Thursday, October 25, 2007

RM & NS: The Creationist and ID Strawman

AUTHOR: Allen MacNeill

SOURCE: Original essay

COMMENTARY: That's up to you...

Creationists and supporters of Intelligent Design Theory ("IDers") are fond of erecting a strawman in place of evolutionary theory, one that they can then dismantle and point to as "proof" that their "theories" are superior. Perhaps the most egregious such strawman is encapsulated in the phrase "RM & NS". Short for "random mutation and natural selection", RM & NS is held up by creationists and IDers as the core of evolutionary biology, and are then attacked as insufficient to explain the diversity of life and (in the case of some IDers) its origin and evolution as well.

Evolutionary biologists know that this is a classical "strawman" argument, because we know that evolution is not simply reducible to "random mutation and natural selection" alone. Indeed, Darwin himself proposed that natural selection was the best explanation for the origin of adaptations, and that natural selection itself was an outcome that necessarily arises from three prerequisites:

Variety: significant differences between the characteristics of individuals in populations);

Heredity: genetic inheritance of traits from parents to offspring; and

Fecundity: reproduction, often resulting in more offspring than are necessary for replacement.

Given these prerequisites, the following outcome is virtually inevitable:

Demography: some individuals survive and reproduce more often than others, and hence their heritable characteristics become more common in their populations over time.

As I have alread pointed out in an earlier post, the real creative factor in evolution isn't natural selection per se, it's the "engines of variation" that produce the various heritable characteristics that natural selection then preserves from generation to generation. According to the creationists and IDers, the only source of such variation is "random mutations", and so there simply isn't enough variation to provide the raw material for evolutionary change.

In my earlier post on the "engines of evolution" I promised a list of the "engines of variation" that provide the raw material for evolutionary change. It's taken me a while, but here it is. This list includes "random mutation,' of course, but also 46 other sources of variation in either the genotypes or phenotypes of living organisms. Note that the list is not necessarily exhaustive, nor are any of the entries in the list necessarily limited to the level of structure or function under which they are listed. On the contrary, this is clearly a list of the minimum sources of variation between individuals in populations. A comprehensive list would almost certainly include hundreds (and possibly thousands) of more detailed processes. Also, the list includes processes that change either genotypes or phenotypes or both, but does not include processes that are combinations of other processes in the list, again implying that a comprehensive listing would be much longer and more detailed.

Anyway, here is the list of the "engines of variation", arranged according to level of structure and function (if a term is underlined, you can click on it and be taken to a definition and explanation of that term, usually at Wikipedia):


Gene Structure (in DNA)

1) point mutations

2) deletion and insertion (“frame shift” / "indel") mutations

3) inversion and translocation mutations

Gene Expression in Prokaryotes

4) changes in promoter or terminator sequences (increasing or decreasing binding)

5) changes in repressor binding (in prokaryotes); increasing or decreasing binding to operator sites

6) changes in repressor binding (in prokaryotes); increasing or decreasing binding to inducers

7) changes in repressor binding (in prokaryotes); increasing or decreasing binding to corepressors

Gene Expression in Eukaryotes

8) changes in activation factor function in eukaryotes (increasing or decreasing binding to promoters)

9) changes in intron length, location, and/or editing by changes in specificity of SNRPs

10) changes in interference/antisense RNA regulation (increasing or decreasing binding to sense RNAs)

Gene Interactions

11) changes in substrates or products of biochemical pathways

12) addition or removal of gene products (especially enzymes) from biochemical pathways

13) splitting or combining of biochemical pathways

14) addition or alteration of pleiotropic effects, especially in response to changes in other genes/traits

Eukaryotic Chromosome Structure

15) gene duplication within chromosomes

16) gene duplication in multiple chromosomes

17) inversions involving one or more genes in one chromosome

18) translocations involving one or more genes between two or more chromosomes

19) deletion/insertion of one or more genes via transposons

20) fusion of two or more chromosomes or chromosome fragments

21) fission of one chromosome into two or more fragments

22) changes in chromosome number via nondisjunction (aneuploidy)

23) changes in chromosome number via autopolyploidy (especially in plants)

24) changes in chromosome number via allopolyploidy (especially in plants)

Eukaryotic Chromosome Function

25) changes in regulation of multiple genes in a chromosome as a result of the foregoing structural changes

26) changes in gene expression as result of DNA methylation

27) changes in gene expression as result of changes in DNA-histone binding

Genetic Recombination

28) the exchange of non-identical genetic material between two or more individuals (i.e. sex)

