Re: Sociobiological Concepts

From: Stevan Harnad (
Date: Sat Oct 11 1997 - 22:23:29 BST

> From: Sonia Whitehead <>
> The evolutionary stable strategy relates to a trait which can
> exist and be passed on to the majority of the population.

ESS is not normally used to refer to EVERY adaptive trait, only the
ones in which the competitive aspect is explicit. It is possible (I
don't know) that every evolutionary adaptation can be reformulated as an
ESS. But the way it is usually used is much more specific than the

> When a new gene does succeed in invading and spreading through the
> evolutionary stable gene pool, the ESS is altered through the natural
> seletion process.

No; if it can be invaded then it is NOT an ESS.

> This normally occurs in times of environmental
> change when the ESS which was previously successful might have
> difficulty in adapting to the new environment, resulting in the
> reproducing population adopting another ESS so that they can progress
> into the next generation.

You are describing ordinary evolution, and what you say is true of any
evolvable trait. ESS is more specific than this. Check the links in the
earlier posting.

> In an artificial environment where environmental change did not
> occur, would the gene pool then become smaller with only the optimum
> genes being present in future generations?

Good question. I don't know. I would think that if there was no adaptive
pressure favouring one genetic trait over another, there would be no
change at all; just a reshuffling of the genes in reproduction plus some
random mutations. But I doubt that there is any such completely
unchanging environment. No environment is completely isolated from the
rest of the world.

> Would this also mean that
> the population could become more alike?

No, unchanging means unchanging. Populations are variable. If no
environmental factor favours some variations over others, then
everything stays the same, including the variability.

> I imagine that in the long
> run this would also make the population more competitive as the
> genetic differences between the indiviuals which were competing would
> be minimal.

I don't know why you say this. But it shows that the idea of a
completely unchanging environment doesn't really make sense, because
the variation in the genes, and hence the traits of these imagined
organisms form the ebvironment for one another. So if there was no
change in climate, say, there could still be changes in combinations of

The way that genetic unifeormity has been attained, by the way, is not
through NATURAL selection (evolution) but through ARTIFICIAL selection,
by, for example, dog breeders, who "fixed" some of the natural variation
in dog traits to shape the breeds we know today, by inbreeding. which
is not a healthy procedure, but after you do it over and over, the
really bad genetic traits are selected out (by nonsurvival of their
carriers), and only the more benign ones get fixed in the survivors.
But most dog breeds do have hereditary problems, some with hips, some
with breathing.

The ultimate inbreeding is with laboratory mice who have been inbred
until they are completely identical genetically: they are all idetical
clones. But what got them that way was not an unchanging environment,
but selective breeding.

> altruistic people who use a
> lot of their energy in helping non-family members and therefore do
> not have enough energy available to ensure the survival of their own
> genes. Dawkins therefore suggests that through evolution the selfish
> gene has become dominant to the altruistic gene as selfish people are
> more likely to reproduce and their genes are more likely to be
> carried on to the next generation.

We are not in the EEA. So it is not relevant to talk about people who
act selfishly or unselfishly today, when, with the help of medicine,
clothes, laws, etc. just about everyone survives. When sociobiologists
speak of selfishness vs. altruism they are describing things
abstractly. The theoretical point is that there is a problem with
explaining how there can be any seemingly altruistic behaviour, as such
behaviour is clearly to the detriment of the doer, and hence to his
genes. Altruism is not an ESS: it is always defeated by selfishness.
The only exception is the one discussed at length in The Selfish Gene:
inclusive fiteness -- the fact that with close kin a selfish gene can
sometimes ensure its replication in the next generation more
successfully if it sacrifices itself for the right numpber of copies of
itself in close relatives.

A clan of close relatives is better thought of as being like a
superordinate organism, if which the relatives are parts. Altruism
would then be like eating part of your own body so that the rest of you
makes it through a famine. (This is not a very good analogy! For one
thing, even close relatives are in genetic competition with one another
too (except possibly identical twins), but a part of your body is not in
competition with another part...

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