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We should not immediately, I
think, assume that a behavioral trait, particularly
a cognitive behavioral trait, is an adaptation.
Now, in order to really understand that statement,
you need to understand what I mean by an 
evolutionary adaptation
I do not mean that it has some current
function or utility. I mean that, historically,
it occurs due to selection shaping that trait
specifically for that function.
There are lots of beautiful examples of adaptations:
 eyes and wings and white coloration
on animals that live in polar environments.
And how do we know that those are adaptations?
One way we can know is by using the comparative
method. For example, arctic foxes are white,
whereas your regular fox is brown. Polar bears
are white, whereas your regular, average bear
is brown. Hares, arctic hares, are white,
whereas most bunnies are brown. You can see
that there is a very clear trend here that
the color of your fur is directly related
to the environment that you are living in.
So that is good evidence that this is an evolutionary
adaptation. But not all traits that you observe
are evolutionary adaptations. Some traits
are really nothing more than a spillover or
what people refer to as a "spandrel."
There was an article written by Stephen Jay Gould, 
a very, very famous article, called,
'The spandrels of San Marco and the Panglossian paradigm:
a critique of the adaptationist program.'
Stephen Jay Gould is a modern-day evolutionary biologist. 
You may have heard of him. He is very famous. 
His point was that,
he described how in Roman architecture, when
you have two arches adjacent to each other...
so if you imagine an arch like this, and then another arch 
right next to it.  Which is, they liked building a lot of arches.
When you have arches like that, you have this space
in the upper portion that inevitably results
when you make two arches. And that is called
a "spandrel."
And the spandrels in the cathedrals
and so on are usually very heavily embellished;
you know, people decorate them and they have
the statues coming out from them. So if somebody
is trying to think about the origin and the
functional significance of spandrels and they
walk into a church and they look at that and
they see all these ornaments and they want
to think about that as the centerpiece of
the whole thing and the reason, the origin
of that, is that was the place the artist
wanted to have all this embellishment...
But, in reality, the spandrel is just an inevitable
outcome of when you have two arches. 
So, if you are thinking about what is the origin
of the trait, it is easy to get sucked in
to the story, especially with spandrels like
that because they have all these embellishments.
But you would be totally wrong in thinking
that that was the focus of any of the architecture.
That was an inevitable byproduct, a side-effect
of building two arches. And so Stephen Jay Gould
uses that as an example to explain
how, when we think about the origin of different
traits, on the one hand, you can think of
those being shaped by natural selection and
carved into function. On the other hand, you
can think of those traits as being mostly
shaped by the constraints of the history of
the organism and the raw materials that it
had and the different development that might take place 
that results in all these different side-effects.
Like, for example, you think
about the human chin. 
What is the origin of the human chin? 
Well, you can talk about, maybe, larger chins were 
sexier and women liked them. 
And you know, you can come up with an explanation 
for it. But another explanation
is just that it is an inevitable byproduct
of the growth fields of the jaw. When you
have a jaw and you need to eat, you know,
one thing that happens is you get a chin.
So his point is that many traits that we observe
could easily be explained as inevitable spinoffs
or side-effects or results of constraints
with the raw materials of how we are able
to do things; like, you build arches next
to each other, you get a spandrel. Or, you
need to build a jaw, you get a chin. And instead
of telling a story about how natural selection
has shaped that for this specific function,
the better story, or the real, the true story,
is that it is an inevitable byproduct or a
side-effect.
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