Sal Cordova is a fascinating example of the danger facing anyone who ignores Pope’s advice “A little learning is a dangerous thing; drink deep, or taste not the Pierian spring: there shallow draughts intoxicate the brain, and drinking largely sobers us again.” Sal’s latest bungling of knowledge comes when he wonders:
Is evolution of antibiotic resistance by bacteria an example of Darwinism? Such a claim is very suspicious since Darwinism deals mainly with the origin of species.
Answering this question would be easy of “Darwinism” existed in some meaningful sense. But it doesn’t. Evolutionary biologists don’t refer to ourselves as “Darwinists” any more than physicists call themselves “Newtonists” or “Einsteinists.”
If we assume that Sal is referring to evolutionary biology as “Darwinism,” it’s trivially easy to show that evolution below the species level is a major part of that ongoing and successful research program. Open a recent issue of Evolution and you’ll find all the evidence you care for.
If Sal means only that Darwin dealt “mainly with the origin of species,” that still doesn’t cut it. After all, his most famous work is called: On the Origin of Species by Means of Natural Selection, or the Preservation of Favored Races in the Struggle for Life. It’s hard not to see antibiotic resistance as “the preservation of favored races in the struggle for life,” isn’t it? What Darwin showed was that selection, a process used by animal and plant breeders from the dawn of humanity, has the ability to describe the patterns of speciation we see in the world around us.
There’s a part of me that wishes people would spend less time talking about Darwin for the reasons I described above. Darwin was a great biologist, but modern biology owes great debts to many later biologists, and it’s a shame that Wallace doesn’t get his share of the credit. Nonetheless, the story of how Darwin came to appreciate the power of natural selection is a useful guide to helping people make those same leaps today.
Elements of evolutionary thinking can be gleaned from various parts of the scientific literature of the early 19th century, and back into the 17th century. Various mechanisms had been proposed, few reasonable, which could explain how new species could form from existing species. Darwin’s leap was understanding that speciation itself does not have to be a separate process from other phenomena that are commonplace and well-understood. Pigeon-fanciers, dog breeders and the other hobbyists he learned from were using principles of selection to produce enormous changes in morphology in relatively short order already, Darwin recognized how those forces could explain speciation. If more people understood how Darwin made that leap, perhaps more would appreciate the ideas that followed.
The insight he gained from the Galapagos can best be appreciated as an example of how to learn the basic concepts of evolutionary biology. He had collected various specimens on the islands, which he gave to the great naturalist John Gould at the British Museum. Darwin had not labeled species by specific island, in part because they seemed to belong to so many families of birds. When Gould discovered that they were all finches which had specialized on particular ecological niches, Darwin began to see things differently. Using the better records kept by other members of the Beagle’s crew, he was able to see how different species existed on different islands.
That realization, coupled with what he and everyone else knew about the power of selection, suggested something powerful to him. A finch or two from the mainland, being blown out to the islands, would face a very different set of pressures than it would have on the mainland. Its surviving offspring would represent a very different set of selective pressures. Over time, those pressures would make the population descending from those first migrants extremely different from their ancestors. Indeed, a process of evolution exactly like what we see with antibiotic resistance would ultimately produce one population very different from the parent species.
Isolation on each of the islands of the Galapagos would allow that pattern to repeat, producing the collection of finches which seemed to represent so many families of birds. Each species would be the result of normal processes of selection acting on a different population. If pigeon fanciers could produce such gaudy results in a single person’s lifetime, surely nature could do the same over much greater swaths of time.
On seeing that, patterns of species distributions he’d seen elsewhere began to make sense, and the beginnings of modern evolutionary biology were sown.