“…I look with confidence to the future,—to young and rising naturalists, who will be able to view both sides of the question with impartiality. Whoever is led to believe that species are mutable will do good service by conscientiously expressing his conviction; for thus only can the load of prejudice by which this subject is overwhelmed be removed.”
– Charles Darwin, The Origin of Species, 6th edition
Today is Charles Darwin’s 200th birthday, and like all occasions that happen to fall on a multiple of 10, it seems a good opportunity for reflection.
There has been a debate for the last week on the vertpaleo listserv, concerning the idea of “Darwin hero worship.” One line of this debate concerns the possible public perception that evolution is all about Darwin, while the other is that Darwin is overrated as the founder of evolutionary theory (for lack of a better term).
Addressing the first issue, giving the perception that the Origin of Species is the final word on evolution is a pitfall that people teaching about evolution would do well to avoid. Evolution lessons tend to go one of two routes; they either lay out evolution as they would any other scientific principle, without reference to its developmental history, or they describe the history of how the idea developed (or a combination of the two). I tend to emphasize the former approach; good and established science can be introduced independent of the players who originated the idea. That’s not to say the history of the idea isn’t important and informative, and in fact I discuss that as well, but in a secondary fashion. When I talk about the history of evolutionary thought, Darwin is one piece among many, and is neither the beginning nor the end of the story. Darwin’s work was one step in the process of understanding evolution (albeit a big step).
That idea brings us to the second issue, that Darwin’s contributions are overstated, both because others came up with the same ideas, and because some of what Darwin suggested was incorrect. I think the attempt to diminish Darwin’s contributions are just as incorrect as pretending that no one else had a role to play. I’m reminded of this every time I reread the Origin of Species. With each reading, I’m freshly amazed at Darwin’s thoroughness and scientific rigor. Alternative theories were explored at length, with detailed descriptions of their shortcomings. He approached the problem from a variety of different angles, incorporating observations about comparative anatomy, biogeography, developmental patterns, ecology, and behavior (amongst others) into his argument. I think he was tantalizingly close to working out the basics of Mendelian genetics; I’m convinced that if he had worked on something that reproduced more rapidly and in larger numbers than pigeons he would have worked that out as well. There were some details Darwin missed or misinterpreted, mostly based on information or technologies that weren’t available in 1859, but he deserves his status as the single most significant contributor (among many) to understanding evolution.
I want to reproduce here some passages from the Origin of Species that I find particularly representative of this work; these are all from the 6th edition. (The images at the top of the page are just decoration; we had a beautiful sunset at VMNH a few weeks ago).
“Perhaps the correct way of viewing the whole subject would be, to look at the inheritance of every character whatever as the rule, and non-inheritance as the anomaly.”
“If we look to the islands off the American shore, however much they may differ in geologic structure, the inhabitants are essentially American, though they may be all peculiar species. We may look back to past ages…and we find American types then prevailing on the American continent and in the American seas. We see in these facts some deep organic bond, throughout space and time, over the same areas of land and water, independently of physical conditions. The naturalist must be dull who is not led to inquire what this bone is.
The bond is simply inheritance, that cause which alone, as far as we positively know, produces organisms quite like each other…”
On natural selection:
“A grain in the balance may determine which individuals shall live and which shall die,—which variety or species shall increase in number, and which shall decrease, or finally become extinct.”
“The slightest advantage in certain individuals, at any age or during any season, over those with which they come into competition, or better adaptation in however slight a degree to the surrounding physical conditions, will, in the long run, turn the balance.”
On homologous structures:
“The similar framework of bones in the hand of man, wing of a bat, fin of the porpoise, and leg of the horse,—the same number of vertebrae forming the neck of the giraffe and the elephant,—and innumerable other such facts, at once explain themselves on the theory of descent with slow and slight successive modifications.”
“Nature may be said to have taken pains to reveal her scheme of modification, by means of rudimentary organs, of embryological and homologous structures, but we are too blind to understand her meaning.”
On atrophied structures:
“Organs or parts in this strange condition, bearing the plain stamp of inutility, are extremely common, or even general, throughout nature.”
“Organs in a rudimentary condition plainly show that an early progenitor had the organ in a fully developed condition; and this in some cases implies an enormous amount of modification in the descendants.”
On fossils and geology:
“It has been asserted over and over again, by writers who believe in the immutability of species, that geology yields no linking forms. This assertion…is certainly erroneous.”
“It is notorious on what excessively slight differences many paleontologists have founded their species…”
On isolation and speciation:
“Isolation, also, is an important element in the modification of species through natural selection. In a confined or isolated area, if not very large, the organic and inorganic conditions of life will generally be almost uniform; so that natural selection will tend to modify all the varying individuals of the same species in the same manner. Intercrossing with the inhabitants of the surrounding districts will, also, be thus prevented.”
On invasive species:
“Natural selection tends only to make each organic being as perfect as, or slightly more perfect than, the other inhabitants of the same country with which it comes into competition. And we see that this is the standard of perfection attained under nature. The endemic productions of New Zealand, for instance, are perfect compared to one another; but they are now rapidly yielding before the advancing legions of plants and animals introduced from Europe. Natural selection will not produce absolute perfection, nor do we always meet, as far as we can judge, with this high standard under nature.”
On the effects on science: