Science Literature

During this Bicentennial year, we must expect Darwin's intellectual heirs to flex their muscles and bluntly tell those who want to move beyond neodarwinism that they are wasting their time. Such a stance is taken by Jerry Coyne in a critical review of Mark Lumberg's new book about the Freaks of Nature. Coyne claims that the evidence presented "is not strong enough to upset the orthodox view".

Do developmental quirks tell us about evolution? - or about development? (source here)

In the course of the review, Coyne identifies three threads of thought within evolutionary biology that have been perceived as challenging Darwinism. These are structuralism, evo-devo and epigenetics. He interprets Blumberg's book as a synthesis of concepts generally associated with the evo-devo approach, and recognises that it was written with the intention of challenging neodarwinism.

"Blumberg's ambitions transcend storytelling: he aims to show that developmental biology has made real contributions to evolutionary theory. The theory's problem, as Blumberg maintains, is its "gene-centered, population-level thinking", also described as "simplistic single-cause, gene-centered thinking". What paradigms, then, should supplant our misguided embrace of Gregor Mendel?"

The paradigms that he discusses are epigenetics, phenotypic accommodation and genetic assimilation. It is not the purpose of this blog to align itself with any of these positions, but rather to consider the nature of the response Coyne is making. He starts with a discussion that took place in 1980, when Lewis Wolpert responded to the structuralists present by saying that he also had a radical and heretical view: "Genes control development". To make his point, he switched off the lights in the lecture room: a simple switch has the power to make big changes. Apparently, the structuralists were not impressed, but Coyne thought Wolpert had scored a victory.

"Wolpert was puckishly defending what he saw as a perfectly adequate paradigm against those who minimized the importance of genes."

Coyne returns to the importance of genes again and again in his review. Regarding epigenetics:

"Some adaptive 'epigenetic' phenomena, such as parental imprinting of chromosomes, which influences gene expression depending on which parent passed on the gene, are based on instructions in DNA. [. . .] And in nearly all cases, epigenetic effects peter out after a few generations, unable to promote major evolutionary change. Perhaps the most serious criticism of epigenetics is that of the thousands of inherited mutations found in model organisms such as mice and fruit flies, virtually all reside in DNA."

Phynotypic accommodation was supported in the book by the example of a deformed goat. Without forelimbs, it learned to hop around like a kangaroo. Slijper's autopsy showed numerous modifications that facilitated its bipedal hopping. Coyne is unimpressed (but I doubt that he has any evidence to support his comments about natural selection in the quote below):

"The phenotypic changes in Slijper's goat did not result from some inherent self-regulating property of development. Rather, they reflect an evolved phenomenon: natural selection has given bones and muscles the adaptive property of developing in response to the stresses they experience."

Genetic assimilation is despatched as unsupported by evidence. But here again, Coyne leads with neodarwinian theory by invoking "pre-existing genetic variation" as a given:

"As with phenotypic accommodation, here the phenotype changes before the genes. During assimilation, an initial environmental change alters the phenotype of many individuals, exposing previously hidden genetic variation that can then be selected. Eventually, what was an environmental change becomes genetic, mimicking the inheritance of acquired traits. [. . .] But we can also explain such cases by invoking simple selection on pre-existing genetic variation. In the absence of a single credible example of genetic assimilation in nature, it remains an appealing but untested speculation."

The concluding paragraph is a plea for consensus science to prevail. In his view, there are only unconfirmed hypotheses coming from those who want to go beyond "orthodoxy" (i.e. neodarwinism).

"In the end, the problem with these explanations is not so much that they are wrong, or of no potential importance in evolution. Rather, it is that Blumberg gives the impression that they are established truths rather than hypotheses that have remained unconfirmed for three decades. In his anxiety to boost the status of evo-devo in the pantheon of evolutionary subdisciplines, Blumberg has short-changed orthodoxy. Not only does the traditional view of evolution explain far more than he allows, but Blumberg shapes his own vision of development to inflate its challenge to neo-Darwinism. I, for one, am with Wolpert."

For those of us who think that it is neodarwinism that has given us "hypotheses that have remained unconfirmed for three decades", these comments appear hypocritical. By and large, Darwinism is content with minimalistic "proofs" of its dogmas: the creative role of natural selection is not demonstrated, but only its existence in ecosystems; the incremental nature of evolution is still characterised more by gaps than by identifiable trajectories; crucial stages in evolutionary transformations continue to be mysteries. Past blogs have documented many examples of these problems. Go here for a specific example. Furthermore, some recognition needs to be given to those who are prepared to stick their neck above the parapet and say that neodarwinism is bankrupt. All credit to Lynn Margulis (whose model of an "ancestral cell's ingestion of the bacteria that evolved into mitochondria" is accepted by Coyne), who put matters very plainly:

"Having gained acceptance for her work on the origin of eukaryotic cells, she seems willing to take on any sacred cow. Indeed, she is now aiming for the biggest target in evolutionary biology: neo-Darwinism. First named in 1896, neo-Darwinism is the synthesis of Darwinian natural selection and Mendelian-style genetics. Today, it is the reigning paradigm of the discipline, but to Margulis it is little more than a "quaint, but potentially dangerous aberration" that needs to be tossed out in order for science to answer "basic questions" like why stasis is so prevalent in the fossil record, and how one species can evolve from another."

A worthy addition to the web resources on evolutionary theory is Darwin's Predictions by Cornelius G. Hunter. This demonstrates why Coyne's bold claims for the success of neodarwinism should be interpreted as spin.

"Evolution has a long history of false predictions leading to rising complexity. The evolutionist's claim that all of this is a sign of good science, of learning how evolution actually occurred, is not consistent with evolution's many falsified predictions and complex adjustments. This document summarizes a representative set of such falsifications, including the reactions of evolutionists showing how the contradictory findings were accommodated, and concludes with an examination of why evolutionists believe their theory is a fact and what this tells us about the theory."

Evolution's challenge to genetics
Jerry A. Coyne
Nature, 457, 382-383 (22 January 2009) | doi:10.1038/457382a

Abstract: Do conjoined twins and two-legged goats suggest a minor role for genetics in evolution? The evidence is not strong enough to upset the orthodox view, argues Jerry A. Coyne.

BOOK REVIEWED - Freaks of Nature: What Anomalies Tell Us About Development and Evolution, by Mark S. Blumberg, Oxford University Press: 2009. 344 pp.

See also:

Darwin's Predictions by Cornelius G. Hunter.

Mark S. Blumberg's personal home page for the book

Mann, C. Lynn Margulis: Science's Unruly Earth Mother, Science, 252, 19 April 1991: 378-381.