- and
females of most other species as well -- the situation is quite
different, and, not surprisingly, females tend to be comparison
shoppers, and sexually reticent compared to their male counterparts.
So the interesting thing about the Jackson affair isn't Jackson's
behavior. After all, ever since "The Scarlet Letter" we've been told
that even men of the cloth are still men, under the cloth. Rather,
it's why Karin Stanford, his paramour, went along.
And
here, biologists have finally begun to catch up with common sense.
Women, too, have extramarital affairs, and these need not be limited
to an unmarried woman having sex with a married man, as with
Stanford and Jackson (though it has been reported that she had a
boyfriend at the time of her affair with Jackson), or Monica
Lewinsky and President Clinton, or Donna Rice and Gary Hart, or ...
There are plenty of Madame Bovarys and Anna Kareninas. Adultery is a
favorite human topic, in more ways than one.
Enter DNA
fingerprinting, and not just for Monica's fabled blue dress. This
laboratory technique isn't only useful for identifying unknown
soldiers or freeing the falsely convicted. In recent years, it has
surprised biologists with a whole new world of screwing around among
animals, with likely implications for that troubled animal, Homo
sapiens, the one that tries so hard to be monogamous and finds it so
terribly difficult.
When we examine
the genes of baby birds, even those species long thought to be
absolute paragons of monogamous fidelity, we find that 10, 20,
sometimes 30 percent of the offspring are not genetically connected
to the socially identified father. Social monogamy (what biologists
still call, somewhat quaintly, a pair bond) is not the same as
sexual monogamy. Several decades ago experimenters vasectomized
redwinged blackbirds in the hope of controlling their numbers. But
many females, ostensibly mated to only those vasectomized males,
laid eggs that hatched! Something funny was going on. But only now,
with the accumulation of literally dozens of research studies using
DNA data, do we know for sure: Females, even females in species long
thought to be sexually faithful, often are not.
In the
movie "Heartburn," based on Nora Ephron's barely fictional account
of her marriage to the philandering Carl Bernstein, the heroine
complains about his infidelity to her father, who responds: You want
monogamy? Marry a swan.
Now we are
discovering that even swans aren't monogamous!
Why
not?
Again, there is no great mystery about why males
often make themselves available for extra-pair copulations, or EPCs.
The evolutionary payoff in fathering additional children can easily
make up for the costs, assuming that some EPCs result in EPFs
(extra-pair fertilizations), and the cuckolded male doesn't find out
and take violent revenge. Of course, an EPCing male runs other risks
as well, such as possible desertion by his own mate, or the chance
that while he is trying to seduce someone else's female, that same
someone else -- or another -- is making time with his own! But the
bigger question, yet to be resolved, is why a female, especially one
already mated, should seek EPCs. The costs of discovery can be great
(notably violence from her mate or abandonment), whereas the
benefits are obscure. Yet seek them they clearly do.
We
now know that in numerous species, females go prospecting on the
territories of adjacent males, especially when their own mate is off
at work, foraging or patrolling the neighborhood perhaps looking for
his own EPCs. Sometimes, to be sure, females are coerced into
mating, but it is clear that even mated females are often sexual
adventurers in their own right, actively soliciting EPCs from males
who are not theirs.
It appears that there is no
one-size-fits-all explanation for female infidelity among animals.
Here are a few; each is valid for at least one species. Some might
also shed light on the Madame Bovarys (or Karin Stanfords) among us:
For an unmated female, reproducing is generally better than not,
even if -- when monogamy is the public norm -- such a reproducing
female has to be a single mother. An EPC can provide a female,
whether socially mated or not, with fertility insurance, just in
case her current partner doesn't produce enough sperm. She might
also increase the genetic variety of her offspring by bearing the
children of more than one male. An especially important
consideration seems to be the genetic quality of her additional
lover(s). It is very rare, for example, for already mated females to
copulate on the sly with males who are socially subordinate to their
current mates. Among those animals in which males sport secondary
sexual traits that indicate unusual health and that females find
sexually stimulating (bright plumage, enlarged feathers, especially
attractive body features of other sorts), females will often mate
with those fortunate males who are unusually good specimens,
particularly if their own mates are less than prepossessing in this
regard.
