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

216 BIOLOGY IS ENGINEERING
vast and interesting, of course, but it does not include very many of the
systems designed by natural selection! The process of evolution is notoriously
lacking in foresight. Since it has no foresight at all, unforeseen or
unforeseeable side effects are nothing to it; it proceeds, unlike human engineers,
via the profligate process of creating vast numbers of relatively
uninsulated designs, most of which are hopelessly flawed because of selfdefeating
side effects, but a few of which, by dumb luck, are spared that
ignominious fate. Moreover, this apparently inefficient design philosophy
carries a tremendous bonus that is relatively unavailable to the more efficient,
top-down process of human engineers: thanks to its having no bias against
unexamined side effects, it can take advantage of the rare cases where
beneficial serendipitous side effects emerge. Sometimes, that is, designs
emerge in which systems interact to produce more than was aimed at. In
particular (but not exclusively), one gets elements in such systems that have
multiple functions.
Elements with multiple functions are not unknown to human engineering,
of course, but their relative rarity is signaled by the delight we are apt to feel
when we encounter a new one. (A favorite of mine is found in the Diconix
portable printer. This optimally tiny printer runs on largish rechargeable
batteries, which have to be stored somewhere; they fit snugly inside the
platen, or roller.) On reflection, we can see that such instances of multiple
function are epistemically accessible to engineers under various salubrious
circumstances, but we can also see that by and large such solutions to design
problems must be exceptions against a background of strict isolation of
functional elements. In biology, we encounter quite crisp anatomical isolation
of functions (the kidney is entirely distinct from the heart; nerves and blood
vessels are separate conduits strung through the body, etc.), and without this
readily discernible isolation, reverse engineering in biology would no doubt
be humanly impossible. But we also see superim-position of functions that
apparently goes "all the way down." It is very, very hard to think about
entities in which the elements have multiple overlapping roles in
superimposed subsystems, and, moreover, in which some of the most salient
effects observable in the interaction of these elements may not be functions at
all. but merely by-products of the multiple functions being served. 18
Until recently, biologists who wanted to be reverse engineers had to
concentrate on figuring out the designed features of "finished products"—
organisms. These they could collect by the hundreds or thousands, study the
variations thereof, take apart, and manipulate ad lib. It was much more
difficult to get any epistemic purchase on the developmental or building
18. The preceding three paragraphs are drawn, with revisions, from Dennett 1994a.
Artifact Hermeneutics, or Reverse Engineering 217
process by which a genotype gets "expressed" in a fully formed phenotype.
And the design processes that shaped the developmental processes that shape
the "finished products" were largely inaccessible to the sorts of intrusive
observation and manipulation that good science (or good reverse
engineering) thrives on. You could look at the sketchy historical record, and
run it in fast-forward (like "elapsed-time" photography of plants growing,
weather developing, etc.—always a nifty way to make the patterns visible ),
but you couldn't "rewind the tape" and run variations on the initial conditions.
Now, thanks to computer simulations, it is possible to study the hypotheses
about the design process that have always lain at the heart of the Darwinian
vision. Not surprisingly, they turn out to be more complicated, and
themselves more intricately designed, than we had thought.
Once the processes of R and D and construction begin to come into focus,
we can see that an affliction of shortsightedness that has often misled
interpreters of human artifacts has multiple parallels in biology. When we
engage in artifact hermeneutics, trying to decipher the design of items
uncovered by archeologists, or trying to recover a proper interpretation of the
ancient monuments that we have grown up with, there is a tendency to
overlook the possibility that some of the features that puzzle us have no
function at all in the finished product, but played a crucial functional role in
the process that created the product.
Cathedrals, for instance, have many curious architectural features that have
provoked functional fantasies and fierce debates among art historians. The
functions of some of these features are fairly obvious. The many "vises" or
circular stairways that twist their way up inside the piers and walls are useful
ways for custodians to gain access to remote parts of the building: to the roof,
say, and to the space between the vault and the roof where the machinery is
hidden that lowers the chandeliers to the floor so that candles may be
replaced. But many of the vises would be there even if no such later access
had been anticipated by the builders; it was simply the best, or maybe the
only, way for the builders to get the building crew and materials where they
needed to be during construction. Other passageways leading nowhere inside
the walls are probably there in order to get fresh air into the interior of the
walls (Fitchen 1961). Medieval mortar took a long time— years, in some
cases—to cure, and as it cured it shrank, so care was taken to keep wall
thickness minimized so that distortion was minimized as the building cured.
(Thus those passageways have a similar function to the heat-dissipation "fins"
on automobile-engine housings, except that their functions lapsed once the
buildings reached maturity.)
Moreover, much that appears unremarkable when you look at a cathedral
as simply a finished product seems deeply puzzling when you start asking
how it could have been built. Chicken-egg problems abound. If you build the
flying buttresses before you build the central vault, they will push the