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14
The Darwinian Revolution: Rethinking Its Meaning and Significance

MICHAEL RUSE

The Darwinian revolution is generally taken to be one of the key events in the history of Western science. In recent years, however, the very notion of a scientific revolution has come under attack, and in the specific case of Charles Darwin and his Origin of Species there are serious questions about the nature of the change (if there was such) and the specifically Darwinian input. This chapter considers these issues by addressing these questions: Was there a Darwinian revolution? That is, was there a revolution at all? Was there a Darwinian revolution? That is, what was the specific contribution of Charles Darwin? Was there a Darwinian revolution? That is, what was the conceptual nature of what occurred on and around the publication of the Origin? I argue that there was a major change, both scientifically and in a broader metaphysical sense; that Charles Darwin was the major player in the change, although one must qualify the nature and the extent of the change, looking particularly at things in a broader historical context than just as an immediate event; and that the revolution was complex and we need the insights of rather different philosophies of scientific change to capture the whole phenomenon. In some respects, indeed, the process of analysis is still ongoing and unresolved.

Department of Philosophy, Florida State University, Tallahassee, FL 32306.



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14 The Darwinian Revolution: Rethinking Its Meaning and Significance MiChAel rUse The Darwinian revolution is generally taken to be one of the key events in the history of Western science. In recent years, however, the very notion of a scientific revolution has come under attack, and in the specific case of Charles Darwin and his Origin of Spe- cies there are serious questions about the nature of the change (if there was such) and the specifically Darwinian input. This chapter considers these issues by addressing these questions: Was there a Darwinian revolution? That is, was there a revolution at all? Was there a Darwinian revolution? That is, what was the specific contribution of Charles Darwin? Was there a Darwin- ian revolution? That is, what was the conceptual nature of what occurred on and around the publication of the Origin? I argue that there was a major change, both scientifically and in a broader metaphysical sense; that Charles Darwin was the major player in the change, although one must qualify the nature and the extent of the change, looking particularly at things in a broader historical context than just as an immediate event; and that the revolution was complex and we need the insights of rather different philoso- phies of scientific change to capture the whole phenomenon. In some respects, indeed, the process of analysis is still ongoing and unresolved. Department of Philosophy, Florida state University, Tallahassee, Fl 32306. 

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 / Michael Ruse T hirty years ago i (ruse, 1979) published a book with the main title The Darwinian Revolution. no one questioned whether or not i had a real topic. There was a Darwinian revolution and my book was about it. Today, one could not be so sure. The idea of scientific revolu- tions has been questioned; Darwin’s contribution has been challenged; and even if you can come up positively on these matters, what on earth are we talking about anyway? These are the 3 questions i shall address in this article. WAS THERE A DARWINIAN REVOLUTION? historian Jonathan hodge (2005) has been one of the strongest naysay- ers on this matter. he thinks that the whole talk of scientific revolutions, something of an obsession by many historians and philosophers of science in the years after Thomas Kuhn’s engaging and influential The Structure of Scientific Revolutions (1962), is deeply misleading. The term is obviously taken by analogy from politics and even there it is doubtful that there are such things (at least that there are such things with common features) and in science likewise we have no reason to think that there are such things with common features. in any case, the talk is wrong-headed because it drives you to concentrate on some people and events and downplay or ignore other people and events. in response, let us agree at once that focusing on revolutions (in science) does rather skew things in certain ways. Dwelling at length on Darwin carries the danger of ignoring the contributions of others in the 19th century, from the Naturphilosophen (people like the German anato- mist lorenz oken who saw homologies everywhere) at the beginning to the orthogeneticists (people like the American paleontologist henry Fairfield osborn who thought that evolution has a momentum that carries it beyond adaptive success) at the end. Worse, it gives the impression that unless you have something dramatic and crisis-breaking, the science is of little value. remember, the alternative to Kuhn’s revolutionary science is normal science, and this has (a perhaps undeserved) reputation of a 3-hour sermon by a Presbyterian minister on a wet sunday in scotland. Against this, however, one can point out that the history of science as a professional discipline is little more than 50 years old and that you have to start somewhere. in the case of Darwin, even 30 years ago there was no real synthesis. The tragedy would have been if historians of science had stopped there and gone no further. But this is clearly not true. in the past 30 years or more, staying just with the history of evolutionary thinking, there has been a huge amount of work on people before and after Darwin, and on his contemporaries like Thomas henry huxley [for instance, Desmond (1999)]. To name but 3 researchers, one can pick out robert J. richards

