The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design

by Richard Dawkins

Darwin, although he laid his main stress on survival and the struggle for existence, recognized that existence and survival were only means to an end. That end was reproduction.

Selection will favour qualities that make an animal successful at reproducing, and survival is only part of the battle to reproduce.

we must turn our attention to females, and how they choose their mates. It may seem rather sexist to assume that it is the females that would choose their mates, rather than the other way round. Actually, there are good theoretical reasons for expecting it to be this way round

A male has a great deal to gain by being attractive to females. A female has little to gain by being attractive to males, since she is bound to be in demand anyway.

If I am a male with a long tail, my father is more likely than not to have had a long tail too. This is just ordinary heredity. But also, since my father was chosen as a mate by my mother, my mother is more likely than not to have preferred long-tailed males. Therefore, if I have inherited genes for a long tail from my father, I am also likely to have inherited genes for preferring long tails from my mother. By the same reasoning, if you have inherited the genes for a short tail, the chances are that you have also inherited the genes for making females prefer a short tail.

to carry around, and more to make it in the first place. Males with 4-inch tails might well pull the female birds, but the price the males would pay is their less-efficient flight, greater energy costs and greater vulnerability to predators.

utilitarian optimum. At first sight the very idea seems silly. Fashion-conscious females, with a taste for tails that are longer than they should be on good design criteria, are going to have poorly designed, inefficient, clumsily flying sons.

genes that make females choose male tails of a particular length are, in effect, choosing copies of themselves.

The ‘green-beard’ hypothesis puts the same point more generally, if less practically. Kinship, the argument runs, is only one possible way in which genes can, in effect, locate copies of themselves in other bodies. Theoretically, a gene could locate copies of itself by more direct means. Suppose a gene happened to arise that had the following two effects (genes with two or more effects are common): it makes its possessors have a conspicuous ‘badge’ such as a green beard, and it also affects their brains in such a way that they behave altruistically towards green-bearded individuals. A pretty improbable coincidence, admittedly, but if it ever did arise the evolutionary consequence is clear. The green-beard altruism gene would tend to be favoured by natural selection, for exactly the same kinds of reason as genes for altruism towards offspring or brothers. Every time a green-bearded individual helped another, the gene for giving this discriminating altruism would be favouring a copy of itself. The spread of the green-beard gene would be automatic and inevitable.

any gene that happens to have the effect of helping copies of itself will tend, willy nilly, to become more numerous in the population.

When the females of a population have strong preferences for male characteristics, it follows, by the reasoning we have been through, that each male body will tend to contain copies of genes that make females prefer his own characteristics.

Difference between languages, measured in numbers of divergent words, can be plotted on a graph against distance between islands, measured in miles, and it turns out that the points on the graph fall on a curve whose precise mathematical shape tells us something about rates of diffusion from island to island.

Genes island-hop in the bodies of birds, just as words island-hop in canoes.

Languages, then, evolve. But although modern English has evolved from Chaucerian English, I don’t think many people would wish to claim that modern English is an improvement on Chaucerian English. Ideas of improvement or quality do not normally enter our heads when we speak of language. Indeed, to the extent that they do, we often see change as deterioration, as degeneration. We tend to see earlier usages as correct, recent changes as corruptions. But we can still detect evolution-like trends that are progressive in a purely abstract, value-free sense. And we can even find evidence of positive feedbacks, in the form of escalations (or, looking at it from the other direction, degenerations) in meaning.

tautological

aficionados

Darwin’s view was that a complete fossil record, if only we had one, would show gentle rather than jerky change.

They suggested that, actually, the fossil record may not be as imperfect as we thought. Maybe the ‘gaps’ are a true reflection of what really happened, rather than being the annoying but inevitable consequences of an imperfect fossil record.

cogitation

The argument over whether macromutations such as antennapaedia could ever be beneficial (or at least could avoid being harmful), and therefore whether they could give rise to evolutionary change, therefore turns on how ‘macro’ the mutation is that we are considering. The more ‘macro’ it is, the more likely it is to be deleterious, and the less likely it is to be incorporated in the evolution of a species. As a matter of fact, virtually all the mutations studied in genetics laboratories – which are pretty macro because otherwise geneticists wouldn’t notice them – are deleterious to the animals possessing them (ironically I’ve met people who think that this is an argument against Darwinism!). Fisher’s microscope argument, then, provides one reason for scepticism about ‘saltation’ theories of evolution, at least in their extreme form.

