THE DARWINIAN LEGACY, 150 YEARS LATER
Beyond his numerous books and autobiography (Darwin F, 1887a), Darwin left a wealth of personal correspondence (Darwin F, 1887b) and additional written material that science historians can now sift through to better understand Darwin’s developing ideas at different stages of his life. Prominent among these were notebooks that Darwin wrote during the voyage of the Beagle, and a lettered series of Transmutation Notebooks that he wrote in the 2 years following his return. Several authors in this concluding part of the ILE III Proceedings scrutinize these writings to illuminate Darwin’s thought processes and thereby better appreciate and contextualize his scientific legacy.
In Chapter 13, Francisco Ayala describes a fundamental discrepancy between Darwin’s scientific methodology and how Darwin portrayed his methods to the general public. The version for public consumption emphasized how Darwin proceeded on the principles of Baconian induction, which at that time were favored by British philosophers such as John Stuart Mill. Under this approach, facts are collected wholesale—presumably without the bias of preconceived notions—and broader biological principles eventually emerge. The actual methods of Darwin, Ayala contends, were far different from this depiction, falling instead squarely within a hypothetico-deductive framework. The latter scientific method has two steps: the formulation of one or more conjectures or hypotheses about the natural world; and the design and implementation of critical empirical tests of whether deductions derived from each hypothesis are consistent with real-world observations. In support of his contention that
Darwin consistently used the hypothetico-deductive method, Ayala cites examples from Darwin’s work and even uses some of Darwin’s own words, such as “How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service.” Ayala speculates on why Darwin sometimes pretended to be a Baconian inductivist when in fact he mostly practiced what today would be considered modern hypothesis-driven deductive science.
In considering Darwin’s legacy from the current vantage, in Chapter 14 Michael Ruse asks three related questions: Was there a Darwinian revolution? Was there a Darwinian revolution? And, was there a Darwinian revolution? Ruse’s answers to these questions are two resounding yes’s and a qualified yes, respectively. The first resounding yes comes from the fact that after Darwin, rational observers could no longer accept the old picture of humans as somehow the miraculous products of special creation. In other words, the revolution challenged us to rethink dramatically—both emotionally and intellectually—what it means to be human. The second resounding yes comes from the evidence that it was Darwin, rather than his predecessors or contemporaries, who was primarily responsible for the scientific and the metaphysical shifts that society entailed in coming to terms with natural selection’s role in the evolutionary process. The qualified yes comes from the realization that the third question is somewhat philosophical; the answer depends in part on whether to interpret major transformations of thought as continuous and gradual, or discontinuous and abrupt. Ruse discusses philosophical nuances of his own position on these issues.
Natural selection is the key Darwinian concept, and the evolutionary force given top billing in The Origin. But common ancestry is a key concept too, a co-star (albeit not originating strictly with Darwin) of the evolutionary theater. In Chapter 15, Elliott Sober considers how natural selection and common ancestry are related under Darwin’s worldview, and he argues that the latter has a sort of logical (as well as historical) priority over the former. This is because, under Darwinian logic, arguments about natural selection often require the supposition or backdrop of common ancestry (i.e., genealogy and heredity), whereas the logical defense of common ancestry does not require natural selection. In this epistemological sense, Darwin ordered things backward, Sober argues, when he presented natural selection, rather than common ancestry, first and foremost in The Origin. Rather than “evolution by natural selection,” Darwin’s theory might better be described as “common ancestry plus natural selection.”
In Chapter 16, Robert Richards presents a revisionary argument that seems likely to be highly controversial. Using excerpts from Darwin’s writings, Richards makes a case that “Darwin’s theory originally re-infused
nature with moral purpose and employed teleological means of doing so,” and that “Darwinian evolution had the goal of reaching a fixed end, namely man as a moral creature.” These conclusions fly in the face of conventional wisdom, which holds that Darwin’s elucidation of natural selection was philosophically as well as scientifically revolutionary precisely because it banished the necessity for invoking ultimate purpose or goal-directedness in biological evolution. Nevertheless, Richards contends that many of Darwin’s writings are infused with teleological statements, and that to dismiss these, or to rationalize them as rhetorical devices (for example, if Darwin was trying to assuage Victorian readers) is unwarranted. Richards bolsters this argument by tracing various of Darwin’s ideas to his early life, and how these concepts eventually played into the construction of Darwin’s theory. Thus, Richards interprets many of Darwin’s writings as consistent with notions of evolutionary purpose and biological progress. It will be interesting to monitor the responses of other evolutionary historians to this provocative suggestion.
The title of Daniel Dennett’s Chapter 17—Darwin’s Strange Inversion of Reasoning—refers to a quote from one of Darwin’s critics who in 1868 wrote that Darwin, “by a strange inversion of reasoning, seems to think Absolute Ignorance [natural selection; editors’ addition] fully qualified to take the place of Absolute Wisdom [God] in all the achievements of creative skill.” Dennett likens Darwin’s strange inversion of reasoning to another such profound inversion of reasoning, this time by Alan Turing in the physical sciences. In the 1930s, Turing argued that it would be possible to design exquisite calculating machines [such as modern computers] that were absolutely ignorant yet fully capable of performing highly complex mathematical tasks. Whereas the truth of Turing’s strange inversion in physics is universally acknowledged today, many people (namely, creationists) still cannot abide Darwin’s strange inversion in biology. Dennett explores the philosophical ramifications for Darwin’s inversion of reasoning, and finds them to be truly profound.
A recent article in the New York Times (July 15, 2008) was entitled “Let’s get rid of Darwinism.” It was written by Olivia Judson, an evolutionary biologist and the author of a best-selling evolutionary book (Judson, 2002). In that article, Judson wrote, “I’d like to abolish the insidious terms Darwinism, Darwinist, and Darwinian. They suggest a false narrowness to the field of modern evolutionary biology, as though it was the brainchild of a single person 150 years ago, rather than a vast, complex and evolving subject to which many other great figures have contributed…. Obessively focusing on Darwin, perpetually asking whether he was right about this or that, implies that the discovery of something he didn’t think of or know about somehow undermines or threatens the whole enterprise of evolutionary biology today.” The term Darwinism also “suggests that Darwin
was the beginning and the end, the alpha and the omega, of evolutionary biology, and that the subject hasn’t changed much in the 150 years since the publication of The Origin.” Judson went on to suggest that constantly using terms such as Darwinism and Darwinian is rather like calling all of modern aeronautical engineering “Wrightism” after the Wright brothers, or referring to all fixed-wing aircraft as “Wrightian” planes. Similar sentiments were expressed by another well-known biologist, Carl Safina, in a New York Times article (Feb. 10, 2009), entitled “Darwinism must die so that evolution may live.”
Our intent in the Sackler Colloquium and in this book has not been to idolize Charles Darwin, but rather to celebrate the field of evolutionary biology that he played such an important role in developing nearly 2 centuries ago. We submit that if Darwin were alive today, he would be satisfied with his own pioneering efforts, but also completely astonished at the breadth, depth, and vibrancy of the modern field.