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

190 BIOLOGY IS ENGINEERING Darwin Is Dead—Long L ive Darwin! 191
interest in their own right, and if they are carefully divorced from questions
of ultimate justification, they can actually help us see what the scientific
issues really are. What various thinkers think they are doing—saving the
world from one ism or another, or finding room for God in science, or
combating superstition—often turns out to be at right angles to the contribution
their campaigns actually succeed in making. We have already seen
instances of this, and more are in the offing. Probably no area of scientific
research is driven by more hidden agendas than evolutionary theory, and it
certainly will help to expose them, but nothing follows directly from the fact
that some people are trying desperately—whether they realize it or not—to
protect something evil or destroy something evil. People sometimes get it
right in spite of having been driven by the most unpresentable hankerings.
Darwin was who he was, and thought what he thought, warts and all. And
now he is dead. Darwinism, on the other hand, has more than nine lives. It
bids fair to being immortal.
2. DARWIN IS DEAD—LONG LIVE DARWIN!
I have taken the section title from the title of the "Resume" with which
Manfred Eigen ends his 1992 book. There is an unmistakable engineering
flair to Eigen's thinking. His research is a sequence of biological construction
problems posed and solved: how do the materials get amassed at the building
site, and how does the design get determined, and in what order are the
various parts assembled so that they don't fall apart before the whole
structure is completed? His claim is that the ideas he presents are revolutionary,
but that after the revolution, Darwinism is not only alive and well,
but strengthened. I want to explore this theme in more detail, since we will
see other versions of it that are nowhere near as clearcut as Eigen's.
What is supposed to be revolutionary about Eigen's work? In chapter 3 we
looked at a fitness landscape with a single peak, and saw how the Baldwin
Effect could turn a well-nigh-invisible telephone pole on a plain into Mount
Fuji, with a steadily rising surrounding slope, so that no matter where in the
space you started, you would eventually get to the summit if you simply
followed the Local Rule:
Never step down; step up whenever possible.
The idea of a fitness landscape was introduced by Sewall Wright (1932),
and it has become a standard imagination prosthesis for evolutionary theorists.
It has proven its value in literally thousands of applications, including
many outside of evolutionary theory. In Artificial Intelligence, economics,
and other problem-solving domains, the model of problem-solving by in-
cremental hill-climbing (or "gradient ascent") has been deservedly popular. It
has even been popular enough to motivate theorists to calculate its
limitations, which are severe. For certain classes of problems—or, in other
words, in certain types of landscape—simple hill-climbing is quite impotent,
for an intuitively obvious reason: the climbers get stuck on local second-rate
summits instead of finding their way to the global summit, the Mount Everest
of perfection. (The same limitations beset the method of simulated
annealing.) The Local Rule is fundamental to Darwinism; it is equivalent to
the requirement that there cannot be any intelligent (or "far-seeing" ) foresight
in the design process, but only ultimately stupid opportunistic exploitation
of whatever lucky lifting happens your way.
What Eigen has shown is that this simplest Darwinian model of steady
improvement up a single slope of fitness to the optimal peak of perfection
just doesn't work to describe what goes on in molecular or viral evolution.
The rate of adaptation by viruses ( and also of bacteria and other pathogens)
is measurably faster than the "classical" models predict—so fast that it seems
to involve illicit "look-ahead" by the climbers. So does this mean that
Darwinism must be abandoned? Not at all, for what counts as local depends
(not surprisingly) on the scale you use.
Eigen draws our attention to the fact that when viruses evolve, they don't
go single-file; they travel in huge herds of almost identical variants, a fuzzyedged
cloud in the Library of Mendel that Eigen calls a "quasi-species." We
already saw the unimaginably large cloud of Moby Dick variants in the
Library of Babel, but any actual library is likely to have more than one or
two variant editions of a book on its shelves, and in the case of a really
popular book like Moby Dick it is also likely to have multiple copies of the
same edition. Like actual Moby Dick collections, then, actual viral clouds
include multiple identical copies but also multiple copies of minor typographical
variants, and this fact has some implications, according to Eigen,
that have been ignored by "classical" Darwinians. It is the shape of the cloud
of variants that holds the key to the speed of molecular evolution.
A classical term among geneticists for the canonical version of a species
(analogous to the canonical text of Moby Dick ) is the wild type. It was often
supposed by biologists that among the many different genotypes in a population,
the pure wild type would predominate. Analogous would be the
claim that in any library collection of copies of Moby Dick, most copies will
be of the received or canonical edition—if there is one! But this doesn't have
to be the case for organisms any more than for books in libraries. In fact, the
wild type is really just an abstraction, like the Average Taxpayer, and a
population may contain no individuals at all that have exactly "the" wild-type
genome. (Of course, the same is true of books—scholars might debate for
years over the purity of a particular word in a particular text, and until such
debates were resolved, nobody could say exactly what the ca-