WEBVTT

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Prof: As you may have
noticed, the course has been

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proceeding somewhat
historically.

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First with pre-primate animals,
the whole evolution of sex from

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things that swam in the ocean,
and then we discussed the

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primate mating system as you've
seen--

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in the same sense as on the
board.

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The first--the pre-primate is a
few millions of years--I'm

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sorry, tens of millions of
years;

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primates maybe ten million
years or so.

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Then last time we started
discussing the transition from

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ape to human,
and evolutionarily modern

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humans date to something like
150 thousand years ago.

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We're coming up to time and
today we're going to discuss

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fully anatomically modern
humans.

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They have the same brain
capacity that we do,

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etcetera, etcetera.

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The earliest groups that we
have any kind of decent

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demographic data on are hunter
gatherers which would include

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cavemen and people that are
hunter gatherers but do not live

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in caves.

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Last time we asked why there
were so few chimps and so many

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humans and today we're going to
ask very similar questions

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about--
we're going to start with,

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we're going to cover a lot
more;

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we're going to ask very similar
questions about hunter

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gatherers.

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There never was a great density
of hunter gatherers.

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There is certainly not now and
the question is,

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why?

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If you look where hunter
gatherers live now they--

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each small group,
and the again the small group

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is the same size we've been
talking about something like 40,

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are spread out over a very
large area and they use that

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area to hunt in and to collect
fruits and nuts,

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and whatever they can get from
the trees.

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It looks like a very simple
question, why is the density of

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hunter gatherers so low?

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Why are there so few of them?

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For a long time,
the answer was:

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they didn't have much food.

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That they needed all this space
to get enough food to survive,

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and if they overpopulated that
space they couldn't survive.

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In sort of modern hubris,
we looked back and thought

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hunter gatherer is a very
inefficient form of food

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gathering,
not modern, and we're so much

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better than them now.

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The data is quite clear on some
part of those assumptions;

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hunter gatherers,
at the time when all human

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beings were in the stage of
hunter gatherers,

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before--farming starts about
10,000 years ago.

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There's--what is the number
here?

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There may have been like two
million people on the whole

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earth.

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Remember I said hunter
gatherers spread out of Africa,

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spread amazingly over the whole
earth,

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and maybe the total population
of humans at that time was

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something like two million
people.

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Now we have over six billion
people, that's an increase of

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3,000 times in the human
population, so clearly there

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were fewer hunter gatherers than
now.

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This is a very--you'll see this
in lots of discussions of this

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field, but it's a very
elementary kind of

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consideration.

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It talks about the long scale
of human demography,

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of human population growth,
and we came out of being other

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species of primate,
of hominids and we gradually

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grew up to some sort of a limit.

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There's the idea that the
various productive systems that

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we use,
like hunter gathering--limit is

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some sort of a carrying capacity
limit,

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and so the idea is that the
human population increased until

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it reached a limit and then for
a very long period of time it

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can't get beyond that limit.

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Then 10,000 years ago,
maybe it's 12,000,

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farming is invented and all of
a sudden the whole system

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changes,
there's many more people and we

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jump up and then again reach a
limit,

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and we'll talk about that as
some Malthusian limit in this

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particular period,
later we'll discuss that,

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and then around here the
industrial revolution happens

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and all of a sudden the
population increases again.

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This is a logarithmic scale so
it's not linear.

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Each of these jumps is by a
factor of several thousand.

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That's a very,
very schematized version of

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human demographic history and
we're talking about this period.

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What limited hunter gatherers
to this level whereas farmers

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could go up to this level.

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Again, the obvious answer and
looking at this kind of rough

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data is that it was food.

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Whoever then--archeologists,
paleontologists go and actually

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try to examine this and there
turns out to be the data does

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not fit that theory terribly
well.

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What do archeologists do?

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They dig up skeletons and they
have a good representative set

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of skeletons from the last 7,000
years in North and South

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America.

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One study looked at more than
12,500 skeletons so we're

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talking about a good scientific
sample.

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What did they find out?

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These were set into
communities, and communities

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lasted so much time,
so you can date the whole

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archeological site to a certain
period.

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The medical anthropologists got
into it and started looking at

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the bones and dentition and all
this,

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and not only did they find the
violence we talked about last

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time,
but these people were also sick.

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They had diseases at different
times.

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You could see bone problems and
how well the bones grew and from

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the teeth how much calcium they
had, and all this.

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What does it turn out,
that contrary to the idea of

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progress that you'd think the
later people were more healthy,

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in fact, it was earlier people
in the--

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the earlier individuals that
were healthier.

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As time goes on,
the skeletons get less and less

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healthy, that they're getting
less food and less good food,

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and were more subject to
diseases.

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It was quite a shocker when
this status started coming out.

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The researchers attributed this
decline in health in large part

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to the rise in agriculture.

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Two main factors they say,
the rise of agriculture and the

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rise of urban living,
and we'll talk about the urban

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story in a moment.

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If you again go like we did
last time from the archeology to

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the anthropology and look at
current hunter gatherers,

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it's a little bit of a
distorted study because nowadays

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almost all hunter gatherers have
been pushed out of the good

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lands that they used to live in,
into very marginal lands.

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You know this from
U.S. History in high school,

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how the European farmers pushed
the very earlier farmers or

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hunter gatherers of the American
Indians,

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the Native Americans into
Arizona, into desert,

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into the Badlands in the West,
the dry Badlands and to the

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West of the U.S.,
farming peoples push hunter

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gatherers into inhospitable
land.

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There's a story in the
Smithsonian Magazine recently

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about Pygmies in Africa.

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I don't know if you know a
little bit about the history of

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African demography,
which we'll also cover,

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but the Bantus have expanded
from south--

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the bulge of southwest Africa
basically all around and have

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pushed other people's out and
the Pygmies are one of the

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groups that have been very
severely discriminated against

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and really pushed into
inhospitable places.

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Another example is the Bushmen
of Africa who were pushed into

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the Kalahari Desert in southern
Africa.

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Even in the desert these guys
eat 85 different species of

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plants,
and it's almost inconceivable

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in their culture,
for someone to die of

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starvation because plants will
bloom some years and not bloom

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some years.

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They will get a fungus some
year, or a virus,

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plants--any one species is not
generally very reliable.

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When you have 85 different
species to survive on you're not

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going to go without food.

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There will always be some group
of plants that are going to be

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available to you and so you're
not going to starve.

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Further, the anthropologists
lived with these people and they

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start writing down what they're
doing at every point in time.

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Per hour invested,
the Bushmen get more food then

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the early agriculturalists.

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Not modern agriculturalists who
can drive a tractor and in an

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hour do a lot,
but we're comparing

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hunter-gatherers to the first
stages of agriculture.

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The Kalahari--the Bushmen in
Kalahari spent 12 to 19 hours a

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week collecting food and the
rest of the time they used for a

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lot more sleep than current
farmers,

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and a lot more leisure than
farming people,

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so life is more generous to
them.

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You have to think now,
this is for people pushed into

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a desert,
a very inhospitable place,

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and now if they--
if you can imagine them living

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in a lush forest region where
they originated,

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life must have been much,
much easier so the amount of

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time exerted to get your basics
of food and everything must have

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been much-- a lot less.

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Not only do they have to work
less and they get more food per

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hour,
but the variety of foods is

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very good for you because you
need different minerals,

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you need different other
micronutrients,

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you need different vitamins,
and as we are bombarded with in

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the popular press,
a variety of foods is very good

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for you.