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The Darwinian Revolution: Rethinking Its Meaning and Significance /  (1987, 1992, 2002, 2008b) and the work he has done on German evolution - ary thinking in the 19th century, before and after Darwin; Peter Bowler (1976, 1984, 1988, 1996), who started with paleontology in the 18th century and since has written extensively on the post-Darwinian figures in the 19th century, now extending his grasp into the 20th century; and William Provine (1971, 1986), who has offered detailed and brilliant analyses of the impact of genetics on the understanding of evolution. it just has not been the case that focusing first on Darwin led us to an inescapable dead end with respect to the rest of evolution’s history. should we nevertheless persist with the term “revolution”? Well, it surely depends on the case to be made. obviously we can legitimately use the term revolution somewhat generically in politics. no one thinks the American revolution and the French revolution were the same, but they did share characteristics that, for example, the move from ronald reagan as president to George h. W. Bush did not. There was a break from the old government and this was done by a group seizing power, leading to dramatic changes. i see no reason we should not extend the term metaphorically. Think of the technological revolution in the past 20 years or so. laptop computers are commonplace, electronic use of libraries is the norm, and search engines like Google and yahoo have transformed the gathering of information. if this does not all add up to a revolution of some kind, it is hard to know what does. There is as much of a break with the past as there was for an American ruled from Washington rather than london. At an immediate level, the change is probably even greater. so if you want to extend the term revolution to science, if it captures something of what goes on, then all power to the use. But now the ques- tion is whether the Darwinian revolution merits the use. Was there a big break with the past, sufficiently significant to speak of revolution? Did something big, really big, happen around 1859, and does it still merit a special place in the history of evolutionary thought? in respects, our appreciation of what happened is even greater than it was 30 years ago: if you like, today in 2009 the 200th anniversary of Darwin’s birth as opposed to 1982, the 100th anniversary of Darwin’s death. Daniel Dennett (1995) has referred to Darwin’s idea about natural selection as the greatest ever. one could debate this (Plato’s theory of forms gives it a good run for its money), but all will certainly agree that something really big happened around and because of the Origin in 1859 (Darwin, 1859). But here, let us take note of some of hodge’s worries. The basic question is: What are we talking about? in the Darwinian case there are 2 levels of activity and interest. Without pretending that the divisions are completely simon-pure, there is the level of science and the level of metaphysics (recognizing that this includes things that might be considered scientific at one end and religious or otherwise ideological at the other end).

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0 / Michael Ruse on one hand, there is the scientific theory of evolution through natu - ral selection, the central topic of the Origin. on the other hand, there is what scholars like robert M. young (1985), borrowing a title from Thomas henry huxley (1863), used to refer to as the debate over “man’s place in nature.” While today we would never dare to use that kind of language, in essence they got it absolutely right. At some level, the Darwinian revo- lution destroyed forever the old picture of humans as somehow miracu- lously special, symbolically and literally as touched by magic. Admittedly, to this day Christian fundamentalists (and those of other religions) refuse to accept this, but it is true. even if you think that you can still be religious, a Christian even, you have to rethink dramatically, emotionally even more than intellectually, what it means to be a human. starting with a certain modesty about ourselves (ruse, 2001). it is hard to know how one would respond to someone who ques- tioned the significance of the changes at either of these 2 levels. At the level of science, changing over to the idea of evolution in itself is a massive change to make, whether you are moving from a Greek theory of eternal life without change or a more Christianized vision of the instantaneous appearance of life. And then you add in the mechanism of natural selec- tion, used by at least 90% of today’s evolutionists, and you have an even greater break with the pre-Origin past. At the level of metaphysics, the change is yet deeper if that is possible. The violent opposition of the American above-mentioned fundamentalists or creationists shows that if anything could. it is not just a question of who we are but also of how we should live our lives (ruse, 2005). Although it is hardly the only factor, Darwinian thinking is at the center of the move to modernism, in some broad sense. Are we still to be subject to the old ways (women inferior, gays persecuted, abortion banned) or are we to look forward to a truly post-enlightenment world, with reason and evidence making the running in an entirely secular fashion? Grant then that something big did happen. But are we right in put- ting it all on 1859 and the publication of the Origin of Species? This raises my second big question. Divide the answer according to the levels of inquiry. WAS THERE A DARWINIAN REVOLUTION? SCIENCE start with one indubitable fact. There always have been and there always will be people who think that not only was Alfred russel Wal- lace, the codiscoverer of natural selection, unappreciated but that Charles Darwin pinched all of the good ideas from the younger evolutionist. it should be called the Wallacean revolution with Charles Darwin but a minor footnote. [Brackman (1980) is the classic exemplification.] There

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The Darwinian Revolution: Rethinking Its Meaning and Significance /  are other candidates for the job. edward Blyth, an english-born indian naturalist, has long been a popular name. [eiseley (1958) was the source for this one.] More recently, in an award-winning book, James secord (2000) argued that really it was robert Chambers, the anonymous scottish author of the Vestiges of the Natural History of Creation (Chambers, 1844), who did the heavy lifting. Darwin came along at the end to inherit all of the glory. (Try www.darwin-legend.org for a cross-sample of these sorts of charges.) There is little need to spend much time on these claims because basi- cally they don’t hold much water. let it be shouted out loud. Darwin did not steal from Wallace. Darwin’s ideas—the ideas of the Origin that is—are all right there in the 35-page Sketch of his ideas that he wrote in 1842 (Darwin and Wallace, 1958). There was some tweaking about the nature of adaptation; perhaps he hit in the early 1850s on the principle of divergence—although there are certainly hints of that in the species note- books—but the mechanisms (natural and sexual selection) are there, as is the structure of the argument of the Origin (more on this in a moment). even some of the flowery passages, notably the final paragraph about grandeur in views of life, can be found in the early writings. Wallace cer- tainly stimulated Darwin to get moving, but that was it. And incidentally, if you study Wallace’s essay carefully, you see differences from Darwin. Wallace, for instance, denied the pertinence of artificial selection. Wallace never had the term “natural selection.” Wallace had inclinations to group selection in a way absent from the Origin or earlier writings. This is not to belittle Wallace. not at all! But he was not Charles Darwin. The claims of others can be dismissed as well. Before Darwin, there were several people who had thoughts of natural selection and we know that he read some of them. For instance, in a pamphlet by the breeder John sebright, there is an explicit reference to the force of natural selection, a reference that stimulated Darwin to underline the words and make a com- ment in the margin (ruse, 1975a). But there is no real question that these people sparked full evolutionary thoughts in Darwin, and generally the last thing they wanted to do was use natural selection to promote evolu- tion. edward Blyth (1835), with whom Darwin was to have very cordial and helpful correspondence (he actually drew Darwin’s attention to an important earlier essay by Wallace) explicitly denied that his thinking had evolutionary implications. And as far as others were concerned, pre- Darwinian (that is pre-Origin) evolutionists in particular, they certainly had effects on general opinion, but not like Darwin. Chambers’s Vestiges undoubtedly took the sting out of evolution, so by the time that Darwin published, it was to a certain extent old hat, but it did not have the effect of the Origin. The same is true of others, like herbert spencer. For all that spencer (1852), too, hit on the idea of selection, he always thought that

