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

196 BIOLOGY IS ENGINEERING Function and Specification 197
acid sequences can be used as "philological" clues in re-creating the evolutionary
history of the production and use of lysozyme.
And here is a puzzle, first noted by Walter Elsasser (1958, 1966), but quite
conclusively solved by Jacques Monod (1971). Considered very abstractly,
the fact that a one-dimensional code can be "for" a three-dimensional
structure shows that information is added. Indeed, value is added. The
individual amino acids have value (by contributing to the functional prowess
of a protein) not just in virtue of their location in the one-dimensional
sequence that forms the string, but in virtue of their location in threedimensional
space once the string is folded up.
Thus there is a seeming contradiction between the statement that the
genome 'entirely defines' the function of a protein and the fact that this
function is linked to a three-dimensional structure whose data content is
richer than the direct contribution made to the structure by the genome.
[Monod 1971, p. 94.]
As Küppers (1990, p. 120) points out, Monod's solution is straightforward:
"The seemingly irreducible, or excess, information is contained in the
specific conditions of the protein's environment, and only together with these
can the genetic information determine unambiguously the structure and thus
the function of the protein molecule." Monod (1971, p. 94) puts it this way:
... of all the structures possible only one is actually realized. Initial conditions
hence enter among the items of information finally enclosed within
the ... structure. Without specifying it, they contribute to the realization
of a unique shape by eliminating all alternative structures, in this way
proposing—or rather imposing—an unequivocal interpretation of a potentially
equivocal message. 2
What does this mean? It means—not surprisingly—that the language of
DNA and the "readers" of that language have to evolve together; neither can
work on its own. When the deconstructionists say that the reader brings
something to the text, they are saying something that applies just as surely to
DNA as to poetry; the something that the reader brings can be charac-
2. Philosophers will recognize, I trust, that Monod thus both posed and solved
Putnam's (1975) problem of Twin Earth, at least in the context of the "toy problem" of
molecular evolution. Meaning "ain't in the head," as Putnam famously observed, and it
ain't (all) in the DNA either. Twin Earth, otherwise known as the problem of broad
versus narrow content, will get exhumed briefly in chapter 14, so I can give it its proper
Darwinian funeral.
terized most generally and abstracdy as information, and only the combination
of information from the code and the code-reading environment
suffices to create an organism. 3 As we noted in chapter 5, some critics have
fastened on this fact as if it were somehow the refutation of "gene centrism,"
the doctrine that the DNA is the sole information store for inheritance, but
that idea was always only a handy oversimplification. Though libraries are
commonly allowed to be storehouses of information, of course it is really
only libraies-plus readers that preserve and store the information. Since
libraries have not—up till now, at any rate—contained among their volumes
the information needed to create more readers, their capacity to store
information (effectively) has been dependent on there being another
information-storage system—the human genetic system, of which DNA is the
principle medium. When we apply the same reasoning to DNA itself, we see
that it, too, requires a continuing supply of "readers" that it does not itself
entirely specify. Where does the rest of the information come from to specify
these readers? The short answer is that it comes from the very continuities of
the environment—the persistence in the environment of the necessary raw
(and partially constructed) materials, and the conditions in which they can be
exploited. Every time you make sure that your dishrag gets properly dry in
between uses, you break the chain of environmental continuity (e.g., lots of
moisture) that is part of the informational background presupposed by the
DNA of the bacteria in the dishrag whose demise you seek.
We see here a special case of a very general principle: any functioning
structure carries implicit information about the environment in which its
function "works." The wings of a seagull magnificently embody principles of
aerodynamic design, and thereby also imply that the creature whose wings
these are is excellently adapted for flight in a medium having the specific
density and viscosity of the atmosphere within a thousand meters or so of the
surface of the Earth. Recall the example in chapter 5 of sending the score of
Beethoven's Fifth Symphony to "Martians." Suppose we carefully preserved
the body of a seagull and sent it off into space (without any accompanying
explanation), to be discovered by these Martians. If they
3. David Haig (personal communication) has drawn my attention to a fascinating new
wrinkle in this unfolding story about folding proteins: molecular chaperones. "Chaperones
are molecular cranes par excellence. They are proteins with which an amino acid
chain associates while it is folding that allows the chain to adopt a conformation that
would be unavailable in the absence of the chaperone. The chaperone is then discarded
by the folded protein. Chaperones are highly conserved.... Molecular chaperones were
named by analogy to the functions of chaperones at a debutante ball: their role was to
encourage some interactions and to discourage others." For recent details, see Martin et
al. 1993, Ellis and van der Vies 1991.