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You don't want to eat just one
kind of food,

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so they had a very diverse and
healthy kind of diet.

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Agriculture comes in and indeed
it enormously increases the

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amount of food per acre when
land is limited,

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when you have a population
density such that land becomes

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limiting rather than your time
or your need,

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when land becomes limiting then
agriculture becomes important

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because per acre you can get a
lot more food than hunter

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gathering,
but you have to spend lots and

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lots of hours to get that land
to give you that amount of food.

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The question remains 'why are
there are--why were there and

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still are of course,
why are there are so few hunter

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gatherers?

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Again, a Malthusian type
question that,

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if we know they lived quite
well, we know that later people

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going into agriculture lived a
lot less well in terms of basics

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of life,
how come the hunter gatherer

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population did not increase up
to the same level of misery as

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early farmers,
which is basically one of the

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earliest examples of a
Malthusian type question.

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Malthus thought those same kind
of thoughts but for a much later

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population.

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Well in truth,
we don't really know the answer

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to this and it's greatly argued
about, but I can tell you some

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things that are known.

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Current hunter gatherers have a
moderate number of children and

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many survive.

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They do not have an enormous
infant mortality,

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certainly not compared to later
populations which I'll show you

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that have a huge infant
mortality.

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If they are Nomadic,
and I'll tell you about an

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example of that later,
they have to move quite a lot

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and that means carrying children
around.

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I think Bonnie has sort of
indicated to you,

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even dealing with a lot of
children in one place is

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difficult,
but the difficulty of moving

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with very young children,
and packing up everything and

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moving for a very long time,
over a long distance is

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difficult and Nomadic peoples
very often show very clear signs

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of some form of conscious
population control.

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They know they can't cope with
more than "x"

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number of children.

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We'll get to that all societies
have indeed controlled their

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population but mechanism they
were not totally--

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not clear what they think the
reason for their doing things

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were,
but Nomads apparently know what

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they're doing.

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Hunter gatherers are moderately
healthy.

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Again, their burden of sickness
is not severe,

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again compared to later
populations;

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however parasites are always a
problem.

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I'll show you again a modern
case of parasites.

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This is a girl,
modern girl,

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current girl in Central
America, and you may notice the

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swollen belly.

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You know what's inside there to
swell it?

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Worms--exactly and when they
purge her that was what was

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inside that girl,
all those worms.

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Humans have had this problem
since time in memorial.

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Hunter gatherers are not immune
to this.

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Infectious diseases they have
less because they're in small

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groups,
so infectious diseases as you

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know need large groups to keep
spreading and they're hostile to

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their neighbors,
just again like chimpanzees so

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they don't come in a lot of
contact with neighbors,

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so diseases don't spread from
group to group and each

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individual group is not large
enough to allow for the

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maintenance of a disease.

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Each village,
if you--anthropologists go and

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sit in one village for a long
time and they have a high

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population growth rate.

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Each village seems to be
expanding quite noticeably,

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and you think,
well in each village that we go

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study population is increasing,
again, it doesn't make sense

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why haven't they--
been living that way a hundred

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thousand years,
why haven't they filled up

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their space?

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Why is each village surrounded
by lots of--basically unused

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space?

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Even today, a lot of the very
tropical lands are not

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high--densely populated.

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We may have the image that they
are but they're not.

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New Guinea is not densely
populated.

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If you call densely
populated--the Netherlands is I

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think the most densely populated
in the world,

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Bangladesh, the livable regions
of China,

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the livable regions of Japan,
these are densely populated.

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The tropical regions of the
world, nothing like that;

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New Guinea I said,
Borneo very sparsely populated,

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the Amazon, Sub-Saharan Africa
vast open areas,

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so these are not situations of
high population density,

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yet any village that you sit in
is increasing its population.

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What's going on?

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What are the--what the
archeologists find out is that

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when they study a site,
and I sort of mentioned this

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already, what you see is this.

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You go to--you start digging a
site and you actually dig in

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reserve,
but you go to the bottom and

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you see there was nobody there
before certain years,

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and then a small population,
and what you see,

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you can count the amount of
food remains,

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all kinds of things,
the population grows more or

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less exponentially.

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That means that the same
percentage every year.

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A half of a percent a year or
whatever it is,

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and it grows up faster and
faster, because there are more

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people producing that same
percent of population growth.

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You get this phase and then all
of a sudden you reach the top of

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your pile and your village is
gone and there's nothing there.

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Some sort of a crash happened,
where if it's not totally gone

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it's really knocked down
tremendously,

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and then you either wait--look
at that site again like the

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biblical sites which they dig,
and dig, and dig and sometime

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later starts up again,
or a different site starts up

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again and you get the same
phenomenon.

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Forget this line,
this is the idea of -- the

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carrying capacity,
but you can see nothing fits

17:20.116 --> 17:21.576
the carrying capacity.

17:21.578 --> 17:25.198
It just maybe stays there for a
little here, so the idea of

17:25.199 --> 17:28.569
carrying capacity for humans
doesn't work very well.

17:28.568 --> 17:33.038
What are the reasons--so--then
the explanation for the

17:33.038 --> 17:38.268
population staying more or less
constant and not filling up the

17:38.265 --> 17:42.645
space is not that each community
doesn't exist,

17:42.650 --> 17:45.960
but communities--here's your
space filled with community A,

17:45.964 --> 17:48.944
B, C, D, E and as each
community increases some other

17:48.936 --> 17:51.486
community just disappears,
goes out of existence.

17:51.490 --> 17:55.230
If you measure over the whole
big space you have a floating

17:55.226 --> 17:58.186
game of different communities
each growing,

17:58.190 --> 18:01.300
but then disappearing
completely, and the population

18:01.299 --> 18:04.349
and the whole space stays more
or less the same.

18:04.348 --> 18:07.258
I don't want to push that as it
really becomes super duper

18:07.255 --> 18:10.105
constant, but more or less the
same--does not fill up.

18:10.108 --> 18:13.648
What are the reasons why a
community would grow very

18:13.648 --> 18:16.078
happily, more or less,
very vaguely,

18:16.077 --> 18:19.407
exponentially,
and then go out of existence?

18:19.410 --> 18:21.760
One is of course climatic
disaster.

18:21.759 --> 18:26.699
There could be a freeze;
there could be a drought,

18:26.704 --> 18:31.654
these real climatic things,
and if you look at the Anasazi

18:31.645 --> 18:37.365
of Arizona that lived near the
Colorado River regions,

18:37.368 --> 18:39.778
one of the thoughts--they're
one of the communities that fit

18:39.782 --> 18:40.072
this.

18:40.068 --> 18:41.988
They're healthy,
you go see their ruins,

18:41.987 --> 18:43.607
and then they just disappeared.

18:43.608 --> 18:47.038
How many of you have been to
Anazasi site in Arizona?

18:47.038 --> 18:51.898
Just one student,
something you've got to do.

18:51.900 --> 18:55.390
There you're living in a
semi--a true desert now and a

18:55.386 --> 18:58.406
semi-desert back then,
so climatic things are a

18:58.413 --> 19:00.193
reasonable explanation.

19:00.190 --> 19:04.020
You go into the tropical
regions you don't have droughts

19:04.015 --> 19:07.765
that last, you don't have
freezes, and yet you see this

19:07.771 --> 19:09.721
same kind of phenomenon.