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 / Michael Ruse lamarckism is the chief cause of evolutionary change, and while his think - ing did influence some, including his big friend Thomas henry huxley, he likewise did not swing people in the way that the Origin did. having said all of this, however, there are some interesting questions about the extent to which the revolution was truly Darwinian. Clearly some nuanced thinking is needed, starting with the fact that there was 150 years of evolutionary thinking before Darwin, including speculations by his own grandfather erasmus Darwin. Toward a fuller analysis, divide the history of evolutionary thinking into 3 periods (ruse, 1996). The first period, from the early 18th century (the time of the French encyclopediast and early evolutionist Denis Diderot) to the publication of the Origin in 1859, was the time when the status of evolutionary thinking was that of a pseudo science: an emergent on the cultural value of progress. second, from the Origin to the full incorporation of Mendelism into evolutionary thinking, say ≈1930 with the work of ronald Fisher, J. B. s. haldane, and sewall Wright, evolution had the status of a popular science. There was some professional work going on, particularly in the area of phylogeny tracing, but generally evolution was a museum science, still a vehicle for thoughts of progress. Causal thinking was second-rate or (often) absent entirely. Top-quality work in biology was increasingly by young research- ers who turned from phylogeny tracing to microscope-based sciences, especially cytology, and then on to genetics in the 20th century. Finally, from 1930 to the present we have a fully professional science of evolu- tionary biology. We entered the era of neo-Darwinism (as it was called in Britain) or the synthetic theory of evolution (as it was called in the United states). now, frame the discussion against the background of this 3-fold divi- sion of history. if we consider the revolution in a broad sense, from the beginning of the 18th century to the beginning of the 21st century, there are 2 major points at which we want to say that it is a Darwinian revolu- tion. The first was in the transition from being a pseudo science to being a popular science. Before the Origin, the evidence for evolution just was not there. if you believed in evolution, you were fueled primarily by ideologi- cal reasons. it is true that people knew about homologies, the fossil record was starting to fill out, embryology was suggestive, and so forth. But the full picture was not there. After the Origin, being an evolutionist was just plain common sense. And people did become evolutionists. even church people. With the notable exception of American evangelicals, especially in the south, evolution was accepted (roberts, 1988). it is true that there was some backsliding, in the Catholic Church especially by century’s end, but overall people became evolutionists (Artigas et al., 2006). This change was thanks to Darwin, especially to the structure of the argument in the Origin. The methodologists of science of the day, more

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The Darwinian Revolution: Rethinking Its Meaning and Significance /  particularly, the methodologists of science of the 1830s when Darwin was discovering and formulating his theory, insisted that the best science has at its heart a true cause, a vera causa. They differed over what is the mark of a vera causa. John F. W. herschel (1830), with empiricist leanings, insisted that we have direct sensory evidence or something analogical. We know that a force pulls the moon toward the earth because swinging a stone around on a piece of string requires you to pull the stone in toward you. William Whewell (1837, 1840), with rationalist leanings, insisted that we justify the acceptance of our hypothesis through its implying a whole range of empirical evidence, thus manifesting what Whewell called a “consilience of inductions.” As in a court of law, where the guilt is ascribed through the wide range of clues that it explains, Darwin set about satisfying both vera causa criteria (ruse, 1975b). First, he argued analogi- cally from artificial selection (the work and triumphs of the animal and plant breeders) to natural selection, from something known and seen to something not known and seen. Then he turned around, and showed how evolution through selection throws light on topics across biology, instinct, paleontology, biogeography, systematics, anatomy, embryology, and more. As evolution through selection explains, so conversely the explained areas justify our faith in evolution through selection. There are questions about how effective was the appeal to artificial selection. Generally before the Origin it was taken as a reason not to believe in ongoing change (no one has turned a horse into a cow) and i have mentioned how Wallace denied explicitly that it was relevant to the evolution issue. After the Origin, people like huxley took the failure to create new species artificially as a reason to hesitate before full acceptance of natural selection’s powers. however, undoubtedly at some level the analogy softened people up to evolution. Part of Darwin’s genius was always to put his ideas into comfortable contexts. he argued to natural selection via the struggle for existence, which was something that came out of the thinking of the reverend Thomas robert Malthus (1826), who pointed out that population demands will always outstrip potential gains in space and food. everyone knew about these Malthusian calculations, and, even if they did not much like them, generally they accepted the conclusions. likewise with the world of breeders, people at least took some comfort from the arguments provided by Darwin, even if they were not definitive. The consilience was a different matter. here, Darwin did persuade. At least, he persuaded to a point. As noted, evolution after the Origin was nigh a truism. The mechanism was another matter. no one denied natu- ral selection. very few accepted that it could be as powerful as Darwin suggested. People became evolutionists in droves. The number of pure Darwinians, as we might term selectionists, was very few, and the most