29) lateral gene transfer via plasmids and episomes (especially in prokaryotes)

30) crossing-over (reciprocal and non-reciprocal) between sister chromatids in meiosis

31) crossing-over (non-reciprocal) between sister chromatids in mitosis

32) Mendelian independent assortment during meiosis

33) hybridization

Genome Structure and Function

34) genome reorganization and/or reintegration

35) partial or complete genome duplication

36) partial or complete genome fusion

Development (among multicellular eukaryotes, especially animals)

37) changes in tempo and timing of gene regulation, especially in eukaryotes

38) changes in homeotic gene regulation in eukaryotes

39) genetic imprinting, especially via hormone-mediated DNA methylation


40) partial or complete endosymbiosis

41) partial or complete incorporation of unrelated organisms as part of developmental pathways (especially larval forms)

42) changes in presence or absence of mutualists, commensals, and/or parasites


43) changes in behavioral anatomy, histology, and/or physiology in response to changes in biotic community

44) changes in behavioral anatomy, histology, and/or physiology in response to changes in abiotic environment

45) learning (including effects of use and disuse)

Physiological Ecology

46) changes in anatomy, histology, and/or physiology in response to changes in biotic community

47) changes in anatomy, histology, and/or physiology in response to changes in abiotic environment

So, next time you hear or read a creationist or IDer cite "RM & NS" as the sole explanation for evolutionary change, point out to them and everyone else that there are at least 47 different sources of variation (including "random mutations"), and at least three different processes that result from them: natural selection, sexual selection, and random genetic drift.

Comments, criticisms, and suggestions (especially additional items for the list) are warmly welcomed!


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Wednesday, October 17, 2007

Jerry Fodor on Why Pigs Don't Have Wings

AUTHOR: Jerry Fodor

SOURCE: Why Pigs Don't Have Wings
(London Review of Books 29(20):19-22, 18 October 2007)

COMMENTARY: Allen MacNeill

Cognitive scientist and frequent critic of evolutionary psychology, Jerry Fodor, has a long article in the most recent issue of the London Review of Books in which he attacks what most people think of as the core of evolutionary biology: natural selection and adaptations. Fodor has attacked evolutionary psychology before, and spends most of his ammunition attacking it again in this article. However, he now has bigger (Darwin) fish in his sights: "Darwinism" – yes, he uses exactly the same term as the one so favored by creationists and ID theorists. Indeed, the article under discussion here has been lauded by prominent young-Earth creationist and ID theorist, Paul Nelson.

This isn't the first time left-leaning philosophers such as Fodor have joined forces with creationists, nor will it be the last. However, what I would like to discuss (in later posts) is Fodor's serious misrepresentations of evolutionary biology in general, and evolutionary psychology in particular. But, before I do that, you should go and read Why Pigs Don't Have Wings, paying special attention to Fodor's criticisms of natural selection and its role in evolutionary biology. And while you're at it, you might check out this essay by Fodor as well: Against Darwinism.

Then come back here (in a day or two), and I'll get started fisking both articles.


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Tuesday, October 09, 2007

Darwin Day in America

TITLE: Darwin Day in America

AUTHOR: John West

COMMENTARY: Allen MacNeill:

Meanwhile, back at the Discovery Institute/Neo-Creationism Propaganda Ministry, John West has published a much-balleyhooed book that makes the case that virtually all of society’s ills can be traced to poor old Charles Darwin and his latter-day minions. I’m going to force myself to read Darwin Day in America, not because I expect to find any new arguments or evidence in it (IDers like John West and his fellow creationists aren’t interested in new ideas, and are positively repelled by evidence, especially if it involves entering a lab or going out into the field), but because I want to be prepared for the mini-tidal wave of disinformation that it might generate vis-a-vis the pernicious effects of “Darwinism” on society.

This despite the fact that (according to the DI/NCPM’s favorite statistics), less than 10% of Americans believe in non-theistic evolution, and even fewer are atheists. Two thoughts immediately come to mind:

• Shouldn’t the prisons be stuffed with evolutionary biologists and atheists (i.e. greater than 10% of the prison population), and

•Isn’t this in a perverse way empirical evidence that evolutionary biologists and atheists have an influence on society out of all proportion to our numbers?

Ah, but that would imply a direct contradition in logic: something that the DI/NCPM is, of course, perfectly comfortable with, but which strikes the <10% of the population that attempts to be rational as…well, irrational.

So it goes…


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