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- NEW YORK - In Charles Dickens' A Tale of Two Cities, Sydney
Carton goes to the guillotine to spare the lover of the woman he loves.
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- "It is a far, far better thing that
I do, than I have ever done," reflects the self-sacrificing Carton
on the scaffolding.
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- Such acts of human altruism " found
both in fiction and real life " defy the rules of Darwinism. By giving
his life, Carton loses any chance for continuing his genetic line. It's
behavior that has stumped biologists for centuries and inspired them to
scour the animal kingdom for signs of similar behavior among other species.
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- Some say they have looked too hard.
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- "Many of my colleagues have really
wanted to believe that animals are nice to each other," said David
Stephens, a biologist at the University of Minnesota and one of the leading
skeptics of animal altruism. "But often behavior that appears to be
animal generosity turns out to be more selfish when you consider the economics
more closely."
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- Looking Out for Number One
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- Most recently, scrutiny has been placed
on the guarding behavior of the fuzzy, burrowing meerkat in South Africa.
Scientists have long believed that individual meerkats act bravely and
selflessly when they take turns watching out for predators while their
peers forage for insects. When a guarding meerkat spies a predator it yelps
a warning call and the entire group then darts for cover in the nearest
burrows.
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- Not only do the sentinels sacrifice the
chance to feed in order to guard the safety of the group, scientists also
believed the creatures place themselves at higher risk by exposing themselves
at high perches.
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- Not so, says Cambridge University's Tim
Clutton-Brock. After more than 2,000 hours of observing five packs of meerkats,
Clutton-Brock's group reported they did not see a single sentinel attacked
or killed by a predator. That led them to conclude in the current issue
of the journal Science, that individual meerkats that stand guard are actually
looking out for their own skins.
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- "We found because these individuals
were the first to see the predator, they were also the first ones to get
below ground," Clutton-Brock said.
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- The behavior also couldn't be explained
by kin selection " a common explanation of animal altruism that suggests
animals sometimes place themselves at risk to protect their close relatives
" and therefore their genes. Clutton-Brock found that everyone in
a group, whether relatives or not, takes turns standing guard. What's more,
he learned that a meerkat was only likely to stand guard if it had already
fed enough to fill its belly.
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- The meerkat study is only the latest
in a string of newly disproved cases of animal altruism. And Stephens
argues the reason is clear. "Animals seem to act in their own self
interest," he said. "No one should be surprised by that."
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- Strength in Numbers
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- One of Stephens' favorite examples are
ravens who call their mates when they find a carcass. Scientists previously
assumed these individuals were simply being generous. But a biologist at
the University of Vermont recently pointed out that ravens only call their
peers when the carcass they find is in another group's territory. By calling
in their mates, the ravens beef up their defense against rival birds.
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- Swallows also demonstrate seemingly altruistic
behavior when they alert other swallows about a newly-found swarm of insects.
While it may appear the individual swallow is sharing its find by recruiting
others to feed on the swarm, it turns out the bird is actually improving
its chances of catching some dinner. Studies show the birds are more effective
at tracking an insect swarm and nipping bugs out of the air when chasing
them in a group.
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- "It's clearly not as simple as many
imagined it was ten years ago," said Jerry Wilkinson, an animal behaviorist
at the University of Maryland. "Now we are being forced to find alternative
ways to explain these cooperative cases that don't fall neatly into kinship
or reciprocal altruism."
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- Scratch My Back, I'll Scratch Yours
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- Still, there remain incredible cases
of what biologists call reciprocal altruism, or you-scratch-my-back, I'll-scratch-yours
behavior. While animals in these scenarios stand to gain in the long run
by their behavior, they also sacrifice much personal fitness to help others
in the meantime.
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- Male species of the tropical long-tailed
manakin, for example, often team up in musical duos to serenade single
females with elaborate melodies. Typically, one of the males never manages
to mate with the female, but serves as the alpha male's celibate, musical
sidekick for up to seven years.
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- The humble sidekick is not rewarded until
the dominant " and usually older " alpha male dies and the younger
bird takes over its territory. Among manakins, acquiring territory also
mean acquiring mates, and the sidekick's extended abstinence finally comes
to an end.
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- All For One
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- Perhaps most impressive among the kinds
of animal altruism is behavior which hinders the individual, but advances
the welfare of an entire group. Wilkinson has observed female vampire bats
sharing blood with unrelated females in their roosts. Similarly, individual
female desert ants bring back food to share with unrelated ants in their
colony. Even meerkats, while they may act selfishly as sentries, demonstrate
group altruism when females stay behind in burrows to baby-sit unrelated
infants from their colonies.
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- Stephens believes further scrutiny into
these cases may reveal selfish motives behind the behavior, but others
claim there can be selfish reasons behind promoting a group.
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- "Natural selection can operate at
the individual and group level," argued Lee Dugatkin, author of the
new book, Cheating Monkeys and Citizen Bees. "Groups that have individuals
who are willing to take on tasks that incur costs, do better than groups
that do not have those individuals."
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- In fact, many have used group altruism
to explain why humans are often so good to each other. By cooperating,
some argue, people are only ensuring their own best interests as members
of a society.
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- But while the group theory may explain
soldiers sacrificing their lives to defend their country, or societies
supporting a welfare system, it does not explain why Sydney Carton would
lose his head for an unrequited love. Still, Carton met his death feeling
noble in spirit. And, in some rare cases among emotionally-complex humans,
that may be enough.
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- "People say they do things because
it makes them 'feel good,'" said Dugatkin. "Is that a valid reason
biologically? Science hasn't yet figured that one out."
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