Darwin's Dangerous Idea (10 page)

destination, the goal, the point of all that winnowing and competition, and Consider, for instance, the question of why the grains of sand on a beach are our arrival on the scene was guaranteed by the mere holding of the so uniform in size. This is due to a natural sorting process that occurs thanks tournament. This confusion has been fostered by evolution's friends and foes to the repetitive launching of the grains by the surf—alphabetical order on a alike, and it is parallel to the confusion of the coin-toss tournament winner grand scale, you might say. The pattern of cracks that appear in the sun-who basks in the misconsidered glory of the idea that since the tournament baked clay may be best explained by looking at chains of events that are not had to have a winner, and since he is the winner, the tournament had to unlike the successive rounds in a tournament.

produce him as the winner. Evolution can be an algorithm, and evolution can Or consider the process of annealing a piece of metal to temper it. What have produced us by an algorithmic process, without its being true that could be a more physical, less "computational" process than that? The evolution is an algorithm for producing us. The main conclusion of Stephen blacksmith repeatedly heats the metal and then lets it cool, and somehow in Jay Gould's
Wonderful Life: The Burgess Shale and the Nature of History
(

the process it becomes much stronger. How? What kind of an explanation 1989a) is that if we were to "wind the tape of life back" and play it again and can we give for this magical transformation? Does the heat create special again, the likelihood is infinitesimal of
Us
being the product on any other run toughness atoms that coat the surface? Or does it suck subatomic glue out of through the evolutionary mill. This is undoubtedly true (if by "Us" we mean the atmosphere that binds all the iron atoms together? No, nothing like that the particular variety of
Homo sapiens
we are: hairless and upright, with five happens. The right level of explanation is the algorithmic level: As the metal fingers on each of two hands, speaking English and French and playing tennis cools from its molten state, the solidification starts in many different spots at and chess ). Evolution is not a process that was designed to produce us, but it the same time, creating crystals that grow together until the whole is solid.

does not follow from this that evolution is not an algorithmic process that has But the first time this happens, the arrangement of the individual crystal in fact produced us. ( Chapter 10 will explore this issue in more detail.) structures is suboptimal—weakly held together, and with lots of internal Evolutionary algorithms are manifestly interesting algorithms—interesting stresses and strains. Heating it up again—but not all the way to melting—

to us, at least—not because what they are guaranteed to do is interesting to partially breaks down these structures, so that, when they are permitted to us, but because what they are guaranteed to
tend
to do is interesting to us.

cool the next time, the broken-up bits will adhere to the still-solid bits in a They are like tournaments of skill in this regard. The power of an algo-different arrangement. It can be proven mathematically that these rearrangements will tend to get better and better, approaching 58 AN IDEA IS BORN

Processes as Algorithms
59

the optimum or strongest total structure, provided the regime of heating and clearer it becomes that the Mendelian story is at best a vast oversimplifica-cooling has the right parameters. So powerful is this optimization procedure tion. Some would go so far as to say that we have recently learned that there that it has been used as the inspiration for an entirely general problem-really
aren't
any Mendelian genes! Having climbed Mendel's ladder, we solving technique in computer science—"simulated annealing," which has must now throw it away. But of course no one wants to throw away such a nothing to do with metals or heat, but is just a way of getting a computer valuable tool, still proving itself daily in hundreds of scientific and medical program to build, disassemble, and rebuild a data structure (such as another contexts. The solution is to bump Mendel up a level, and declare that he, like program), over and over, blindly groping towards a better— indeed, an Darwin, captured an
abstract
truth about inheritance. We may, if we like, optimal—version (Kirkpatrick, Gelatt and Vecchi 1983). This was one of the talk of
virtual genes,
considering them to have their reality distributed major insights leading to the development of "Boltzmann machines" and around in the concrete materials of the DNA. (There is much to be said in