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4 / Michael Ruse prominent after Darwin himself, namely Wallace (1870), became enamored of spiritualism in the 1860s and he started to deny selection when it came to humans. The reasons for this halfway acceptance are well known. on one side, there were scientific problems with selection. it was thought that it could never be strong enough to overcome the supposed averag- ing nature of heredity. even the best new variations would be swamped into nonbeing in a generation or two (Greg, 1868). Added to this the physicists (ignorant as they were of the warming effects of radioactive decay) denied that there was time enough for such a leisurely process as natural selection (Burchfield, 1975). on the other side, there was the matter of adaptation. selection does not just bring about change. it brings about adaptive change. This ran into trouble from folk at both ends of the spectrum. German-influenced biologists like huxley (1884) thought that adaptation is but a minor phenomenon, and hence felt no need to embrace selection on that score. nonadaptive saltations (jumps, what we today would call “macromutations”) would do the job for evolution. heavily Christian evolutionists like American botanist Asa Gray (1876) thought that selection could not fully explain adaptation and so they wanted (God- ) directed variations. As Darwin said, this rather made natural selection redundant. so after 1859, it was evolution yes; natural selection, much less so. This meant that the dream that Darwin had had of founding a professional sci- ence of evolutionary studies, based on natural selection, never really got off the ground. There certainly was professional evolutionism, particularly that around the German biologist ernst haeckel (1866). But, increasingly, a lot of what was produced lost touch with reality as fantabulous tales were spun using the unreliable biogenetic law, ontogeny recapitulates phylogeny. in Britain you had the incredible paradox that the chief post- Origin evolutionist in the second half of the 19th century, a man deeply involved in and highly influential on postsecondary education, Thomas henry huxley, never taught evolution to his students. he thought they should concentrate on physiology and morphology (ruse, 1996). so evolution became the subject of the popular lecture hall, working men’s clubs, and the public-friendly British Association for the Advance- ment of science, and the leading evolutionists moved from the universities to the museums. huxley student e. ray lankester ran the British Museum (natural history) in london and huxley student henry Fairfield osborn ran the American Museum of natural history in new york. And what you want in museums are displays, with an educational and cultural mes- sage. so this is what was supplied. Terrific displays of fossils, especially of all of those dinosaurs now being discovered and brought back from the American West, and all put in a progressive fashion to demonstrate

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The Darwinian Revolution: Rethinking Its Meaning and Significance /  that life may have started as blobs but that it ends as humans, especially white humans. Finally, ≈1930 came the move from popular science to professional science. First there were the mathematicians, the population geneticists mentioned above. Then came the empiricists, the experimenters, and naturalists, who put flesh on the mathematical bones: e. B. Ford and his school in Britain and Theodosius Dobzhansky and his fellow evolutionists in the United states. now we had university posts, researchers, graduate students and grants, journals, societies, and everything else we associate with professional science, and not just at the sociological level, because the work produced was firmly based on empirical studies with mathematical models doing the explaining. The epistemic virtues of science (consistency, coherence, predictability, fertility, simplicity) were taken seriously and the worth of work was judged by its success against these virtues. And right at the heart was natural selection, which continues to this day. here, again then Darwin has made a major contribution to evolutionary studies. WAS THERE A DARWINIAN REVOLUTION? METAPHYSICS What of the Darwinian revolution in the broader sense, the side deal- ing with our metaphysical view of ourselves, our place in nature? here, Darwin was crucially important if not completely successful. he himself was stone-cold certain that we humans are part of the world of nature. his experience with the native people from the bottom of south America, the Tierra del Fuegians, had convinced him of that (Darwin, 1969). And he made his case publicly, as is well known, not in the Origin (which was somewhat reticent on the human question) but in the Descent of Man, published some 12 years later (Darwin, 1871). however, now we must ask what it means to put ourselves in nature. There are 3 possible answers. First, it can simply be to make humans part of the natural order of things. We are ruled by the laws of physics and chemistry and biology and so forth just like anything else. second, it can be showing that natural selec- tion was the chief causal force making us what we are, and perhaps that selection is still significant. Third, it can be to claim that we are no different from anything else, at least in value or worth. An oak tree, a wart hog, a human, ontologically and axiologically they are the same. if you are thinking of the first of these claims, if you think of the Darwinian revolution as an attempt to make humans entirely natural, in the sense of produced and working according to the same laws of nature as everyone else, one can truly say that for many people this revolution has succeeded and Darwin played a major role in its success. The Origin put us firmly in the natural picture and then following up the Descent of Man was a major analysis of humankind from a naturalistic perspective, cover-

