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Richard Dawkins: "How does learned behavior evolve into inherited instinct?"
Well that's a very advanced question because it wouldn't occur to many people
that that is what happens, but there is a very interesting theory
about how that happens and why it happens.
It's called the Baldwin effect.
In the Baldwin effect, the idea is that an animal learns, for example, some skill.
A good example might be thrushes, which smash the shells of snails and then eat them.
And the closely related blackbirds don't do this.
If you give a blackbird a snail that's been taken out of its shell,
it's very happy to eat it, but a blackbird hasn't the faintest idea how to smash a snail,
whereas thrushes do it all the time, they do it on so called anvils.
Now the Baldwin effect idea would be that some ancestral bird,
ancestral to thrushes,
learned how to smash snails.
A very, perhaps a very skilled bird, a very clever individual bird
that learned how to smash snails and then maybe other thrush ancestors copied it.
They also learned how to smash snails and got rewarded for it
and so they learned and learned and learned.
And then as the generations went by, the progeny, the next generation,
of these ancestral birds also learned.
Perhaps by imitating their parents.
And as the generations went by,
the ones who learned fastest, were the ones who got the most food.
And so any genetic tendency to be fast at learning
how to smash snails would have been favored by natural selection.
And so natural selection, by choosing genes over many generations,
would eventually build into the gene pool
a skill which started out as a learned skill.
Now learned skills are very important in birds.
A beautiful example is the habit of tits, blue tits and grey tits,
of opening milk bottles.
Nowadays not many milk bottles are delivered on doorsteps,
but there was a time when I was young,
when every day the milkman would deliver milk and place it on the doorstep.
And grey tits and blue tits discovered,
some individual birds discovered,
how to open the either tinfoil or cardboard tops to these bottles
and drink the cream.
Fascinatingly, this habit spread like an epidemic.
Birds copied each other and ornithologists were able to
actually trace the flow of this habit, of this skill,
in radiating circles outwards from focal points in the country in Britain,
where particularly clever individual birds
had discovered how to do it.
So it was a learned skill.
As far as I know, nobody has investigated
the Baldwin effect in this particular case,
but the way it would work would be
that as the epidemic, the learned habit spread,
over generations, those individual birds who learned fastest
were the ones who got the most cream,
therefore had the most offspring, passed on the genes,
not initially genes for opening milk bottles,
but genes for learning quickly to open milk bottles.
And in the end they would learn so fast, they wouldn't need to learn at all
and then you might call it an instinct.
And that would be the full Baldwin effect.
So the Baldwin effect would be a way in which a learned habit
can get built into the gene pool as an instinct by natural selection of genes.
Superficially, the Baldwin effect sounds like Lamarckism.
Lamarck was the French naturalist predating Darwin,
who had a theory of evolution which was based upon
the inheritance of acquired characteristics
and that's wrong, that doesn't happen,
or almost certainly doesn't happen.
But the Baldwin effect produces something which looks like Lamarckism
and is therefore very interesting.
Acquired characteristics, something that an animal learns,
are not automatically incorporated in the genes.
That would be Lamarckism.
Injuries, uh...
My mother once had a dog, who sometimes, like many small dogs,
limped on three legs.
And there was another dog in the village who had lost a leg in a car accident,
and the owner of this three-legged dog thought that
her dog must be the father of our dog, because it limped on three legs.
That would be Lamarckism.
In the case of the thrushes or the tits that I've just been mentioning,
it would be Lamarckism if the learned habit just was pumped straight into the genes,
but the way it happens is not like that.
The way it happens in the Baldwin effect
is that there must be some genetic variation in there,
which affects the rate of learning this particular habit
or even the rate of learning generally,
and that is what's being naturally selected.
So it's not that the habit gets pumped into the genes.
What happens is that there is spontaneous variation among the birds,
in proper Darwinian fashion, ultimately due to mutation;
variation in ability to learn a habit such as this.
And then natural selection favors those individuals who learn fastest,
until in the end they learn so fast that it looks as though
they haven't learned at all.
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