"Hopfield nets" and the other constraint-satisfaction schemes that are the favor of this option, which I will discuss further in chapters 5 and 12.) basis for the Connectionist or "neural-net" architectures in Artificial But then, to return to the question raised above, are there any limits at all Intelligence. (For overviews, see Smolensky 1983, Rumelhart 1989, on what may be considered an algorithmic process? I guess the answer is No; Churchland and Sejnowski 1992, and, on a philosophical level, Dennett if you wanted to, you could treat any process at the abstract level as an 1987a, Paul Churchland 1989)

algorithmic process. So what? Only some processes yield interesting results If you want a deep understanding of how annealing works in metallurgy, when you do treat them as algorithms, but we don't have to try to define you have to learn the physics of all the forces operating at the atomic level,

"algorithm" in such a way as to include only the
interesting
ones (a tall of course, but notice that the basic idea of how annealing works (and philosophical order!). The problem will take care of itself, since nobody will particularly
why
it
works)
can be lifted clear of those details—after all, I just waste time examining the algorithms that aren't interesting for one reason or explained it in simple lay terms (and I don't know the physics!). The ex-another. It all depends on what needs explaining. If what strikes you as planation of annealing can be put in
substrate-neutral
terminology: we puzzling is the uniformity of the sand grains or the strength of the blade, an should expect optimization of a certain sort to occur in any "material" that algorithmic explanation is what will satisfy your curiosity—and it will be the has components that get put together by a certain sort of building process and truth. Other interesting features of the same phenomena, or the processes that that can be disassembled in a sequenced way by changing a single global created them, might not yield to an algorithmic treatment.

parameter, etc. That is what is common to the processes going on in the Here, then, is Darwin's dangerous idea: the algorithmic level
is
the level glowing steel bar and the humming supercomputer.

that best accounts for the speed of the antelope, the wing of the eagle, the Darwin's ideas about the powers of natural selection can also be lifted out shape of the orchid, the diversity of species, and all the other occasions for of their home base in biology. Indeed, as we have already noted, Darwin wonder in the world of nature. It is hard to believe that something as mindless himself had few inklings ( and what inklings he had turned out to be wrong ) and mechanical as an algorithm could produce such wonderful things. No about how the microscopic processes of genetic inheritance were accom-matter how impressive the products of an algorithm, the underlying process plished. Not knowing any of the details about the physical substrate, he could always consists of nothing but a set of individually mindless steps succeeding nevertheless discern that if certain conditions were somehow met, certain each other without the help of any intelligent supervision; they are "auto-effects would be wrought. This substrate neutrality has been crucial in matic" by definition: the workings of an automaton. They feed on each other, permitting the basic Darwinian insights to float like a cork on the waves of or on blind chance—coin-flips, if you like—and on nothing else. Most subsequent research and controversy, for what has happened since Darwin algorithms we are familiar with have rather modest products: they do long has a curious flip-flop in it. Darwin, as we noted in the preceding chapter, division or alphabetize lists or figure out the income of the Average Taxpayer.

never hit upon the utterly necessary idea of a gene, but along came Mendel's Fancier algorithms produce the dazzling computer-animated graphics we see concept to provide just the right structure for making mathematical sense out every day on television, transforming faces, creating herds of imaginary ice-of heredity ( and solving Darwin's nasty problem of blending inheritance).

skating polar bears, simulating whole virtual worlds of entities never seen or And then, when DNA was identified as the actual physical vehicle of the imagined before. But the actual biosphere is much fancier still, by many genes, it looked at first (and still looks to many participants) as if Mendel's orders of magnitude. Can it really be the outcome of nothing but a cascade of genes could be simply
identified
as particular hunks of DNA. But then algorithmic processes feeding on chance? And if so, who designed that complexities began to emerge; the more scientists have learned about the cascade? Nobody. It is itself the product of a blind, algorithmic process. As actual molecular biology of DNA and its role in reproduction, the Darwin himself put it, in a letter to the geologist Charles Lyell shortly after 60 AN IDEA IS BORN

publication of
Origin,
"I would give absolutely nothing for the theory of Natural Selection, if it requires miraculous additions at any one stage of descent __ If I were convinced that I required such additions to the theory CHAPTER THREE

of natural selection, I would reject it as rubbish..." (F. Darwin 1911, vol. 2, pp. 6-7).

