From Ivan Erill, Biological Sciences Department, University of Maryland, Baltimore County
Jerry Fodor and Massimo Piattelli-Palmarini discuss what they see as flaws in Darwin’s theory (6 February, p 28). They argue that Darwin, and his uncritical neo-Darwinian synthesis followers, got things wrong by attributing so much power to natural selection.
Their opinion piece covers two major themes: endogenous constraints and genetic free-riding. Darwin clearly acknowledged the first, and the neo-Darwinian synthesis has long accepted the latter. No sane evolutionary biologist would deny that evolution is time-constrained and that it must act on whatever designs are available at the time. So pigs could not evolve wings easily these days – big news.
Fodor and Piattelli-Palmarini argue that genetic linkage of phenotypic traits, in which one is selected and the other “free-rides”, are counter-examples to natural selection. That is just plain wrong. Linked phenotypic traits, or spandrels, can only free-ride for as long as they remain “silent”. If they ever decrease fitness in a significant manner and become a burden, natural selection will either lower the fitness of the linking trait, or select for individuals that happen to unlink both traits.
Ever since biologist Motoo Kimura popularised the concept of neutral evolution in the late 1960s, evolutionary biologists have widely accepted that natural selection is not the only factor in evolution. However, it still plays the leading role in the main evolutionary changes leading to the fundamental taxonomical differences observed between species.
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From Ian Stewart
Judging by their arguments, Fodor and Piattelli-Palmarini seem to be aiming at the wrong target in entitling their book What Darwin Got Wrong.
The points they raise do not relate to flaws in the idea of natural selection, but to the many and varied constraints and influences under which it must operate. This has long been known: similar observations can be found in The Collapse of Chaos, which Jack Cohen and I wrote in 1994, as part of a critique of certain gene-centred aspects of neo-Darwinism.
The idea that natural selection involves a static measure of fitness influenced solely by the environment is naive and outdated. It is true that some models of evolution are restricted to these ingredients, particularly in classical population genetics, but few geneticists imagine that their models are complete descriptions of reality.
The transmission of genetic and epigenetic information to the next generation is a dynamic process: the fitness landscape changes in response to the evolving organisms, genes near to others can hitch a free ride, and what works is a compromise. All this is well known and has been for decades.
The issue is therefore not natural selection, but what this process involves and how it works. Darwin did not address these questions, and deserves no blame for the misconceptions of other people.
Warwick, UK
From Michael Crick
In discussing evolutionary pressure by “endogenous variables”, Fodor and Piattelli-Palmarini have put forward as new an idea about the evolutionary process that I thought was well understood.
The genome is part of nature and a source of pressure for selection. The first test for any new mutation is that it should be compatible with the existing genome. That the mutation need not be of benefit to the host is one reason for the redundant material accumulated by genomes. It is only after meeting this first requirement that the more obvious selection by external environmental factors becomes significant.
Darwin was unaware of the modern concept of the genome, but he was not wrong.
Hexham, Northumberland, UK
Baltimore, Maryland, US
