Nesse: So it just doesn't seem fair, does it?
That guys like us are gonna die on the average
seven years younger than women. You'd think,
especially natural selection, if it wanted
to favor males, could have at least allowed
us to live longer. But we don't. So is it
just here in this country and in Western
society? No, it turns out to be every place.
I got data from the World Health Organization
that lists mortality rates, what percentage
of people died at each age for twenty different
countries, at different ages of life. And I
wanted to figure out for every hundred
women who die, how many men die,
at age twenty? And my guess was, oh about
one hundred and twenty men die for every
hundred women who die, about a 20% excess.
But when I looked at the data, for every
hundred London women age twenty who die,
three hundred men die. The death rate is
three times higher. I was flabbergasted
even though I was a properly educated
doctor, no one had ever mentioned this.
And then I looked at twenty other countries,
same pattern in every country. It ranges
between about 2.5 and 5 for that peak.
Then I looked across the age span,
throughout the entire lifespan, males
die more. So how come? Why did natural
selection discriminate against men? And of
course once again we're back to tradeoffs.
Males that invested more in competition,
and certain kinds of muscular vigor and all
the rest, ended up having more offspring
than other men. There's variation in the
amount of investment in that kind of
reproductive competition. For women,
competing for mates doesn't influence the
amount of babies they have very much.
Most women can find a mate, and they don't
have to compete in the same way. As a result,
natural selection has invested much more
of life's energies into mate competition for
males, and less in females. So for us we have
less investment in repairing our tissues,
Nesse: and as a result, we die young. Dawkins: Those three hundred that
Dawkins: you mentioned, what are they actually dying of?
Nesse: We actually looked at that. It turns
out that for the twenty leading causes of
death, nineteen of them are higher for males.
Now we also looked to see if it was all
explained by riding motorcycles without
a helmet, and drinking too much too fast,
and unsafe sex. About half of it's accounted
for by those behavioral kinds of factors.
But cancer, lots of other things as well,
pneumonia, they're more frequent and
more deadly for males. So our bodies
seem to be designed- and it's in other
species too of course. You look at chimpanzees
you see the same pattern. The males are
competing and fighting and dying young
on average compared to the females.
Dawkins: So let me see...So let me see if
I've got this right. We're all governed by
compromises, and there's a compromise
between reproduction and long life, and that
Dawkins: applies to both sexes, Nesse: That's the big compromise.
Dawkins: that's the big compromise. Nesse: That's right.
Dawkins: But the compromise comes out at
a different place for males than for females
because for females, they can reproduce
more if they live a longer time, and have
a child, and then another one, and then
another one and a then another one.
But for males, it's not like that?
Is that what you're saying?
Nesse: Well in sets they can live longer,
and some people have suggested, in fact
particularly Ruth Mace who does research
right here at University College London,
has looked at whether lifespan for
females has been increased because women
make good grandmothers and therefore
Nesse: help their own genes... Dawkins: Well I was going to say because
Dawkins: I mean, on the face of it, we're
contradicted by the menopause aren't we?
Because men can go on reproducing well
Dawkins: into old age, but women can't. Nesse: So in that, in that same 1957
paper, George Williams suggested a possible
explanation for menopause. He said, it
may be that after a certain age the risk
of pregnancy in terms of killing a woman,
and resulting in the death of her existing
children, back in ancestral times, would be
so grave, that it would be better for her to
stop reproducing herself, and instead take
care of her children and her grandchildren.
Now since then there have been a dozen
papers published on this with mathematical
models and data, and it's beginning to look
like he had the right idea of an answer.
It looks like women who do stop reproducing
may have a better ability to care for
children and grandchildren and...
it's still a controversial issue actually.
Dawkins: We're all of us descended from
an unbroken line of ancestors, not
a single one of whom died young.
