Where the Conflict Really Lies: Science, Religion, and Naturalism (30 page)

Finally, Draper ingeniously argues that Behe hasn’t even shown that direct routes to the systems he discusses are impossible.

It’s important to note that the possibilities Draper suggests are merely abstract possibilities. Draper doesn’t argue or even venture the opinion that in fact there are routes of these kinds that are not prohibitively improbable; he simply points out that Behe has not eliminated them. And of course this is quite proper, inasmuch as Draper is doing no more than evaluating Behe’s argument. All he is trying to show is that Behe’s conclusion doesn’t deductively follow from his premises. Draper’s conclusion:

Since my objections concerning both complicated and simple direct routes establish only conceptual possibilities rather than probabilities, I believe Behe’s most promising reply to these objections would be to admit the possibility of direct routes to irreducible complexity, but claim that, like indirect routes, they are very unlikely to produce the specific biochemical systems on which Behe builds his case. Of course, it would not be enough for Behe simply to
claim
that direct routes to these systems are very unlikely; he would need to argue for that claim. And it is an open question whether or not a good argument is available.
¹²

As far as I can make out, Draper is right: Behe’s argument, taken as Draper takes it, is by no means airtight. Behe has not demonstrated that there are irreducibly complex systems such that it is impossible or even monumentally improbable that they have evolved in a Darwinian fashion—although he has certainly provided Darwinians with a highly significant challenge. We have some of the same problems as with the fine-tuning argument of the last chapter: we don’t have a good way to ascertain the probability of these irreducibly
complex systems, given the Chance hypothesis, and we also don’t have a good way to evaluate the probability of these phenomena, given an intelligent designer.

Behe fluttered the dovecotes again with his book
The Edge of Evolution
.
¹³
Like
Darwin’s Black Box, Edge
argues that there are structures at the molecular level of life that could not have been produced by (unguided) natural selection. His argument is serious and quantitative, and is one of the few serious and quantitative arguments in this area. Consider the living cell, both prokaryotic and eukaryotic, with its stupefying complexity and its multitude of elaborately complex protein machines. According to Bruce Alberts, president emeritus of the National Academy of Sciences and no friend of Intelligent Design,

as it turns out, we can walk and we can talk because the chemistry that makes life possible is much more elaborate and sophisticated than anything we students had ever considered. Proteins make up most of the dry mass of a cell. But instead of a cell dominated by randomly colliding individual protein molecules, we now know that nearly every major process in a cell is carried out by assemblies of 10 or more protein molecules. And, as it carries out its biological functions, each of these protein assemblies interacts with several other large complexes of proteins. Indeed, the entire cell can be viewed as a factory that contains an elaborate network of interlocking assembly lines, each of which is composed of a set of large protein machines.
¹⁴

Behe argues that natural selection (and again, I believe he means
unguided
natural selection) is very probably incapable of producing these
protein machines. His argument is quantitative and empirical rather than a priori; its centerpiece is the saga of the malaria parasite,
Plasmodium falciperum
, and its long trench warfare with the human genome.

I won’t go into his argument here, but the brief overview, in Behe’s own words, is as follows:

In its battle with poison-wielding humans, the malaria genome has… been terribly scarred. In the past half century a number of genes have been broken or altered to fend off drugs such as chloroquine…. Has the war with humanity caused malaria to evolve any new cellular protein-protein interactions? No. A survey of all known malarial evolutionary responses to human drugs includes
no
novel protein-protein interactions.

Since widespread drug treatments first appeared about fifty years ago, more than 10
²⁰
, a hundred billion billion, malarial cells have been born in infested regions. It thus appears that the likelihood of the development of a new, useful, specific protein-protein interaction is less than one in 10
²⁰
.
¹⁵

Behe goes on to argue that we get roughly the same results from an examination of the AIDS virus and its battle with the various drugs employed to combat it; here too there have been roughly 10
²⁰
examples of this virus over the past several decades, during which it has been assaulted by the drugs used to combat it, but in this case too, no new protein-protein interaction sites have arisen. But if it takes 10
²⁰
organisms to develop one new protein-protein interaction site, then a mutation issuing in two new (simultaneous) protein-protein interaction sites will require 10
⁴⁰
organisms.
¹⁶
Estimates of the total number
of organisms that have so far come to be in the history of Earth put that number at less than 10
⁴⁰
. But then, so the thinking goes, it will be improbable that unguided natural selection should produce three protein-protein interaction sites in the history of Earth, and enormously improbable that it should produce the large protein machines involving assemblies of 10 or more proteins of which Alberts speaks.

Reviews of
The Edge of Evolution
by mainstream biologists have been predictably hostile.
¹⁷
But again, the high proportion of vitriol, invective, mockery, ridicule, and name-calling makes it hard to trust these reviews. In addition, the reviewers seem to suffer from an inability to pay attention to what Behe actually says. For example, Dawkins and Jerry Coyne both point out that artificial selection over the last few millennia has produced very different breeds of dogs, as if this somehow counted against Behe’s thesis. But of course it doesn’t; these different breeds of dogs do not involve new protein-protein interaction sites. Behe sets the “edge of evolution” at the level of orders, families, and genera; unguided evolution, he thinks, could produce new species, and therefore could certainly produce new varieties of the same species, as with dogs.
¹⁸
A stronger criticism is that Behe’s sample may be biased;
P. falciperum
and the HIV virus involve host-parasite interaction, and perhaps what holds for host-parasite interaction doesn’t hold generally. Perhaps; to see whether this is in fact so will of course require further empirical work. Still another criticism: where two or more new protein-protein interaction sites are required, perhaps one of these appears, and is in some way adaptive, so that it persists until the other also appears.