19:09.720 --> 19:14.560
While undoubtedly climatic
things happened occasionally in

19:14.557 --> 19:18.187
the temperate zones,
certainly in the northern

19:18.193 --> 19:21.973
zones, most hunter gatherer
societies probably that's not

19:21.969 --> 19:23.249
the explanation.

19:23.250 --> 19:27.150
The next thing is diseases of
the crops, that some fungus came

19:27.151 --> 19:29.071
by and wiped out your crops.

19:29.068 --> 19:32.758
Well we've just talked about
that, that since they're eating

19:32.756 --> 19:35.626
85 different kinds of things in
the desert,

19:35.630 --> 19:39.630
there isn't any kind of
microorganism that cuts across

19:39.625 --> 19:44.705
species like that,
so that explanation doesn't

19:44.705 --> 19:46.515
seem to work.

19:46.519 --> 19:49.199
Diseases of humans,
same thing, not diseases of

19:49.196 --> 19:51.496
plants,
but diseases of humans,

19:51.499 --> 19:54.489
again, the data just doesn't
fit that,

19:54.490 --> 19:59.120
that because of the isolation
they don't have a huge problem

19:59.115 --> 20:01.385
with communicable diseases.

20:01.390 --> 20:05.940
That leaves the possibility of
violent confrontation from one

20:05.943 --> 20:07.693
community to another.

20:07.690 --> 20:11.230
We've seen in the chimps how
the northern group will

20:11.234 --> 20:14.994
completely wipe out the southern
group and so forth.

20:14.990 --> 20:19.120
What kind of evidence can one
adduce that this might be what's

20:19.124 --> 20:19.874
going on?

20:19.868 --> 20:25.728
If one looks at any modern
population and looks at the

20:25.726 --> 20:30.806
survival curve,
so this is the number of deaths

20:30.807 --> 20:33.347
per 1,000 per year.

20:33.348 --> 20:35.488
This is India,
for instance,

20:35.487 --> 20:38.017
and it's fairly recent--1960s.

20:38.019 --> 20:41.439
Antibiotics are just coming in
at this stage,

20:41.440 --> 20:44.560
so very high infant mortality
rate,

20:44.558 --> 20:48.948
80 per 1,000--one out of every
12 kids dies almost immediately

20:48.952 --> 20:52.482
and then that high rate
continues until about--

20:52.480 --> 20:56.640
comes down to something about
six or seven years old so a lot

20:56.635 --> 21:00.165
of your population is just wiped
out immediately.

21:00.170 --> 21:05.020
Then you have a pretty low
level of death and fairly flat

21:05.016 --> 21:09.946
until it gets to be what's
considered old age in different

21:09.949 --> 21:13.929
populations and then the death
rate rises.

21:13.930 --> 21:16.330
You have this very standard
u-shaped curve,

21:16.328 --> 21:19.028
and here after you have sort of
modern medicine--

21:19.028 --> 21:21.238
this is Sweden in the same year
as the infant--

21:21.240 --> 21:24.410
primarily the main thing is the
infant mortality drops like

21:24.413 --> 21:28.323
crazy and the old age stuff--
everything drops but the main

21:28.318 --> 21:30.528
drop is in infant mortality.

21:30.528 --> 21:32.788
The idea is--what I just want
you to get out of this--

21:32.788 --> 21:36.658
we'll see this graph again and
again in a couple of times,

21:36.660 --> 21:40.450
is that during the adult years
the death rate is very low

21:40.449 --> 21:42.749
compared to either here or here.

21:42.750 --> 21:48.900
Now if you look at what we can
gather from archeological data

21:48.901 --> 21:53.821
from hunter gatherer
communities, you have a high

21:53.821 --> 21:56.181
death rate of kids.

21:56.180 --> 21:58.370
Not as high as when you get all
these communicable diseases in

21:58.371 --> 22:00.411
modern societies,
and then you have a flat

22:00.414 --> 22:03.514
period, and then all of a sudden
there's this big bump.

22:03.509 --> 22:07.469
What they call an excess
mortality in exactly the young

22:07.470 --> 22:10.010
adult years,
and then it comes back down

22:10.007 --> 22:13.147
again and you get a more or less
normal old age situation.

22:13.150 --> 22:16.850
Well what is it that kills
people in their middle years?

22:16.849 --> 22:19.239
Violence.

22:19.240 --> 22:22.470
So this kind of data--again we
don't totally--

22:22.470 --> 22:25.380
we don't really know the
answer, but this kind of data

22:25.384 --> 22:28.744
leads you to suspect that indeed
one of the major reasons,

22:28.740 --> 22:32.530
not the only reason,
but a major reason that the

22:32.527 --> 22:36.877
hunter gatherer communities and
the early archeological

22:36.877 --> 22:41.307
communities disappear so
suddenly is that they are wiped

22:41.308 --> 22:44.128
out by some sort of violence.

22:44.130 --> 22:49.900
We're right back in hunter
gatherer times as far as we can

22:49.904 --> 22:54.874
tell to what you've seen before
of these mass--

22:54.868 --> 22:59.898
I've showed you last time these
mass graves that are

22:59.895 --> 23:03.045
characteristic of this period.

23:03.048 --> 23:06.708
Okay, nevertheless,
over the very long scale of

23:06.711 --> 23:09.061
time--
our period of being cavemen and

23:09.057 --> 23:12.197
hunter gatherers lasted hundreds
of thousands of years--

23:12.200 --> 23:16.070
but gradually population did
slowly increase,

23:16.068 --> 23:20.368
and as population increases,
the land available to people

23:20.367 --> 23:21.287
gets less.

23:21.288 --> 23:23.918
We talk, I think next time
about Africa,

23:23.920 --> 23:27.380
which has a culture where land
is not a scarce commodity and

23:27.383 --> 23:30.723
now it's getting to be scarce,
but in their traditions,

23:30.722 --> 23:32.772
land is not the scarce
commodity,

23:32.769 --> 23:37.649
but as the population grows the
land per person gets less and

23:37.645 --> 23:42.435
then you have to make a more
intense utilization of the land

23:42.441 --> 23:44.881
and farming gets invented.

23:44.880 --> 23:48.070
A big discussion whether it
actually was the population

23:48.069 --> 23:51.729
pressure that caused farming to
be invented or whether that was

23:51.732 --> 23:55.162
just some brilliant stroke by
somebody that invented--

23:55.160 --> 23:58.520
that people slowly figured it
out.

23:58.519 --> 24:04.149
They actually can trace the
origin of agriculture to--

24:04.150 --> 24:07.520
the current data is 11,700
years ago in the Middle East,

24:07.519 --> 24:10.769
in Anatolia,
what's now Turkey,

24:10.772 --> 24:14.912
now eastern Turkey,
and it expands on the average

24:14.909 --> 24:18.589
from the original sites you can
watch it expand and it expands

24:18.589 --> 24:20.219
at one kilometer a year.

24:20.220 --> 24:21.390
That's the average.

24:21.390 --> 24:25.270
Then it eventually takes over
the whole world.

24:25.269 --> 24:27.569
The number of people,
and when you invent

24:27.570 --> 24:30.850
agriculture, the number of
people that can be supported on

24:30.851 --> 24:33.211
one plot of land grows up
enormously.

24:33.210 --> 24:36.560
We've seen that and so these
people become more numerous and

24:36.556 --> 24:39.956
so in military confrontations
and warlike confrontations,

24:39.960 --> 24:42.150
they're going to be dominant,
almost no matter what the

24:42.150 --> 24:44.920
technology is,
no matter what the bravery is,

24:44.921 --> 24:49.081
if you have an awful lot more
people you're going to wipe out

24:49.083 --> 24:53.043
or push out groups that don't
have that kind of population

24:53.038 --> 24:53.938
density.

