Nesse: And as the example we just talked
about with regards to the eye, natural
selection can never go back and start fresh.
It has to use what it has to make very, very
tiny changes. And again, I"m talking about
natural selection almost as if it has a mind.
It's so easy to talk that way, isn't it?
In fact, what we're dealing with are tiny,
tiny changes in the eye, or the bones,
and individuals with bones that are too
thick here aren't gonna do as well as
individuals who can rotate their wrist
very nicely around that axis.
Dawkins: Compromises and historical legacies
are one reason why we are not perfect,
why we get ill. But of course there are,
there are other genes in us, there are
other creatures in us. There are bacteria,
there are worms. And so the Darwinian
has to look at them as well.
Nesse: Indeed, and I am amazed Richard,
that what we call "metazoans," multi-celled
organisms, have actually been able to evolve.
And the reason is that bacteria and
viruses replicate so quickly, a few hours
sometimes they can reproduce themselves,
that they can evolve very, very quickly.
And we're stuck with twenty years at
least, around- between generations.
How is it that we can resist infection when
they can evolve so quickly to find ways
around our defenses? We're getting answers
to this question. There are things called
"innate defenses" that are in most organisms that
protect us, but this is one of the huge transitions
Nesse: in the process of the origins of life. Dawkins: Well above all, we have an
Dawkins: immune system, don't we? Which Nesse: We do.
Dawkins: Kind of does a sort of Darwinian job.
Nesse: But exactly what that transition was,
between one cell or a few celled organisms
and multi-celled organisms, the ability of
the immune system that can protect us
from other things that evolve so much faster
than we do, that want to have us for lunch,
must be very crucial in the origins of life.
Dawkins: But isn't it right that the immune
system actually is a selective, there is a kind of
selection going on in the immune system?
Nesse: It's a version. Dawkins: Within your own body?
Nesse: It's a version of selection. It's not
exactly like natural selection because it's
very carefully orchestrated. I mean, certain
cells that are making the kind of antibodies
that kill a particular bacteria that's in you
this time, those cells reproduce themselves
more, and make more antibody, and they even
remember, so that if you've had measles once,
you probably won't get it a second time
because the immune system has this memory.
Nesse: It's not exactly the same as- Dawkins: And when you say the immune system
Dawkins: has a memory, that again is a
Dawkins: selective process. I mean, it's the Nesse: That's right.
Dawkins: ones that have the- Nesse: The individuals who don't have that
Nesse: memory don't do very well. Dawkins: Yeah, yes.
Nesse: On the negative side of things, however,
there's another process within the body
that's very much like natural selection.
And we should emphasize that this principle
of selection is one where there's all kinds
of variation. And certain individuals in that
population go forward, you know the best
way of talking about it, what I like to say is
is to think about the jar of coins that you
have where you empty your pockets every night.
And every night you reach into your pocket
and you take out the coins and you throw
them in that jar, it's a random selection
of coins that goes into the jar. But in
the morning, you reach in and take out coins,
but you don't take out a random sample.
You take out the silver ones, the ones that
are worth something. What happens over
weeks and months? That jar changes from a
mixture of all kinds of coins, to one that's
almost all pennies. And once it's all
looking coppery, it's hardly worth digging
anymore in there. Now this is an example of
a selection process, not natural selection,
but selection nonetheless, that explains
how it's changed from a mixture to a
pure, copper kind of jar.
Dawkins: As a Darwinian, I'm used to thinking
of everything as being good for the body,
but what about something like sneezing,
or vomiting? I mean, how is that...
Nesse: You know, there are two different
kinds of problems people bring to their doctors.
Some of them are caused directly by
the disease: there's a tumor, or there's
seizures, or there's the yellow color your
skin turns when you get jaundice because
your liver fails. Nothing good about them,
they just indicate that something's wrong
in a mechanism. But most of the problems
that people bring to their doctors, are
actually diseases that are the body's
protection against something going wrong.
You mentioned sneezes, fever, cough,
vomiting, fatigue, anxiety, diarrhea, all of
those things, nasty as they are, are useful.
Otherwise they wouldn't be there. How about a
life without pain, wouldn't it be great?
Dawkins: Go on. (laughter)
Nesse: Well, you can guess that because
we have this capacity for pain, it wouldn't
Nesse: be there unless...yes. Dawkins: It had to be good for something.
Nesse: And indeed there are a few very
unfortunate people who are born with no
capacity for pain. They're almost all dead
Nesse: by early adulthood. Dawkins: What killed them?
Nesse: It turns out that most of us don't
stand still like this, we wiggle a little bit.
And we can't sit still because we wiggle.