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 / Michael Ruse ing not just our physical frames but also our moral beliefs and social and intellectual natures generally. no one would want to say that it was Darwin alone. huxley and his Man’s Place in Nature (1863) was a key figure back then and of course there have been literally hundreds of other contributors, in and out of biology, since. But Darwin deserves his name up there. even those who may not much care for the work actually being produced seem to agree that the naturalistic program is the right one and that it must take evolution into account. Although having said this, it must be admitted that there are many for whom this program is unacceptable, and who would deny that Darwin has succeeded or indeed could succeed. The official Catholic position, for instance, is that we have souls and these are created and inserted miraculously into human frames, actually, human zygotes (John Paul ii, 1997). And this obviously is but one end of the spectrum that goes all of the way, through the kind of directed evolution allowed by some members of the intelligent design theorists (Behe, 1996), across to the hard-line young earth creationists who think that humans were created miraculously on the sixth day (Whitcomb and Morris, 1961). second, what about natural selection? Again, Darwin is very impor- tant, perhaps indeed more important than just the naturalism part. The Descent of Man showed in detail how natural selection (combined with sexual selection) is a crucial explanatory factor behind much that we think of as human, physical, and social. This is a path that many have followed, most notably in recent times by harvard biologist edward o. Wilson in his On Human Nature (1978), a work that covers morality, religion, conflict, and much more. Wilson is not a hard-line evolutionary determinist, but he does argue that (in his language) the twig is bent. The human mind is not a tabula rasa but shaped by the forces of natural selection. And many workers in the evolutionary field today would agree, from physical anthropologists through human behavioral ecologists and on to evolution- ary psychologists. however, 2 reservations must be expressed. First, much that has been claimed in the name of Darwinian selection bears but a passing resem- blance to the program of the Descent. historically, one thinks of social Darwinism, a movement that covered many different ideologies and that generally owed more to herbert spencer than to Charles Darwin (ruse, 2000). When, to take a particularly egregious example, German general Friedrich von Bernhardi (1912) claimed that Darwin showed that might is right and that the Motherland has almost an obligation to seize from its neighbors, he owed little to the old evolutionist who had worked away in his study in the english countryside. one might as much credit Plato because the doctrine more closely resembled the thinking of Thrasymachus in the Republic. Today one has similar divisions. For instance, philosopher Peter singer (2000) has claimed the authority of Darwin for an explicitly

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The Darwinian Revolution: Rethinking Its Meaning and Significance /  left-wing manifesto. Philosopher larry Arnhart (2005) has no less enthusi- astically claimed Darwin’s support for a right-wing view of society. second, it must be appreciated that (apart from those who reject the naturalistic program in itself) there are those who argue that natural selection is not the appropriate tool to analyze human nature. Clearly a lot of social scientists think this, but so also do prominent biologists. The harvard geneticist richard lewontin, a committed Marxist, is one who denies that evolutionary biology is the key to understanding Homo sapiens. he opts rather for economic and like forces (levins and lewontin, 1985). it may well be that the late stephen Jay Gould shared his sentiments. With some few exceptions, notably elliott sober (1981) who has not only argued for the influence of selection on our modes of thinking in the realm of sci- ence but who has also coauthored a spirited defense of the selection-based nature of human morality (sober and Wilson, 1997), the philosophical community feels negatively inclined to the selection-explains-humans program. The particulars are thought wrong; feminist philosopher lisa lloyd (2005) launched a heavy attack on the putative biological basis of the human female orgasm. But more importantly the overall program is declared ideological and inadequate. even those who think there might be a possibility of a selection-based approach to human nature declare regretfully that the quality of the work produced thus far falls far short of the standards of adequate science (Buller, 2005; richardson, 2007). We come to the third claim, namely that we humans are not in any way special. you might think that proving this was Darwin’s intent; after all, he did caution himself never to use the terms “higher” and “lower” (writing this on the flyleaf of his copy of Vestiges) and the mechanism of natural selection is nothing if not egalitarian. What is it better to be, the AiDs virus or a lowland gorilla? speaking purely biologically, there are few who would speak up for the ape. however, it cannot be gainsaid that if this was indeed the intent of the Darwinian revolution it would have been news to Darwin himself. he always thought of humans as being at the top of the tree of life and european humans as being on the highest branches of all (richards, 1992; ruse, 1996). indeed, in later editions of the Origin he added material suggesting that natural selection leads to prog- ress and ultimately to intelligence. he invoked what today’s evolution- ists call “arms races” where lines compete against each other, improving adaptations in the process, and argued that eventually this would lead to intelligence and progress. if we take as the standard of high organisation, the amount of differ- entiation and specialization of the several organs in each being when adult (and this will include the advancement of the brain for intellectual purposes), natural selection clearly leads toward this standard: for all