24:53.940 --> 24:57.440
Agriculture spreads;
in the early days of

24:57.442 --> 25:02.612
agriculture you don't know an
awful lot yet and you probably

25:02.612 --> 25:07.082
have one crop that you really
know how to grow.

25:07.078 --> 25:08.858
For instance,
in the Americas,

25:08.864 --> 25:12.564
the big crop was corn that most
of Latin America even to this

25:12.555 --> 25:16.315
day lives on corn,
and the North American Indians

25:16.317 --> 25:17.957
lived a lot on corn.

25:17.960 --> 25:20.740
Of course in Southeast Asia a
great big population,

25:20.740 --> 25:22.940
it was rice,
and you basically lived off

25:22.939 --> 25:27.219
most of your calories,
most of your food from one

25:27.215 --> 25:28.645
single crop.

25:28.650 --> 25:33.330
That's not very healthy because
each crop is missing something.

25:33.328 --> 25:36.248
Corn, you may know,
misses lysine,

25:36.248 --> 25:41.468
one of these essential amino
acids and over a very long time

25:41.465 --> 25:46.515
the Americans learned to--
a rather complicated procedure

25:46.519 --> 25:51.079
for boiling it in lime to
extract this amino acid from the

25:51.078 --> 25:53.638
plant,
but until that was discovered

25:53.644 --> 25:56.144
they must have been extremely
unhealthy.

25:56.140 --> 25:58.970
Rice, you know,
is missing all kinds of

25:58.970 --> 26:03.370
vitamins and people have very
severe vitamin deficiencies if

26:03.365 --> 26:05.745
their diet is too much rice.

26:05.750 --> 26:10.360
You're not getting a health--in
early farming you're not getting

26:10.362 --> 26:14.902
a particularly healthy diet and
you're not getting the vitamins

26:14.901 --> 26:17.611
and micronutrients that you
need.

26:17.608 --> 26:19.838
Furthermore,
your food security goes down.

26:19.838 --> 26:23.078
Again, as I've mentioned,
that a virus or a fungus,

26:23.078 --> 26:26.388
or something attacks your
crops, and that's 80% of your

26:26.388 --> 26:29.758
calories and that is wiped out
in a year you're gone.

26:29.759 --> 26:34.749
Or if locusts come by and eat
them up or some insect

26:34.750 --> 26:37.490
infestation comes through.

26:37.490 --> 26:44.850
Also an increase in calorie
availability;

26:44.848 --> 26:49.698
you can--more people can stay
alive and so you get dense

26:49.695 --> 26:50.925
populations.

26:50.930 --> 26:54.810
The social structure changes,
now previously each person

26:54.807 --> 26:58.827
could only get enough food
basically for himself and maybe

26:58.827 --> 27:00.517
a very small family.

27:00.519 --> 27:03.219
As you develop the technology
of agriculture,

27:03.221 --> 27:06.471
an individual can produce a
surplus, not everything he

27:06.474 --> 27:07.094
feeds.

27:07.088 --> 27:09.338
Well who's going to get that
surplus?

27:09.338 --> 27:13.568
In an egalitarian society he
keeps the surplus himself,

27:13.573 --> 27:15.693
his family, and so forth.

27:15.690 --> 27:19.280
But there's other guys that are
either stronger and nastier then

27:19.284 --> 27:22.484
you and they come in and steal
your surplus from you,

27:22.480 --> 27:24.810
and they have to leave you just
with a small part of your

27:24.813 --> 27:27.193
production to just keep you
alive because they want you to

27:27.188 --> 27:30.408
work for them,
and so you get societies now

27:30.410 --> 27:32.580
where there are classes.

27:32.578 --> 27:36.078
There are people who in way or
another take the excess food

27:36.077 --> 27:38.787
from the farmer and use it for
other purposes,

27:38.789 --> 27:40.659
usually their own purposes.

27:40.660 --> 27:44.750
They can largely hire military
to keep them in power and to

27:44.750 --> 27:47.080
protect them from other places.

27:47.078 --> 27:51.118
That's a large use of the food
surplus which agriculture puts

27:51.123 --> 27:51.463
up.

27:51.460 --> 27:55.610
Also manufacturers come in;
they hire artisans to make

27:55.608 --> 27:59.338
beautiful gold objects for them,
or to make beds,

27:59.338 --> 28:03.038
or chairs or all the
manufacturing starts on the

28:03.038 --> 28:07.518
agricultural surplus that
agriculture brings in because an

28:07.522 --> 28:12.402
individual human now can produce
more calories than he needs to

28:12.403 --> 28:15.633
keep going at a subsistence
level.

28:15.630 --> 28:18.720
What you see as agriculture
progresses is the hunter

28:18.718 --> 28:22.108
gatherer societies are generally
quite an egalitarian.

28:22.108 --> 28:24.878
They'll more or less have a
head man but he won't--or a wise

28:24.876 --> 28:27.266
man or an old man,
but they won't have authority.

28:27.269 --> 28:29.299
He can't order other people
around;

28:29.298 --> 28:33.118
the community has to agree on
some project if they undertake

28:33.123 --> 28:34.293
projects at all.

28:34.288 --> 28:38.658
As more food wealth becomes
available,

28:38.660 --> 28:44.480
societies start stratifying,
you get social classes,

28:44.480 --> 28:49.450
you get castes,
and this inequality changes

28:49.446 --> 28:54.056
everything about the way humans
live.

28:54.058 --> 28:57.268
The congestion in the
cities--cities start growing up

28:57.265 --> 29:00.715
and then you start getting the
spread of these infectious

29:00.717 --> 29:04.167
diseases where one person
spreads it to the next in large

29:04.169 --> 29:06.079
agglomerations of humans.

29:06.078 --> 29:10.268
That just gets worse and worse
up through the 1400s in Europe

29:10.273 --> 29:14.403
when you get the Black Death and
wipes out a huge number.

29:14.400 --> 29:19.290
That is--as civilization
progresses the death rate from

29:19.287 --> 29:23.357
infectious diseases just keeps
going on up.

29:23.358 --> 29:27.508
Adding all this together and
the data we have,

29:27.512 --> 29:33.422
is that hunter gatherers--their
lifespan is ballpark 50 years.

29:33.420 --> 29:38.330
In early agriculture societies
that goes down to 35 years,

29:38.328 --> 29:43.968
so we're really--and I'll show
you data that in a lot of places

29:43.965 --> 29:47.325
it's probably even lower than
that.

29:47.328 --> 29:51.238
We have this situation where
humans--

29:51.240 --> 29:53.810
not counting violence that
humans live--

29:53.808 --> 29:55.708
when they weren't being
attacked by their neighbors,

29:55.710 --> 29:59.050
humans were living very well,
the hunter gatherer society;

29:59.049 --> 30:00.869
sort of Garden of Eden.

30:00.868 --> 30:04.138
Then agriculture comes in and
the vast mass of humans become

30:04.140 --> 30:06.510
peasants;
the land becomes owned not by

30:06.505 --> 30:09.745
them but by someone else,
and they have to give most of

30:09.749 --> 30:11.969
what they've produced to someone
else,

30:11.970 --> 30:13.860
so life becomes miserable.

