Tuesday, February 21, 2012

Randomness and Fitness

Darwinian evolution depends on the concept of biological fitness, but, to the degree that the notion avoids being a tautology, it's pretty much meaningless. There's no way to determine whether an organism is fit other than by seeing if it survives. But if survival is the measure by which we assess fitness then survival of the fittest equates to the vacuous claim that those organisms are fittest which survive and those which survive are fittest.

Stephen Talbot at The New Atlantis has a fine essay on the conceptual problems involved with the notion of Darwinian fitness. He starts out talking about the claim that evolutionary history is driven by random purposeless processes, a claim he finds untenable. He cites biologist Richard Dawkins and philosopher Daniel Dennett to make his point:
Dennett, in one of his characteristic remarks, assures us that “through the microscope of molecular biology, we get to witness the birth of agency, in the first macromolecules that have enough complexity to ‘do things.’ ... There is something alien and vaguely repellent about the quasi-agency we discover at this level — all that purposive hustle and bustle, and yet there’s nobody home.”

Then, after describing a marvelous bit of highly organized and seemingly meaningful biological activity, he concludes: "Love it or hate it, phenomena like this exhibit the heart of the power of the Darwinian idea. An impersonal, unreflective, robotic, mindless little scrap of molecular machinery is the ultimate basis of all the agency, and hence meaning, and hence consciousness, in the universe."
And we read this in Dawkins:
Wherever in nature there is a sufficiently powerful illusion of good design for some purpose, natural selection is the only known mechanism that can account for it.” And: “Natural selection, the blind, unconscious, automatic process which Darwin discovered, and which we now know is the explanation for the existence and apparently purposeful form of all life, has no purpose in mind. It has no mind and no mind’s eye. It does not plan for the future. It has no vision, no foresight, no sight at all.
In other words, both Dawkins and Dennett hold that at bottom life is mindless, meaningless, and purposeless. Any indications to the contrary are illusions. Talbot, however, has serious problems with this view. If all the purposes and meanings in living things are just illusions, as Dawkins insists, then:
[W]hat is the difference between merely illusory purpose and the real thing? If Dawkins means that there is only illusion, then, if there is nothing for the illusion to be a convincing illusion of, it hardly makes sense to say it is an illusion at all, as opposed to being just what it seems to be.

On the other hand, if Dawkins admits that meaning and purpose actually exist as realities and are therefore available to be mimicked in an illusory way, what grounds does he have for claiming meaninglessness and purposelessness as fundamental to the world’s character?
Indeed. Talbot then goes on to reflect on the emptiness of the concept of survival of the fittest:
[F]irst, evolution can be explained by the fact that, on the whole, only the fitter organisms survive and achieve reproductive success; and second, what makes an organism fit is the fact that it survives and successfully reproduces. This is the long-running and much-debated claim that natural selection, as an explanation of the evolutionary origin of species, is tautological — it cannot be falsified because it attempts no real explanation. It tells us: the kinds of organisms that survive and reproduce are the kinds of organisms that survive and reproduce.

Stephen Jay Gould pointed out back in 1976, however, that Darwin and his successors hypothesized independent conditions — “engineering criteria,” as biologists like to say — for the assessment of fitness. These conditions may facilitate and explain reproductive success, but do not merely equate to it. In other words, the concept of fitness need not rely only on the concept of survival (or reproductive success).
The problem, though, is that there's no way to test these "engineering criteria." Talbot again:
To make the problem worse, evolutionary biologists are driven to arrive at scalar values for fitness — values enabling reasonable comparison of traits and organisms, so that we can determine which is the fittest. But how do you take all the infinitely wide-ranging and interwoven considerations that might bear on fitness and reduce them to a scalar value? It is a practical impossibility.

As a pair of philosophers put it in a 2002 article, “Suppose a certain species undertakes parental care, is resistant to malaria, and is somewhat weak but very quick. How do these fitness factors add up? We have no idea at all.”
His conclusion is that the claim that meaning and purpose are illusions, a claim which I would argue is certainly entailed by naturalism, is simply wrong and that the concept of survival of the fittest is hopelessly muddled. Of course, if a claim entailed by naturalism is wrong then naturalism must be wrong, but Talbot chooses not to explore this aspect of the argument.

At any rate, those with an interest in the biological sciences and/or the philosophy of biology will find his essay a rewarding and challenging read.