Barn swallows, for example, have deeply forked
tails. The deeper the fork, the greater the appeal to females.
Female barn swallows paired with males whose tails are only so-so
tend to sneak copulations with neighboring males whose tail forkings
have been artificially enhanced by researchers. Among the European
birds known as yellowhammers, older males are brighter yellow; their
enhanced brightness indicates that they have good longevity genes
and also makes them more attractive to female yellowhammers,
especially those mated to males whose yellow is less
prepossessing.
A female can also gain immediate
personal payoffs from successful EPCs. In some cases, she may be
permitted to forage on territory maintained by a male, provided that
she first copulates with him. When several adults cooperate in
provisioning the young, males often adjust their parental efforts
depending on their sexual access to the female: more fucking, more
feeding. By inducing more than one male to have an interest -- or
think he has an interest -- in the outcome of a bout of sex, cagey
females reduce their own parenting duties. There are some species,
including lions and a number of primates, in which adult males are
likely to kill young they have not fathered. It has been suggested
that in such cases females may have evolved to be sexually receptive
to more than one male as a way of reducing the risk eventually faced
by their offspring.
The evidence is now undeniable:
Monogamy among animals is more myth than reality. What about human
beings?
Here, too, there is no doubt. We are not naturally
monogamous. Anthropologists report that the overwhelming majority of
human societies either are polygynous or were polygynous prior to
the cultural homogenization of recent decades. They also suggest
that individuals are mildly polygynous, having evolved in a system
in which one man maintains a harem. This, incidentally, helps
explain the persistent sex appeal of successful, dominant men,
whether they be high-ranking politicians, movie or rock stars,
glamorous athletes or wealthy entrepreneurs. Power, as Henry
Kissinger once noted, is the ultimate aphrodisiac. At the same time,
women can and do seek additional sex partners, even when already
mated. Thus, monogamy -- when it occurs -- is shot through with
EPCs, not just among birds. Otherwise, why would men have such a
powerfully developed tendency for sexual jealousy?
Why, then,
does monogamy occur at all? Maybe it's like Winston Churchill's
observation that democracy is the worst possible form of government
except for all the others that have been tried. At least monogamy is
a great equalizer (in theory). It assures that in a species with
equal numbers of males and females, no one need be left out. But at
the same time, it cannot and does not prevent individuals of either
sex from looking elsewhere.
Imagine a society of rigid
social monogamy in which women nonetheless seek to be inseminated by
the best possible males. Such males are rare, and likely to be
already taken. So women might well adopt a kind of ratcheting-up
tactic, in which they pair with the best man they can get, and
thereby obtain his child-rearing assistance as well as whatever
additional material resources he can provide, while also making
themselves available for men further up in the hierarchy -- probably
charismatic men like Jesse Jackson.
Such a motivation
need not be conscious. In fact, a woman who has an affair with an
attractive married man may intentionally avoid becoming pregnant.
The point is that part of the underlying sexual motivation for the
affair likely derives from these factors.
When
right-wing Christian moralists worry that family values are under
assault, they don't know how right they are! Monogamy, perhaps the
poster child of family values, is under profound assault -- but not
from any progressive, gay or feminist agenda. Rather, nature is the
culprit.
We are imbued by Western culture with
monogamous ideals. Yet, like other living things, we're often
compelled by our biology to depart from monogamy. Neither men nor
women are the primordial purveyors of extra-pair copulations, yet
EPCs have dogged and delighted human beings throughout recorded
history, and doubtless before. It takes two to do the EPC tango. And
human beings love to dance.
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About the writer
David P. Barash is professor of psychology
at the University of Washington in Seattle. His most recent book,
"The Myth of Monogamy," coauthored with his wife, Judith Eve Lipton,
M.D., is to be published this
spring.