But suppose, just for purposes of argument, that the criticisms are ineffective. How shall we think of Behe’s argument? The conclusion
of the argument is that the living cell, with all its protein machines, is the product of intelligent design. How does the argument go? One possibility: the main alternative to intelligent design is unguided evolution, but the probability that unguided evolution should produce these protein machines is so low that we must conclude that it is false. Is this right? Not clearly. First, exceedingly improbable things do happen, and happen all the time. Consider a deal in a hand of bridge. If you distribute the fifty-two cards into four groups of thirteen cards each, there are some 10
²⁸
possible combinations. Therefore the probability that the cards should be dealt just as they are dealt is in the neighborhood of 10
^–28
. So consider a rubber of bridge that takes four deals: the probability that the cards should be dealt precisely as they are, for those four deals, is about 10
^–112
. At any given time, there are certainly at least 1000 rubbers of bridge being played in living rooms and rest homes around the world; the probability that the cards should be dealt just as they are dealt for those rubbers will be about 10
^–112,000
. That is an overwhelmingly small probability; yet the thing happens. What is the probability that unguided evolution should produce these protein machines? Is it less than 10
^–112,000
? How can we tell? We don’t have anything like the means of making the relevant calculations.

Well, should we instead compare P(protein machines/unguided evolution), the probability of the existence of these protein machines given unguided evolution, with P(protein machines/intelligent designer), the probability of the existence of these protein machines given the existence of an intelligent designer? Here, again, the problem is that we don’t have a very good grasp of either of those probabilities. Surely P(protein machines/unguided evolution) is low; but it is hard
in excelsis
to say
how
low. P(protein machines/intelligent designer) is also really hard to determine. Suppose there is an intelligent designer: how likely is it that he or she (or it) would design and cause to come to be just
these
protein machines?
Intelligent
designer
as a description is so generic that it is hard to make much of a guess here. As Behe puts it,

I strongly emphasize that it is not an argument for the existence of a benevolent God….. Thus, while I argue for design, the question of the identity of the designer is left open. Possible candidates for the role of designer include: the God of Christianity; an angel–fallen or not; Plato’s demiurge; some mystical new-age force; space aliens from Alpha Centauri; time travelers; or some utterly unknown intelligent being.
¹⁹

An intelligent designer that really hated life, or proteins, or protein machines, would be very unlikely to design protein machines; one that really liked protein machines would probably design some. But an intelligent designer just as such—I don’t think we can make any very good guesses here. It is therefore exceedingly difficult to compare P(protein machines/unguided evolution) with P(protein machines/intelligent designer). My guess is that the latter is greater than the former; this isn’t just obvious, however, and it is unclear that the difference in probability is sufficient to constitute serious support for the existence of an intelligent designer.

In this chapter and the last we have been thinking about fine-tuning arguments for design, and Behe’s biological arguments for design. We
have been calling them, naturally enough, “arguments.” But perhaps there is a better way to think about what is going on here. You are hiking up Ptarigan Ridge towards Mt. Baker in the North Cascades; your partner points out a mountain goat on a crag about two hundred yards distant. She thus gets you to form a belief—that there is a mountain goat there. But of course she doesn’t do so by giving you an
argument
(you are appeared to in such and such a way; most of the time when someone
S
is appeared to that way there is a mountain goat about two hundred yards distant in the direction
S
is looking). Perhaps what is going on in the arguments like Behe’s, as well as the fine-tuning arguments of the last chapter, can be better thought of as like what is going on in this sort of case, where it is
perception
(or something like it) rather than argument that is involved.
²⁰

Fine-tuning and Behe-type arguments are ordinarily thought of as contemporary versions of a venerable theistic argument, the so-called “argument from design” (although a better name would be “argument
for
design” or
to
design). Design arguments go back to the “fifth way” of Thomas Aquinas and can also be found in the ancient world.
²¹
A particularly well known (and often cited) version is due to William Paley (1743–1805):

In crossing a heath, suppose I pitched my foot against a
stone
, and were asked how the stone came to be there, I might possibly answer, that, for anything I knew to the contrary, it had lain there for ever; nor would it perhaps be very easy to show the absurdity of this answer. But suppose I had found a
watch
upon the ground,
and it should be inquired how the watch happened to be in that place, I should hardly think of the answer which I had before given, that, for any thing I knew the watch might have always been there. Yet why should not this answer serve for the watch as well as for the stone? Why is it not as admissible in the second case as in the first? For this reason, and for no other, namely, that, when we come to inspect the watch, we perceive (what we could not discover in the stone) that its several parts are framed and put together for a purpose.
²²

Paley goes on to describe in more detail what we perceive, citing the intricacy of the design of the parts, the precision with which the various parts fit together to accomplish their function, the dependence of each part on others, and the like. He then claims that the same holds with respect to various features of the organic world: here too, he proposes, we can perceive design.

Every indication of contrivance, every manifestation of design, which existed in the watch, exists in the works of nature; with the difference, on the side of nature, of being greater and more, and that in a degree which exceeds all computation. I mean that the contrivances of nature surpass the contrivances of art, in the complexity, subtlety, and curiosity of the mechanism; and still more, if possible, do they go beyond them in number and variety; yet, in a multitude of cases, are not less evidently mechanical, not less evidently contrivances, not less evidently accommodated to their end, or suited to their office, than are the most perfect productions of human ingenuity.
²³