 
[PLAYING MUSIC]
This topic is Designed
By Evolution.
I'd like to talk you about the
design of your body and the
evidence for evolution that
exists in the way
your body is built.
If we look all over the human
body, what we often find are
kind of glitches.
They're weird little design
choices, bad ideas,
imperfections.
And in fact, this is really
important to understanding how
evolution has produced
us over time.
In fact, the flaws and the
imperfections are so important
that I don't even really
like the word design.
I think it misleads us.
It makes us think that there's
some kind of plan or maybe
even a designer out there, who
is sitting behind the scenes
programming all of this stuff.
Evolution has no plan.
When it built the human body, it
was really working from no
design at all.
Instead, it's organic processes
working over
millions of years that
have produced
this wonderful creation.
And let me tell you
what I mean.
I'll start with your eyes.
The eyes are actually really
poorly designed, if you look
at them from an engineering
point of view.
The layer of nerves that comes
out of the retina, instead of
being on the back of the retina,
is in fact on the
front of the retina.
So to get to your retina,
light has to
pass through the nerves.
It's as though the cabling for
the detectors was put in front
of the detectors.
That make your eye
less sensitive.
But it also creates another
structural problem, which is
that all those nerves wind up on
the inside of your eyeball.
And so they have to kind of come
together in a bundle and
go out somewhere.
This creates a little blind
spot in your retina.
You're not aware of it because
your brain tricks you into
thinking that your retina is one
smooth, complete picture.
But in fact, if you know where
to look, you can see that you
have a blind spot.
If you were a design student and
you brought in the design
for the eye, so your instructor
would probably say,
back to the drawing board.
Why did you put the nose
on the inside?
You could do all kinds of other
things too to make the
eyes better.
You could give us a bit of
vision in the ultraviolet
spectrum, like reindeer have.
Reindeer can see lichen
and food.
They can even see predators'
urine on the ice, when to us,
we would be snow blind, because
they can see into the
ultraviolet part of
the spectrum.
Or you could see into a bit of
the infrared part of the
visual spectrum.
It would show us heat sources.
You could walk around at night
and be able to see creatures
out there because their
bodies give off heat.
Another flaw in the human
body is the design
of the human knee.
It's held together
by ligaments.
The bones themselves just sit
one on top of the other.
It makes the knee especially
liable to tearing.
If you were an engineer and you
saw this, you'd say look,
this is not structurally
strong enough.
Given the force that the body
is going to put on the knee
and given the fact that you have
no spare legs, well it's
a terrible design.
Every time you're at sporting
event and you see some poor
athlete crumpled on the ground,
sometimes with a torn
ACL or other ligament, simply
because of the way they turned
when they ran, we should realise
that's part of the
problem with the knee's
engineering.
The reason for it is the knee
started off as a hinged joint
in a fish's fin.
And for the purpose of the
fish, that structure is
totally adequate.
Sometimes evolutionary theorists
refer to these kinds
of weird design solutions
as kludges.
It's an engineering term.
And it means something that's
unnecessarily complicated.
It's a kind of jerry-rigged
solution to a problem, like
when you gaff or tape
an antenna to the
side of your car.
It's not really well designed,
but it's sort of put together
from what you've got.
Some people like to talk about
how they think that the body
is an example of intelligent
design.
But in fact when you look at all
these details, you have to
kind of come to the
same conclusion
that Don Weiss does.
Don Weiss is a former geologist
who likes to argue
with creationists.
And he said it's not an example
of intelligent design.
Actually what we have is an
example of incompetent design.
And that's precisely the
fingerprints of evolution.
In the next topic, we're going
to talk about some of the
errors that this kind of
thinking can lead us to, the
worst kind of errors for
thinking about evolution.
 
