Science Literature

This Bicentennial year will provide numerous opportunities to examine Darwin's life and work. The journal Science has published an interesting review by Peter Bowler with the title "Darwin's Originality". The topics covered are numerous and many of them give useful leads into discussions. For example, David Coppedge builds on what Bowler says about Social Darwinism. He considers how "Darwin's world view in which nature ruthlessly destroys the "unfit" in an unending struggle for existence was used by later political leaders to justify their atrocities as a rational outworking of the laws of nature." However, this blog will limit its scope to Darwin's thinking about the question "What is a species?"

Darwin's first evolutionary tree diagram in Notebook B (Source here)

The concept involved a fluid morphology which exhibited a branching pattern with the passing of time. This was a radical departure from the perception that species had their own essence and were not part of a continuum. Bowler emphasises the significance of animal and plant breeding for Darwin: breeders selected traits they desired and managed their breeding programmes to preserve and enhance those traits. Thus, variations (or breeds) merged into species which (it was argued) merged into genera, families and the higher taxonomic categories.

"Traditionally, species were treated as idealized types with a fixed essence, any variation from the norm being trivial and impermanent. The breeders knew that they could produce huge changes in structure by accumulating normal variations over a number of generations. When Darwin linked this information with his conviction that species could change indefinitely over time, he was driven toward a new form of species concept in which the population becomes paramount. The natural range of variability becomes part of the species' character, not the result of accidental deviations from a fixed norm. This is what Mayr called the transition from typological thinking to population thinking [. . .]"

Bowler finds originality in Darwin's thinking about the analogy between breeding programmes and natural selection. I do not see how this can be described as "truly unique" because in 1831 the plant breeder Patrick Matthew proposed such a link and identified natural selection as the mechanism of evolutionary transformation. Bowler also points out that Wallace did not make a connection between artificial selection and natural selection.

"Darwin's study of breeding in the formulation of his theory is much debated by historians, but there can be little doubt of how important the analogy between artificial and natural selection became in his later thinking. In this case, Darwin was truly unique, because even Wallace did not take this step and dissociated himself from the link with artificial selection expressed in Darwin's later writings."

Whilst it is true that Wallace differed from Darwin in this matter, it can be argued that Wallace was justified in the judgment he made. For those interested in the details of how they saw the issue, Kutschera's comparative analysis of Darwin and Wallace is here. The specific comment on this point is as follows:

"Wallace emphasized the distinction between domestic and natural varieties. In fact, he regarded domestic animals as "abnormal" and pointed out that they cannot be regarded as "model systems" for animals in nature. Darwin, however, stressed the similarities between domestic and natural variants in the construction of his argument." (pages 350-351)

This aspect of Darwin's originality is perceived by Bowler as a major reason why his contemporaries questioned his proposed mechanism:

"One of the most disturbing aspects of Darwin's theory was its appeal to the struggle for existence as the natural process that equates with the breeder's activity as a selecting agent. This very harsh vision of nature certainly threatened the traditional belief in a benevolent Creator. The term "struggle for existence" occurs in Thomas Robert Malthus's An Essay on the Principle of Population, although used in the context of tribal groups competing for limited resources. Darwin saw that population pressure would lead to competition between individuals and was perhaps the first to realize that it might represent a means by which the population could change through time. The process worked by eliminating the least fit variants within the population and allowing the better adapted to survive and breed. This was what the philosopher Herbert Spencer would later refer to as the "survival of the fittest." Strictly speaking, natural selection requires only differential reproduction among variants, but Darwin thought that the pressure of competition was necessary to make it effective. It seems that without the input from Malthus, he would not have come up with the theory."

It was not just that his contemporaries were disturbed by these ideas - they doubted, on scientific grounds, that natural selection was capable of doing the work required of it. They were not disputing the existence of natural selection, but were not convinced that it could be be incorporated into a creative process. Stephen Jay Gould drew attention to this in The Structure of Evolutionary Theory (2002, p. 139):

"Darwin's theory therefore cannot be equated with the simple claim that natural selection operates. Nearly all his colleagues and predecessors accepted this postulate. Darwin, in his characteristic and radical way, grasped that this standard mechanism for preserving the type could be inverted, and then converted into the primary cause of evolutionary change. Natural selection obviously lies at the center of Darwin's theory, but we must recognize, as Darwin's second key postulate, the claim that natural selection acts as the creative force of evolutionary change. The essence of Darwinism cannot reside in the mere observation that natural selection operates - for everyone had long accepted a negative role for natural selection in eliminating the unfit and preserving the type."

There was, and still is, a scientific debate to be made about the efficacy of natural selection as an element of evolutionary theory. Peppered moths, finch beaks and lizard legs certainly give us evidence of selection forces in the natural world, but they do not demonstrate natural selection as a creative process. Students and scholars therefore need the academic freedom to consider the implications - without the threat of being taken to court for bringing religion into science lessons.

There was, and still is, a scientific debate to be made about the natural limits of variation. In Darwin's day, people were aware that artificial selection ran up against natural limits, and this finding has been abundantly confirmed since then. The science of genetics reveals that most of the domestic breeding variations Darwin was considering were because of innate genetic material. To get beyond that reservoir of variation, mutations of various kinds are needed. This area of knowledge was unknown to Darwin, so references today to artificial selection which make no reference to the genetics of variation are likely to be very misleading. Students and scholars therefore need the academic freedom to consider the implications of both variation and stasis - without the threat of being taken to court for bringing religion into science lessons.

Furthermore, anyone reading Bowler's essay would have to be naive to think that there is a rigid divide between science and religion. Darwin's theory replaced thinking based on order and predictability with "a ruthless 'struggle for existence' [that] did not seem the kind of process that would be instituted by a benevolent God". Note also Bowler's closing sentence:

"But if we accept science's power to upset the traditional foundations of how we think about the world, we should also accept its potential to interact with moral values."

Darwin's Originality
Peter J. Bowler
Science, 9 January 2009: 323, 223-226 | DOI: 10.1126/science.1160332

Abstract: Charles Darwin's theory of natural selection has been hailed as one of the most innovative contributions to modern science. When first proposed in 1859, however, it was widely rejected by his contemporaries, even by those who accepted the general idea of evolution. This article identifies those aspects of Darwin's work that led him to develop this revolutionary theory, including his studies of biogeography and animal breeding, and his recognition of the role played by the struggle for existence.

See also:

Coppedge, D.F. Darwinists Cannot Deny "Disturbing" Implications, (Creation-Evolution Headlines, 15 January 2009)