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

by Richard Dawkins

This is that I am about to embark on two interwoven analogies which I find inspiring but which can be taken too far if we are not careful. The first is an analogy between various processes that are united by their resemblance to explosions. The second is an analogy between true Darwinian evolution and what has been called cultural evolution.

Positive-feedback systems are used less than negative feedback, both by engineers and by living bodies, but nevertheless it is positive feedbacks that are the subject of this chapter.

After a short piece of reasoning he concluded (in his book The Genetical Theory of Natural Selection): plumage development in the male, and sexual preference for such developments in the female, must thus advance together, and so long as the process is unchecked by severe counterselection, will advance with ever-increasing speed. In the total absence of such checks, it is easy to see that the speed of development will be proportional to the development already attained, which will therefore increase with time exponentially, or in geometric progression. It is typical of Fisher that what he found ‘easy to see’ was not fully understood by others until half a century later.

While I would not be so pessimistic as Fisher himself who, in the Preface to his 1930 book, said ‘No efforts of mine could avail to make the book easy reading’, nevertheless, in the words of a kind reviewer of my own first book, ‘The reader is warned that he must put on his mental running shoes’.

We can express this by saying that there is a utilitarian optimum tail length, which is different from the sexually selected optimum: an ideal tail length from the point of view of ordinary useful criteria; a tail length that is ideal from all points of view apart from attracting females.

The only general criteria that successive generations of females can use are the indicators that any vet might use — bright eyes, glossy plumage, and so on. Only genuinely healthy males can display these symptoms of health, so selection favours those males that display them to the full, and even exaggerate them into long tails and spreading fans.

What he found was that males with artificially elongated tails attracted nearly four times as many females as males with artificially shortened tails. Those with tails of normal, natural length had intermediate success.

The fact that real tails are shorter than females would prefer suggests that there must be some other selection pressure keeping them shorter. This is ‘utilitarian’ selection.

Cultural ‘evolution’ is not really evolution at all if we are being fussy and purist about our use of words, but there may be enough in common between them to justify some comparison of principles.

To a lesser extent, the same phenomenon of popularity being popular for its own sake is well known in the worlds of book publishing, womens’ fashions, and advertising generally.

The radiocarbon stopwatch buzzes round at a great rate, so fast that, after some thousands of years, its spring is almost wound down and the watch is no longer reliable.

https://en.wikipedia.org/wiki/Radiocarbon_dating It takes 5,730 years for half the carbon-14 to decay to nitrogen; this is the half-life of carbon-14. After another 5,730 years, only one-quarter of the original carbon-14 will remain. After yet another 5,730 years, only one-eighth will be left. The relatively short half-life of carbon-14, 5,730 years, makes dating reliable only up to about 60,000 years

For the evolutionary timescale other kinds of watch, such as the potassium-argon watch, are suitable.

https://en.wikipedia.org/wiki/Potassium%E2%80%93argon_dating One of the most widely used is potassium–argon dating (K–Ar dating). Potassium-40 is a radioactive isotope of potassium that decays into argon-40. The half-life of potassium-40 is 1.3 billion years.

Other radioactive ‘stopwatches’, each with its own characteristic rate of slowing down, are the rubidium-strontium, and the uranium-thorium-lead watches.

https://en.wikipedia.org/wiki/Uranium%E2%80%93thorium_dating As time passes after such material has formed, uranium-234 in the sample with a half-life of 245,000 years decays to thorium-230. Thorium-230 is itself radioactive with a half-life of 75,000 years.

The same is true even of one of the fastest known evolutionary changes, the swelling of the human skull from an Australopithecus- like ancestor, with a brain volume of about 500 cubic centimetres (cc), to the modern Homo sapiens’s average brain volume of about 1,400 cc. This increase of about 900 cc, nearly a tripling in brain volume, has been accomplished in no more than three million years.

For example the Cambrian strata of rocks, vintage about 600 million years, are the oldest ones in which we find most of the major invertebrate groups. And we find many of them already in an advanced state of evolution, the very first time they appear.