30:13.858 --> 30:17.798
There's a lot of thought that
the various of Garden of Eden

30:17.798 --> 30:20.408
myths--
I mean almost every culture has

30:20.413 --> 30:24.363
some sort of glorification of a
very distant past where people

30:24.359 --> 30:26.429
did not have to work so hard.

30:26.430 --> 30:28.800
In our culture we call it the
Garden of Eden;

30:28.798 --> 30:31.688
everything was perfect,
then something happened,

30:31.688 --> 30:35.378
and after the fall of one sort
or another, now it's the sweat

30:35.375 --> 30:36.355
of our brow.

30:36.358 --> 30:39.898
It's a very nice description of
what I've been telling you of

30:39.895 --> 30:43.015
the hunter gatherers living in a
lush environment--

30:43.019 --> 30:44.739
before they're pushed into the
desert--

30:44.740 --> 30:47.430
living quite well,
and however,

30:47.434 --> 30:51.124
later on then they have to be
farmers,

30:51.119 --> 30:52.549
the sweat of the brow.

30:52.548 --> 30:59.978
And violence like Cain and Abel
is what is the fly in the

30:59.980 --> 31:05.290
ointment of that beautiful Eden
story.

31:05.288 --> 31:11.168
Now we come to the agricultural
period in our historical romp

31:11.165 --> 31:12.925
through history.

31:12.930 --> 31:17.010
There are some really
fundamental issues that you have

31:17.013 --> 31:21.953
to understand to understand what
was happening with population in

31:21.945 --> 31:23.175
these times.

31:23.180 --> 31:27.660
There's constraints on human
population, and the first was

31:27.661 --> 31:31.751
this enormous infant mortality
which I showed you.

31:31.750 --> 31:36.890
Again, we're looking at 1960
here in a very civilized place,

31:36.890 --> 31:41.730
poor India in 1960,
but still even into the 1960s

31:41.733 --> 31:47.083
where we're very modern,
the infant mortality is

31:47.079 --> 31:48.219
enormous.

31:48.220 --> 31:50.940
You go, even currently,
to a less well developed place,

31:50.940 --> 31:55.960
just cut out this quote from
Haiti in 1979,

31:55.960 --> 31:59.670
before this recent rash of
problems,

31:59.670 --> 32:02.660
a Cornell trained Haitian,
comes from Haiti to Cornell,

32:02.660 --> 32:05.570
gets a medical degree,
returns to Haiti,

32:05.568 --> 32:08.808
and he gets a job at a
pediatric hospital:

32:08.810 --> 32:12.370
"40% of the infants,
of the babies,"

32:12.367 --> 32:15.357
the birth rate--
he's working in among other

32:15.357 --> 32:18.627
things a maternity clinic,
"40% of the babies were

32:18.626 --> 32:20.366
dying of endemic diarrhea.

32:20.368 --> 32:25.298
A man would come to pick up the
bodies three times a day with a

32:25.304 --> 32:26.104
big bag.

32:26.098 --> 32:29.488
The noise of the skulls in the
bag was unbearable."

32:29.490 --> 32:35.370
And this is 1979 in--how far is
Haiti from Miami?

32:35.368 --> 32:39.468
A hundred and fifty miles or
something like that.

32:39.470 --> 32:45.110
The data--we have various data
sets for what life expectancy

32:45.112 --> 32:49.692
was like,
and this is various populations

32:49.688 --> 32:53.578
and what this is,
this is a survivorship curve.

32:53.578 --> 32:59.298
So you take--for 1,000 people
born in any given space of time,

32:59.298 --> 33:01.918
in an earlier period--so this
is Cisalpine Gaul,

33:01.920 --> 33:05.580
this is Roman times,
that's the part of Gaul that's

33:05.575 --> 33:08.715
this side of the Alps according
to them,

33:08.720 --> 33:11.660
Cisalpine Gaul.

33:11.660 --> 33:16.640
Out of 1,000 children born,
and actually this shows females

33:16.635 --> 33:21.695
but it's more or less the same
for males, almost immediately

33:21.698 --> 33:23.498
half of them die.

33:23.500 --> 33:30.230
That's very characteristic of
human societies until modern

33:30.233 --> 33:35.553
sanitation comes in,
which is in Europe 1700s,

33:35.550 --> 33:38.860
and in Asia maybe 1900s.

33:38.858 --> 33:43.578
You have this tremendous death
rate of children and then it

33:43.576 --> 33:48.126
continues at a fairly high but
decreasing death rate,

33:48.130 --> 33:50.850
and then finally there's very
few people left.

33:50.848 --> 33:53.588
This is not the curve which
showed you the percentage of

33:53.589 --> 33:55.979
death in age thing,
but how many people are still

33:55.981 --> 33:56.681
surviving?

33:56.680 --> 34:01.720
At any point in--by age 15
here, this dotted line,

34:01.724 --> 34:07.294
only about 40% of people are
still alive, 60% have died

34:07.286 --> 34:09.136
before age 15.

34:09.139 --> 34:11.789
This again is women,
so a lot of these deaths in

34:11.789 --> 34:14.179
this middle period,
by the time--this is the

34:14.175 --> 34:18.945
reproductive years,
these dotted lines is 15 to 45

34:18.945 --> 34:21.715
or so,
I think 50 in this case,

34:21.717 --> 34:25.987
which is the years in which
women can reproduce and most of

34:25.989 --> 34:30.409
the death in females in this
period is childbirth itself.

34:30.409 --> 34:32.829
In a developing population,
in a pre-medical population,

34:32.829 --> 34:37.599
childbirth itself is one of the
most dangerous things in these

34:37.599 --> 34:41.819
years and the death rates are
very high from childbirth

34:41.820 --> 34:46.030
itself,
so a lot of that is female--is

34:46.030 --> 34:47.340
childbirth.

34:47.340 --> 34:52.380
If you looked a male population
it might even be more extreme

34:52.380 --> 34:57.170
due to the--probably due to the
violence that we've talked

34:57.168 --> 34:58.008
about.

34:58.010 --> 35:00.260
Now as times goes on--we're
going to come back to this

35:00.257 --> 35:02.167
graph,
but as time goes on,

35:02.173 --> 35:05.783
this is Italy in 1921 and
things have gotten--

35:05.780 --> 35:09.070
at all ages the death is less,
so there's more people

35:09.068 --> 35:11.728
surviving,
and then you come to Japan;

35:11.730 --> 35:16.030
again 1984 and you have very,
very little infant mortality,

35:16.030 --> 35:20.280
very little mortality through
this period and then again old

35:20.278 --> 35:22.798
age takes over and people do
die.

35:22.800 --> 35:27.950
This kind of bump here compared
to say this, is again possibly

35:27.951 --> 35:31.921
violence in that era,
but again, we don't really

35:31.920 --> 35:32.680
know.

35:32.679 --> 35:34.869
For our purposes,
going back in time,

35:34.869 --> 35:38.179
we're really interested in this
lower graph which is

35:38.181 --> 35:41.881
characteristic of humans from
way back until really almost

35:41.880 --> 35:45.020
Napoleonic times,
maybe through Napoleonic times

35:45.018 --> 35:47.818
but the death--
the violence in Napoleonic

35:47.817 --> 35:49.267
times was enormous.

35:49.268 --> 35:52.208
If you look at women,
consider this just a graph for

35:52.208 --> 35:52.668
women.

35:52.670 --> 35:56.330
Of 1,000 women born,
400 are still alive at the

35:56.329 --> 36:01.179
beginning of their reproductive
period and about 200 are still

36:01.181 --> 36:05.161
alive at the end of their
reproductive period.

