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

316 CONTROVERSIES CONTAINED
process, and the rationale of the design aimed for, actually did play a role in
the process. In these cases, the goal was explicitly represented in the minds of
the breeders who did the selecting. So the theory of evolution must allow for
the existence of such products, and such historical processes, as special
cases—organisms designed with the help of supercranes. Now the question
arises: can such special cases be distinguished in retrospective analysis?
Imagine a world in which actual hands from another galaxy supplemented
the "hidden hand" of natural selection. Imagine that natural selection on this
planet was aided and abetted over the eons by visitors: tinkering, farsighted,
reason-representing organism-designers, like the animal- and plant-breeders
of our actual world, but not restricting themselves to "domesticated"
organisms designed for human use. (To make it vivid, we may suppose they
treated Earth as their "theme park," creating whole phyla for educational or
entertainment purposes.) These bioengineers would have actually formulated,
and represented, and acted on, the rationales of their designs—just like
automobile engineers or our own contemporary gene-splicers. Then, let's
suppose, they absconded. Now, would their handiwork be detectable by any
imaginable analysis by biologists today?
If we found that some organisms came with service manuals attached, this
would be a dead giveaway. Most of the DNA in any genome is unexpressed—
often called "junk DNA"—and NovaGene, a biotechnology company in Houston,
has found a use for it. They have adopted the policy of "DNA branding":
writing the nearest codon rendering of their company trademark in the junk
DNA of their products. According to the standard abbreviations for the
amino-acid specifiers, asparagine, glutamine, valine, alanine, glycine, glutamic
acid, asparagine, glutamic acid = NQVAGENE ( reported in Scientific
American June 1986, pp. 70-71). This suggests a new exercise in "radical
translation" (Quine I960) for philosophers: how, in principle or in practice,
could we confirm or disconfirm the hypothesis that trademarks—or service
manuals or other messages—were discernible in the junk DNA of any species?
The presence of functionless DNA in the genome is no longer regarded
as a puzzle. Dawkins' ( 1976) selfish-gene theory predicts it, and elaborations
on the idea of "selfish DNA" were simultaneously developed by Doolittle and
Sapienza (1980) and Orgel and Crick (1980) (see Dawkins 1982, ch. 9, for the
details). That doesn't show that junk DNA couldn't have a more dramatic
function, however, and hence it could have a meaning after all. Our imagined
intergalactic interlopers could as readily have exapted the junk DNA for their
own purposes as the NovaGene engineers exapted it for theirs.
Finding the high-tech version of "Kilroy was here" written in the genome
of a cabbage or a king would be unnerving, but what if no such deliberate
clues were left around? Would a closer look at the organism designs themselves—the
phenotypes—reveal some telltale discontinuities? Gene-splicers
A Clutch of Harmless Heresies 317
are the most powerful cranes we have yet discovered. Are there designs that
simply could not be erected without the help of this particular crane? If there
are designs that cannot be approached by a gradual, stepwise redesign process
in which each step is at least no worse for the gene's survival chances than its
predecessor, then the existence of such a design in nature would seem to
require, at some point in its ancestry, a helping hand from a foresightful
designer—either a gene-splicer, or a breeder who somehow preserved the
necessary succession of intermediate backsliders until they could yield their
sought progeny. But could we ever conclusively establish that some design
had this feature of requiring such a saltation in its ancestry? For over a
century, skeptics have hunted for such cases—thinking that, if they ever
found one, it would conclusively refute Darwinism—but so far their efforts
have shown a systematic weakness.
Consider the most familiar example, the wing. Wings could not evolve in one
fell swoop, runs the standard skeptical argument; and if we imagine—as we
Darwinians must—that wings evolved gradually, we must admit that partially
completed wings would not only not have provided partial value but would
have been a positive hindrance. We Darwinians need admit no such thing.
Wings that are good only for gliding (but not powered flight) have manifest net
benefits for many actual creatures, and still stubbier, less aerodynamically
effective protuberances could have evolved for some other reason, and then
been exapted. Many versions of this story—and other stories—have been told
to fill in the gap. Wings are not an embarrassment to orthodox Darwinians, or if
they are, they are an embarrassment of riches. There are too many different
plausible ways of telling the story of how functioning wings could have
evolved by gradual increments! This shows how hard it would be for anyone to
devise an insurmountable argument to prove that a particular feature must have
arisen by a saltation, but at the same time it shows that it would be just as hard
to prove that a feature must have arisen without a saltation, unaided by human
or other intelligent hands.
Indeed, all the biologists I have queried on this point have agreed with me
that there are no sure marks of natural, as opposed to artificial, selection. In
chapter 5, we traded in the concept of strict biological possibility and
impossibility for a graded notion of biological probability, but even in its
terms, it is not clear how one could grade organisms as "probably" or "very
probably" or "extremely probably" the products of artificial selection. Should
this conclusion be viewed as a terrible embarrassment to the evolutionists in
their struggle against creationists? One can imagine the headlines-. "Scientists
Concede: Darwinian Theory Cannot Disprove Intelligent Design!" It would be
foolhardy, however, for any defender of neo-Darwinism to claim that
contemporary evolution theory gives one the power to read history so finely
from present data as to rule out the earlier historical pres-