Darwin's Dangerous Idea - Evolution and the Meaning of Life

214 BIOLOGY IS ENGINEERING Artifact Hermeneutics, or Reverse Engineering 215
pretty-good version of the machine on hand, either an earlier model, or a
"mockup" or scale model that we have built. We examine it carefully, and try
out various alterations: "If we just bend this jaw up a little bit like so, and
move this zipper-bit over a tad like so, it would work even better." But that is
not the way evolution works. This comes out especially clearly at the
molecular level. A particular molecule is the shape it is, and won't tolerate
much bending or reshaping. What evolution has to do when it improves
molecular design is to make another molecule—one that is almost like the
one that doesn't work very well—and simply discard the old one.
People are advised never to switch horses in midstream, but evolution
always switches horses. It can't fix anything, except by selecting and discarding.
So in every evolutionary process—and hence in every true evolutionary
explanation—there is always a faint but disconcerting odor of
something dicey. I will call this phenomenon bait-and-switch, after the shady
practice of attracting customers by advertising something at a bargain price
and then, when you've lured them to the store, trying to sell them a substitute.
Unlike that practice, evolutionary bait-and-switch is not really nefarious; it
just seems to be, because it doesn't explain what at first you thought you
wanted explained. It subtly changes the topic.
We saw the ominous shadow of bait-and-switch in its purest form in
chapter 2, in the weird wager that I can produce somebody who wins ten
consecutive coin-tosses without a loss. I don't know in advance who that
somebody is going to be; I just know that the mantle will pass—has to pass,
as a matter of algorithmic necessity—to somebody or other so long as I
execute the algorithm. If you overlook this possibility and take my sucker bet,
it is because you are too used to the human practice of tracking individuals
and building projects around identified individuals and their future prospects.
And if the winner of the tournament thinks there has to be an explanation of
why he won, he is mistaken: there is no reason at all why he won; there is
only a very good reason why somebody won. But, being human, the winner
will no doubt think there ought to be a reason why he won: "If your
'evolutionary account' can't explain it, then you are leaving out something
important!" To which the evolutionist must calmly reply: "Sir, I know that is
what you came in here wanting, but let me try to interest you in something a
little more affordable, a little less presumptuous, a little more defensible."
Has it ever occurred to you how lucky you are to be alive? More than 99
percent of all the creatures that have ever lived have died without progeny,
but not a single one of your ancestors falls into that group! What a royal
lineage of winners you come from! (Of course, the same thing is true of every
barnacle, every blade of grass, every housefly.) But it's even eerier than that.
We have learned, have we not, that evolution works by weeding out the unfit?
Thanks to their design defects, these losers have a "pathetic but praiseworthy
tendency to die before reproducing their kind" (Quine
1969, p. 126). This is the very engine of Darwinian evolution. If, however,
we look back with tunnel vision at your family tree, we will find many
different organisms, with a wide variety of strengths and weaknesses, but,
curiously enough, their weaknesses never led a single one of them to a
premature demise! So it looks from this angle as if evolution can't explain
even a single feature that you inherited from your ancestors! Suppose we
look back at the fan-out of your ancestors. Notice first that eventually it stops
fanning out and begins to double up; you share multiple ancestors with
everybody else alive today, and are multiply related to many of your own
ancestors. When we look at the whole tree over time, we see that the later,
more recent ancestors have improvements that the earlier ones lacked, but all
the crucial events—all the selection events—happen offstage: not a single
one of your ancestors, all the way back to the bacteria, succumbed to
predation before reproducing, or lost out to the competition for a mate.
Of course, evolution does explain all the features that you inherited from
your ancestors, but not by explaining why you are lucky enough to have
them. It explains why today's winners have the features they do, but not why
these individuals have the features they do. 17 Consider: You order a new car,
and specify that it be green. On the appointed day, you go to the dealership
and there it sits, green and new. Which is the right question to ask: "Why is
this car green?" or "Why is this (green) car here?" (In later chapters we will
look further at the implications of bait-and-switch.)
The second important difference between the processes—and hence the
products—of natural selection and human engineering concerns the feature of
natural selection that strikes many people as most paradoxical: its utter lack
of foresight. When human engineers design something (forward engineering),
they must guard against a notorious problem: unforeseen side effects. When
two or more systems, well designed in isolation, are put into a supersystem,
this often produces interactions that were not only not part of the intended
design, but positively harmful; the activity of one system inadvertently
clobbers the activity of the other. The only practical way to guard against
unforeseen side effects, since by their very nature they are unforeseeable by
those whose gaze is perforce restricted to just one of the subsystems being
designed, is to design all subsystems to have relatively impenetrable
boundaries that coincide with the epistemic boundaries of their creators.
Human engineers typically attempt to insulate subsystems from each other,
and insist on an overall design in which each subsystem has a single, welldefined
function within the whole.
The set of supersystems having this fundamental abstract architecture is
17. "But this is not to explain why, e.g., contractile vacuoles occur in certain protozoans;
it is to explain why the sort of protozoan incorporating contractile vacuoles occurs"
(Cummins 1975, in Sober 1984b, pp. 394-95).