Nesse: Yes
Dawkins: But they all potentially died old,
many of them died old. Would that
be one way of summarizing the whole
Dawkins: Darwinian medicine...message? Nesse: And those who died at age twenty
Nesse: on the average had fewer offspring
than those who died at age forty or sixty.
So indeed. Everything is a tradeoff,
and there's variation, which has resulted
in selection for genes that maximize
reproduction. Usually they maximize
health also, but not always.
Dawkins: So we're really not designed for
health, we're designed for reproduction,
and if there's any competition between
those, reproduction wins.
Nesse: That's right. Absolutely.
It's a sad thought, isn't it?
Dawkins: It doesn't mean we all have to rush
around reproducing like crazy. (laughter)
Nesse: No, that certainly doesn't. In fact
it might make you think that maybe
natural selection's played a bit of a trick
on us, encouraging us to do things
that are good for our genes, but not
necessarily good for us.
Dawkins: I think it is important to remember
that although natural selection does
explain why we're here, it doesn't provide
us with a recipe for how we ought to behave
Dawkins: necessarily, morally or politically Nesse: Absolutely.
Dawkins: or anything like that. Nesse: No.
Nesse: And even, I mean, finding out that
on the African Savanah there were good
reasons for eating a lot of fat and sugar,
that's not a good reason for eating a lot
of fat and sugar. And what's worse, even
knowing that doesn't really change much our
ability to resist eating those tasty things.
Dawkins: Why is life so full of suffering?
Nesse: You know, it's such a profound and
awful question you hardly dare touch it.
But thinking about it from an evolutionary
point of view there's a quite specific answer.
Most of the kinds of suffering we experience,
whether it's pain, or even vomiting or
fever or anxiety or depression, those are
adapted defenses in their place. The question
is why do they get dis-regulated? Why do
we have so much of them when we don't
really need it? And it's because of how
natural selection has shaped the mechanisms
that regulate them. It shaped them to go
off when they could possibly be useful,
because most of them are inexpensive.
And as a result, many of us spend our lives
feeling like we're missing something or
too anxious or depressed or something,
or in pain. And we don't need these feelings
in modern life especially, but even an
earlier life, but they've been good for
our genes, for our ancestors on the average,
so we have them.
Dawkins: It's the Smoke Detector Principle again. Nesse: It is the Smoke Detector Principle.
Nesse: It has profound implications for the
future and our ability to change human life.
You know, right now we're in the midst
of a revolution in psychopharmacology
where we're beginning to use medication
to influence our anxiety and our mood
and all of the rest. Usually that's talked
about in terms of the brain being broken
in some way, and in many people it is,
but in many people they're having more
of an emotional, negative response than
is useful. And blocking that response with
medications is just as useful and appropriate
as blocking a fever with aspirin, and it's
doing very much the same kind of thing.
But the key is thinking about what we're
doing, and the key to thinking about what
we're doing is asking the evolutionary
question about why hasn't natural selection
Nesse: made the body better? Dawkins: Right.
Dawkins: Randy I know that you
wrote a book with George Williams in America,
it's called "Why We Get Sick." In Britain
it's called, "Evolution and Healing,"
and it really should be called "The Dawn of
Dawkins: Darwinian Medicine." Nesse: We tried to call it that,
Nesse: they wouldn't let us. Dawkins: Yes. Publishers are like that.
Dawkins: But nowadays, that book's quite
old now, but there's still a lot of good
stuff in it. But what about now? Is there
anything else you could recommend?
Nesse: Well it turns out that there are
two other books by Oxford Press, one called
"Evolutionary Medicine," anther called
"Evolution, Health, and Disease," it came
out about six years ago. Both have new
editions coming out early in 2008. So that's
happening fast. Also there's a new organization
called Evolution and Medicine. And anyone
who's interested can go to evolutionmedicine.org,
all one word, and that's the latest information.
You can even get on an email list,
to find out where the latest meetings
are and what's happening in the field.
Dawkins: Okay. I'll go there myself Nesse: Great.