Bowler, Charles Darwin
Peter Bowler's study Charles Darwin: The Man and His Influence intends to give an accurate portrait of the ideas of the nineteenth-century naturalist within their historical context, while also correcting certain misconceptions and myths. To a certain extent, Bowler is writing a recognizable type of work -- a history of science that emphasizes twentieth century notions about the history of science, namely that new ideas do not emerge from nowhere and are immediately accepted neither by the scientific community nor by the general public. If Bowler's title sounds like this is a straightforward biography of Darwin, it is worth noting that his real purpose is to place Darwin in a greater context, whereby his ideas seem less radical -- and more related to pre-existing schools of thought -- than they have frequently been portrayed. The only radicalism, perhaps, is the way in which Darwin's theory ultimately undercuts complacent Victorian notions about progress.
The chief misconception that Bowler approaches in this biography is that Darwin was the first, or only, person to propose a theory of evolution. In point of fact, Darwin's theory emerged after a long process of speculation about various facts that had become unavoidable but remained unaccountable according to existing scientific paradigms (about geology especially). Bowler gives a rather useful summary of the basic objections to seeing Darwin as some sort of lone genius who emerged with his idea wholly devoid of historical context; as Bowler points out, Darwin's specific intellectual context even included (for fans of his theory) a nod in the direction of heredity, by way of his own grandfather:
…[O]pponents of Darwinism have always complained about the one-sidedness of the assumption that Darwin's was the first real theory of evolution. In 1879 the novelist Samuel Butler, who had conceived a violent distaste for the theory of natural selection, published his Evolution, Old and New to argue that Darwin was by no means the first to advance a theory of evolution. Butler pointed out that a number of earlier naturalists had openly suggested natural processes of organic change. These included the French biologists Georges Buffon and J.B. Lamarck and Darwin's own grandfather, Erasmus Darwin, whose Zoonomia of 1774-6 had contained a chapter on transmutation. In 1844 the anonymously published Vestiges of the Natural History of Creation (actually by the Edinburgh writer Robert Chambers) had generated a public outcry with its suggestion that mankind had emerged from the lower animals. Writers more sympathetic to Darwin have always conceded that some earlier statements on evolution were made, but argue that no pre-Darwinian naturalist was able to generate widespread support for the idea. (Bowler 18)
What is important to note about these earlier theorists -- Buffon, Lamarck, Erasmus Darwin, and Robert Chambers -- is that they were indeed responding to facts that seemed to demand some sort of explanation in the face of the existing paradigm. For example, the existing paradigm held that species were immutable: even Darwin himself held this idea at the time he boarded the Beagle. The extent to which this now-superseded scientific notion was regarded as gospel by the scientists of Darwin's time (including Darwin himself) is revealed in a rather shocking letter that Bowler quotes. The letter was written by Darwin to a colleague, the botanist Joseph Dalton Hooker, in 1844: in it, Darwin claims
I am almost convinced (quite contrary to opinion I started with) that species are not (it is like confessing a murder) immutable. Heaven forfend me from Lamarck nonsense of a 'tendency of progression' 'adaptation from the slow willing of animals' & c -- but the conclusions I am led to are not widely different from his -- though the means of change are wholly so -- I think I have found out (here's presumption!) the simple way by which species become exquisitely adapted to various ends. (Bowler 96-7)
The rhetorical shock of this letter should make it clear that Darwin did not feel it was easy to challenge the existing scientific orthodoxy -- he compares his belief that species are "not immutable" to "confessing a murder" -- but it is also worth noting that evolutionary ideas were also in some disrepute because the version that had been advanced by the Frenchman Jean-Baptiste Lamarck...
Bowler acknowledges this crucial deep influence in his account of Lamarck:
It was Lamarck who sketched in the outlines of an evolutionary compromise that would deeply influence the young Darwin. Lamarck suggested that instincts are, in effect, learned habits that have been followed for so long that they have been converted into hereditary instincts. The inheritance of acquired characters works for mental functions as well as physical structures such as the giraffe's neck. (Bowler 182)
Lamarck believed in the inheritance of acquired characteristics: in his view, the giraffe must have evolved from an animal with a much shorter neck that was perpetually straining to reach leaves, and the "slow willing" that Darwin refers to would indicate that over time these animals basically acquired their long neck through effort.
Darwin by contrast had developed his notion of how the mechanism of evolution worked as early as the tentative 1844 letter to Hooker quoted above, even if the full exposition would still wait another fifteen years until the publiciation of On The Origin Of Species. Darwin's proposed mechanism was "natural selection": this is the notion that in large populations of animals variations exist, and the competition for resources among those populations inevitably means that some variations are more successful than others at surviving and reproducing. The neck of the giraffe is no longer a Lamarckian story about the willpower of earlier proto-giraffes stretching to reach tasty foliage on the highest branches -- natural selection instead turns this into a story about an extremely large population of proto-giraffes in which variation in neck length occurs, and a competition for resources in which the ability to reach the tasty foliage on the highest branches becomes the crucial element for survival and reproduction. Thus over the course of generations, nature ends up selecting the longer-necked animals as better adapted to environment, these reproduce more successfully, and over time the animal develops a giraffe's neck. What is crucial to note is that Darwin arrived at this conclusion through a combination of empirical evidence obtained during his travels on the Beagle, and a synthesis of existing scientific work that had (recently at the time of his theorizing) challenged the existing scientific orthodoxy.
The account of Darwin's empirical evidence is, at this point, extremely familiar. Even Bowler concedes that "the story of how his discovery of the different finches inhabiting the Galapagos islands convinced him of the reality of transmutation has been told over and over again" (Bowler 49). The simple answer here was that Darwin was able to discover -- and confirm, with the help of more skilled taxonomists in Britain examining the various specimens Darwin had collected -- that there were different species on different islands in the Galapagos in which the differences were relatively minute. Yet these minute differences were clearly fine-tuned to adapt to the minute differences in environmental conditions on the separate tiny islands. The Galapagos were important to Darwin because, to some extent, an isolated archipelago provided a sort of natural laboratory: it is easy to assume that virtually all life on these remote islands had arrived there by a series of unlikely accidents in which organisms (like the famous tortoises of the archipelago) had traveled from the mainland and reproduced and colonized the islands. Yet this difficulty in traveling from the continent to the islands, and also from island to island, led to noticeable differences in the populations of each islands. Darwin noted that the beaks of the finches on individual islands seemed -- somewhat implausibly by the scientific theories of the time -- to be precisely tailored to the available food sources on whichever island housed that species. As Bowler notes, this led him ultimately to the conclusion suggested by the idea of natural selection: "it was Darwin alone who decided that the resemblances between the species he had discovered in the Galapagos and in South America were so close they must imply community of descent." (Bowler 78). In other words, each of the individual species of finch must have had a common ancestor -- a proto-finch that had arrived on the archipelago from the mainland, presumably -- in which the sparse available food sources became the environmental factors that selected for characteristics in the finch, eventually altering the finches over time into divergent species. This, in essence, was Darwin's account of the mechanism whereby evolution occurred -- the "simple way" referred to in the 1844 letter to Hooker -- and the evidence that had persuaded him of it.
It is crucial to note, however, that Darwin's arrival at…
A survey of scientific responses to extinction at the present moment is fairly unambiguous, however. Paleontologist James Kirchner calculated in 2002 that extinction rates could more or less be statistically inferred from the fossil record, and uses this to quantify what he terms "evolutionary speed limits," which is to say the rate at which the Darwinian process of natural selection (which depends upon the effective extinction of species insofar as