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Thursday, September 11, 2008

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!


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

3 comments :

A. Vargas said...

if you think that A) evolution occurs in populations (forgetting organisms) then there is only selection and drift; and then only selection is interesting because B) Selection is the "only" thing related to adaptation.

If you consider A and B to be true, you are a synthesis man.

I'm not. I don't accept either. To me it's just funny to see a biochemist pontify about these topics.

A. Vargas said...

By excluding development, Larry shows typically amateur ignorance, since you cannot really bypass the importance of the genotype-phenotype relationship.

"Synthesis men" only know how to think about population frequencies. Everything else is a black box.

Gregorio said...

One key point of Altenberg not spoken of here is the removal from centrality of genetics in evolution. The limits of genetics for understanding the origins of life is something few give much thought to. The same forces that formed life from chemistry are also determinant in the evolution of that life. It turns out these same forces affect strongly the pace of genetic change beyond random drift or anything natural selection might involve. This was the point of Cairn's 1988 paper in Science entitled "The Origin of Mutations" which tied this type of mutation to metabolic considerations - called starvation-induced mutation. Genetics is inadequate for accounting for massive cell suicide in embryonic development, and for the specialization of cell types in an organism. Genetics is unable to account for affects on gene expression related to methylation alteration resulting from metabolic/energy considerations. Contra Ernst Mayr, evolutionary change can involve macroscopic or systemic changes rather than merely continuous genetic changes, and these changes can occur in the individual, to be passed on in the population. Such changes occur as an increase in the number of emergent axons from nervous tissue, that subsequently synapse with somatic structures. This is a whole number, and not subject to gradations or anything like continuity, genetic or otherwise.

In Harvard's Department of Organismic and Evolutionary Biology can be found the Program for Evolutionary Dynamics - an attempt to put Darwin in mathematical form. The Program has no equation for metabolism, and begins with the RNA/DNA world. This is where the modern synthesis is, and it needs amending. For in this school there is disputation about whether, in the origins of life, replication preceded metabolism, or the other way around. Replication is tied to RNA/DNA. The math of metabolism models the two as inseparable, without any reference to the existence of RNA/DNA, but on the basis of energy fluctuations alone, acting upon the covalent bonds of biomass, where metabolic rate is the recharge rate of these bonds. This math suggests that the line between life and non-life is illusory, if not arbitrary. This suggestion is supported by work on nano-bacteria that has determined such things are not alive, but merely organic phosphates interacting chemically in a way that simulates life; and by work on electrical fields within cells that are far more complex (and related to cytoskeletal structure and organelle functioning) than just a simple membrane voltage. The math also relates genome mass to the eating habits and average metabolic efficiency of the organism comprised of the cells with that genome mass. Metabolic efficiency in the equation is a ratio of amperages in an expression of the redox coupling efficiency of the organism.

Characterization of the Altenberg call for a new synthesis of evolution as hype is something that emerges from the mouths of those who have incomplete understanding of evolution based upon it being all about genetics, random drift, and natural selection. These things are entirely inadequate for many of the new phenomena coming to light.