Charles Darwin had a big idea, arguably the most powerful idea ever. A powerful idea assumes little to explain much. It does a lot of explanatory “heavy lifting” while expending little in the way of assumption or postulation. It gives you plenty of bang for your explanatory buck. Its Explanation Ratio—what it explains divided by what it needs to assume in order to do the explaining—is large.
|Power of a theory||=|
|That which it explains|
|That which it needs to assume in order to do the explaining|
If any reader knows of an idea that has a larger explanation ratio than Darwin’s, let’s hear it. Darwin’s big idea explains all of life and its consequences, and that means everything that possesses more than minimal complexity. That’s the numerator of the Explanation Ratio, and it is huge. Yet the denominator is spectacularly small and simple: natural selection, the non-random survival of genes in gene pools (to put it in neo-Darwinian terms rather than Darwin’s own).
|Power of Darwin’s theory||=|
|The diverse complexity of life|
Natural selection is an improbability pump—a process that generates statistical improbability. It systematically seizes the minority of random changes that have what it takes to survive and accumulates them, step by tiny step over unimaginable timescales, until evolution eventually scales mountains of improbability and diversity whose height and range seem to know no limit. Yet it is so magnificently simple that you can pare Darwin’s big idea down to a single sentence (again, this is a neo-Darwinian way of putting it, not quite Darwin’s): Given sufficient time, the non-random survival of hereditary entities (which occasionally miscopy) will generate complexity, diversity, beauty, and an illusion of design so persuasive that it is almost impossible to distinguish from deliberate intelligent design.
I have put “which occasionally miscopy” in parentheses because mistakes are inevitable in any copying process. We don’t need to add mutation to our assumptions. Mutational “bucks” are provided free. “Given sufficient time” is not a problem either—except for the problem of comprehension by human minds struggling to take on board the terrifying magnitude of geological time.
It is mainly its power to simulate the illusion of design that makes Darwin’s theory seem threatening to a certain kind of mind. The same power constitutes the most formidable barrier to understanding it. People are naturally incredulous that anything so simple could explain so much. To a naïve observer of the wondrous complexity of life, it seems self-evident that it must be intelligently designed. But intelligent design (ID) is the polar opposite of a powerful theory: its explanation ratio is pathetic. The numerator is the same: everything we know about life and its prodigious complexity. But the denominator, far from Darwin’s pristine and minimalistic simplicity, is at least as big as the numerator itself: an unexplained intelligence big enough to be capable of designing all the complexity we are trying to explain in the first place!
|Power of ID theory||=|
|An unexplained intelligence big enough to design everything|
Darwin understood the immense power of his theory. So did Alfred Russel Wallace, the magnanimous hero whose independent discovery galvanized Darwin into shelving his magnum opus on natural selection in favor of what he called its “abstract”: On the Origin of Species. Claims to priority were made on behalf of others, including Patrick Matthew in the appendix to a work on raising trees for shipbuilding, as Darwin punctiliously acknowledged in later editions of Origin. However, though Matthew understood the principle of natural selection, it is not clear that he understood its power to explain the whole of life. Unlike Darwin and Wallace, he seems to have seen selection as a purely negative, weeding-out force, not the universal driving force. Indeed, he thought natural selection so obvious as to need no positive discovery at all.
Here may lie the answer to a nagging puzzle in the history of ideas. After Newton’s brilliant synthesis of physics, why did it take nearly two hundred years for Darwin to arrive on the scene? Newton’s achievement seems so much harder! Maybe the answer is that Darwin’s eventual solution to the riddle of life is so staggeringly simple, nobody thought to look for it.
It is so simple that in the guise of “survival of the fittest” (the renaming that Darwin adopted from Herbert Spencer at the urging of Wallace), it has even been described as a tautology: the fittest are defined as those that survive, so the catchphrase amounts to “those that survive survive.” But if it were really a tautology, the same mud should stick to artificial selection, the non-random breeding of domestic animals and plants (to which Darwin devoted so much attention). Imagine the dusty reception a certain kind of bad philosopher might get after saying this to a cattle breeder: “You are wasting your time. No improvement in milk yield can come from a tautology!” But Darwin didn’t define the fittest as those that survive. His “fittest” were those endowed with the best equipment to survive, and that makes all the difference.
By the way, Darwin had plenty of other good ideas (for example his ingenious and largely correct theory of how coral reefs form), but it is his big idea of natural selection that I am talking about here. I think it is even more powerful than I have so far suggested. Not only is it the explanation for life on this planet, it is the only theory so far suggested that could, even in principle, explain life on any planet. If life exists elsewhere in the universe (and my tentative bet is that it does), however strange and alien and weird its nature may be (and my tentative bet is that it will be weird beyond imagining), some version of evolution by Darwinian natural selection will almost certainly turn out to underlie its existence. That is at least how I would bet: on the principle that I have called “Universal Darwinism.”
There is a different sense of Universal Darwinism that I want to counsel against. This is the uncritical dragging of some garbled version of natural selection into every available field of human discourse, whether it is appropriate or not. Maybe the “fittest” firms survive in the marketplace, or the fittest theories survive in the scientific marketplace, but we should at the very least be cautious before we get carried away. And of course there was Social Darwinism, culminating in the obscenity of Hitlerism. Less obnoxious but still intellectually unhelpful is the loose and uncritical way in which amateur biologists apply selection at inappropriate levels in the hierarchy of life. “Survival of the fittest species, extinction of poorly adapted species” sounds superficially like true natural selection, but the apparent resemblance is positively misleading. As Darwin himself was at pains to point out, natural selection is all about differential survival within species, not between them.
Darwin’s great idea has moved on. Twenty-first century evolutionary science, if Darwin could return to see it, would enthrall, excite, and amaze him. But he would recognize it as his own. We are just coloring in the details. For my money, the most important thinker the human species has ever produced was Charles Darwin.
I’ll end on a subtler legacy of Darwin’s big idea. Darwin raises our consciousness to the sinewy power of science to explain the large and complex in terms of the small and simple. In biology we were fooled for centuries into thinking that extravagant complexity in nature needs an extravagantly complex explanation. Darwin triumphantly dispelled that illusion. There remain big questions, in physics and cosmology, that await their own Darwins. Why are the laws of physics the way they are? Why are there laws at all? Why is there a universe at all? Once again, the lure of “design” is tempting, but we have the cautionary tale of Darwin before us. We’ve been through all that before. Darwin raised our consciousness, and we are emboldened to seek true explanations of genuine power.
Richard Dawkins, F.R.S., is emeritus professor of the Public Understanding of Science at Oxford. His latest book is The God Delusion (First Mariner Books Edition, 2008).