Re: Evolutionarily Stable Strategies (ESSs)

From: Stevan Harnad (
Date: Sun Nov 02 1997 - 12:37:24 GMT

> From: ben payne <>
> I understand that it is the survival of the gene that is
> perhaps the most important concept to drive evolution.

Actually, it is replication rather than survival that matters.
Organisms, the vehicles of the selfish genes, need to survive long
enough to produce offspring that survive and produce offspring, etc.
Their genes merely have to replicate in each successive generation.

> Looking at the vast ways in which the behaviours of different
> species live and reproduce, it is surely the environment
> that determines the strategies these creatures use to ensure
> their greatest chance of survival of a species.
> behaviour? I am just thinking aloud here!

Try it first for anatomical traits: Sure the environment "shapes" wings
in creatures whose survival is promoted by being able to fly, but the
process consists of random variation that produces some forms that come
closer to flying (e.g., something like the webbed arms of "flying
squirrels"); then this continues to be selected for until the wings are
useful enough to handicap any creature that doesn't have them, but not
to advantage any further evolution in their form. It is this kind of
blind variation and then environmental selection on the basis of success
in surviving and reproducing that Dawkins meant by "The Blind

The evolution of behaviour is more complicated than the evolution of
anatomy, because it is not advantageous for an organism's behaviour to be
too rigid. To successfully "design" an organism that is nothing but a
set of pre-programmed responses, the Blind Watchmaker would have to be
able to anticipate every relevant situation that the organism would ever
find itself in. As this is not possible, even for the simplest of
organisms, evolution selects for flexibility, "offloading" on a
predictable environment some of the "wiring" of behaviours:

The newborn duckling is not born already knowing what its mother looks
like; it is just born with a tendency to follow the first moving thing it
sees. This is normally the mother (this is why the "Environment of
Evolutionary Adaptedness" [EEA] can also be thought of as the
"Genetically Anticipated Environment). The duckling's brain is wired to
follow the first moving thing it encounters because it is highly probable
that this will be its mother. If it turned out to be a wolf, the duckling
would be doomed anyway, so no need to anticipate that.

The duckling is also not wired to know what kind of thing it will mate
with when it grows up: The early imprinting experience teaches it that,
so in adulthood it tries to mate with things that look and move the way
their mother did, i.e., female ducks. The ducklings that imprint on
people (like the pet ducks of Konrad Lorenz, the discoverer of
imprinting) will at adulthood try to mate with people instead of ducks.
But this outcome would not have been possible in the EEA, where the
duckling that followed people instead of ducks would have been eaten
long before it could ever reproduce.

So the evolution of behaviour is economical, hard-wiring only those
things that could not be predictably learned from the genetically
anticipated environment. Learning makes the organism much more flexible
in its adaptive capacity than rigid inborn behaviour patterns can do.

> But why
> should these creatures behave in such a way? how do they
> know that their object in life is to pass on their genes as
> successfully as they can? this is of course not a literal
> question, but is it simply copied behaviour from their own
> parents or an inherent instinct that patterns their

Organisms do NOT know that "their object in life is to pass on their
genes as successfully as they can." That is the "distal," Darwinian cause
of their behaviour, but they are unconscious of that cause, just as the
child with the sweet tooth is unconscious of any sugar-scarcity or
blood-sugar raising mechanisms underlying its behaviour: Organisms
eat and mate, etc. because it feels good. Evolution shaped them so the
kinds of things that felt good and that they felt like doing were
precisely those that would maximise their genes' chances of making it
into the next generation.

The things you FEEL like doing are the PROXIMAL causes of your behaviour.
I want to eat that slice of pizza because I feel hungry and it looks
delicious. My selfish genes' chances of making it into the next
generation never cross my mind. But it is those genes' success at
replicating the traits they code for (e.g., wanting to eat when I feel
hungry; wanting to mate when I feel horny) that are the DISTAL cause
of our behaviour. My "objects in life," the things I feel like doing, are
what they are because they are what my selfish genes make me feel like

Needless to say, the genes' capacity to "anticipate" our environment only
applies to the EEA in which we actually evolved. Our current environment
is very little like the EEA, and many of the things we do and feel in it
have little or nothing to do with our survival and reproduction. They are
products of the great flexibility that our learning (and language)
capacities have given us. So the differences between our present
environment and our EEA only matter evolutionarily if they start to
selectively affect our survival and reproduction; as long as just about
every one of us survives and reproduces, the Blind Watchmaker does not

On the other hand, differences between our present environment and our
EEA do make it much harder for evolutionary biologists and psychologists
to determine the distal causes of our feelings and behaviour. They can
often only speculate; and those speculations sometimes sound like
"Just-So" stories (Kipling's tales in which the reason something is the
way it is is given in an arbitrary and circular way: "Why do I have a
neck?" "It's just so your head should not sink into your chest.").

[I believe that it was Stephen Jay Gould, whose books on Evolution and
Biology are well worth reading, who was the first to call
sociobiological explanations "Just-So Stories."]

> We talked about egg layers, and the ways in which birds will
> lay the number of eggs that ensure they can bring up a
> healthy offspring, but at the same time produce enough to
> optimise the chance of passing on successful genes. Other egg
> layers, it occurred to me, such as turtles behave very
> differently to the flying form of egg layers. This is what I
> find interesting as I can see how the environment shapes the
> way these different species behave. By laying a large number
> of eggs on beaches, it gives their genes a greater chance of
> survival as there is a considerable risk of death soon after
> they emerge from the sand. The underlying question concerned
> with this difference in behaviours is how these turtles know
> to do this as there is no parental guidance or behaviour to
> learn from, and how has evolution enabled such animals to
> pass on such vital strategies. I understand that this is all
> the work of the gene and ESS, and it raises some interesting
> considerations of ideas of instinct, and can also question
> our understanding of animal "psychology' and behaviour as far
> learning is concerned.

You're talking about the bear/care (or k/R) strategies of
reproduction: Bear few offspring and invest your energy into caring
for them to make sure they survive to reproduce, or invest your energy
into bearing as many offspring as you can instead of caring for a few,
leaving statistics to ensure that some of them make it to reproductive

None of these strategies is conscious: Evolution shapes these species
to feel like doing, and to do, exactly what they do. Some think the same
difference in bear/care strategies distinguish human males and females
(to a limited extent, because although there is a conflict between the
sexes in what is best for each, there has to be a lot of collaboration as
well, otherwise neither sex makes it into the next generation's gene
pool). The important point is that if there really are bear/care
differences between men and women, they will be seen even among men and
women who have no wish to have children and use contraceptives all the
time. Most men will still feel like "spreading their seed" with many
women whereas most women will still feel like having committed
long-term partners rather than many one-night stands.

Don't mix up distal and proximal causes; only the proximal causes are
conscious: they are what you feel like doing. The distal causes in the
EEA were what shaped you into the kind of organism that feels like
doing that.

> I am not sure that this is all as clear as IT Should be, and
> I would like to know if my approach is right. Am i asking
> enough questions or giving a clear idea of my views? At the
> moment I have just looked at the general ideas that we have
> covered and written some of what i have thought so far. I
> understand that for a better, more complete outline of the
> ideas we have approached, I need to look at it more
> thoroughly, but would like to know that what I have done so
> far is a start!

This was fine; keep reading and skyreading and skywriting!

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