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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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