Saturday, 5 June 2010

Disagreeing With Dawkins?

I wrote this a while ago but only recently typed it up. The font is probably going to go crappy on me, but ah well.The picture I have chosen contains a gorgeous ammonite fossil which is clearly from the Mesozoic. It has quite well developed sutures so came quite late during the period which is often seen as the age of the dinosaurs when it was equally the age of the ammonites, particularly in the oceans.

Professor Richard Dawkins (1941-) is a world renowned author and scientist from Oxford university who has increased public awareness of evolution over the years. Studying under the eminent Niko Tinbergen, as a scientist he is an ethologist who studied the adaptive significance of animal behavioural patterns such as "Selective Pecking in the Domestic Chick". With this as his basis he has written some of the best popular science books expounding evolution, with selection and adaptation being prominent topics. He has, in recent years, shot to fame in wider circles due to his book "The God Delusion". I have decided to take a little time to show where I agree and disagree with Dawkins.

It barely needs stating that we both agree that all life has evolved over the last 4 billion years from a common ancestor which probably resembled bacteria. Dawkins' books make it clear that evolution is a distinctly non-random process and that it occurs in a very slow, incremental fashion; we are again in agreement. We both clearly agree on the main concepts in the theory of evolution, but when looked at deeper some differences occur.

Much of Dawkins' work focuses on the power of natural selection. He rightly states that selection is the only mechanism which can construct adaptations (though some recent evidence suggests that drift can give it a little helping hand). Genetic drift and neutral theory are not ignored as 'pluralists' would claim, but are both acknowledged as occurring but with no adaptive advantage.

"The Selfish Gene" and subsequent books presented his gene selection views, which are perhaps what e is best known for in evolutionary biology. It is not always obvious that this is not a case of overzealous reductionism. Dawkins talks frequently of gene complexes and of bodies as vehicles or 'robots' of the genes; these are not to be ignored. He eloquently argues that selection must act on agents which persist over generations with a degree of conservation; only genes satisfy this replication criterion.

Gene selection overlooks some key issues. One issue with the statement that selection requires a degree of conservation is that phenotypes do fit this if it is viewed broadly. Although the individual phenotype is broken down by recombination with each generation, the differences between each generation are most often very small; enough perhaps for selection to be at work.

It also overlooks the concept that selection acts upon interactors, which is fulfilled by selection on the individual organism. Genes go through complex processes before being expressed phenotypically, the web of development can make gene selection seem implausible. Moreover, Dawkins has occasionally made it appear that gene selection is synonymous with selection on the individual. This is not to say that gene selection does not occur, for outlaw genes are proving increasingly common and there are genes with direct phenotypic expression (likely the exception to the rule and often deleterious). I also do not know Dawkins' views on epigenetics, as some experiments have shown epigenetic factors altering phenotypic traits, effectively muting the voice of the genes. I therefore reject gene selection as most prominent and appear to be more open to other levels of selection. I view it as predominately on the individual, though modular selection is also an attractive prospect. My mind is open to group selection, though I do not feel I have sufficient mathematical knowledge to judge it properly.

Species selection is an interesting concept which remains difficult to test. Dawkins does not often talk about species selection, though his views appear to be that it is plausible in determining which lineages diversify or go extinct, but with little to no effect on adaptation. Species have emergent properties not found in individuals such as geographical range and diversity, though such traits are arguably not passed on. My views are similar to this, though it is a difficult one as we run the risk of zooming in too close and not seeing the species as a whole, or conversely zooming out too far and seeing only species as individuals; balance is required.

Evolutionary arms races are one of Dawkins' insightful contributions which aid understanding in evolution and have evidence to back (though it must be noted that there are circumstances where it can be drowned out by other occurrences). It is a solid explanation for many evolutionary trends and adaptations. He also famously promotes the idea of extended phenotypes, a useful model for understanding the interaction of organisms with environments, particularly parasites.

"Extrapolationism" is a term which was often used by Stephen Jay Gould when referring to scientists like Dawkins who view large scale evolution as simply local events scaled up over longer time. I do not disagree with such  a view, but find it deficient as it cannot easily take mass extinction into account and tends to ignore fossil trends which need explaining. Simple speciation mechanisms coupled with genetic change in local populations cannot account for the variety of patterns found in the fossil record. For example, phyletic gradualism and punctuated equilibrium both occur on large scales; these are not plausibly extrapolated from microevolutionary trends in local populations, the bigger picture is a necessity.

Dawkins once dared to write about evolvability, almost taboo at the time, though since his effort many others have taken up the torch on this subject. I find Dawkins' case for the evolution of evolvabilityevolvability involved watershed events, Dawkins describes segmentation, which raised the upper bound of complexity and enabled lineages to become more able to diversify and adapt. Other examples include multicellularity and sexual reproduction. Interestingly this may open the door for selection of an entire clade (though then the issue would be whether the crown or stem groups are selected).

I enter shaky ground when I attempt to discuss contingency and convergence. Dawkins speaks more positively of convergence and my own position is not yet firm. I sit somewhere in the middle, finding some aspects seem inevitable whereas others seem almost to be pot luck. I don't feel that there is sufficient data to judge what would happen with a replaying of the tape.

Dawkins appears to believe that selection has a large range of variation to act upon and that the plausible variations which we do not see were selected against. This ignores the possibility that certain variation did not occur and thereby naively removes the need for an explanation of how much variation can occur. Constraints are found not only from the physical laws of nature but also from changes frozen into our lineage which cannot be reversed. Historical changes effect developmental possibilities, narrowing the variation available for selection.

Richard Dawkins had a very prominent and vocal rival in the late Stephen Jay Gould. Gould's main contribution to the theory of evolution was punctuated equilibrium. Dawkins dismissed 'punk eek' as a minor yet interesting empirical observation demonstrating different "gears" (presumably stasis, bradytely, horotely and tachytely). His dismissal was perhaps too rash, though in retrospect it was not completely out of order. Punctuated equilibrium was almost unnecessarily hyped as it carried a lot of potential which had not stood the test of time. Dawkins was clearly correct that it is still a form of gradualism, but ignored the overall pattern which had the potential to uncouple micro and macro evolution as well as bringing prominence to species selection. It necessitated a wider view of evolution, not just gene changes in a population. In recent years it is seen as one palaeontological pattern among many and appears to be a lot more than simple "gear" changes in response to environmental pressures.

An area I rarely discuss is psychology and cultural evolution, unlike Dawkins who confidently states his opinion. Evolutionary psychology clearly has value, but perhaps too much is given to it. A behavioural trait should not simply be given adaptationist explanation, for the brain is an organ which is full of possibilities for non-adapted traits to occur. Scrutiny and caution are of the utmost importance.

Dawkins kick started the field of memetics, used to explain cultural evolution. It strays close to pseudoscience, embracing 'just-so' stories and ignoring other possibilities in favour of an ideology. The only plausible place for memes to exist is the internet, or so it seems to me.

In conclusion, I agree with Dawkins on many issues within the theory of evolution. Some differences occur, though many are subtle and some are simply due to a different degree of scepticism. Unlike Dawkins I have not had a long, fruitful career allowing m to think about and test these ideas, so I am open to the possibility that our disagreements may slowly vanish as I delve deeper and deeper into the wondrous theory. On the other hand, palaeobiology may lead me closer to the views of Gould as opposed to Dawkins' ethology of the gene! Who knows?

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