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 / Michael Ruse physiologists admit that the specialization of organs, inasmuch as in this state they perform their functions better, is an advantage to each being; and hence the accumulation of variations tending toward specialisation is within the scope of natural selection. Peckham (1959) Although most of Darwin’s contemporaries did not rely on selection, they, too, virtually automatically assumed that evolution was progressive, with humans at the top. one possible exception was the older Thomas henry huxley who in 1893, 2 years before his death, argued that evolution is not progressive and that if we are to succeed morally we must conquer the evolved beast within (huxley, 1893). Perhaps even he thought we are spe- cial; it is just that we must use our evolved moral senses and intelligence to claim our rightful places at the top. Where do we stand today? Few actual working scientists are going to make any such claims, especially not in their science. The exceptions, people like the Cambridge paleontologist simon Conway Morris (2003) who argues that there are niches and that organisms seek them out and occupy them and that at the topic is the intelligence-cultural niche that we humans uniquely have found, tend to keep such speculations for books that are aimed at the general audience. Moreover, there are those, stephen Jay Gould (1988, 1989) was a leader in this respect, who would say that there is no progress and that the Darwinian revolution shows that there cannot be. Ultimately, natural selection is not a progress-producing mechanism. so we could say that the Darwinian revolution does prove the nonspecial status of humans, and finally today people recognize the fact. however, this may not be the entire truth. A case can be made for saying that still today the popular perception is of progress leading to humans. That was Gould’s lament. surveys suggest that this is what schoolteachers, even those favorable to evolution, tend to teach to their students (Zimmerman, 1987). And museums as often as not give the same impression. Go to the Museum d’histoire naturelle in Paris and find that the display starts with blobs and ends with you yourself on television. if you are in any doubt as to the message, the floor above has a display of technology from the crudest beginnings to the sophisticated forms that we have today. summing up: Darwin played a major role in moving us to a naturalis - tic view of human nature, although there are those (generally if not always working from a religious perspective) who would deny that this can ever be done completely and successfully. Darwin played no less (and perhaps more of) a role in convincing people that natural selection is the key causal factor in molding and perhaps today controlling human nature, although one should be wary of all that is claimed in his name and now there are

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The Darwinian Revolution: Rethinking Its Meaning and Significance /  many more critics (not necessarily religious) who are uncomfortable with this program and would reject it in part or in whole. one can make an argument that Darwin paved the way for a view of humankind that gives us no special status here on this earth, although this was certainly not Darwin’s own aim and, especially in the public domain, beliefs privileg- ing humans persist today. WAS THERE A DARWINIAN REVOLUTION? Finally, how does one analyze conceptually what happened because of the Origin of Species? let us start with 2 basic theories of theory change. on one hand, we have the fairly traditional view, represented by the logical empiricists like ernest nagel (1961) and Carl hempel (1966). This view tends to stress continuity, with moves made driven by the evidence and reason. To a certain extent, there will be replacement of old theories by newer, truer theories. something like this happened when Copernicus knocked out Ptolemy. But there will probably be continuity. There was in the Copernican case. it was the same world that the two were describing: the same earth, the same sun, the same moon, the same planets, the same stars. Both sides agreed that circular motion must be preserved. Both sides used epicycles and deferents. it is true that almost all of this was changed as the years went on, but the growth of science was evolutionary not revolutionary. you can have revolutions, but they are gradual, not abrupt, and important is the notion of reduction, when one theory is absorbed in another, or more accurately when one theory can be shown the special consequence of another theory. supposedly the macroscopic understand- ing of gases (Boyle’s law and so forth) could be shown a special instance of the kinetic theory of gases. on the other hand, we have the revolutionary view of Thomas Kuhn (1962). here, the change is abrupt. in Kuhn’s terminology we go from one paradigm to another, and there is no continuity. hence, the change of viewpoint, from one paradigm to another, can never be fueled by reason. it always has to be more of a conversion experience. This is the reason there is often such bitter fighting between scientists. There is no common or shared set of beliefs that can be decisive. As with political disputes, everyone argues from within their own system. Without wanting to homogenize everything into a gray blandness, it is probable that both positions have things to say that throw light on Darwin and his achievements. Clearly, as the logical empiricists would lead one to expect, in some respects Darwin was replacing old positions with new ones. if you think for instance of Darwin’s old friend and mentor, the violently antievolutionist, Cambridge paleontologist Adam sedgwick (1850), Darwin is simply saying that sedgwick’s reading of the

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00 / Michael Ruse fossil record is wrong. sedgwick argues that there are and always will be gaps in the record and that these represent real breaks in the continuity. Darwin is saying that the gaps are artifacts of incomplete fossilization and that there were bridging organisms, even if we never find them, although that should never stop us in the pursuit of such links. An analogous argu- ment holds for the problem of the pre-Cambrian period. At the time of the Origin, there were no organisms at all from this period and their absence was rightly taken as a major problem for Darwin’s theory. The earliest organisms of all, like trilobites, were highly complex and sophisticated invertebrates. how could they have just arrived on the scene? sedgwick said simply that there were no pre-Cambrian organisms. Darwin said that they had existed. Two conflicting views and as Darwin’s overall theory was accepted, sedgwick was pushed out. Today we have many such organisms, and we know that Darwin was right (Knoll, 2003). We had a simple case of one theory being right and the other wrong, and the right one pushing out the wrong one. What about reduction? one does not see any cases of whole posi- tions being taken up by Darwin’s theory, but if you look at the range of other pre-Origin positions, talk of reduction does not seem entirely inap- propriate. Think of the position of someone like richard owen, deeply influenced by the Naturphilosophen. in a work like On the Nature of Limbs (owen, 1849), it is hard to say if he is actually endorsing evolution; the answer is that he probably was but that he wanted to be sufficiently ambiguous to escape the critics. (even as it was, sedgwick was highly suspicious.) More importantly, although owen certainly does not deny adaptation, he stresses homology in a very big way. now when Darwin comes along with the Origin, he is certainly not going to stress homology over all other things as did owen, but he is not going to deny it either. Most interestingly, he argues that it follows as a consequence of evolution through natural selection. it is generally acknowledged that all organic beings have been formed on two great laws: unity of type and the conditions of existence. By unity of type is meant that fundamental agreement in structure, which we see in organic beings of the same class and which is quite independent of their habits of life. on my theory, unity of type is explained by unity of descent. The expression of conditions of existence, so often insisted on by the illustrious Cuvier, is fully embraced by the principle of natural selection. For natural selection acts by either now adapting the varying parts of each being to its organic and inorganic conditions of life; or by having adapted them during long-past periods of time: the adaptations being aided in some cases by use and disuse, being slightly affected by the direct action of the external conditions of life, and being in all cases subjected to the several laws of growth. hence, in fact, the law of

