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'Why We Do It': Sex and the Single Cell
By ROBERT J.
RICHARDS
Published: June
20, 2004
 IRDS do it. Sullen teenagers sneak
around to do it. Even biologists think about doing it, though it puzzles
them. The problem is that sex has its costs. If women reproduced by giving
birth asexually, like aphids, to exact genetic duplicates, any beneficial
mutations occurring in the mother would pass to all of her offspring. But
in sexual reproduction, since newborns share but half the mother's genes,
only half of her children would probably reap the genetic advantage. Sex
seems a bad idea, evolutionarily speaking. It's a puzzle, then, why our
ancestors -- those one-celled creatures thriving in ancient seas -- ever
bothered to try it.
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In
''Why We Do It,'' the eminent paleontologist Niles Eldredge,
of the American Museum of Natural History, takes up the
problem. His goal in this accessible book, however, is not so much to solve
the puzzle as to discover the purpose of life, which for him is not sex. He
takes his stand against scientists who adhere to the theory of the selfish
gene and, more generally, the doctrines of sociobiology and evolutionary
psychology. They (prominently, Richard Dawkins and E. O. Wilson) maintain
that most of life's activities are ultimately aimed at procuring a sex
partner for the propagation of one's genes.
Like
Darwin, with whom he declares his allegiance,
Eldredge pursues a quasi-teleological
investigation of the main objective of life. In ''The Origin of Species,''
Darwin proposed that the struggle for existence, which involved much
suffering and death, yielded the most exalted object we were capable of
conceiving -- namely, ''the production of the higher animals.'' Eldredge, though, regards the purpose of life to be
neither the generation of the higher animals nor the spread of one's genes;
rather, it's economics. This may sound like an echo from the halls of the University of Chicago -- and Eldredge
does slide in that direction. But he initially suggests a more
comprehensive meaning for economics.
He
defines economics as energy transfer and flow throughout an ecological
system. On African savannas elephants consume huge quantities of grasses,
absorbing the energy to carry on their physiological processes, including
the production of large piles of dung, which dung beetles reprocess into
soil nutrients, which feed plants on which elephants graze. All organisms
live in intersecting ecological systems through which energy flows and is
transformed. Eldredge glides from this abstract
notion to a somewhat more concrete meaning of economics when he declares that in Darwin's conception, the struggle for
existence indicated the effort to secure energy resources -- food -- not
the attempt to produce offspring. (Contemporary evolutionists frequently
recruit Darwin to their side and, often as not,
bend him into unlikely positions.) Eldredge does
allow that with most animals, the effort to get food ultimately serves the
aim of reproduction; but with human beings, he contends, sex has been shorn
of its baby-making function.
He
describes those mundane varieties of human sexuality that have scant
reproductive outcome: masturbation, homosexuality, contraceptive coitus,
pornography, rape, sex slavery and theme parks of the teenage imagination.
He considers these now to be the predominant modes of human sexual
activity. Moreover, we have evidence that economics controls sexual
reproduction, not the reverse. The rich, demographers have shown, are
different from the rest of us: they generally have fewer offspring. Such examples
demonstrate, Eldredge
believes, that our getting and spending lay waste to the sociobiological assumption that all human activities
have the ultimate evolutionary goal of spreading successful genes to the
next generation. For him sex is merely a fraction of the currency flow
consolidating a community.
If
sex no longer has the primary purpose of spreading successful genes and
thus furthering evolution of the species, what is it good for? Eldredge says the real reason for sex is its function
in producing stable species that are more resistant to extinction than
colonies of simple, asexual organisms. His logic, never explicitly stated,
seems to be that when the superficial procreative function of sex is
conceptually demoted, the real significance of sex will be revealed. He
sees bonobo chimpanzees, our closest living
relatives, as illustrating its stabilizing and unifying power. Their
rampant sexual gymnastics, with both the same and different sexes, and with
astounding frequency, do seem to effect social bonding
throughout a local community. Yet comparable behavior in human communities,
as many utopian experiments testify, would quite likely have the opposite
result: disintegration. Also, Eldredge offers no evidence that sexual
species are more resistant to extinction than bacteria -- after all,
blue-green algae have been around since the beginning. Even if sexual
behavior has become partly decoupled from its procreative function --
though only in human societies -- this development alone hardly supplies a
reason to believe it has deeper, species-unifying features.
THE
hidden lever by which Eldredge attempts to lift
his argument to plausibility is the highly controverted
notion of species selection, which is natural selection applied at the
species level. For this argument to work, a species must itself have the
character of an individual, as opposed to that of a mere collection of
individuals. And the trait selected -- sexuality -- would have to benefit
that individual (in this case a species) in competition with other individual
species lacking the trait. But do sexual species compete with bacteria for
resources or to produce more daughter species? Only the speculative
imagination might hazard an answer to this question, and Eldredge doesn't even try. And while the frenzied flow
of energy coursing through New York clubs might suggest otherwise,
neither our species nor any other sexual species seems to possess the
structure of a coherently unified individual, so that selection could act
upon it. A more vigorous and explicit metaphysics would be needed to make
the idea of species as unit of selection spring to life.
Contemporary
science has cast aside many veils from the sexual
dance, but a few yet remain to sustain the mystery.
Robert
J. Richards, a professor of the history and philosophy of science at the
University of Chicago, is the author of ''The Romantic Conception of Life:
Science and Philosophy in the Age of Goethe.''
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