742 MCGRAW-HILL’S SAT
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but devastating events can reset the evolution-
ary timetable and destroy complex life while
sparing simpler life forms. Such discoveries
suggest that the conditions allowing the rise
and existence of complex life are far more rig-
orous that are those for life’s formation. On
some planets, then, life might arise and ani-
mals eventually evolve—only to be soon
destroyed by a global catastrophe.PASSAGE 2
It is always shaky when we generalize from
experiments with a sample size of one. So we
have to be a bit cautious when we fill the cos-
mos with creatures based on the time scales
of Earth history (it happened so fast here,
therefore it must be easy) and the resourceful-
ness of Earth life (they are everywhere where
there is water). This is one history, and one
example of life.
I am not convinced that the Earth’s
carbon-in-water example is the only way for
the universe to solve the life riddle. I am not
talking about silicon, which is a bad idea, but
systems of chemical complexity that we have
not thought of, which may not manifest them-
selves at room temperature in our oxygen at-
mosphere. The universe is constantly more
clever than we are, and we learn about com-
plex phenomena, like life, more through ex-
ploration than by theorizing and modeling.
I think there are probably forms of life out
there which use different chemical bases than
we, and which we will know about only when
we find them, or when they find us.
An obvious rejoinder to this is, “But no one
has invented another system that works as
well as carbon-in-water.” That is true. But to
this I would answer, “We did not invent
carbon-in-water!” We discovered it. I don’t
believe that we are clever enough to have
thought of life based on nucleic acids and pro-
teins if we hadn’t had this example handed to
us. This makes me wonder what else the uni-
verse might be using for its refined, evolving
complexity elsewhere, in other conditions that
seem hostile to life as we know it.
I think it is a mistake to look at the many
specific peculiarities of Earth’s biosphere and
how unlikely such a combination of charac-
teristics seems, and to then conclude thatcomplex life is rare. This argument can only
be used to justify the conclusion that planets
exactly like Earth, with life exactly like Earth-
life, are rare.
My cat, “Wookie” survived life as a near
starving alley cat and wound up as a beloved
house cat through an unlikely series of bio-
graphical accidents, which I won’t take up
space describing but, trust me, given all of the
incredible things that had to happen in just
the right way, it is much more likely that there
would be no Wookie than Wookie. From this I
do not conclude that there are no other cats
(The Rare Cat Hypothesis), only that there are
no other cats exactly like Wookie.
Life has evolved together with the Earth. Life
is opportunistic. The biosphere has taken ad-
vantage of the myriad of strange idiosyncrasies
that our planet has to offer. So it is easy to look
at our biosphere and conclude that this is the
best of all possible worlds; that only on such a
world could complex life evolve. My bet is that
many other worlds, with their own peculiar
characteristics and histories, co-evolve their
own biospheres. The complex creatures on
those worlds, upon first developing intelligence
and science, would observe how incredibly well
adapted life is to the many unique features of
their home world. They might naively assume
that these qualities, very different from Earth’s,
are the only ones that can breed complexity.- The discussion of the Drake equation in the first
paragraph indicates that the author holds which
of the following assumptions?
(A) The Drake equations are too complicated
for most people to understand.
(B) Mathematical formulas can influence
public opinion.
(C) Sagan did not substantially alter the
Drake equation.
(D) Mathematics tend to obscure scientific
exploration.
(E) Drake was not as reputable a scientist as
Sagan was.