Wednesday, February 11, 2009

Natural Selection

In anticipation of tomorrow’s anniversary, here a few reflections on that interesting concept in biology, natural selection. It is quite clear from Darwin’s own words that this concept central to his doctrine merely means that, in nature, a selection takes places analogous to that which humanity exercises in nurturing and shaping animal and plant varieties by husbandry. If variations occur naturally—and we know that they occur by human intervention—

Can it, then, be thought improbable … that other variations useful in some way to each being in the great and complex battle of life, should occur in the course of many successive generations? If such do occur, can we doubt (remembering that many more individuals are born than can possibly survive) the individuals having any advantage, however slight, over others,would have the best chance of surviving and procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favorable individual differences and variations, and the destruction of those which are injurious, I have called Natural Selection, or the Survival of the Fittest. [Charles Darwin, The Origin of Species, Great Books of the Western World, Encyclopaedia Britannica, Vol. 49, p. 40.]

Shortened and sharpened, the gist of this is that preservation and destruction take place in nature, favoring good and eliminating bad variations that come about somehow. That he means nothing else Darwin himself emphasizes by speaking of natural selection as a metaphorical expression. He does not intend to personify nature except as a way of speaking concisely of complex matters. “I mean by Nature, only the aggregate action and product of many natural laws, and by laws the sequence of events as ascertained by us.”

What strikes me here is that this so-called cornerstone of modern biology is just a common-sense observation.

Darwin offered natural selection as his general explanation for biological change. But it amounts to saying that some species survive while others go extinct—and if we look for better explanations, we shall discover that those that passed away had a worse environment (internal, external, or some combination) than those that have stayed around.

If we introduce genetic changes taking place at random—changes natural selection can work upon—we don’t improve the theory. Change is change. An internal modifications is equivalent to one outside if both take place by chance. If the creature could modify itself at will in order to adapt, then we’d have something to discuss.

To be sure—a difficult subject. To say that things are tough, bad things happen, creatures cope as best they can, and what you get is that which happens (explain it as you will)—this formulation is not a theory so much as a description of the way things are. Natural selection as a mechanism is nothing more than saying that in an unruly and chaotic world some are lucky, some are not.

Something in the nineteenth century European soul favored Darwin’s theory. Another time might have shrugged it off as naïve or self-evident. The elites of that time had wearied of the older theory. It was based on a similar projection of an agency, God, another all-purpose arranger of reality. What happened here is that Darwin substituted another concept, nature. He was careful to point out that he meant everything that happens, all the laws of nature working on species. But the public understood him to have switched one universal concept for another. Within the stream of modern history, natural selection rose to an exalted principle. Part of the change arose, I’m fairly sure, by cultural embrace of secularism. The old theory had a large, to the public costly, and well-established institutional presence with demanding teachings inconvenient to many. The new one, science, was just beginning to emerge.

It amuses me to note that Lucretius (96-55 BC) wrote as follows 1,800 years or so before the birth of Darwin. Lucretius was trying to explain the dying off of what he called monstrous breeds: “Nature set a ban on their increase and they could not reach the coveted flower of age nor find food nor be united in marriage… And many races of living things must then have died out and been unable to beget and continue their breed.” Surviving breeds, according to Lucretius, had characteristics that “protected and preserved each particular race.” [Quoted in the essay “Evolution” in The Great Ideas, written by Mortimer J. Adler, Vol. 1, Encyclopaedia Britannica, Inc., p. 451]

Lucretius was the last notable Epicurean, the last ancient atomist, convinced atheist, who, like Darwin’s followers, needed something equivalent to God, Nature in Lucretius’ case too, to act as an agent able to set bans and such.

In the context of tomorrow’s anniversary, it is worth noting that evolution as “development from simple to complex” appears in the thought of Anaximander (611-547 BC), Empedocles (5th c. BC), Aristotle (384-322 BC), Augustine (354-430), Aquinas (1225-1274), Locke (1632-1704), Buffon (1707-1788), Kant (1724-1804), Lamarck (1744-1829), and, not least, Darwin’s own grandfather, Erasmus. Here’s his take in verse:

Organic life beneath the shoreless waves
Was born and nurs'd in ocean's pearly caves;
First forms minute, unseen by spheric glass,
Move on the mud, or pierce the watery mass;
These, as successive generations bloom,
New powers acquire and larger limbs assume;
Whence countless groups of vegetation spring,
And breathing realms of fin and feet and wing.
Erasmus Darwin. The Temple of Nature. 1802.

Looking at the organic order we cannot escape the intuition of continuity, relatedness, and increasing complexity. No names on the list above appear from periods when cultures were deeply religious—for the simple reason that in those times the eyes of the elites were directed inward and science was dormant then.

Darwin coined a concept to describe that species that survive survive. That notion itself is not remarkable, and in that form would not have spawned a branch of science. His concept as he used it is ordinary enough. The rhetorical flourish that he gave it caught on in a time not given to rigorous philosophical analysis—and elites were suddenly entranced. Yes, perhaps tea leaves can tell the future; and, yes, perhaps clouds actually do at times show faces, horses. But such discoveries are better explained by looking at the viewer—or his times—than at the clouds or at the bottom of his cup.

No comments:

Post a Comment