Re: "The Selfish Gene"

From: Stevan Harnad (
Date: Sun Nov 02 1997 - 22:20:52 GMT

> From: Tom Hart <>
> planning and genemanship. Any replicator that coded it's survival
> machine to 'take out' their brothers and sisters would greatly reduce
> the chance of success of the genes. As your brothers and sisters carry
> half of the same genes as you, killing two (in gene terminology) would
> be the same as killing yourself. Another possible reason for the
> 'fratricide gene' not gelling with The selfish Gene theory is the
> explanation given for reduction in clutch size. If, due to
> environmental constrictions, the mother reduces her no. of offspring to
> the optimum size for the best chance of success in rearing them to
> reproductive age so they can reproduce , a gene for fratricide would
> reduce the clutch size even further . Even though greatly increasing
> the chance of survival to adulthood of a few, they would be at a
> disadvantage compared to members of the same species who didn't contain
> the 'fratricide gene' at birth, and so that trait would be selected out
> through evolution.

You're right to puzzle over this reasoning. If the fratricidal
inclination is self-limiting and context-dependent (feel like pushing
your sibs out of the nest when there are many, not when there are few)
then this could be an ESS.

> It seem that in order for the parent's gene to win or even compete in
> 'the battle of the generations' in a species with the fratricide gene,
> the parents best defence would be to contain a gene that coded for many
> offspring at one time to give them a chance of ending up with the
> optimum clutch size.

It's the usual trade-off: bear vs. care. Bearing many and having them
fight it out is a costly investment, balanced against the benefits of
having fewer offspring, more care, and better chances of surviving.

> I understand that the
> apparently altruistic behaviour of the infertile workers is actually
> them working for the good of their genes in their kin. What confused
> me seems to be a basic principle in The Selfish Gene. Namely offspring
> contain a ratio of father/mother genes which seems to be able to vary
> in these Hymenoptera Insects.

Yes; two ways of arriving at an ESS are to have a stable balance of
organisms, each organism coding for only one of the strategies, or to
have all the strategies within each organism, and their expression
governed by context cues (such as degree of crowding, the presence of a
fertile queen, etc.).

> If this is therefore true then how does a gene for producing sterile
> workers spread through the population. It seems that even if the entire
> population at one time were reproductive and genetic variation produced
> a sterile member who just worked for the good of others (or the genes
> of other's and therefore their own),and this was successful, there
> would be no way to pass on the trait to another generation. However,
> this isn't the case and there are these types of workers within
> Hymenopteran insects. It may have been explained by Dawkins and I
> missed it.

One way is to have the sterile sisters all identical multiplets of one
another; another way is to have the offspring of the queen more closely
related to the sterile sisters than to herself. Another is to make the
sterile/fertile "lever" contextual, so it is the circumstances that
decide which outcome is best.

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