A final element in this ‘climate of opinion’, this ‘something in the air’, as regards ‘progressionism’ and how it was achieved, was the work of Alfred Russel Wallace. Wallace’s reputation, and role, in the discovery of evolution have gone through their own progression in recent times. For many years it was accepted that the paper he sent to Darwin in 1858, ‘On the Tendencies of Varieties to Depart Indefinitely from the Original Type’, contained a clear exposition of natural selection, such that Darwin was forced to begin a move towards publication of his own book, On the Origin of Species. As a result, some scholars have argued that Wallace was never given the recognition he deserves and have even implied that Darwin and his followers deliberately kept him out of the limelight.71 More recently, however, a closer reading of Wallace’s paper has shown that his idea about natural selection was not the same as Darwin’s, and that it was much less powerful as an explanatory device. In particular, Wallace did not stress competition between individuals, but between individuals and the environment. For Wallace, the less fit individuals, those less well-adapted to their environment, will be eliminated, especially when there are major changes in that environment. Under this system, each individual struggles against the environment and the fate of any one individual is independent of others.72 This difference, which is fundamental, may explain why Wallace appears to have shown no resentment when Darwin’s book was published the year after he had sent him his paper.73
None of the foregoing, however, should be allowed to cloud the fact that when On the Origin of Species did appear, in 1859, it introduced ‘an entirely new and – to Darwin’s contemporaries – an entirely unexpected approach to the question of biological evolution’. Darwin’s theory explained, as no one else had done, a new mechanism of change in the biological world. It showed how one species gave rise to another and, in Ernst Mayr’s words, ‘represented not merely the replacement of one scientific theory (“immutable species”) by a new one, but demanded a complete rethinking of man’s concept of the world and of himself; more specifically, it demanded the rejection of some of the most widely held and most cherished beliefs of western man.’ For Peter Bowler, ‘The historian of ideas sees the revolution in biology as symptomatic of a deeper change in the values of western society, as the Christian view of man and nature was replaced by a materialistic one.’74 The most notable flash of insight by Darwin was his theory of natural selection, the backbone of the book (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). Individuals of any species show variations and those better suited were more likely to reproduce and give rise to a new generation. In this way, accidental variations that fitted better than others were encouraged. No ‘design’ was necessary in this theory, or process, which was at the same time far more parsimonious than any other, and could be observed on all sides.75
Although Darwin had been stimulated to published the Origin after being contacted by Wallace, he had been germinating his ideas since the late 1830s, after his now-famous voyage on the Beagle. His time in South America, in particular the Galapagos Islands, had taught him to think in terms of populations rather than individuals, as he studied variation from island to island. He had become familiar with the common rhea, a flightless bird, while travelling the open pampas of Patagonia, and had eaten different forms of the creature as he moved around. He noticed that, at the edges of the territory occupied by the two populations, there was a struggle for supremacy. And he began to wonder why there were related species on different islands and continents – would the Creator have visited each location and made these fine adjustments?76 From a study of barnacles he noted how much variety was possible in a species, and all these observations and inferences gradually came together. When the book was published, on 24 November 1859, 1,250 copies were snapped up on the first day. He himself took the waters at Ilkley, in Yorkshire, waiting for the storm to break.77 It did not take long and it is not hard to see why: Ernst Mayr concluded that there were six major philosophical implications of Darwin’s theories: (1) the replacement of a static by an evolving world; (2) the demonstration of the implausibility of creationism; (3) the refutation of cosmic teleology (the idea that there was a purpose in the universe); (4) the abolition of any justification for absolute anthropocentrism (that the purpose of the world is the production of man); (5) the explanation of ‘design’ in the world by purely materialistic processes; (6) the replacement of essentialism by population thinking.
We must be clear about the impact of the Origin. It owed something to Darwin’s solid reputation and because his book was packed with supporting details – it was not produced by a nobody.78 Yet its impact also had something to do with the fact that, as James Secord has pointed out, the book resolved – or appeared to resolve – a crisis, not because it sparked one. Natural selection was, essentially, the last plank in the evolutionary argument, not the first one, the final filling-in of the theory, providing the mechanism by which one species gave rise to another. The non-revolutionary nature of the Origin, to use Peter Bowler’s term, is shown by Secord’s chart in his book, which records that the Origin did not decisively outsell Vestiges until the twentieth century.79
That said, the Origin did promote enormous opposition. Darwin himself realised that his theory of natural selection would prove the most contentious element in his argument and he was not wrong. John F. W. Herschel, a philosopher whom Darwin admired, called natural selection the ‘law of higgledy-piggledy’, while Sedgwick (who was both a divine and a scientist) condemned it as ‘a moral outrage’.80 Many of the favourable reviews of the Origin were lukewarm about natural selection: Lyell, for example, never accepted it fully, and described it as ‘distasteful’, while T. H. Huxley did not think it could be proved.81 In the late nineteenth century, while the theory of evolution was widely accepted, natural selection was ignored, and this was important because it allowed people to assume that evolution was ‘intended to develop toward a particular goal, just as embryos grew to maturity’. Viewed in this way, evolution was not the threat to religion it is sometimes made to appear.82 Indeed, the Origin had two chapters on the geographical distribution of living forms, making use of the geology and palaeontology reported above, and people had much less difficulty accepting this than the mechanism of selection. Vestiges had prepared part of the way. Ernst Mayr says the selection aspect of Darwin’s theory was not finally accepted until the evolutionary synthesis of the 1930s and 1940s.83 Many people simply thought that the implications of the Origin were immoral and remained convinced that the world was manifestly well-ordered – evidence for a divinity – and that Darwin’s ideas about accidental (‘higgledy-piggledy’) evolution could not produce such harmony. Darwinism was selfish and wasteful, they said, and a benevolent deity would never allow such a process. What was the Darwinian purpose of musical ability, or the ability to perform abstract mathematical calculations?84 Darwin, it should be said, was never entirely happy with the word ‘selection’, and many misunderstood how to interpret the term ‘fittest’. Several critics argued that Darwin’s method of theorising was unscientific because his theory could not be falsified.