36:05.159 --> 36:08.309
If you average that out
something like--it would be the

36:08.311 --> 36:11.351
same as if something 300 women
lived throughout their

36:11.347 --> 36:12.747
reproductive period.

36:12.750 --> 36:17.280
Well, if that society is going
to keep going,

36:17.280 --> 36:23.150
what is needed to happen that
these more or less 300 women

36:23.148 --> 36:27.368
have to reproduce 1,000 women,
right?

36:27.369 --> 36:32.399
If they reproduce 1,000 women
they also have to reproduce

36:32.400 --> 36:33.570
1,000 boys.

36:33.570 --> 36:37.910
So 300 women have to give rise
to 2,000 children and if they

36:37.905 --> 36:42.015
don't do that then there's fewer
and fewer people in each

36:42.021 --> 36:46.801
generation and rapidly you don't
see this population anymore.

36:46.800 --> 36:50.240
How many children is that that
each woman has to have?

36:50.239 --> 36:53.729
Three hundred women making
2,000 children--

36:53.730 --> 36:57.570
6 2/3, almost 7,
so that means that in--

36:57.570 --> 37:00.260
when you have a mortality curve
like this,

37:00.260 --> 37:02.800
which again is most of human
recorded history,

37:02.800 --> 37:06.100
most of human history not
counting hunter gatherers who

37:06.097 --> 37:09.327
did live longer apparently,
the absolute minimum that a

37:09.326 --> 37:12.426
society could cope with is women
have basically an average of

37:12.429 --> 37:13.359
seven children.

37:13.360 --> 37:17.060
Wait a minute,
I've made this a better case,

37:17.061 --> 37:21.971
that's of the--all that this
graph shows is women that are

37:21.967 --> 37:24.117
alive in this period.

37:24.119 --> 37:26.319
What fraction go infertile?

37:26.320 --> 37:28.480
What fraction have infertile
husbands?

37:28.480 --> 37:30.170
What fraction never get married?

37:30.170 --> 37:32.680
What fraction are too sick to
have children?

37:32.679 --> 37:36.929
What fraction of women are worn
out after two or three children

37:36.931 --> 37:38.441
and can't bear many?

37:38.440 --> 37:41.760
That's also a very large number
which depends on the population,

37:41.760 --> 37:45.200
so if you subtract those--let's
call them infertile women for a

37:45.195 --> 37:48.185
variety of reasons in which they
or their husbands,

37:48.190 --> 37:53.540
or their health they're
infertile, then there's even

37:53.539 --> 37:58.259
fewer people alive and so this
curve goes--

37:58.260 --> 38:01.810
if you didn't graph just women
alive but women that are alive

38:01.807 --> 38:05.567
and in childbearing condition,
the curve gets much lower,

38:05.572 --> 38:08.292
so the number of children that
women--

38:08.289 --> 38:12.179
the women that were physically
capable of it had to have in

38:12.177 --> 38:15.257
these pre-modern times was more
than seven,

38:15.260 --> 38:19.090
and probably eight or nine,
or you have to do the

38:19.085 --> 38:23.625
calculation and people don't
know how to evaluate the--

38:23.630 --> 38:29.340
what fraction of Roman women
were fertile or infertile?

38:29.340 --> 38:31.970
You can't calculate that.

38:31.969 --> 38:40.519
We have a huge problem that
somehow there must be cul--

38:40.518 --> 38:43.908
there must be mechanisms to
insure that no women are wasted,

38:43.909 --> 38:46.729
that any woman that can
reproduce does reproduce,

38:46.730 --> 38:49.480
and when they reproduce they go
at it.

38:49.480 --> 38:53.410
They just keep going and going,
and of course men have an equal

38:53.405 --> 38:57.075
part--well they don't do the
amount of work but they have a

38:57.079 --> 38:58.029
part in it.

38:58.030 --> 39:03.120
As I said, this level of
mortality continues into quite

39:03.123 --> 39:06.523
modern times,
it's quite striking.

39:06.518 --> 39:10.998
Europe got out of it a little
bit earlier, I say somewhere in

39:11.001 --> 39:15.111
1700s, but for instance in 1912
in Australia--we have an

39:15.110 --> 39:16.530
Australian T.A.

39:16.530 --> 39:17.820
is she here today?

39:17.820 --> 39:22.690
Went to the--she got a ticket
to the inauguration--1912

39:22.688 --> 39:27.828
Australian census shows that 60%
of all children born died

39:27.827 --> 39:29.087
unmarried.

39:29.090 --> 39:32.080
That's this number,
we have them--well it was about

39:32.083 --> 39:35.743
the same number as this,
this shows that only 40% are

39:35.737 --> 39:39.157
left and this says in Australia
60% are dead,

39:39.159 --> 39:43.219
so that's the same number.

39:43.219 --> 39:46.089
Sixty percent of children born
died unmarried,

39:46.090 --> 39:49.480
and among the married one-ninth
of marriages were sterile,

39:49.480 --> 39:53.710
and just 11% of the men and 14%
of the women produced half of

39:53.710 --> 39:54.770
the children.

39:54.768 --> 39:59.628
That means those that could
reproduce and were married and

39:59.632 --> 40:03.472
had to really have very,
very high birthrates,

40:03.472 --> 40:05.182
as late as 1912.

40:05.179 --> 40:11.219
China, as late as 1930,
had a nearly aboriginal birth

40:11.224 --> 40:13.204
and death rate.

40:13.199 --> 40:17.089
The total fertility level was
at these levels of six,

40:17.094 --> 40:21.144
seven, eight children per
woman, yet the population was

40:21.141 --> 40:24.601
not increasing,
which means the death rate was

40:24.597 --> 40:28.317
just as high and they were in
this kind of a situation for

40:28.315 --> 40:29.355
reproduction.

40:29.360 --> 40:33.220
We're going to talk a lot about
China later of course.

40:33.219 --> 40:37.459
At that death rate,
and this is data for China,

40:37.460 --> 40:41.230
in order to have a 50%
certainty--so as you know many

40:41.230 --> 40:43.640
cultures,
and Chinese included in

40:43.635 --> 40:47.985
traditional times,
for sure wanted at least one

40:47.989 --> 40:49.929
child to survive.

40:49.929 --> 40:53.879
They do a calculation at this
death rate how many children is

40:53.880 --> 40:57.830
the minimum you have to have to
give yourself a 50% chance of

40:57.831 --> 41:01.161
having one son survive;
five children.

41:01.159 --> 41:04.969
If you're not thinking of
reproducing the population,

41:04.969 --> 41:08.169
but just reproducing your own
family which is the way

41:08.172 --> 41:12.362
individual families think,
and they have to have a son and

41:12.360 --> 41:16.650
you have this mortality rate,
at five children you have a 50%

41:16.650 --> 41:17.140
chance.

41:17.139 --> 41:19.839
If you want to have an 80%
chance of something you're back

41:19.838 --> 41:23.058
up to eight,
nine, ten children which

41:23.059 --> 41:26.389
explains the desire--
not necessarily--they don't

41:26.394 --> 41:28.894
necessarily keep this birth rate
but the desire for these very,

41:28.889 --> 41:31.679
very high birth rates.

41:31.679 --> 41:35.929
The result is that in most
pre-modern societies,

41:35.929 --> 41:40.359
women spend their whole
post-pubertal lives either

41:40.358 --> 41:42.708
pregnant or lactating.

