(The third part in a series celebrating Charles Darwin.)
Charles Darwin was a giant. He did not merely write “On the Origin of Species” — one of the most important books ever written by anyone — in which he describes how evolution by natural selection works, and what some of its consequences and implications are. He also wrote — and this list is not exhaustive— a treatise on the formation of coral reefs that is still thought to be correct; a definitive monograph on barnacles, both extinct and extant; a book about how earthworms make soil; a now-classic text on carnivorous plants (the ones, like Venus fly-traps, that ensnare and digest insects); a book about the strange ways that orchids get themselves fertilized; and an account of the five years he spent aboard the ship HMS Beagle, which has become a classic of travel writing.
As if that wasn’t enough, he proposed sexual selection — the idea that decorations and ornaments, like peacocks’ tails, evolve because females in many species prefer to mate with the most beautiful males. Sexual selection has since become a major field of research in its own right.
In short, Darwin did more in one lifetime than most of us could hope to accomplish in two. But his giantism has had an odd and problematic consequence. It’s a tendency for everyone to refer back to him. “Why Darwin was wrong about X”; “Was Darwin wrong about Y?”; “What Darwin didn’t know about Z” — these are common headlines in newspapers and magazines, in both the biological and the general literature. Then there are the words: Darwinism (sometimes used with the prefix “neo”), Darwinist (ditto), Darwinian.
Why is this a problem? Because it’s all grossly misleading. It suggests that Darwin was the beginning and the end, the alpha and omega, of evolutionary biology, and that the subject hasn’t changed much in the 149 years since the publication of the “Origin.”
He wasn’t, and it has. Although several of his ideas — natural and sexual selection among them — remain cornerstones of modern evolutionary biology, the field as a whole has been transformed. If we were to go back in a time machine and fetch him to the present day, he’d find much of evolutionary biology unintelligible — at least until he’d had time to study genetics, statistics and computer science.
Oh, there would be so much to tell him! A full list would take me weeks to write out. But the obvious place to begin would be the discoveries of genetics, especially DNA. We’d have to explain that cells in each organism contain a code describing how to build that organism, written in chemical form — DNA — that evolutionary forces are constantly rewriting. Indeed, the study of DNA allows us to see the action of natural selection on a molecule-by-molecule basis. We can see the genes where natural selection acts to prevent evolutionary change, those where it drives change and those where it has no effect at all.
Then there’s the fusion of genetics with natural selection, which has enormously expanded our understanding of how natural selection can work. For example, it has led to the discovery that natural selection does not just shape individuals — the length of a beak, the color of a fin. It can also act on family groups, and thus drive the evolution of cooperation and other altruistic behaviors.
The reason is that evolutionary success can now be measured in terms of the number of genes an individual contributes to the next generation. Anyone who dies without reproducing does not directly contribute any. But because individuals have some genes in common with their family members, they can make an indirect genetic contribution if they help their relations to reproduce instead of reproducing themselves. Such “kin selection” is thought to have contributed to the evolution of the social insects — especially, ants, bees, wasps and termites — where only a few individuals reproduce and everyone else looks after the offspring.
We’d want to discuss evolution beyond natural selection — the other forces that can sometimes cause (or prevent) evolutionary change. For although natural selection is the only creative force in evolution — the only one that can produce complex structures such as wings and eyes — it is not the only force that affects which genes will spread, and which will vanish.
And, and, and.
What would he make of it all?
I think his reaction would be a mix of satisfaction and astonishment. Satisfaction: that natural selection has turned out to be such a powerful idea, explaining such a wide range of phenomena. Astonishment: for the same reason. He would, I think, be fascinated by the weird natural history that has been discovered in the past 150 years — such as Wolbachia, bacteria that pervert the reproduction of insects for their own ends. (Wolbachia can have a number of effects, but one of the most common is to kill all a female’s sons. The reason is that sons don’t transmit Wolbachia, so from Wolbachia’s point of view, they are a waste of space.) I’m not sure he’d enjoy analyzing DNA sequences — he might find it a bit too abstracted from the living organism — but I think he’d be delighted to learn the results. I think he would be shocked by how much we know about the so-called model organisms — worms, toads, fruit flies, mice, humans and the bacterium E. coli — and how little we know about everything else. And I think he’d be startled by the nature of scientific research — the scale of the enterprise, the cost, the pressures to publish and the degree of specialization that results. His brand of science — 20 years of thinking about a problem before publishing — could not be done today.
But I digress. To return to my argument: I’d like to abolish the insidious terms Darwinism, Darwinist and Darwinian. They suggest a false narrowness to the field of modern evolutionary biology, as though it was the brainchild of a single person 150 years ago, rather than a vast, complex and evolving subject to which many other great figures have contributed. (The science would be in a sorry state if one man 150 years ago had, in fact, discovered everything there was to say.) Obsessively focusing on Darwin, perpetually asking whether he was right about this or that, implies that the discovery of something he didn’t think of or know about somehow undermines or threatens the whole enterprise of evolutionary biology today.
It does not. In the years ahead, I predict we will continue to refine our understanding of natural selection, and continue to discover new ways in which it can shape genes and genomes. Indeed, as genetic data continues to flood into the databanks, we will be able to ask questions about the detailed workings of evolution that it has not been possible to ask before.
Yet all too often, evolution — insofar as it is taught in biology classes at all — is taught as the story of Charles Darwin. Then the pages are turned, and everyone settles down to learn how the heart works, or how plants make energy from sunshine, or some other detail. The evolutionary concepts that unify biology, that allow us to frame questions and investigate the glorious diversity of life — these are ignored.
Darwin was an amazing man, and the principal founder of evolutionary biology. But his was the first major statement on the subject, not the last. Calling evolutionary biology “Darwinism,” and evolution by natural selection “Darwinian” evolution, is like calling aeronautical engineering “Wrightism,” and fixed-wing aircraft “Wrightian” planes, after those pioneers of fixed-wing flight, the Wright brothers. The best tribute we could give Darwin is to call him the founder — and leave it at that. Plenty of people in history have had an -ism named after them. Only a handful can claim truly to have given birth to an entire field of modern science.
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NOTES:
A full account of the range of Darwin’s activities and accomplishments can be found in any biography. Many publications are guilty of the “Was Darwin wrong?” trope, and some of the biggest quarrels in modern evolutionary biology have concerned the validity of “non-Darwinian” evolution. A number of popular accounts discuss aspects of modern evolutionary biology; one of the best is “The Ancestor’s Tale,” by Richard Dawkins. Much has been written about male-killing by Wolbachia; see, for example, Jiggins, F. M., Hurst, G. D. D., Dolman, C. E., and Majerus, M. E. N. 2000. “High-prevalence male-killing Wolbachia in the butterfly Acraea encedana.” Journal of Evolutionary Biology 13: 495-501.
This article was inspired (as so many others have been) by a conversation with Oliver Morton — many thanks, as always. Thanks, too, to Dan Haydon, Gideon Lichfield, Dmitri Petrov, Daniel Richler and Jonathan Swire for insights, comments and suggestions.
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