Darwin's Dangerous Idea (44 page)

in distinguishing the forced moves from what we might call the
ad lib
moves, Reverse engineering insists that wherever there is a highly particular lock, and we saw how Mother Nature could be predicted to "discover" the forced there must be a highly particular key to fit it.
Why are these receptors here?

moves again and again. The idea that we can impute such "free-floating (Mother Nature could not have foreseen the development of mor-rationales" to the mindless process of natural selection is dizzying, 234 SEARCHING FOR QUALITY

The Power of Adaptationist Thinking

235

phine!) There must be some molecules produced internally under some conditions, the original keys that these locks were designed to receive. Seek a calls for too much growth-enhancer. The type 2 receptors are just there to molecule that fits this receptor and is produced under circumstances in which soak up—to "capture and degrade"—all the excess growth-enhancer that the a shot of morphine might be beneficial. Eureka! Endogenously created paternal chromosome would pump into the fetus if it had its way. Since mice morphine—endorphin—was discovered.

are a species in which females tend to mate with more than one male, males Even more devious Sherlock-Holmesian leaps of deduction have been in effect compete to exploit the resources of each female, a competition from executed. Here, for instance, is a general mystery: "Why do some genes which females must protect themselves (and their own genetic contributions).

change their pattern of expression depending on whether they are maternally Haig and Westoby's model predicts that genes would evolve in mice to or paternally inherited?" (Haig and Graham 1991, p. 1045). This phe-protect females from this exploitation, and this imprinting has been con-nomenon—in which the genome-reading machinery
pays more attention,
in firmed. Moreover, their model predicts that type 2 receptors shouldn't work effect, to either the paternal text or the maternal text—is known as
genomic
this way in species in which genetic conflict of this sort can't arise. They
imprinting
(for a general account, see Haig 1992), and has been confirmed to shouldn't work this way in chickens, because offspring can't influence how occur in special cases. What do the special cases have in common? Haig and much yolk their eggs receive, so the tug-of-war can never get started. Sure Westoby (1989) developed a model that purports to solve the general mystery enough, the type 2 receptors in chickens don't bind to IGF-II. Bertrand by
predicting
that genomic imprinting would be found only in organisms "in Russell once slyly described a certain form of illicit argument as having all which females carry offspring by more than one male during their life span the advantages of theft over honest toil, and one can sympathize with the and a system of parental care in which offspring receive most of their hardworking molecular biologist who reacts with a certain envy when some-postfertilization nutrients from one parent (usually the mother) and thus body like Haig swoops in, saying, in effect, "Go look under that rock—I bet compete with offspring fathered by other males." In such circumstances, they you'll find a treasure of the following shape!"

reasoned, there should be a conflict between maternal and paternal genes—

But that is what Haig was able to do: he predicted what Mother Nature's paternal genes will tend to favor exploiting the mother's body as much as move would be in the hundred-million-year game of mammal design. Of all possible, but maternal genes would "view" this as almost suicidal—and the the possible moves available, he saw that there was a good reason for this result should be that the relevant genes will in effect choose sides in a tug-of-move, so this is what would be discovered. We can get a sense of the war, and genomic imprinting will result ( Haig and Graham 1991, p. 1046).

magnitude of the leap that such an inference takes by comparing it with a See the model at work. There is a protein, "Insulin-like Growth Factor II"

parallel leap that we can make in the Game of Life. Recall that one of the (IGF-II), which is, as its name suggests, a growth-enhancer. Not surprisingly, possible denizens of the Life world is a Universal Turing machine composed the genetic recipes of many species order the creation of large quantities of of trillions of pixels. Since a Universal Turing machine can compute any IGF-II during embryonic development. But, like all functioning machines, computable function, it can play chess—simply by mimicking the program of IGF-II needs the right supportive environment to do its work, and in this case any chess-playing computer you like. Suppose, then, that such an entity it needs helper molecules known as "type 1 receptors." So far, our story is just occupies the Life plane, playing chess against itself, in the fashion of Sam-like the endorphin story: we have a type of key (IGF-II) and a kind of lock uel's computer playing checkers against itself. Looking at the configuration (type 1 receptors) in which it fits and performs an obviously important role.