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The Darwinian Revolution: Rethinking Its Meaning and Significance / 0 the conditions of existence is the higher law; as it includes, through the inheritance of former adaptations, that of unity of type. Darwin (1859) This is what theory reduction is all about. Darwin would not have accepted every aspect of owen’s thinking. But there was continuity, with older ideas being absorbed into newer ones, and this is an important thing to note about Darwin and his work and his importance. now let us express some sympathy for the Kuhnian view. Take the question of homology and pick up on the point where Darwin and his supporters would break with owen. huxley (1857–1859) brings out this opposition in his Croonian lecture on the vertebrate skull, given at the royal society the year before the Origin appeared. he faulted owen for being an idealist rather than a naturalist, claiming (correctly) that for owen the archetype represents a divine platonic pattern rather than some- thing produced purely by mechanical laws. As it happens, he also claimed correctly that this led owen to see more than was justified, namely that the skull is made from transformed vertebrae, a claim that Darwin had accepted and that he dropped smartly before the Origin appeared. The point is that, evolutionist or not, owen did have a vision of the world that was fundamentally different from that of Darwin. And it persisted after the Origin, as he tied himself in knots over the hippocampus, present or not in humans and apes (rupke, 1994). it was not the facts as such that counted, but different visions of reality. so in this sense, we do have something Kuhnian going on, different paradigms if you will. But note that it is not just a question of evolution or not evolution, and certainly not of selection or not selection. nor is it simply a matter of biblical literalism. There were literalists, increasingly in the American south, but by and large this is not an issue in the debate around the Origin. literalism had more to do with a defense of slavery than with the interpretation of fossils (noll, 2002; ruse, 2005). The big religious critics like sedgwick and Bishop Wilberforce all accepted an old earth and a lot more. it is rather “man’s place in nature” that was at stake. owen was on one side. so was sedgwick. Darwin’s great American supporter Asa Gray was on this side, too, a point that Darwin saw, when he grumbled that Gray’s appeal to directed variations took the discus- sion out of the realm of science. And we could include more, especially Darwin’s old friend, the geologist Charles lyell, who staggered across the evolutionary line but bitterly regretted having “to go the whole orang” (Wilson, 1970). on the other side, we have Darwin and huxley (for all that the latter downplayed the significance of selection). And also there was Joseph hooker, the botanist, and increasingly a host of younger workers

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0 / Michael Ruse who did not depend on church appointments for their incomes and who wanted to work and think in a secular fashion. And in confirmation of Kuhn, this is where we tend to get the nasti- ness: sedgwick (1860a,b) writing irate letters to the newspaper about Darwin’s methodology; Bishop Wilberforce (huxley, 1900) sneering at huxley’s ancestry; owen (1860) doing everything he could to give the Darwinians a bad name; and so forth. There were certainly vigorous debates about the science, but rarely did the science itself cause unpleas- antness. it was always (as in the huxley-owen squabble over the brain) in the cause of the bigger metaphysical picture. very instructive is the age-of-the-earth question. Physicist William Thompson (later lord Kel- vin) did not much like Darwin’s naturalistic approach to humankind, but he objected publicly to the long time span that Darwin needed. As it happens, Thompson’s research assistant was none other than George Darwin, Charles Darwin’s mathematically gifted son. so Charles Darwin was not allowed to forget or escape the problem. however, even though in the end they simply had to disagree, neither Charles Darwin nor Kelvin thought that the disagreement was personal or ideological. it was just not that sort of difference (Burchfield, 1974). so in the sense that there were differences of that sort, differences where because of rival metaphysical views people talked past each other, one could claim that the Darwinian revolution was Kuhnian. There is another way in which Kuhn’s thinking is insightful. A para- digm is a world picture, within which a scientist works, that gives him or her tasks for the future, and which seems obvious or certain in some sense. obvious or certain in the sense that (as just noted) you cannot see the point of view of others not in the paradigm (ruse, 1999). Think again of the divide in biology between formalism and functionalism and put it in a broader historical context. As Aristotle pointed out, on one hand we have the adaptive side to organisms, what he called final causes, meaning that the parts function for the benefit of the whole. on the other hand, we have homologies (isomorphisms) where the parts may well be used for dif- ferent ends. Down through the ages people have continued to note these 2 sides to organisms, and interestingly people tend not to be ecumenical on the matter. like Darwin, they are partisans for one side or the other. either they opt for function with form secondary or form with function secondary. What is fascinating is the way that this divide goes right across the Darwinian revolution. At the beginning of the 19th century one had formalists who did not accept evolution, many of the Naturphilosophen for instance. The philosopher hegel (1817) is a case in point. one also had functionalists who did not accept evolution. The great French comparative anatomist Georges Cuvier (1817), with his theory about the conditions of

