The Origin of Species (Barnes & Noble Classics) - Charles Darwin [14]
The third chapter, “Struggle for Existence,” finally gives Darwin the conditions he needs to account for the heritability of variations and thus for species change that does not require an intelligent selector. The chapter asks, “How have all those exquisite adaptations of one part of the organisation to another part, and to the conditions of life, and of one distinct organic being to another being, been perfected?” (p. 59). Darwin’s answer is simple: “All these results ... follow inevitably from the struggle for life” (p. 60). The chapter lays out what we would call today an ecological vision of nature, a series of intricate dependencies manifesting themselves sometimes in literal “struggle,” for space or food, and sometimes in ways profitable to both—as with bees both feeding on flowers and pollinating them. Darwin shows that “there is no exception to the rule that 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” (p. 62). Every creature produces more seeds and offspring than can possibly survive, and those that survive (so the metaphor comes into action) are “selected” by virtue of their superior adaptation to these conditions:
In looking at Nature, it is most necessary to keep the foregoing considerations always in mind—never to forget that every single organic being around us may be said to be striving to the utmost to increase in numbers; that each lives by a struggle at some period of its life; that heavy destruction inevitably falls either on the young or old, during each generation or at recurrent intervals (p. 64).
It is, as Darwin puts it, “the doctrine of Malthus applied with manifold force to the whole animal and vegetable kingdoms” (p. 62).
Finally, then, in the fourth chapter, Darwin is ready to introduce the idea of natural selection. All the conditions are in place: the presence of abundant variations, their heritability, overproduction and crowding; this leads to a struggle for scarce resources, which gives success to those whose variations are best adapted to the conditions, and which thus assures that organisms with those characteristics will have the best chance to mate and transmit their adaptive variations. The irony and for many the difficulty of Darwin’s argument is that he finds that mindless nature, with no “design” whatsoever, makes a far better breeder than the finest of human breeders working on their pigeons or dogs or horses. “Man,” says Darwin, “can act only on external and visible characters: nature cares nothing for appearances, except in so far as they may be useful to any being. She can act on every internal organ, on every shade of constitutional difference, on the whole machinery of life. Man selects only for his own good; Nature only for that of the being which she tends” (p. 76).
Natural selection is the mechanism of evolution, but she “tends” to her children like a mother. Other writers before Darwin had argued for evolution, most famously Jean-Baptiste Lamarck, whose theories had been contested and mocked since their first publication. In his Philosophie Zoologique of 1809, Lamarck had proposed a theory of transmutation, but the mechanism he proposed for it was not convincing. Lamarck believed that animals passed on to their offspring