150 years after the publication of On the Origin of Species, it is useful to reflect on how evolutionary theory has changed with time. Which of his contributions have stood the test of time? This was the exercise chosen by Massimo Pigliucci for a piece appearing in Philosophy Now. He refers to the "Darwinian view of the world" and goes on to explain why this can be understood as a paradigm shift in the mindset of scientists and other scholars in the Nineteenth Century.
It is important to analyse the philosophical ideas underpinning Darwinism (Source here)
Pigliucci traces three main stages in Darwinism's evolution. However, even before Darwin, it must be recognised that evolutionary thinking was to be found among the intelligentsia. What was lacking, however, was a theory of transformation. Lamark had proposed some ideas, but "already in Darwin's day there was compelling empirical evidence that Lamarckism didn't work." So, Stage 1 of Pigliucci's story concerns the contribution of Charles Darwin. His approach was to draw on a large body of empirical evidence and interpret it all with the help of two guiding principles.
"Darwin's fundamental insight was grounded on thousands of observations and two principles: common descent and natural selection. Based on his detailed studies of the character and distribution of species across the world, Darwin built a robust inference to the conclusion that all living organisms share common ancestors and are therefore related to each other by a process of 'descent with modification'. But what was doing the modifying? The brilliant answer was: natural selection."
It has to be said that Darwin's approach was more controversial with scientists than most people think. Natural selection was already recognised as a force in nature by many: e.g. Auguste Comte, Comte de Buffon and particularly the research of Edward Blyth. However, these people understood it to be a conserving force in nature rather than a means of transformation. "Few people doubted the idea of common descent, but natural selection was not yet accepted as a sufficient, or even important, mechanism for evolutionary change." Furthermore, Darwin did not have a theory of heredity that worked: his "blending inheritance" did not stand up to critical scrutiny. When Mendel's research was known, it "appeared to deal a fatal blow to Darwinism" because it explained much of the variation observed and discussed by Darwin as innate. Later, with Weissman's work, the situation became even more problematic for Darwin.
"[W]hatever the answer to the question of heredity was going to be, it had to take into account that living organisms completely separate the reproductive cells (the germ line) which convey inheritance from their body cells (the somatic line)."
Stage 2 brings us to the "Modern Synthesis", which Pigliucci describes as "still the standard model in biology". This was the outcome of the collective work of some "theoretical biologists" who employed "statistical analysis" to unify the contributions of Darwin and Mendel. This synthesis is the one that dominates the textbooks and is being hailed as robust by most of the people lauding Darwin's contribution in this Bicentennial year.
"It is founded on Darwin's original principles, with the addition of a mathematical-statistical theory, a theory of heredity, and a much more extensive empirical base than Darwin and his contemporaries had been able to assemble."
However, Pigliucci is not finished. He has more to write! Stage 3 has a question mark after it - but it also has a name: "The Extended Synthesis". Pigliucci is a member of the Altenberg 16, a group that some regard as subversive of the neodarwinian consensus. (For more on this, go here). There are significant sources of dissatisfaction with what Pigliucci calls "the current version of the theory":
"An increasing number of scientists - including yours truly - have grown dissatisfied with the fact that the current version of the theory does not adequately address many important questions. These include the role of developmental processes in evolution, the origin of completely novel traits (such as the turtle's shell, for instance), the increasingly-plausible possibility of so-called 'soft' inheritance (ie, mechanisms of heredity that do not depend on DNA), and even whether and how the propensity to evolve - the so-called 'evolvability' of a lineage - can change during the course of evolution."
These scientists find the Modern Synthesis too restrictive, and they also are taking seriously "the possibility that natural selection may not be the only natural mechanism generating complexity." They are interested in "emergent" properties of complex systems, and are wondering whether additional complexity can be generated "for free". Evo-Devo is said to be a well-established sub-discipline of this new direction of thought. Other avenues of exploration are more speculative, but they are needed in order to "break new theoretical barriers".
Finally, Pigliucci considers whether any of these changes to Darwinian biology constitute a paradigm shift in the sense advanced by Thomas Kuhn. Should any of these developments be regarded as fundamental? Reference is made to 'incommensurable' theories: from the vantage point of one model of reality, there is no way to make sense of a different model. Pigliucci argues that the transitions within Darwinism are gradual, rather than punctuated.
"But when it comes to the evolution of evolutionary theory we see much more continuity than incommensurability. [. . .] In this sense, therefore, I do not think that evolutionary theory has ever undergone a true paradigm shift. With one exception."
It is to that exception we must now turn. Before Darwin, although there had been many significant moves towards the secularisation of science (the so-called Enlightenment), design thinking was still widespread because no one had found a viable mechanism to explain biological complexity. This is what Darwin achieved: an "alternative explanation for the complexity and diversity of life". Darwin brought about a change of worldview - a true paradigm shift in the Kuhnian sense.
"That job was Darwin's chief contribution to humanity - and this alternative explanation truly was a paradigm shift, whose effects still reverberate in the modern creation-evolution 'controversy'. To abandon a supernaturalist view of life on earth in favor of explanations based on natural causes does create an incommensurability - one that finally moved biology from the realm of natural theology and mythology to that of serious science. Charles Darwin will justly be celebrated this year for this momentous achievement in the history of thought."
There you have Pigliucci's analysis. The Darwinian revolution did involve a change of view about the world in which we live. The only explanations deemed to be "scientific" involved natural causes. Pigliucci uses the word "supernaturalist" whereas he should be referring to intelligent causation, but this simply reflects the fact that Pigliucci is a product of the Darwinian worldview and he finds it difficult to appreciate thinking within a different paradigm. In a similar way, he portrays science prior to Darwin as belonging to "the realm of natural theology and mythology" rather than the realm of "serious science". In this he does a grave injustice to the pioneers of science, including biological science, who saw no incompatibility between their research activities and the recognition of intelligent causation. Here again, Pigliucci reveals that he has difficulty understanding what life is like for scholars working within a different paradigm.
The take-home message from Pigliucci is clear: Darwin's major contribution was not in the originality of his thought or the details of his theory (which have evolved and developed with the passing of time) but in championing a science committed to naturalism: i.e. only natural causes are acceptable within science. Once people grasp this, many things become clear.
1. Scientists committed to naturalism find it really difficult to understand Intelligent Design primarily because they are operating within a different paradigm.
2. Those who regard ID as a threat to science and education are actually seeking to promote a version of science and education that is committed to philosophical naturalism.
3. The Bicentennial celebrations for Darwin are more inspired by a commitment to the Darwinian worldview rather than to Darwin's contribution to science.
4. Gould's NOMA thesis and the complementarity approach of theistic evolutionists are way off the mark because they fail to acknowledge the critical role played by naturalistic philosophy in contemporary science.
The Evolution of Evolutionary Theory
Philosophy Now, Jan/Feb 2009
First para: Evolution is arguably one of the most profound and controversial ideas ever to hit a human mind. On the Origin of Species flew off the bookshelves when it was published 150 years ago, and it remains one of the most crucial books in the history of science. However, despite the fact that the Darwinian view of the world was swiftly embraced by scientists, as much as half of the population in the United States still today doesn't buy it, because it seems to undermine their view of who we are, where we came from, and what we are here for.
Tyler, D. How much of evolutionary theory needs fixing? ARN Literature Blog (25 July 2008)
Wells, J. Happy Darwin Day? The Washington Times (February 12, 2009)
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