mixed survivors imbued with opportunities that would never have come
their way in a world of purposeful wedging.
We may be indifferent to most of these quirky shifts that eliminated
highly successful groups of the moment and passed a potential torch to
unheralded creatures in the wings--groups that fortuitously held a
winning ticket purchased for a different reason long ago in other circumstances.
Few people lament the loss of ammonites, so long as we still have nautiloids.
(In fact, I have proof that very few people have ever heard of nautiloids
at all, and therefore don't give a damn in the fullest sense. Last month,
the World Weekly News, king of the shopping-mall tabloids, published--with
absolutely shameless faith in our ignorance--an unretouched photograph
of a chambered nautilus labeled as a giant monster now on an earthbound
path from Mars and scheduled to arrive well before the millennium.) Who
cares (who even knows the names) that all crinoids are now articulates
and not inadunates, that reef corals are now seleractinians and not tabulates?
Well, you may choose to disdain the details of marine invertebrate life,
but you cannot be indifferent to the closest application of the different
rules model--the death of dinosaurs and the resultant possibility
of human evolution.
You may react to this essay by denying its claim to be conceptually
troubling in the light of traditional hopes. You might say, after all,
that the different rules model only validates a cliché so old and
widely appreciated that it became the motto of such straight arrow groups
as the Boy Scouts and such jokers as Sancho Panza--"forewarned
is forearmed; to be prepared is half the victory." Yes, "be
prepared"; flexibility is a virtue. If you can keep a whole deck
up your sleeve, you will surely have a useful card for any circumstance.
But the cruel dilemma, the Catch-22, of evolution lies in recognizing
that a species cannot consciously or actively prepare for future contingencies.
It can only evolve for current benefits and deliver its future fate to
the wheel of fortune. Round and round she goes, and where she stops....
No, it's even worse than that. For the wheel never stops, but only speeds
and slows, tacks and turns, bringing us along on a grand chase that has
somehow produced "from so simple a beginning," to quote the
final words of Darwin's great book, "endless forms most beautiful
and most wonderful."
Stephen Jay Gould teaches biology, geology, and the history of science
at Harvard University.
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