We Need to Soften the Modern Synthesis

Lately there's been a lot of talk about updating evolutionary theory. Much of the hype has been generated by journalist Susan Mazur who has been drawing attention to a meeting that took place in July. At that meeting there were 16 people interested in evolution. They met at the Konrad Lorenz Institute for Evolution and Cognition Research in Altenberg, Austria. Their goal was to reach a consensus on what needs to be added to evolutionary theory in order to bring it up to date. They've been dubbed the "Altenberg 16."

The current version of evolutionary theory is often referred to as the Modern Synthesis—a term coined by Julian Huxley to describe the consensus reached by evolutionary biologists in the late 1940's. That version of evolutionary theory was appropriately pluralistic, giving prominence to random genetic drift as an important mechanism of evolution.

By the time of the Darwinian centennial celebrations in 1959, the Modern Synthesis had hardened to the point where random genetic drift was barely mentioned. Most prominent evolutionary biologists were confirmed adaptationists—including those who had been more open-minded a decade earlier.

The Altenberg 16 have some interesting ideas but unfortunately, they are also lending their reputations to some ideas that are just plain crazy. Let's see how a prominent science journalist, Elizabeth Pennisi, handles the issue in an article for Science magazine [Modernizing the Modern Synthesis].

That hyperbole has reverberated throughout the evolutionary biology community, putting Pigliucci and the 15 other participants at the forefront of a debate over whether ideas about evolution need updating. The mere mention of the "Altenberg 16," as Mazur dubbed the group, causes some evolutionary biologists to roll their eyes. It's a joke, says Jerry Coyne of the University of Chicago in Illinois. "I don't think there's anything that needs fixing." Mazur's attention, Pigliucci admits, "frankly caused me embarrassment."

That's a pretty accurate commentary on how the Alternberg 16 are viewed by most evolutionary biologists. They don't think the Modern Synthesis needs fixing. But—and this is a big "but"—they are referring to the hardened version of the Modern Synthesis; the version that can be described as ultra-Darwinian. The version that Stephen Jay Gould and others have been trying to change since 1970.

Elizabeth Pennisi seems completely unaware of this controversy in evolution. Here's how she describes modern evolutionary theory ...

Modern tradition

The modern synthesis essentially represents a marriage of the 19th century concept of evolution with Mendelian genetics, which was rediscovered at the beginning of the 20th century; the birth of population genetics in the 1920s added to the intellectual mix. By the 1940s, biologists had worked out a set of ideas that put natural selection and adaptation at evolution's core. Julian Huxley's 1942 book, Evolution: The modern synthesis, brought together this work for a broad audience.

Simply put, the modern synthesis holds that organisms have a repertoire of traits that are passed down through the generations. Mutations in genes alter those traits bit by bit, and if conditions are such that those alterations make an individual more fit, then the altered trait becomes more common over time. This process is called natural selection. In some cases, the new feature can replace an old one; in other instances, natural selection also leads to speciation.

This is definitely not the pluralism promoted by Gould and others and it's not even the original version of the Modern Synthesis published in the 1940's. Two of the key principles of the original Modern Synthesis were ...

5. Evolutionary change is a populational process: it entails, in its most basic form, a change in the relative abundances (proportions or frequencies) or individual organisms with different genotypes (hence, often with different phenotypes) within a population. One genotype may gradually replace other genotypes over the course of generations. Replacement may occur within only certain populations, or in all the populations that make up a species.

6. The rate of mutation is too low for mutation by itself to shift a population from one genotype to another. Instead, the change in genotype proportions within a population can occur by either of two principle processes; random fluctuations in proportions (genetic drift), or nonrandom changes due to the superior survival and/or reproduction of some genotypes with others (i.e., natural selection). Natural selection and random genetic drift can operate simultaneously. (Futuyma, 2005)

The hardened version of the Modern Synthesis only talks about natural selection and random genetic drift barely gets mentioned. It's too bad that Pennisi only interviewed adaptationists and it's too bad that she didn't bother to read an evolution textbook.

The current, most popular view of evolutionary theory needs to be changed. Random genetic drift needs to be restored to its rightful place. At the same time, other points of view should be considered. The problem with the current debate is that the emphasis is on the wrong problem. It's not that we need to incorporate evo-devo; instead. we need to re-incorporate well-established ideas (random genetic drift) that have been known for fifty years!

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Futuyma, D. (2005) Evolution, Sinauer Associates, Inc. Sunderland, MA, USA (p. 10)