Chapter 1: The New Biology
9 - Darwin’s Daring Debut
Evolution is the keystone of modern biological theory, and all biology during the nineteenth century stands in relation to Charles Darwin. It’s true that before he published On the Origin of Species in 1859, the basic concepts of evolution were in the air: from Erasmus Darwin, Adam Smith, Thomas Malthus, Lamarck, Saint-Hilaire, Robert Chambers, Herbert Spencer. It’s also well known that Alfred Russel Wallace was the theory’s codiscoverer. But it was Charles Darwin who became its most effective champion, who compelled what was by then called the scientific establishment to look at it plainly.
Although the popular response to evolution was and remains fractious—so far it’s the only scientific theory ever judged by the U.S. Supreme Court—Darwin’s ideas were welcomed by his peers. For them, the theory offered a practical description of how diversity and complexity arise in nature. It’s worth noting that a key element in Darwin’s credibility was his use of fossil evidence. Ironically, that was available largely through the efforts of evolution’s great opponent, Georges Cuvier.
Darwin’s theory also reached back to economics. In the previous century Adam Smith’s Wealth of Nations argued that decentralized markets, individual action, and competition can bring collective benefit. Then came Thomas Malthus, who in his 1798 Essay on the Principle of Population described how population expands exponentially while food supply only grows arithmetically. He said that creates a necessary check on population growth through things like impoverishment, disease, war, and crime. Darwin drew on Smith’s notion that individual competition could bring collective gain. He also recognized in natural systems the same tension between growth and limits to growth described in Malthus. He then combined that observation with his stockbreeder’s notion of the “pick of the litter”—that is, natural selection—to show how nature profits from the tension.
On the overproduction of offspring in nature he wrote, “Every organic being naturally increases at so high a rate, that if not destroyed, the earth would soon be covered by the progeny of a single pair.” That was no hyperbole. Without environmental constraints, for instance, a single E. coli bacterium, in just twenty-four hours, would reproduce itself into a mass equal to all the living things on earth.
In a famous passage, Darwin wrote of how that impulse to expand is restrained and shaped by environmental limits: “As more individuals are produced than can possibly survive, there must in every case be a struggle for existence, either one individual with another of the same species, or with individuals of distinct species, or with the physical conditions of life.”
The result, he said, was natural selection. “Owing to this struggle for life, any variation, however slight and from whatever cause…if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to external nature, will tend to the preservation of that individual and will generally be inherited by its offspring.” Those offspring, he concluded, then have a better chance of surviving and continuing the line. This was “Nature, red in tooth and claw,” as Tennyson put it. Often overlooked, though, is the fact that when introducing the term “struggle for existence,” Darwin added, “I should premise that I use this term in a large and metaphorical sense, including dependence of one being on another.”
What all these effects produce are branching lines of offspring gradually separating and expanding through time—each shaped differently by the limits of its environment—to produce the kingdoms, phyla, classes, orders, families, genera, and species familiar to biologists today. Though that is commonly referred to as the tree of life, the various crossings and connections typical of nature in the wild are more like the “tangled bank” of shrubbery often found near a body of water. It was Darwin’s tireless champion Thomas Huxley who described that as “the web and woof of matter and force interweaving by slow degrees.”
