Evolution and Progress

ACCORDING TO ONE STRAND of Darwinian thinking, evolution is fundamentally a relative notion, and that there is in Darwin’s theory no necessity that the development of evolutionary processes should be progressive in any sense other than ‘better at surviving and reproducing’. Proponents of this interpretation will point out that in The Origin of Species Darwin hardly uses the term ‘evolution’ (which definitely has connotations of progress in a more general sense), but tends to speak of the laws of variation, natural selection and descent with modification. ‘Descent with modification’ carries with it no implication that the modifications brought about through natural selection will necessarily be bigger or more complex or more beautiful or more intelligent. Indeed they definitely won’t be any of these things if the costs of greater complexity, intelligence, etc., in terms of energy consumption and so on outweigh the survival advantages they bring.

On this austere understanding of what is going on, success in the struggle for survival is all that really counts, and all that natural selection guarantees, and that may come in all sorts of ways. What the theory says is that variations which benefit their possessors in the struggle for survival will do better and eventually displace their competitors and their less successful con-specifics.

But success is always relative to a given environment, and may not require greater complexity or perfection viewed in absolute terms. Thus a longer neck might benefit its possessor if there are tall, food-bearing trees, but not if the trees all die out. If that happened the very same characteristic which was once an advantage will later prove a disadvantage. This effect can be quite radical in leading to the shedding of costly characteristics within a species when they are no longer required. Thus we see cave-dwelling descendants of sighted creatures with no sight, or flightless birds in New Zealand (before humans arrived with their rodent followers). In each case the effort and energy needed to produce sight and flight was not necessary for survival, so the faculties in question simply dropped off. They constituted a cost with no consequent advantage, and so long as there is no better equipped competitor there will be no evolutionary impetus towards what we might regard as an improvement, or what might indeed be an improvement, absolutely speaking.

Darwin was well aware of all of this: ‘As natural selection acts by competition, it adapts the inhabitants of each country only in relation to the degree of perfection of their associates… Nor ought we to marvel if all the contrivances of nature be not, as far as we can judge, absolutely perfect; and if some of them be abhorrent to our idea of fitness.’ And having mentioned bees being killed by their own stings, drones being produced in vast numbers for just one act, then to be slaughtered, ichneumonidae feeding in the bodies of live caterpillars, and other examples of waste, profligacy and worse in nature, he concludes ‘the wonder indeed is, on the theory of natural selection, that more cases of the want of absolute perfection have not been observed.’ (The Origin of Species, Penguin Books, Harmondsworth, 1982, p 445).

Logically what Darwin says here is impeccable. Relative fitness and non-progressive development, fit enough just for the relevant environment, is all that is strictly implied by the theory of natural selection. Indeed we could argue that if species’ longevity and geographical spread are the criteria of evolutionary success the most successful species may well be certain types of insect. Certainly mammals in general and human beings in particular will be nowhere near the most successful. And, more generally, Darwin is keen on occasion to point out that our own ideas of what constitute perfection in a species might just be a little, shall we say, anthropocentric: he wrote in a letter that while to us intelligence may seem the chief mark of progress, to a bee it would no doubt be something else. This last sentiment might well seem to some to put Darwin in a favourable light, as immune to the race and species progressivism characteristic of his age. Unfortunately (perhaps) Darwin turns out to have had no such immunity, nor did he see evolution in general in strictly relative terms.

This is actually perfectly evident from the closing pages of The Origin of Species. ‘As natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection’, he writes at the end of the penultimate paragraph. What he says there is something of a non sequitur, especially given our earlier observations on the logic of natural selection, which would license no such perfectionist optimism. One wonders, moreover, what Darwins’s own standard of progress and perfection is. Is a horse more perfect than a dinosaur, a fish than an amoeba? Is mankind more perfect than the bee? If we think we know what Darwin’s answers might be to at least some of these questions, there is more than a hint that in his judgements he would be implicitly judging the animal kingdom by the human characteristics of intelligence, rationality, morality, brain complexity and the rest.