According to Darwin, then, evolution is an algorithmic process. Putting it
Universal Acid

this way is still controversial. One of the tugs-of-war going on within evolutionary biology is between those who are relentlessly pushing, pushing, pushing towards an algorithmic treatment, and those who, for various submerged reasons, are resisting this trend. It is rather as if there were metal-lurgists around who were disappointed by the algorithmic explanation of annealing. "You mean that's all there is to it? No submicroscopic Superglue specially created by the heating and cooling process?" Darwin has convinced all the scientists that evolution, like annealing,
works.
His radical vision of
how
and
why
it works is still somewhat embattled, largely because those who 1. EARLY REACTIONS

resist can dimly see that their skirmish is part of a larger campaign. If the game is lost in evolutionary biology, where will it all end?

Origin of man now proved.
—
Metaphysics must flourish.
—
He who
understands baboon would do more towards metaphysics than Locke.

—CHARLES DARWIN, in a notebook not

CHAPTER 2:
Darwin conclusively demonstrated that, contrary to ancient
intended for publication, in P. H. Barrett et al.

tradition, species are not eternal and immutable; they evolve. The origin of
1987, D26, M84

new species was shown to be the result of "descent with modification." Less
conclusively, Darwin introduced an idea of how this evolutionary process
His subject is die 'Origin of Species,' & not die origin of Organization;
took place: via a mindless, mechanical
—
algorithmic—process he called

& it seems a needless mischief to have opened the latter speculation at

"natural selection." This idea, that all die fruits of evolution can be explained
all.

as the products of an algorithmic process, is Darwin's dangerous idea.

—H

-

ARRIET MARTINEAL , a friend of Darwin's, in a

letter to Fannie Wedgwood, March, 13, 1860,

CHAPTER 3:
Many people, Darwin included, could dimly see
that
his idea of
quoted in Desmond and Moore 1991, p. 486

natural selection had revolutionary potential, but just what did it promise to
overthrow? Darwin's idea can be used to dismantle and then rebuild a
Darwin began his explanation in the middle, or even, you might say, at the
traditional structure of Western thought, which I call die Cosmic Pyramid.

end. starting with the life forms we presently see, and showing how the
This provides a new explanation of the origin, by gradual accumulation, of
patterns in today's biosphere could be explained as having arisen by the
all the Design in the universe. Ever since Darwin, skepticism has been aimed
process of natural selection from the patterns in yesterday's biosphere, and so
at his implicit claim that the various processes of natural selection, in spite of
on, back into the very distant past. He started with facts that everyone
their underlying mindlessness, are powerful enough to have done all the
knows: all of today's living things are the offspring of parents, who are the
design work that is manifest in the world.

offspring of grandparents, and so forth, so everything that is alive today is a branch of a genealogical family, which is itself a branch of a larger clan. He went on to argue that, if you go back far enough, you find that all the branches of all the families eventually spring from common ancestral limbs, so that there is a single Tree of Life, all the limbs, branches, and twigs united by descent with modification. The fact that it has the branching organization of a tree is crucial to the explanation of the sort of process involved, for such 62 UNIVERSAL ACID

Early Reactions
63

a tree
could
be created by an automatic, recursive process: first build an
x,
Did you ever hear of universal acid? This fantasy used to amuse me and then modify
x's
descendants, then modify those modifications, then modify some of my schoolboy friends—I have no idea whether we invented or the modifications of the modifications— If Life is a Tree, it could all have inherited it, along with Spanish fly and saltpeter, as a part of underground arisen from an inexorable, automatic rebuilding process in which designs youth culture. Universal acid is a liquid so corrosive that it will eat through would accumulate over time.