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On genes and natural selection
May. 15th, 2011 03:57 pmBecause I'm finally near a university library again, I have been feeding my hunger for books. Birmingham has a stash of Stephen Jay Gould books, even if, for whatever reason, several of them appear to be hidden in the stores.
There are many reasons why I like his writing, mostly that it's approachable and friendly without being dumbed down. While science may have moved on in the ten years since his death and in the 30 years since 'The Panda's Thumb' (the book I'm presently reading) but on those occasions where he's wrong, he's wrong because no one had the facts at that time and science moves on sometimes.
In 'The Panda's Thumb' there is the best refutation of the selfish gene hypothesis I've yet found. My own issues with the selfish gene hypothesis are that it gives too much power to genes but I couldn't explain why that was a problem. This book does, and, since I can't I shall quote from it:
"No matter how much power Dawkins wishes to assign to genes, there is one thing he cannot give them - direct visibility to natural selection. Selection simply cannot see genes and pick among them directly. It must use bodies as an intermediary. A gene is a bit of DNA hidden within a cell. Selection views bodies. It favours some bodies because they are stronger, better insulated, earlier in their sexual maturation, fiercer in combat, or more beautiful to behold.
If, in favouring a stronger body, selection acted directly upon a gene for strength, then Dawkins might be vindicated. If bodies were unambiguous maps of their genes, then battling bits of DNA would display their colours externally and selection might act upon them directly. But bodies are no such thing.
There is no gene 'for' such unambiguous bits of morphology as your left kneecap or your fingernail. Bodies cannot be atomized into parts, each constructed by an individual gene. Hundreds of genes contribute to the building of most body parts and their action is channeled through a kaleidoscopic series of environmental influences: embryonic and postnatal, internal and external. Parts are not translated genes, and selection doesn't even work directly on parts. It accepts or rejects entire organisms because suites of parts, interacting in complex ways, confer advantages. The image of individual genes, plotting the course of their own survival, bears little relationship to developmental genetics as we understand it. Dawkins will need another metaphor: genes caucusing, forming alliances, showing deference for a chance to join a pact, gauging probable environments. But when you amalgamate so many genes and tie them together in hierarchical chains of action mediated by environments, we call the resultant object a body.
Moreover, Dawkins's vision requires that genes have an influence upon bodies. Selection cannot see them unless they translate to bits of morphology, physiology, or behaviour that make a difference to the success of an organism. Not only do we need a one-to-one mapping between gene and body (criticized in the last paragraph), we also need a one-to-one adaptive mapping. ... It may be that many, if not most, genes work equally well (or at least well enough) in all their variants and that selection does not choose among them. If most genes do not present themselves for review, then they cannot be the unit of selection."
(Text taken from The Panda's Thumb by Stephen Jay Gould, published 1980 by Pelican)
It really does explain my issues with the selfish gene hypothesis far better than I ever could.
There are many reasons why I like his writing, mostly that it's approachable and friendly without being dumbed down. While science may have moved on in the ten years since his death and in the 30 years since 'The Panda's Thumb' (the book I'm presently reading) but on those occasions where he's wrong, he's wrong because no one had the facts at that time and science moves on sometimes.
In 'The Panda's Thumb' there is the best refutation of the selfish gene hypothesis I've yet found. My own issues with the selfish gene hypothesis are that it gives too much power to genes but I couldn't explain why that was a problem. This book does, and, since I can't I shall quote from it:
"No matter how much power Dawkins wishes to assign to genes, there is one thing he cannot give them - direct visibility to natural selection. Selection simply cannot see genes and pick among them directly. It must use bodies as an intermediary. A gene is a bit of DNA hidden within a cell. Selection views bodies. It favours some bodies because they are stronger, better insulated, earlier in their sexual maturation, fiercer in combat, or more beautiful to behold.
If, in favouring a stronger body, selection acted directly upon a gene for strength, then Dawkins might be vindicated. If bodies were unambiguous maps of their genes, then battling bits of DNA would display their colours externally and selection might act upon them directly. But bodies are no such thing.
There is no gene 'for' such unambiguous bits of morphology as your left kneecap or your fingernail. Bodies cannot be atomized into parts, each constructed by an individual gene. Hundreds of genes contribute to the building of most body parts and their action is channeled through a kaleidoscopic series of environmental influences: embryonic and postnatal, internal and external. Parts are not translated genes, and selection doesn't even work directly on parts. It accepts or rejects entire organisms because suites of parts, interacting in complex ways, confer advantages. The image of individual genes, plotting the course of their own survival, bears little relationship to developmental genetics as we understand it. Dawkins will need another metaphor: genes caucusing, forming alliances, showing deference for a chance to join a pact, gauging probable environments. But when you amalgamate so many genes and tie them together in hierarchical chains of action mediated by environments, we call the resultant object a body.
Moreover, Dawkins's vision requires that genes have an influence upon bodies. Selection cannot see them unless they translate to bits of morphology, physiology, or behaviour that make a difference to the success of an organism. Not only do we need a one-to-one mapping between gene and body (criticized in the last paragraph), we also need a one-to-one adaptive mapping. ... It may be that many, if not most, genes work equally well (or at least well enough) in all their variants and that selection does not choose among them. If most genes do not present themselves for review, then they cannot be the unit of selection."
(Text taken from The Panda's Thumb by Stephen Jay Gould, published 1980 by Pelican)
It really does explain my issues with the selfish gene hypothesis far better than I ever could.
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