On the Origin of Evolutionary Biology

English naturalist Charles Darwin is often credited with proposing the theory that living things evolved from simpler life forms, but this idea did not originate with him. Scientists and other prominent thinkers were already discussing evolutionary hypotheses decades before Darwin was born. In fact, some key tenets of the modern theory were proposed more than a century before Darwin’s work hit the press. As early as 1751, French mathematician Pierre Louis Maupertuis proposed an evolutionary hypothesis strikingly similar to the theory accepted by mainstream science today:

May we not say that, in the fortuitous combination of the productions of Nature, since only those creatures could survive in whose organization a certain degree of adaptation was present, there is nothing extraordinary in the fact that such adaptation is actually found in all those species which now exist? Chance, one might say, turned out a vast number of individuals; a small proportion of these were organized in such a manner that the animals’ organs could satisfy their needs. A much greater number showed neither adaptation nor order; these last have all perished…. Thus the species which we see today are but a small part of all those that a blind destiny has produced.quoted in Arthur O. Lovejoy, “Some Eighteenth Century Evolutionists. I.” The Popular Science Monthly 65 (1904), 242-243. Available here.

Maupertuis also suggested the possibility of universal common descent, and he was not the only one to broach this idea in the eighteenth century. The idea was considered again by German philosopher Immanuel Kant, who wrote the following in his widely-read Critique of Judgment (1790):

So many genera of animals share a certain common schema on which not only their bone structure but also the arrangement of their other parts seems to be based…. Despite all the variety among these forms, they seem to have been produced according to a common archetype, and this analogy among them reinforces our suspicion that they are actually akin, produced by a common original mother. For the different animal genera approach one another gradually: from … man, all the way to the polyp, and from it even to mosses and lichens…Kant, Critique of Judgment (1790), p. 304

Yet another early proponent of evolutionary hypotheses was Charles Darwin’s own grandfather, Erasmus Darwin, who suggested that all warm-blooded animals—and perhaps all biological life—had descended from just one living organism “in the great length of time, since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind.”Erasmus Darwin, Zoonomia, Vol. I, available here

In 1800, French biologist Jean-Baptiste Lamarck proposed the first detailed theory of how biological evolution might occur. He hypothesized that the organs, limbs, and other functional parts of an animal improve with use and atrophy with disuse, just as muscles grow stronger with exercise and weaken when unused. Lamarck believed (mistakenly) that these behaviorally-induced changes would be inherited by the animal’s offspring. So, if the offspring behaved in a similar way, the inherited changes would accumulate with each generation. For example, the ancient ancestor of the giraffe had a relatively short neck, Lamarck speculated, but its neck grew slightly longer as it habitually stretched to reach overhanging leaves. Its descendants inherited modestly lengthened necks and continued the behavior of stretching upward, thereby growing even taller. Over many generations, these incremental changes produced the greatly protracted necks giraffes have today.

Lamarck’s account of evolution was not widely accepted in the scientific community, and later experiments showed that offspring don’t inherit changes caused by behavioral habits as his theory required.In the 1880s, German biologist August Weismann conducted one of the most famous experiments refuting Lamarck’s theory. Weismann amputated the tails of mice for multiple generations, to see whether the offspring would have successively shorter tails (due to disuse) as Lamarck’s theory predicted. However, the baby mice still grew tails of normal length, regardless of whether their parents and grandparents had used their tails. (No matter how much you exercise your own muscles, for example, your children won’t inherit stronger muscles.) Although the foundational assumptions of Lamarck’s theory proved incorrect, recent discoveries in epigenetics have revealed that some behaviorally-induced changes are heritable after all. We’ll touch on this “neo-Lamarckian” idea later in this chapter. Nevertheless, Lamarck’s ideas helped to popularize the notion that law-like natural processes might cause one species to evolve into another.

The concept of biological evolution rose to greater prominence in 1844, when a book promoting evolutionary hypotheses was published by an anonymous author. The mysterious book, titled Vestiges of the Natural History of Creation, quickly became an international bestseller and went through twelve editions. The twelfth edition finally revealed that the author was Scottish journalist Robert Chambers. Despite its enormous popularity in the general public, however, Vestiges met with little enthusiasm in the scientific community because it offered no plausible explanation of the specific processes by which evolution might occur. Leading scientists of the day regarded Chambers’ view as unscientific speculation rather than a respectable scientific theory.Notable opponents of Chambers’ and Lamarck’s evolutionary views included the eminent naturalist Georges Cuvier, zoologist Louis Agassiz, anatomist Richard Owen, paleontologist William Buckland, and geologists Adam Sedgwick and Charles Lyell. For a more detailed discussion of the scientific establishment’s response to pre-Darwinian theories of evolution, see chapter 2 of Edward J. Larson’s book Evolution: The Remarkable History of a Scientific Theory (New York: Random House, 2004).

A few years after the tenth edition of Vestiges had gone to press, however, a new book on evolution commanded the respect of scientists and laity alike. In 1859, Charles Darwin published On the Origin of Species, which would serve as a new foundation for the emerging science of evolutionary biology. Its full title was On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life, but it is better known today by the abbreviated title On the Origin of Species. The sixth and final edition dropped the word “on” from the title, so that edition is called simply The Origin of Species. Darwin had begun to develop his theory two decades earlier but was hesitant to publish it, in part because he wanted to tighten his arguments and consider possible objections before subjecting his new ideas to the scrutiny of the scientific community.Historian of science Edward J. Larson explains: “Darwin conceived his theory in 1838, but he did not publish anything about it for twenty years. Recognizing the depth of opposition among scientists to the transmutation hypothesis [i.e., the hypothesis that one species could evolve into another], he spent much of this time endeavoring to anticipate and answer in advance objections to his theory.” Larson, Evolution: The Remarkable History of a Scientific Theory (New York: Random House, 2004), pp. 70-71. Finally, in 1858, a younger scientist named Alfred Russel Wallace sent Darwin a manuscript of a paper on evolution, asking Darwin to review and forward it to the renowned geologist Charles Lyell on his behalf. Upon reading Wallace’s paper, Darwin was shocked and dismayed to find that Wallace was proposing a theory of evolution essentially identical to Darwin’s own view! Darwin dutifully forwarded the manuscript to Lyell with his endorsement, but in his cover letter he lamented that Wallace would be credited as the originator of the new theory instead of himself.Previously, Darwin had privately shared his theory with a few colleagues, including Lyell, who had encouraged him to publish it promptly. So, in his cover letter forwarding Wallace’s paper, Darwin expressed regret that he hadn’t followed the advice: “Your words have come true with a vengeance that I should be forestalled. You said this when I explained to you here very briefly my views of ‘Natural Selection” depending on the Struggle for existence. I never saw a more striking coincidence. If Wallace had my manuscript sketch written out in 1842 he could not have made a better short abstract! ... So all my originality, whatever it may amount to, will be smashed.” The complete text of Darwin’s letter is available here. Lyell responded by arranging for two of Darwin’s previously-written private essays on evolution to be published alongside Wallace’s paper, so that both men would receive due credit for independently proposing the same theory.For more details on this extraordinary story, see Edward J. Larson, Evolution: The Remarkable History of a Scientific Theory (New York: Random House, 2004), pp. 72-75. Meanwhile, Darwin hurriedly finished writing On the Origin of Species, which developed and defended the new theory more thoroughly. We’ll discuss the key tenets of this theory on the next page.