of dots that accomplishes this marvel would almost certainly be unillumi-But in mice, for instance, there is another kind of lock (type 2 receptors) in nating to anyone who had no clue that a configuration with such powers which it also fits. What are these secondary locks for? For nothing, could exist. But from the perspective of someone who
had the hypothesis
that apparently; they are descendants of molecules that in other species (toads, for this huge array of black dots was a chess-playing computer, enormously instance) play a role in cells' "garbage-disposal" systems, but this is not what efficient ways of predicting the future of that configuration are made avail-they do when they bind to IGF-II in mice. Then why are they there? Because able.

they are "ordered" by the genetic recipe for making a mouse, of course, but Consider the savings you could achieve. At first you would be confronted here is the telltale twist: whereas both the maternal and paternal contributions by a screen on which trillions of pixels flash on and off. Since you know the to the chromosome contain recipe instructions for making them, these single rule of Life Physics, you could laboriously calculate the behavior of instructions are
preferentially expressed
from the maternal chromosome.

each spot on the screen if you wanted, but it would take eons. As a first cost-Why? To counteract the instruction in the recipe that cutting step, you could shift from thinking about individual pixels to thinking about gliders and eaters and still lifes, and so forth. Whenever you 236 'SEARCHING FOR QUALITY

The Power of Adaptationist Thinking

237

saw a glider approaching an eater, you would just predict "consumption in
sual
patterns but, you might say,
intellectual
patterns. Squinting or twisting four generations" without bothering with the pixel-level calculations. As a your head in front of the computer screen is not apt to help, whereas posing second step, you could move to thinking of the gliders as symbols on the fanciful interpretations (or what Quine would call "analytical hypotheses")

"tape" of a gigantic Turing machine, and then, adopting this higher design may uncover a gold mine. The opportunity confronting the observer of such a stance towards the configuration, predict its future
as
a Turing machine. At Life world is analogous to the opportunity confronting the cryptographer this level you would be "hand-simulating" the "machine language" of a staring at a new patch of cipher text, or the opportunity confronting the computer program that plays chess, still a tedious way of making predictions, Martian peering through a telescope at the Super-bowl Game. If the Martian but orders of magnitude more efficient than working out the physics. As a hits on the intentional stance—otherwise known as folk psychology3—as the third and still more efficient step, you could ignore the details of the chess-right level to look for pattern, shapes will readily emerge through the noisy playing program itself and just assume that, whatever they are, they are
good
!

jostling of people-particles and team-molecules.

That is, you could assume that the chess-playing program running on the The scale of compression when one adopts the intentional stance towards Turing machine made of gliders and eaters played not just legal chess but the two-dimensional chess-playing computer galaxy is stupendous: it is the good legal chess—it had been well designed (perhaps it has designed itself, difference between figuring out in your head what White's most likely (best) in the manner of Samuel's checkers program ) to find the good moves. This chess move is versus calculating the state of a few trillion pixels through a permits you to shift to thinking about chessboard positions, possible chess few hundred thousand generations. But the scale of the savings is really no moves, and the grounds for evaluating them—to shift to reasoning about greater in the Life world than in our own. Predicting that someone will duck reasons.

if you throw a brick at him is easy from the intentional or folk-psychological Adopting the intentional stance towards the configuration, you could stance; it is and will always be intractable if you have to trace the photons predict its future
as
a chess-player performing intentional actions—making from brick to eyeball, the neurotransmitters from optic nerve to motor nerve, chess moves and trying to achieve checkmate. First you would have to figure and so forth.

out the interpretation scheme that permits you to say which configurations of For such vast computational leverage one might be prepared to pay quite a pixels count as which symbols: which glider pattern spells out "QxBch"

steep price in errors, but in fact the intentional stance, used correctly, provides (Queen takes Bishop; check) and the other symbols for chess moves. But then a description system that permits extremely reliable prediction of not only you could use the interpretation scheme to predict, for instance, that the next intelligent human behavior, but also the "intelligent behavior" of the process configuration to emerge from the galaxy would be such-and-such a glider that designed organisms. All this would warm William Paley's heart. We can stream—say, the symbols for "RxQ" (Rook takes Queen). There is risk put the burden of proof on the skeptics with a simple challenge argument: if involved, because the chess program being run on the Turing machine may there weren't design in the biosphere, how come the intentional stance
works?

