- WASHINGTON (AP) --Only about 10 percent of the birds and mammals that seem
to mate for life are actually faithful to their partners, according to
studies that suggest infidelity may be nature's way. Blame it on biology,
say the experts.
-
- Animal parents may gain important benefits
for the future of their species by a little hanky-panky, research shows.
A female may stray to pick up the best genes possible for her offspring,
say the experts, while males may be driven by an impulse to father as many
and as often as possible.
-
- New studies using genetic testing techniques
show that even the most apparently devoted of partners often mate around,
visiting nearby nests or dens or clans to enjoy the sexual company of strangers.
Birds do it, apes do it, and, of course, so do some people, researchers
say in reports being published Friday in the journal Science.
-
- "True monogamy actually is rare,"
said Stephen T. Emlen, an expert on evolutionary behavior at Cornell University.
He describes a great difference between "social monogamy," where
mating pairs bond and work together to raise their young, and "genetic
monogamy," where parents are faithful sex partners.
-
- Social monogamy is relatively common,
but genetic monogamy is the exception rather than the rule, the studies
report.
-
- Emlen said among the primates, the animal
order that includes humans, only two monkeys, the marmoset and the tamarin,
are truly monogamous. All the rest, monkeys, apes and people, often mate
outside their partnerships.
-
- Most primates, in fact, make no pretense
of faithfully bonding for life, and it is difficult to know for sure that
males actually know which of the young in the clan are their children,
he said.
-
- That may even be true for humans. An
Oregon study suggested that about 10 percent of children were not sired
by the male partner of the parental pair.
-
- Among the birds, faithful sex partnership
has been thought for years to be widespread. Some species, such as the
eastern bluebird, gained reputations as shining examples of devotion. Male
and female partners work together closely to build nests, incubate eggs,
then feed and raise their young.
-
- The truth is, bluebirds have a sex life
that rivals a television soap opera.
-
- Patricia Adair Gowarty, a behavioral
ecologist at the University of Georgia, has found that 15 percent to 20
percent of chicks cared for by a bonded pair of bluebirds were not fathered
by the male. Gowarty reports that of 180 socially monogamous species, only
about 10 percent are sexually faithful.
-
- Emlen said female birds and mammals that
seek sexual partners outside their partnership may be pushed by the biological
drive to produce the best possible children.
-
- "One of the patterns is that females
seek males of high status and high quality," he said. "By doing
so, they are able to produce offspring of higher quality that will be able
to do better and survive better. There is a lot of research going on to
see if these ideas are correct."
-
- Several studies have shown that "females
socially bonded with very high quality males do not have copulations outside
the pair bonds," said Emlen. In effect, such females believe they
already have the best, so why look for better?
-
- Males, some researchers suggest, are
biologically driven to stray by the desire to spread their genes into as
many future generations as possible. Among some species, such as lions,
mountain gorillas and grizzly bears, this drive to influence the future
genetically leads dominant males to kill and even eat the young of competing
males.
-
- Impulses that drive humans to seek sex
outside their partnership are far more complex. Emlen cautioned against
drawing "simplistic" conclusions about human biology from the
studies of animals.
-
- Researchers generally believe that monogamy
originated among species whose young survived best when raised by a bonded
pair. This may have been what led to the rise of monogamy among people,
since human children take so long to mature.
-
- One of the most sexually faithful of
animals is the California mouse, Science reports. These golden brown rodents
invariably pair up for life. Genetic testing has shown that both male and
female partners ignore sexual temptations outside the nest.
-
- David Gubernick of the University of
California, Davis, reports in Science that one reason for this fidelity
is that both parents are required to keep newborn pups alive through their
birth winter.
-
- The parents must take turns cuddling
and warming the young, Gubernick said, and if the male leaves, the mother
will kill or abandon the young.
|