41:42.710 --> 41:47.010
There's basically never a time
when they're free of the

41:47.012 --> 41:50.042
biological aspects of
childbearing,

41:50.039 --> 41:55.129
not counting the children that
are now not breastfeeding

41:55.134 --> 41:58.844
anymore that Bonnie was talking
about.

41:58.840 --> 42:01.580
For instance,
in Bangladesh in the 1990s,

42:01.583 --> 42:05.703
we're coming up very--75% of
the women in the age group of 20

42:05.701 --> 42:08.721
to 39 were either pregnant or
lactating.

42:08.719 --> 42:10.889
That means four out of every
five women were,

42:10.889 --> 42:12.689
at that moment,
any moment that you look,

42:12.690 --> 42:15.050
they're either pregnant or
breastfeeding,

42:15.050 --> 42:19.620
and there's a small period in
which they rest and then it

42:19.617 --> 42:21.247
starts over again.

42:21.250 --> 42:25.700
We're not talking--in the need
for these very high birth rates,

42:25.699 --> 42:29.059
we're not just talking about
primitive tribes by any means,

42:29.059 --> 42:33.179
we're talking about the period
in which all the world's great

42:33.182 --> 42:34.972
civilizations developed.

42:34.969 --> 42:38.719
Civilization--one of the things
that civilizations had to do was

42:38.715 --> 42:40.615
insure a birth rate like this.

42:40.619 --> 42:45.149
In the period in which cultures
were learning to write and

42:45.148 --> 42:49.878
producing a classic literature,
and developing the great world

42:49.878 --> 42:52.928
religions,
all of these if you read

42:52.929 --> 42:58.339
through them are calculated in
some sense to keep fertility

42:58.342 --> 42:59.092
high.

42:59.090 --> 43:03.230
All of these things glorify
high fertility.

43:03.230 --> 43:09.510
The religious doctrines push it;
there's community sanctions;

43:09.510 --> 43:12.860
the cultures just developed in
a way that--

43:12.860 --> 43:15.680
in order to increase fertility
and any culture that doesn't do

43:15.679 --> 43:17.759
that and doesn't increase it
successfully,

43:17.760 --> 43:19.240
they're just not here anymore.

43:19.239 --> 43:22.109
Of course most cultures that
you read about are not here

43:22.105 --> 43:24.185
anymore, and they were not
successful.

43:24.190 --> 43:28.930
In our Western culture,
the most famous of these things

43:28.927 --> 43:34.717
is the First Commandment in the
Bible: be fruitful and multiply.

43:34.719 --> 43:37.889
Well that fits us,
if you didn't do that then the

43:37.891 --> 43:41.131
Hebrews would be gone,
and we wouldn't have any of

43:41.128 --> 43:44.298
what we currently have in terms
of religion;

43:44.300 --> 43:46.340
any kind of the monotheistic
religions.

43:46.340 --> 43:50.780
There's all kinds--you look at
the culture--the religious

43:50.780 --> 43:55.060
tradition of any culture,
you'll find all kinds of laws

43:55.061 --> 43:57.521
about regulating sexuality.

43:57.518 --> 44:01.268
Now, Yale students don't know
much about the Bible--

44:01.268 --> 44:04.548
how many of you know--you know
masturbation is supposed to a

44:04.547 --> 44:07.287
bad thing,
do you know what the Bible is

44:07.293 --> 44:09.183
supposed to prohibit that?

44:09.179 --> 44:14.639
Student:  Story of Onan
spilling his seed.

44:14.639 --> 44:17.889
Prof: Yes,
so it's the story Onan spilling

44:17.885 --> 44:22.005
his seed, and do you know why he
was spilling his seed or what

44:22.010 --> 44:23.430
the situation is?

44:23.429 --> 44:25.239
Student:  There's
different versions,

44:25.242 --> 44:27.612
one is that he was having sex
with his brother's wife and

44:27.605 --> 44:29.035
didn't want to impregnate her.

44:29.039 --> 44:31.479
Prof: Why was he
having--so she said he was

44:31.478 --> 44:34.068
having sex with his brother's
wife and didn't want to

44:34.067 --> 44:35.807
impregnate her;
that's correct.

44:35.809 --> 44:37.799
Student:  Well he was
doing it because his brother had

44:37.802 --> 44:39.492
passed away,
and according to the Levirate

44:39.489 --> 44:41.649
marriage tradition,
he was then supposed to do it,

44:41.654 --> 44:43.224
in order to have a kid that
would--

44:43.219 --> 44:45.289
have his brother's kid,
but he didn't want to have a

44:45.286 --> 44:47.106
kid that would count as the
brother's kid,

44:47.110 --> 44:48.950
he wanted his kid to count as
his kid,

44:48.949 --> 44:51.389
so he would always pull out and
spill his seed on the ground,

44:51.389 --> 44:54.379
and God said that's immoral and
struck him dead.

44:54.380 --> 44:57.860
Prof: Right,
exactly correct.

44:57.860 --> 45:00.930
I have to repeat this for the
camera.

45:00.929 --> 45:03.789
The situation--it's a very
short passage,

45:03.789 --> 45:07.679
a very interesting passage,
and it's giving out various

45:07.681 --> 45:10.351
moral--
it's in a section giving out

45:10.351 --> 45:12.401
moral laws,
and it says,

45:12.402 --> 45:16.392
'someone had sons and one of
them was Ur,

45:16.389 --> 45:18.409
and Ur was married,
and Ur died.'

45:18.409 --> 45:20.469
It doesn't say much about Ur
except that he died.

45:20.469 --> 45:22.049
Onan was the next brother.

45:22.050 --> 45:27.340
Repeated in the Old Testament
many times is that if a man's

45:27.338 --> 45:32.528
brother dies he has the moral
obligation to inseminate the

45:32.534 --> 45:36.734
sister--
the sister-in-law--in order to

45:36.731 --> 45:40.561
secure an heir for the dead
brother.

45:40.559 --> 45:44.809
That if he fathers a child with
his sister-in-law then that is

45:44.809 --> 45:48.519
not considered his child,
it is considered the dead

45:48.521 --> 45:50.931
brother's child,
and that's one of these

45:50.929 --> 45:54.049
important things of carrying on
the family lines which is one of

45:54.054 --> 45:56.934
the ways of course insures a
high population birthrate.

45:56.929 --> 46:02.139
This is a way of keeping women,
whether they're married or not,

46:02.139 --> 46:03.939
whether their husband is dead
or not,

46:03.940 --> 46:06.850
you've got to keep them
reproducing or the culture

46:06.847 --> 46:07.617
disappears.

46:07.619 --> 46:11.339
Why doesn't Ur want to do--why
doesn't Onan want to do this?

46:11.340 --> 46:15.940
Well he may or may--it's not
his kid so it was born--

46:15.940 --> 46:19.750
there's none of this sort of
power and authority,

46:19.750 --> 46:22.390
and macho stature to come with
having a lot of kids because

46:22.393 --> 46:24.623
it's the brother's kid,
in the culture it was the

46:24.621 --> 46:27.051
brother's kid,
but on top of that he would

46:27.052 --> 46:28.752
have to support this kid.

46:28.750 --> 46:31.200
Economically he would have to
support not only the wife but

46:31.195 --> 46:33.605
the kid,
and he didn't want to have to

46:33.612 --> 46:37.512
support kids that weren't his,
so he engaged in the sex act

46:37.514 --> 46:40.134
because that was the fun part of
it and--

46:40.130 --> 46:44.290
but at the last minute he pulls
out and spills his seed upon the

46:44.286 --> 46:44.876
ground.