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The Darwinian Revolution: Rethinking Its Meaning and Significance / 0 existence (that he explicitly tied to final-cause thinking), was one such person. Then at the time of the Origin we have people who crossed the evolutionary divide who were one or the other, but not both. Darwin was a hard-line functionalist. That is the whole point of natural selection. huxley equally was a hard-line formalist (huxley and Martin, 1875). That’s why he could not see much need of natural selection. Today, the differences persist. Take the 2 great popularizers of evolution, englishman richard Dawkins and American stephen Jay Gould. Dawkins (1976, 1986) is and always has been an ardent functionalist. For him, it is adaptation all of the way and the only problem really worth solving. he thinks natural selec- tion is a universal law of nature. Gould (1977b, 1989, 2002) was notoriously ambivalent about natural selection and function, thinking it a holdover from english natural theology, and he again and again stressed form. This was the central message of his famous paper on spandrels, cowritten with geneticist richard lewontin (Gould and lewontin, 1979). i would argue that in a real sense we have Kuhnian paradigm differ- ences operating here. Different visions, unable to bridge the gap (ruse, 2003). i find it interesting that metaphors are involved, things that Kuhn stresses as being important in paradigm thinking. We have the organic world as a human artifact. [see Darwin’s use of this metaphor in the little post-Origin book on orchids (Darwin, 1862).] We also have the organic world as a snowflake [Kant’s 1790 picture (Kant, 1951)] or as a crystal [used by Whewell (2001)]. Admittedly, this sense of paradigm does not fit exactly with the senses of paradigm found in the Structure of Scientific Revolutions. For a start, both sides do recognize some of the merits of the other side. it is hard to think that the ontologies are completely dif- ferent. For a second, with respect to the same things 2 people could be in and out of different paradigms. With respect to homology, owen and huxley were divided over the idealistic/naturalistic issues, and yet with respect to thinking that homology more important than function, they were together. Third, perhaps most importantly, the 2 paradigms (without prejudice, let us call them this) persist, down through the ages. it is not a matter of one beating out the other. it is true that today functionalism has the upper hand, but things could change. in fact, in the past 20 years things have moved, with evolutionary development enthusiasts coming onside in a very strong way for formalism. The homologies they find, for instance between humans’ and fruitflies’ genetic sequences, strike them as absolutely fundamental and calling for a total revision of evolutionary thinking. The homologies of process within morphogenetic fields provide some of the best evidence for evolution, just as skeletal and organ homolo- gies did earlier. Thus, the evidence for evolution is better than ever. The

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04 / Michael Ruse role of natural selection in evolution, however, is seen to play less an important role. it is merely a filter for unsuccessful morphologies gener- ated by development. Population genetics is destined to change if it is not to become as irrelevant to evolution as newtonian mechanics is to contemporary physics. Gilbert et al. (1996) We shall have to see how this all pans out. An ardent Darwinian like me is less than overwhelmed (ruse, 2006, 2008). But then i am an ardent functionalist, so i am proof of the point i am making about the divide. obviously, the ideas do persist and not just as fossils. CONCLUSION if the point being made now is well taken, then perhaps hodge was right all along. There was no Darwinian revolution. The paradigms of form and function went in before Darwin and came out after Darwin. This taken as a general conclusion is obviously false. Because of Darwin and the Origin of Species, major things did happen in biological science. less paradoxically, let us say that a complex phenomenon like the Darwinian revolution demands many levels of understanding. Blunt instruments will fail us as we try to understand scientific change. it is necessary to tease strands apart and consider them individually as we try to understand and to assess what is going on. There are other controversies (unmentioned thus far here) very active today. often these involve not just the events directly around Darwin but aspects of the broader picture. robert J. richards (who has been noted as a major contributor to the history of evolutionary biology) argues that the post-Darwinian period, especially that influenced by the German evolu- tionist ernst haeckel, was much more pure-Darwinian than people have recognized. he thinks that Darwin was deeply romantic in his thinking, influenced by the currents that came from Germany at the beginning of the 19th century, and that after the Origin people like haeckel were simply responding to and building on that which was already there (Bowler, 1976; richards, 2002). other students of the period (including myself) disagree strongly, thinking that (as Karl Marx noted) Darwin was quintessentially english in his thinking and that it is right to see haeckel as responding to non-Darwinian themes, an attitude that inflected evolutionary biology until the synthesis of the 1930s (ruse, 2004). Another controversy centers on the work and interpretations of Peter J. Bowler (also noted above as a major contributor). he agrees that post-Darwinian thought was deeply non-Darwinian, but he nevertheless thinks that it was good-quality sci- ence and that it fed smoothly into the synthesis. indeed the latter would not have occurred without the former (Bowler, 1988, 1996). others, again

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The Darwinian Revolution: Rethinking Its Meaning and Significance / 0 including me, disagree strongly, arguing that post-Darwinian evolution- ary biology was often really poor-quality science (notoriously following haeckel in spinning unsustainable analogies between embryology, ontog - eny, and paleontology, phylogeny) and that the synthesizers of the 1930s had to cleanse the Augean stables and return to the thinking of the Origin (melded admittedly with the new genetics) before further advance was possible (ruse, 1996). These controversies, however, must be the topic of another essay. here, i rest confident that i have shown why, for a philosopher and histo- rian of science, analyzing the Darwinian revolution is such a worthwhile challenge.

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