The important point is that if we consider mutations of ever-increasing magnitude, there will come a point when, the larger the mutation is, the less likely it is to be beneficial; while if we consider mutations of ever-decreasing magnitude, there will come a point when the chance of a mutation’s being beneficial is 50 per cent.

In the biomorph model we assumed that this kind of multidimensional improvement could not occur. To recapitulate on why that was a reasonable assumption, to make an eye from nothing you need not just one improvement but a large number of improvements. Any one of these improvements is pretty improbable by itself, but not so improbable as to be impossible. The greater the number of simultaneous improvements we consider, the more improbable is their simultaneous occurrence. The coincidence of their simultaneous occurrence is equivalent to leaping a large distance across Biomorph Land, and happening to land on one particular, predesignated spot.

Darwin’s answer to the question of the origin of species was, in a general sense, that species were descended from other species. Moreover, the family tree of life is a branching one, which means that more than one modern species can be traced back to one ancestral one.

(I cannot help being reminded here of the humiliation of my first school report, written by the Matron about my performance as a seven-year-old in folding clothes, taking cold baths, and other daily routines of boarding-school life: ‘Dawkins has only three speeds: slow, very slow, and stop’).

How do we explain it? Some of us would say that the lineage leading to Latimeria stood still because natural selection did not move it. In a sense it had no ‘need’ to evolve because these animals had found a successful way of life deep in the sea where conditions did not change much.

For Darwin, any evolution that had to be helped over the jumps by God was not evolution at all. It made a nonsense of the central point of evolution.

Orderly classification is often represented as a measure of convenience, a practical necessity, and this is indeed a part of the truth. The books in a large library are nearly useless unless they are organized in some nonrandom way so that books on a particular subject can be found when you want them.

What it does mean is that there is no single classification system which, in a world of perfect information, would be universally agreed as the only correct classification.

In cladistic taxonomy, the ultimate criterion for grouping organisms together is closeness of cousinship or, in other words, relative recency of common ancestry.

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.

True cladistic taxonomy is strictly hierarchical, an expression which I shall use to mean that it can be represented as a tree whose branches always diverge and never converge again.

In my view (some schools of taxonomists, that we shall discuss later, would disagree), it is strictly hierarchical not because hierarchical classification is convenient, like a librarian’s classification, nor because everything in the world falls naturally into a hierarchical patte...

The myth that mammals, for instance, form a ladder or ‘scale’, with ‘lower’ ones being closer to fish than ‘higher’ ones, is a piece of snobbery that owes nothing to evolution. It is an ancient, pre-evolutionary notion, sometimes called the ‘great chain of being’, which should have been destroyed by evolution but which was, mysteriously, absorbed into the way many people thought about evolution.

Such is the breathtaking speciesism of our Christian-inspired attitudes, the abortion of a single human zygote (most of them are destined to be spontaneously aborted anyway) can arouse more moral solicitude and righteous indignation than the vivisection of any number of intelligent adult chimpanzees!

Perhaps the most dramatic example of a truly species-level trait concerns the mode of reproduction, sexual versus asexual.

The African porcupine was long believed to be closely related to the American porcupines, but the two groups are now thought to have evolved their prickly coats independently.

The phyleticists, the taxonomists that openly try to discover evolutionary relationships, further split into two schools of thought. These are the cladists, who follow the principles laid down in Willi Hennig’s famous book Phylogenetic Systematics; and the ‘traditional’ evolutionary taxonomists. Cladists are obsessed with branches.

There are indeed virtues in both cladism and traditional evolutionary taxonomy, and I don’t much mind how people classify animals so long as they tell me clearly how they are doing it.

As Mark Ridley more mildly said, in a review of the book in which Nelson and Platnick made that remark about Darwinism being false, Who would have guessed that all that they really meant was that ancestral species are tricky to represent in cladistic classification? Of course it is difficult to pin down the precise identity of ancestors, and there is a good case for not even trying to do so.

My argument will be that Darwinism is the only known theory that is in principle capable of explaining certain aspects of life.