They have no pain standing still, so their
joints deteriorate, and they get sores on
their skin from not moving. And of course
if they get appendicitis or something like
that they never know it. And so they're
really prone to bad things happening.
Pain, when you experience it, it means
there's something going wrong, but the
capacity for pain is absolutely essential.
Dawkins: Well if I came to you and said
"Doctor I've got a terribly high temperature,
please give me a drug to bring the temperature
down," I mean, what would you say to that?
Nesse: You know, people want an easy answer
to that question, and it's terribly important
not to give one. I had a dear friend once
who called from a hospital bed saying,
"I have a high temperature, the doctors want to give me something
but I know that fever is useful, therefore I won't reduce my fever."
But we have to think, as evolutionists, about
how fever is controlled and how it's useful.
Dawkins: So if I understand you right,
something like a fever, a high temperature,
might actually not be a bad thing, it might
actually be a good thing because it might
be making life difficult for some, bacteria say?
Nesse: Exactly so. The best experiments
have been done on lizards, not people,
and if you give them an infection, they
crawl close to a lightbulb and create an
artificial fever in themselves, which
decreases their death rate a lot.
Dawkins: Right, and lizards normally control their
temperature, not in the way we do internally,
they normally control it by moving into the sun.
Dawkins: So that's what, they're using that Nesse: That right.
Dawkins: to create an artificial fever.
Nesse: And it works. I continue to be
amazed that we don't really know the
answer to whether we should reduce fever
Nesse in everyday colds... Dawkins: Oh, so if I came to you as a
Dawkins: doctor and said "I've got a fever,
please give me a drug to bring it down,"
you might not immediately say
"No, I won't." You might actually say,
Dawkins: "We'll think about that." Okay. Nesse: Let's think. Thank you so much,
Nesse: that's exactly the right attitude
Nesse: to evolutionary medicine. Dawkins: Right.
Nesse: Some people imagine that it tells
you how to practice. It does not. It tells
you what questions to ask, and what
studies need to be done. And these studies,
even though we've know they need to be
done for quite a long time now, have not
been done properly. If you get, for instance...
Nesse: So fever is certainly useful, but
if it's so useful, then how is general
medicine possible? Because a lot of what
general medicine does is block perfectly
normal defenses: fever, pain, nausea,
vomiting, diarrhea, cough, doctors are
very good at relieving the suffering
associated with those things. And when I
first realized that these were all useful
defenses, I wondered "What are we doing
to our patients? Are we hurting them somehow?
Or maybe natural selection just isn't that
cleaver. What's going on here?" And it
finally dawned on me that everyday when I
made toast in the morning my smoke
detector went off, and I put up with it.
And the reason I put up with it is that the
cost of a false alarm in a smoke detector
is not much. But I want my smoke detector
to go off every single time there's a fire.
I don't want it to go off half of the time
when there's a big fire. And so the principle
here is, so take something like vomiting;
unpleasant to talk about, but what happens,
it might cost you about two-hundred calories.
But not vomiting if you have a potentially
fatal illness is going to kill you, and
therefore the normal system is set by
what we call a "smoke detector principle"
to express these painful defenses much
more often than they're needed, as-
Dawkins: As a kind of asymmetry of risk.
Nesse: That's exactly the right way of
putting it. Yes, it's quite asymmetrical.
And this means that it's safe to block
cough, fever, vomiting, much of the time.
Except for the times when it's not safe.
And I think the next phase of understanding
these things in general medicine, is going
to be making sharper distinctions about
when it's safe and when it's not. Now in
fact, many doctors know all about most
of this already. If you've just had surgery,
your doctor will tell you "Please cough."
and you'll say "I don't want to cough,
it hurts." And the doctor will say "Cough
anyhow. If you don't cough, you'll probably
get pneumonia." So doctors are quite on
to this, and they won't give you codeine,
it will completely block your cough
if you have pneumonia, because they want
you to use the normal protective response.
But much more work needs to be done,
and that said, can be done quite quickly.
Dawkins: Right. All animals have this problem of
historical legacies which means that they're
not perfectly designed machines. But are
humans particularly unfortunate with respect
to our historical legacy do you think?
Nesse: Well you know, our environment is
not just a new one that we've moved into.
It's one that we've constructed. And I think
one of the saddest ironies about modern
human life, is that we now created for
ourselves environments that, even the kings
of England a few centuries ago, couldn't have
dreamed of. Hot and cold running water,
all the delicious food we want to eat,
light so we can read all night if we want to
and listen to music at high volumes. I mean,
it's a fabulous life we've constructed for
ourselves. It really satisfies those needs
that natural selection shaped in us.
On the other side of it though,
those needs are killing us.