Debating philosophers: The Modern Synthesis

I'm discussing a paper by Lu and Bourrat (2017) [Debating philosophers: The Lu and Bourrat paper]. They begin by describing current evolutionary theory, known (to them) as the Modern Synthesis. The paper is about challenges to current evolutionary theory from those who advocate an extended evolutionary synthesis or from those who would replace, rather than extend, current evolutionary theory. It is reasonable to begin with a description of the theory that's being challenged.

Here's what Lu & Bourrat say,

By the 1940s, the marriage between Darwinian theory of evolution (Darwin 1859) and Mendelian genetics (Correns [1900]; Tschermak [1900]; de Vries [1900]; Mendel [1865]) was integrated into a general consensus known as the Modern Synthesis (MS). This synthesis provided theoretical foundations for a quantitative understanding of evolution. It has been regarded as a paradigm for evolutionary theory over the last sixty years. The original MS has been extended in at least three regards. First, since the 1950s, classical population genetics has been generalized to quantitative genetics for continuous traits (Falconer and Mackay [1996], p. 100). Although the former focuses on allele frequencies and genotypes, whereas the latter by its nature begins from the phenotype, the mathematical models of the two can be formally connected (Wade [2006]). Therefore, we will regard both disciplines as formal evolutionary theory in this paper. Second, formal evolutionary theory is now better suited to account for the evolution of microorganisms and plants, which used to be the glaring omission of classical population genetics (Ayala et al. [2000]). Third, progress made in various biological sub-fields has extended evolutionary theory in many respects. The discovery of DNA structure in 1953 (Watson and Crick [1953]), for instance, prompted the development of molecular genetics and stimulated the discussion of gene selectionism. Also, the integration of development and evolution resulted in the new research field of evolutionary developmental biology (Goodman and Coughlin [2000]). In spite of these three extensions, current evolutionary theory is still remarkably reliant on the tenets of the MS.

I don't think I've ever heard of those three extensions before—at least not in the way they are described here. The problem with this description is that the really important modification of the classical Modern Synthesis is completely ignored. I'm referring, of course, to Neutral Theory and the increased emphasis on random genetic drift. This has led to all kinds of developments that are completely foreign to the original tenets of the classic Modern Synthesis. It's rather silly to refer to current evolutionary theory without mentioning these changes.

It's impossible to imagine how proponents of the old Modern Synthesis could possibly understand concepts such as the drift-barrier hypothesis [Learning about modern evolutionary theory: the drift-barrier hypothesis] or constructive neutral evolution [Constructive Neutral Evolution (CNE)] or junk DNA. How could they have understood sequence comparisons and molecular clocks without incorporating Neutral Theory and random genetic drift?

Lu & Bourrat have fallen into the same trap as those who promote an extended evolutionary synthesis. They are describing a strawman version of evolutionary theory that hasn't represented the current view for over 40 years [Kevin Laland's new view of evolution] [More calls to extend the defunct Modern Synthesis] [Rethinking evolutionary theory].

I'm reminded of a comment by Arlin Stoltzfus [Arlin Stoltzfus explains evolutionary theory] who said,

Every scientist with a PhD knows that it takes years of study to be an expert-- you not only have to ingest hundreds of books and papers, you have to digest this information, sifting it and evaluating it, and converting it into knowledge and judgment. Yet evolutionists all think they are automatic experts on the topic of "the Modern Synthesis" or "the history of evolutionary thought" without doing original research on it, or reading hundreds of secondary sources.

Understanding current evolutionary theory is hard. I urge philosophers (and others) to work harder at the task. They could begin by reading a modern evolutionary biology textbook and then read the primary literature written by experts in evolutionary theory and modern population genetics.

What they can't do is rely on the secondary literature written by opponents of the old classical Modern Synthesis. If you are going to write a paper on challenges to the Modern Synthesis then you'd better do your homework or you are going to look rather foolish.

There are many scientists who don't understand evolution (e.g. ENCODE researchers). They have no excuse. If they are going to write about evolution in their papers then they'd better get it right. However, philosophers of science who write about evolutionary theory are in a somewhat different category since they portray themselves as experts in the subject. It is, after all, their specialty. When they publish a philosophical paper about evolution one holds them to a very high standard. They don't often meet that standard and that's surprising.

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Lu, Q., and Bourrat, P. (2017) The evolutionary gene and the extended evolutionary synthesis. The British Journal for the Philosophy of Science, (advanced article) April 20, 2017. [doi: 10.1093/bjps/axw035] [PhilSci Archive]