One way in which to dramatize this point is to make a prediction. I predict that, if a form of life is ever discovered in another part of the universe, however outlandish and weirdly alien that form of life may be in detail, it will be found to resemble life on Earth in one key respect: it will have evolved by some kind of Darwinian natural selection.

There is one particular property of living things, however, that I want to single out as explicable only by Darwinian selection. This property is the one that has been the recurring topic of this book: adaptive complexity.

If you put the inheritance of acquired characteristics together with the principle of use and disuse, you have what looks like a good recipe for evolutionary improvement. It is this recipe that is commonly labelled the Lamarckian theory of evolution.

The legendary examples are the blacksmith’s arms and the giraffe’s neck. In villages where the blacksmith inherited his trade from his father, grandfather and great grandfather before him, he was thought to inherit the well-trained muscles of his ancestors too. Not just inherit them but add to them through his own exercise, and pass on the improvements to his son. Ancestral giraffes with short necks desperately needed to reach high leaves on trees. They strove mightily upwards, thereby stretching neck muscles and bones. Each generation ended up with a slightly longer neck than its predecessor, and it passed its head start on to the next generation.

George Bernard Shaw devoted one of his enormous Prefaces (in Back to Methuselah) to a passionate advocacy of the inheritance of acquired characteristics. His case was based not upon biological knowledge, of which he would cheerfully have admitted he had none. It was based upon an emotional loathing of the implications of Darwinism, that ‘chapter of accidents’: it seems simple, because you do not at first realize all that it involves. But when its whole significance dawns on you, your heart sinks into a heap of sand within you. There is a hideous fatalism about it, a ghastly and damnable reduction of beauty and intelligence, of strength and purpose, of honor and aspiration.

For the same reason we can never prove that fairies do not exist. All we can say is that no sightings of fairies have ever been confirmed,

For example, this is true of the allegation, sometimes made on spurious biblical grounds, that the universe was created only about 6,000 years ago.

The field of discourse, then, is embryology. There has traditionally been a deep divide between two different attitudes to the way single cells turn into adult creatures. The official names for them are preformationism and epigenesis, but in their modern forms I shall call them the blueprint theory and the recipe theory.

The early preformationists believed that the adult body was preformed in the single cell from which it was to develop. One of them imagined that he could see in his microscope a little miniature human — a ‘homunculus’ — curled up inside a sperm (not egg!). Embryonic development, for him, was simply a process of growth. All the bits of the adult body were already there, preformed.

Now to consider the other great theory of embryology, epigenesis, the recipe or ‘cookery book’ theory.

But a recipe is not a scale model, not a description of a finished cake, not in any sense a point-for-point representation. It is a set of instructions which, if obeyed in the right order, will result in a cake.

Nevertheless, the indications are very strong that the genes are much more like a recipe than like a blueprint. Indeed, the recipe analogy is really rather a good one, while the blueprint analogy, although it is often unthinkingly used in elementary textbooks, especially recent ones, is wrong in almost every particular. Embryonic development is a process.

My claim at the outset of this chapter was stronger: that, even if acquired characteristics could be inherited, the Lamarckian theory would still be incapable of explaining adaptive evolution. This claim is so strong that it is intended to apply to all life-forms, everywhere in the universe. It is based upon two lines of reasoning, one concerned with difficulties over the principle of use and disuse, the other with further problems with the inheritance of acquired characteristics. I shall take these in reverse order.

Most of the characteristics that any machine acquires as it gets older tend to be the accumulated ravages of time: it wears out. If they were gathered up by some kind of scanning process and fed into the blueprint for the next generation, successive generations would get more and more decrepit. Instead of starting afresh with a new blueprint, each new generation would begin life encumbered and scarred with the accumulated decay and injuries of previous generations.

If parents could somehow transcribe the wisdom of a lifetime’s experience into their genes, so that their offspring were born with a library of vicarious experience built in and ready to be drawn upon, those offspring could begin life one jump ahead. Evolutionary progress might indeed speed up, as learned skills and wisdom would automatically be incorporated into the genes.