DARWINISM. — In DARWIN’s work, a distinction must be drawn between his original scientific research and the speculative views that take their name from him. DARWIN was certainly one of the most prolific and clear-sighted naturalists of the 19th century, even though some of his hypotheses and interpretations, such as those concerning the formation of coral reefs or the circumnutation of climbing plants, have been abandoned. His researches on the formation of plant species (1858–77), which established the law of dichogamy, and on the importance of worms in the formation of humus, would suffice to preserve his fame. However, on the problem of the “species,” which occupied him constantly for 40 years, he produced nothing comparable to the work of MENDEL, NAUDIN, or JORDAN. In the history of biological philosophy and the social sciences, however, “Darwinism” is important, properly understood as the theory of the causes of the alleged transformation of living forms.
DARWIN began from the facts of domestication: how have the numerous breeds of pigeons, horses, cattle, and dogs arisen? They have been produced by the “selection” (conscious or unconscious) of the breeder. Now, in nature there are species that vary, and the variability and heredity of the characters that appear in the varieties of species may perhaps be effective in finding the factor that corresponds to the artificial selection of the breeder. DARWIN postulated natural selection. The breeder’s selection draws from the species the most diverse and distant varieties; natural selection, having at its disposal a much longer time, succeeds in causing forms to cross the boundaries of the species, that is, to produce new species.
In the struggle for existence, individuals do not perish at random; the less fit perish, the more fit survive; natural selection is the consequence of the struggle for existence among forms in continuous variation. Nature makes a choice of individuals that present and accentuate useful variations, and these slowly modify themselves until they produce new species. Darwinism is thus essentially founded on the analogy between natural (supposed) and artificial selection; natural selection accounts for the utility of the organs of adaptation.
DARWIN felt so strongly the paternity of this conception that, barely after 1859, he was scarcely willing to “diminish the glory of selection” (letter to Hooker, 24 Nov. 1862), recognizing the importance of the direct action of physical conditions on living organisms and then appealing to “sexual selection.” But that pure Darwinism, that is, the efficacy of natural selection, is a mere interpretative hypothesis, DARWIN himself conceded: “The belief in natural selection must today rest entirely on general considerations. When we descend to details, we can prove that no species has changed, that is, we cannot prove that even a single species has changed, nor can we prove that the supposed changes are useful, which is the foundation of the theory” (letter to Bentham, 22 May 1863).
In the last century, at least one conclusion was clear: with artificial selection, a new species cannot be obtained. Therefore, from the methodological point of view, HUXLEY felt compelled to reserve: “I accept DARWIN’s hypothesis with the reservation that proof be produced of the possibility of the production of physiological species through elective mating.” The same experimental method dictated SPENCER’s rigorous critique, which he ultimately summarized thus: “There is no inductive proof of natural selection. The facts attesting to the effects of artificial selection are numerous, but none appear to attest to the effects of natural selection. Until the production of even a single species by natural selection has been shown, there is not even the principle of inductive proof.”
Then came the work of the geneticists, led by JOHANSEN: “The pure line” isolated by artificial selection is fixed, oscillating only within certain limits for given characters beyond which it is impossible to go with small continuous and hereditary variations.
Other findings then emerged, suggested even to evolutionists themselves by the development of certain series of fossil forms that had to be called “orthogenetic,” that is, suggesting the idea of an evolution directed from the outset in a determined sense, without the multitude of failed proofs, inefficient variations, useless and unselected ones that the theory envisages and demands. According to OSBORN, paleontology demonstrates that “in evolution, law prevails over chance.”
It is thus understandable that some naturalists, evolutionists by principle and philosophical prejudice, declare themselves anti-Darwinists and write that “Darwinism might well have succeeded in making biologists themselves forget the obsession with the problem of life” (BRIEN); see also EVOLUTION.