HOW BEAUTY IS MAKING SCIENTISTS RETHINK EVOLUTION
The extravagant splendor of the animal kingdom can’t be explained by natural selection alone — so how did it come to be?
By Ferris Jabr
"male
flame bowerbird is a creature of incandescent beauty. The hue of his
plumage transitions seamlessly from molten red to sunshine yellow. But
that radiance is not enough to attract a mate. When males of most
bowerbird species are ready to begin courting, they set about building
the structure for which they are named: an assemblage of twigs shaped
into a spire, corridor or hut. They decorate their bowers with scores of
colorful objects, like flowers, berries, snail shells or, if they are
near an urban area, bottle caps and plastic cutlery. Some bowerbirds
even arrange the items in their collection from smallest to largest,
forming a walkway that makes themselves and their trinkets all the more
striking to a female — an optical illusion known as forced perspective
that humans did not perfect until the 15th century.
Yet
even this remarkable exhibition is not sufficient to satisfy a female
flame bowerbird. Should a female show initial interest, the male must
react immediately. Staring at the female, his pupils swelling and
shrinking like a heartbeat, he begins a dance best described as
psychotically sultry. He bobs, flutters, puffs his chest. He crouches
low and rises slowly, brandishing one wing in front of his head like a
magician’s cape. Suddenly his whole body convulses like a windup alarm
clock. If the female approves, she will copulate with him for two or
three seconds. They will never meet again.
The
bowerbird defies traditional assumptions about animal behavior. Here is
a creature that spends hours meticulously curating a cabinet of wonder,
grouping his treasures by color and likeness. Here is a creature that
single-beakedly builds something far more sophisticated than many
celebrated examples of animal toolmaking; the stripped twigs that
chimpanzees use to fish termites from their mounds pale in comparison.
The bowerbird’s bower, as at least one scientist has argued, is nothing
less than art. When you consider every element of his courtship — the
costumes, dance and sculpture — it evokes a concept beloved by the
German composer Richard Wagner: Gesamtkunstwerk, a total work of art, one that blends many different forms and stimulates all the senses.
This
extravagance is also an affront to the rules of natural selection.
Adaptations are meant to be useful — that’s the whole point — and the
most successful creatures should be the ones best adapted to their
particular environments. So what is the evolutionary justification for
the bowerbird’s ostentatious display? Not only do the bowerbird’s
colorful feathers and elaborate constructions lack obvious value outside
courtship, but they also hinder his survival and general well-being,
draining precious calories and making him much more noticeable to
predators...."
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