If they do hybridize with them the resulting offspring are sickly, or sterile like mules. So natural selection penalizes any predilection, on the part of individuals on either side, towards hybridizing with the other species or even race. Natural selection thereby finishes off the process of ‘reproductive isolation’ that began with the chance intervention of a mountain range. ‘Speciation’ is complete. We now have two species where previously there was one, and the two species can coexist in the same area without interbreeding with one another.

Many species once formed never undergo any further change …; and the periods, during which species have undergone modification, though long as measured by years, have probably been short in comparison with the periods during which they retain the same form.

Something like the transition from Amoeba to man, he pointed out, goes on in every mother’s womb in a mere nine months. Development is admittedly a very different process from evolution but, nevertheless, anyone sceptical of the very possibility of a transition from single cell to man has only to contemplate his own foetal beginnings to have his doubts allayed.

Organisms can never be totally unrelated to one another, since it is all but certain that life as we know it originated only once on earth.

Biological classificatory rings never intersect in this way, because biological evolution above the species level is always divergent.

Our legal and moral systems are deeply species-bound.

I have heard decent, liberal scientists, who had no intention of actually cutting up live chimpanzees, nevertheless passionately defending their right to do so if they chose, without interference from the law. Such people are often the first to bristle at the smallest infringement of human rights. The only reason we can be comfortable with such a double standard is that the intermediates between humans and chimps are all dead.

There must be some groups or species in which, as it happens, what is best for the individual pretty much coincides with what is best for the species.

when taxonomists tell us that two animals really are closely related – say rabbits and hares – how do we know that the taxonomists haven’t been fooled by massive convergence?

The genetic dictionary has 64 DNA words of three letters each. Every one of these words has a precise translation into protein language (either a particular amino acid or a punctuation mark). The language appears to be arbitrary in the same sense as a human language is arbitrary (there is nothing intrinsic in the sound of the word ‘house’, for instance, which suggests to the listener any attribute of a dwelling). Given this, it is a fact of great significance that every living thing, no matter how different from others in external appearance it may be, ‘speaks’ almost exactly the same language at the level of the genes.

Convergent evolution is really a special kind of coincidence. The thing about coincidences is that, even if they happen once, they are far less likely to happen twice. And even less likely to happen three times.

I said that taxonomy was one of the most rancorously ill-tempered of biological fields. Stephen Gould has well characterized it with the phrase ‘names and nastiness’. Taxonomists seem to feel passionately about their schools of thought, in a way that we expect in political science or economics, but not usually in academic science. It is clear that members of a particular school of taxonomy think of themselves as a beleaguered band of brothers, like the early Christians. I first realized this when a taxonomist acquaintance told me, white-faced with dismay, the ‘news’ that So-and-so (the name doesn’t matter) had ‘gone over to the cladists’.

I was once approached by a colleague, a celebrated Marxist historian and a most cultivated and well-read man. He understood, he said, that the facts all seemed to be against the Lamarckian theory, but was there really no hope that it might be true? I told him that in my opinion there was none, and he accepted this with sincere regret, saying that for ideological reasons he had wanted Lamarckism to be true. It seemed to offer such positive hopes for the betterment of humanity.

N. I. Vavilov, a geneticist of worldwide reputation, died of malnutrition in a windowless prison cell after a prolonged trial on ludicrously trumped up charges such as ‘spying for the British’.

There are, in truth, many respects in which mutation is not random.

If you take ‘random mutation’ to mean that mutations are not influenced by external events, then X-rays disprove the contention that mutation is random. If you think ‘random mutation’ implies that all genes are equally likely to mutate, then hot spots show that mutation is not random. If you think ‘random mutation’ implies that at all chromosomal loci the mutation pressure is zero, then once again mutation is not random. It is only if you define ‘random’ as meaning ‘no general bias towards bodily improvement’ that mutation is truly random. All three of the kinds of real non-randomness we have considered are powerless to move evolution in the direction of adaptive improvement as opposed to any other (functionally) ‘random’ direction.