be far from perfectly rational, and, at a different level, debris may wander We can even get a rough measure of the design in the biosphere by comparing onto the scene and "break" the Turing-machine configuration before it the cost of making predictions from the lowest-level physical stance (which finishes the game. But if all goes well, as it normally will, if you have the assumes no design—well, almost no design, depending on how we treat the right interpretation, you can astonish your friends by saying something like "I evolution of universes) with the cost of making predictions from the higher predict that the next stream of gliders to emerge in location L in this Life stances: the design stance and the intentional stance. The added leverage of galaxy will have the following pattern: a singleton, followed by a group of prediction, the diminution of uncertainty, the shrinkage of the huge search three, followed by another singleton ..." How on Earth were you able to space to a few optimal or

predict that that particular "molecular" pattern would appear then?2

In other words, real but (potentially) noisy patterns abound in such a configuration of the Life world, there for the picking up if only you are lucky or clever enough to hit on the right perspective. They are not
vi-3.1 introduced the term "folk psychology" in 1978 (Dennett 1981, 1987b) as the name for the natural, perhaps even partly innate, talent human beings have for adopting the intentional stance. See Baron-Cohen 1995 for a fascinating contribution to the current state of play. There is more agreement among philosophers and psychologists about the 2. In case you wondered, I imagined "RxQ" to be spelled out in Morse code, and "R" in existence of the talent than there is about my analysis of it. See, for instance, the recent Morse is dot-dash-dot—the group of three gliders counts as a dash.

anthologies on the topic—Greenwood 1991, and Christensen and Turner 1993. See Dennett 1987b, 1990b, and 1991b for my account.

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The Leibnizian Paradigm
239

near-optimal paths, is a measure of the design that is observable in the world.

what it is to be a possible world, and on what we can infer about the actual The biologists' name for this style of reasoning is
adaptationism
It is world from the fact of its actuality. In
Candide,
Voltaire created a famous defined by one of its most eminent critics as the "growing tendency in caricature of Leibniz, Dr. Pangloss, the learned fool who could rationalize evolutionary biology to reconstruct or predict evolutionary events by
as-any calamity or deformity—from the Lisbon earthquake to venereal dis-suming
that all characters are established in evolution by direct natural ease—and show how, no doubt, it was all for the best. Nothing
in principle
selection of the most adapted state, that is, the state that is an optimum could prove that this was not the best of all possible worlds.

'solution' to a 'problem' posed by the environment" (Lewontin 1983). These Gould and Lewontin memorably dubbed the
excesses
of adaptationism the critics claim that, although adaptationism plays
some
important role in

"Panglossian Paradigm," and strove to ridicule it off the stage of serious biology, it is not really all that central or ubiquitous—and, indeed, we should science. They were not the first to use "Panglossian" as a term of criticism in try to balance it with other ways of thinking. I have been showing, however, evolutionary theory. The evolutionary biologist J. B. S. Haldane had a that it plays a crucial role in the analysis of every biological event at every famous list of three "theorems" of bad scientific argument: the Bellman's scale from the creation of the first self-replicating macromolecule on up. If Theorem ("What I tell you three times is true"; from "The Hunting of the we gave up adaptationist reasoning, for instance, we would have to give up Snark" by Lewis Carroll), Aunt Jobisca's Theorem ("It's a fact the whole the best textbook argument for the very occurrence of evolution (I quoted world knows"; from Edward Lear, "The Pobble Who Had No Toes"), and Mark Ridley's version of it on page 136): the widespread existence of Pangloss's Theorem ("All is for the best in this best of all possible worlds"; homologies, those suspicious similarities of design that are
not
functionally from
Candide).
John Maynard Smith then used the last of these more par-necessary.