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By Root 1839 0

characteristics that they had developed during their lifetime. Thus his “evolution” was guided by the desires and needs of the animals, and so, unlike Darwin, he allowed for a kind of “design” in nature. Even if the animals were unselfconscious about the strivings that led them to develop adaptive characteristics, their world was shaped by their desires. Lamarck’s world, even without invocation of God, was in a sense intelligently designed. But Lamarck’s failure to be convincing here, like other failures of the few evolutionists before Darwin, kept the culture or the scientific community from taking evolution seriously. Darwin’s argument has endured because the mechanism he imagined in explanation of adaptation has turned out to be the mechanism that actually functions in nature. Ironically, Darwin himself did not entirely junk the theory of the inheritance of acquired characteristics; in editions of Origin that followed the first, he increasingly employed it to get around objections to his own theory. But the idea of natural selection as Darwin worked it out, the inheritance of chance but potentially adaptive variations leading to gradual transformations over long periods of time, is distinctly not Lamarckian.

Darwin brilliantly and doggedly insisted on heritability and the internal conditions of the organisms: “the most frequent cause of variability,” he argued, “may be attributed to the male and female reproductive elements having been affected prior to the act of conception” (p. 18). He understood somehow, without knowing anything of genetics or, certainly, of DNA, that species change evolved from internal conditions of the organism. The giraffe does not, as some popular and wrongheaded versions of Darwin’s argument would have it, grow a long neck by stretching it and inheriting the stretching necessary in each generation (that is Lamarckian). Darwin would say, however, that those giraffes with necks that allow them to reach food unavailable to others would be more likely to survive and to reproduce than those with shorter necks. The change would have what we would call genetic causes, and relates not at all to acquired characteristics. A giraffe might stretch itself as far as it likes, but that stretching cannot be transmitted through inheritance. The variations emerge by chance—some animals, for existence, might emerge with longer tails, but this would not help them acquire food and that variation would not therefore increase the chance of survival or of reproduction. Natural selection, then, effectually culls the shorter-necked giraffes, increases the opportunity for longer-necked ones to breed together, and eventually likely produces an animal with an optimal-length neck for the conditions in which it will have to live. Those conditions might, however, change over time, and those changes would likely entail the animals taking advantage of different chance variations more adaptable to new environmental conditions. Darwin puts it simply:

Every slight modification, which in the course of ages chanced to arise, and which in any way favoured the individuals of any of the species, by better adapting them to their altered conditions, would tend to be preserved; and natural selection would thus have free scope for the work of improvement (p. 75).

The improvement, it is important to note, can never be perfect in an absolute sense. Natural selection only works to select those organisms best suited to their niches in nature under present conditions, but “no country can be named in which all the native inhabitants are now so perfectly adapted to each other and to the physical conditions under which they live, that none of them could anyhow be improved” (p. 76).

The cumulative argument is powerful. Daniel Dennett cites a critical passage from the “summary” section of the chapter on natural selection (chapter IV) to show how Darwin’s argument is constructed. Although it is a lengthy passage, it is worth repeating here because it summarizes, as Darwin meant it to do, the movement of the first four chapters of his book and