Here's an exercise for those of you who are truly interested in teaching accurate science. Go to the recent posting by Casey Luskin on Evolution: News & Views and figure out how to respond to his challenge. He's claiming that a great deal of evolution is "random" but that's not what the "Darwinists" are saying ["Random" Samples of Media and Textbook Descriptions of Darwinian Evolution]. Is he right?1 What should we teach in school?
1. Yes, and no. As usual Casey Luskin has only a superficial understanding of evolution and a very weak grasp of reality. However, from time to time he accidentally stumbles onto an important point. Let's set aside the fact that he has no idea what he's talking about and address how we should respond to such criticisms. My view is here: [Evolution by Accident].
I'm not a biologist, so this may turn out ot be pretty dumb. Nevertheless, I have been wondering about it for quite a while.
ReplyDeleteHow much could the controversy about "selectionism" be resolved by applying the terms necessary and sufficient condition?
It seems to me that natural selection is the necessary condition of all biological function whatsoever. Creatures that lose characters (such as blind cavefish or whales that have no sense of smell) prove that when selection is absent, function is lost.
But that does not mean that natural selection is the sufficient condition for function, or at least not the sole sufficient condition. In order to understand why a particular feature is thus and so, we have to understand the history of genetic changes that underlie the feature, and how that feature came to be fixed in the population.
I recall from my logic course that some disageements are factual, and some are purely verbal, and still others are verbal disasgreements that mask a factual disagreement. Which is the case here?
Creationists love to play up the random aspects of evolution so they can mock such things as the probability of a jumbo jet self assembling from a whirlwind in a junkyard or a team of monkeys on typewriters cranking out the complete works of Shakespeare.
ReplyDeleteOf course they neglect the whole point that while genetic mutations are usually random and that there is no master plan guiding the outcome of evolutionary processes, genetic traits are 'selected', that is they survive according to their suitability for existence in the real world.
Replication is also distinctly non-random, allows changes to be preserved.
ReplyDeleteIn the case of mammalian genome evolution, according to naturalism, all of the mutations are random while most changes in allele frequency result from random genetic drift. On the other hand, a small fraction of random mutations are fixed by positive natural selection. And most evolutionary changes in morphology resulted from mutations that were fixed by positive natural selection.
ReplyDeletepaul01 is right on the money. Even if drift and random mutaiton are the predominant mechanisms that give rise to genotypic diversity, thus making allele frequency highly random, the fact remains that it is non-random selection that governs which alleles produce viable phenotypes.
ReplyDeleteThat is to say, not all alleles are compatible with life. Yes, drift may push them around in random combinations, and random mutation may create new alleles; but all alleles, new and old (lest we forget the concept of synthetic lethality) must be filtered through selection to ensure they are, at the very least, compatible with life.
Evolution is non-random. That jumbo jet could easily be built up in the junkyard, so long as each change that increased "jumbo jet-ness" was maintained as we went along.
IMO, all of this is just word play. If you were to bring all the evolutionary biologists into a giant hall (and toss in a few token biochemists to keep them honest) and had them work up a narrative description of how different mechanisms interact to produce change in genomes, structures, and behavioral strategies, there would be relatively little disagreement about how things play out in the real world.
ReplyDeleteThe problem with the way Luskin and others like to frame the issue that seems to give the illusion of disagreement lies with the rather diffuse definitions of “random”, “evolution”, and “importance”. If you define “evolution” as a change in the genome, and consider any change as equally “important”, then >99% is due to randomness, regardless of how you define “random.” If you define “random” as the opposite of “there is only one possible solution that will work”, then all is random, regardless of how you define “evolution” or “importance”. But no combination of definitions will change the fact that if you were to take any two biologists (or biochemists) they would agree on what goes on, once the definitions are set for the purpose of that particular conversation.
The term “evolution” has different connotations to different people. Dawkins is typical of the “phenotypologist”, and consequently his definitions of “evolution” is weighted towards genetic changes that produce phenotypic changes. Larry Moran is a typical gene-jock biochemist, and his definition is weighted towards any nucleotide change. Neither is wrong, as each definition is appropriate to the problems they each grapple with. But unless one understands their different views of what evolution is, one could easily mistake their statements about the mechanisms of evolution as indicative of an underlying fundamental disagreement.
Phenotypic evolution (the definition that the bulk of non-specialists also think of when they hear the term “evolution”) is a highly contingent process, and so on one level is very “random”. Consider an animal population that is exposed for the first time in its history to a predator population: the prey species (currently without any defense) would do well to develop some sort of defense mechanism. Whether it is horns, winged flight, running speed, protective coating, poisonous secretions, camouflage, etc. will probably be a matter of chance: what does it have to work with in terms of existing characteristics and existing variation. The new presence of the predator has altered the fitness landscape, and the prey finds itself in a hole. There are lots of pathways up, and chance will likely determine which one it embarks on. Assuming the prey species successfully evolves a defense, selection will be the mechanism that moves it along that path, with random chance continuing to be the mechanism that converts theoretical steps into actualizable steps. When all is said and done, Dawkins and Moran might disagree about what they consider to be the relative “importance” of chance/randomness in the process, but they would nonetheless be in complete agreement with what happened and in their descriptions of what role different mechanisms played in the process.
Larry, you are being far too generous to Casey Luskinsoism. Do you honestly think that he is genuinely interested in real question of adaption versus drift and contingency?
ReplyDeleteThe whole ploy of the DI is selling snake-oil to the religious masses. They invent a controversy and then claim they've got the answer.
There is always a temptation for the pro-science people to take the anti-evolutionist points as something to make technical arguments about. To the general public, this only gives the impression that there is some genuine scientific controversy involved in creationism.
ReplyDeleteI would just prefer to point out, for example, that if all complex patterns in the world of life are due to the goals of some intelligent designer(s), then there are extremely complex patterns, much more complex than "the bacterial flagellum", that are being ignored by the anti-evolutionists.
Such as the pattern of correspondences between the human body and the bodies of chimps and other apes.
Does this relationship show that the intelligent designer(s) deliberately chose to make humans and chimps very similar? Does it mean that the designer(s) had similar purposes in mind for humans and chimps?
Or does it mean that the designer(s) had little choice in the matter? That they were constrained by the properties of the material that they were working with?
Or does it mean that the designer(s) weren't interested enough to make humans to a fresh design? That they had more concern for bacteria, in giving them flagella?
Or does it mean that the existence of extremely complex patterns is not a reliable indicator of purposeful design?
Tom S.