46:44.880 --> 46:48.450
Then the Bible passage is very
curt, it doesn't say more--and

46:48.449 --> 46:49.759
then God killed him.

46:49.760 --> 46:52.360
There's not a lot of
explanation for this.

46:52.360 --> 46:55.070
It's repeated,
this particular law called the

46:55.072 --> 46:57.912
levirate laws,
as a student said is repeated

46:57.905 --> 47:00.605
in several places in the Bible
and it's very,

47:00.614 --> 47:03.144
very clear that people didn't
do this.

47:03.139 --> 47:06.459
People did not insem--did not
want to inseminate their

47:06.456 --> 47:10.396
brother's wives because of these
reasons and so whenever you see

47:10.400 --> 47:13.660
a law sort of demanding
something over and over again

47:13.657 --> 47:17.217
you know people weren't doing it
and that's why the law is

47:17.224 --> 47:18.544
demanding it.

47:18.539 --> 47:24.409
That's just one example of how
religion gets involved in

47:24.413 --> 47:28.433
enforcing fertility,
and in this particular example,

47:28.434 --> 47:31.514
it's one of the mechanisms for
keeping every woman pregnant as

47:31.514 --> 47:35.624
much of the time as possible,
independent of her state of

47:35.623 --> 47:36.533
marriage.

47:36.530 --> 47:42.850
The--anybody know why the
Muslims took to polygamy?

47:42.849 --> 47:48.069
Why Mohammed allowed four wives;
no Muslims in the class?

47:48.070 --> 47:49.020
Student:  To free women
from slavery.

47:49.019 --> 47:51.749
Prof: What?

47:51.750 --> 47:53.740
Student:  To free women
from slavery.

47:53.739 --> 47:57.149
Married women--that's the
version that I remember.

47:57.150 --> 47:57.970
Prof: No.

47:57.972 --> 48:00.802
The standard version is they
were going through a lot of

48:00.797 --> 48:01.207
wars.

48:01.210 --> 48:03.100
The Muslims were conquering the
whole world, they were

48:03.101 --> 48:04.851
constantly at war,
the men were getting killed.

48:04.849 --> 48:08.439
There weren't enough men,
so what do you do with the

48:08.443 --> 48:09.433
other women?

48:09.429 --> 48:11.869
They--I mean many reasons but
one of--

48:11.869 --> 48:15.309
they need support and so it's a
beneficial thing,

48:15.309 --> 48:18.019
but their society needed more
men, more children,

48:18.018 --> 48:20.988
so let them get married
multiply.

48:20.989 --> 48:24.079
You just--whatever religion you
want to look at you'll find

48:24.077 --> 48:25.567
similar kinds of examples.

48:25.570 --> 48:33.070
When we get to family planning
issues later on,

48:33.070 --> 48:36.140
how people controlled their
reproduction,

48:36.139 --> 48:38.609
one of the major beliefs that
the early--

48:38.610 --> 48:41.060
we don't really know again,
but in the West was that the

48:41.059 --> 48:43.509
mechanism people used was
coitus interruptus,

48:43.510 --> 48:45.290
because it was the only thing
they knew about.

48:45.289 --> 48:47.229
It's in the Bible,
it tells you what you do,

48:47.230 --> 48:51.750
it tells you the result of it,
and so that Onan passage is

48:51.753 --> 48:55.643
currently interpreted to say
that masturbation and

48:55.641 --> 48:58.431
contraception,
all kinds of things are bad,

48:58.432 --> 49:00.912
when in fact the passage has
nothing to do with that.

49:00.909 --> 49:03.879
That's not what that passage is
about but that's what it's used

49:03.876 --> 49:06.746
for today, but it's been used
absolutely for the opposite.

49:06.750 --> 49:09.930
People use this,
oh that's how I can avoid

49:09.929 --> 49:13.729
having children and so
it's--culture twists itself

49:13.731 --> 49:16.991
about and has unexpected
consequences.

49:16.989 --> 49:23.419
Okay, so I've been stressing
for you that culture pushes up

49:23.423 --> 49:27.643
fertility and up to this high
limit.

49:27.639 --> 49:32.179
What is the limit of human
fertility?

49:32.179 --> 49:34.409
We have to evaluate that.

49:34.409 --> 49:38.149
There's a very famous
calculation of this and it's set

49:38.146 --> 49:41.316
by the number of years a woman
is fertile,

49:41.320 --> 49:44.180
which is generally 15 to 45
more or less,

49:44.179 --> 49:45.859
it can be a little bit younger,
occasionally a little bit

49:45.860 --> 49:50.540
older,
but they usually consider 30 or

49:50.538 --> 49:53.808
so years of fertility.

49:53.809 --> 49:57.289
At that--well if she gets
pregnant, she's pregnant for

49:57.289 --> 49:58.209
nine months.

49:58.210 --> 50:02.730
Ovulation rarely starts again
before at least three months,

50:02.730 --> 50:08.460
if she's lactating and
therefore going through--

50:08.460 --> 50:12.100
not ovulating again,
there's going to be more

50:12.103 --> 50:12.853
months.

50:12.849 --> 50:16.709
If a woman has sexual
intercourse it takes an average

50:16.710 --> 50:19.160
of five cycles to get pregnant.

50:19.159 --> 50:21.899
When we talk about abortion
we'll talk about why that is,

50:21.900 --> 50:24.400
but if a woman's having normal
sex trying to get pregnant,

50:24.400 --> 50:28.130
the average is five months
before she actually does get

50:28.126 --> 50:31.366
pregnant and we'll see where
that comes from.

50:31.369 --> 50:35.149
If the child dies,
fetal mortality introduces a

50:35.148 --> 50:39.178
month there--
anyway you add all of this up

50:39.184 --> 50:44.154
and you get 18 months that--
pretty much the maximum that

50:44.152 --> 50:48.712
human females can do is 18
months or one and a half years.

50:48.710 --> 50:50.980
Dividing--what they usually do
is choose 20--

50:50.980 --> 50:53.530
any particular woman will
probably be fertile for 25

50:53.530 --> 50:56.040
years,
divide that by 18 months,

50:56.038 --> 51:00.648
and you get a theoretical
possibility of 16.7 children.

51:00.650 --> 51:05.410
Now how many of you know
somebody's who has had more than

51:05.405 --> 51:05.995
that?

51:06.000 --> 51:10.420
What's the maximum number of
children you know about?

51:10.420 --> 51:11.980
Student:  I know someone
with 18 children.

51:11.980 --> 51:14.820
Prof: Eighteen;
I'm bid 18.

51:14.820 --> 51:16.610
Only one in the class?

51:16.610 --> 51:19.150
Student:  I think the
world record for a woman is

51:19.152 --> 51:21.512
somewhere--it's really high,
much higher than 18.

51:21.510 --> 51:24.240
I thought it was like in the
60s.

51:24.239 --> 51:25.449
Prof: Oh, no not 60.

51:25.449 --> 51:28.509
That's really crazy unless
there's some crazy multiple

51:28.507 --> 51:28.967
birth.

51:28.969 --> 51:32.859
Now with modern drugs sometimes
there's multiple,

51:32.856 --> 51:33.906
but not 60.

51:33.909 --> 51:36.699
This is an unusual class,
but as time goes on,

51:36.699 --> 51:39.739
families get smaller and people
don't remember.

51:39.739 --> 51:43.769
The maximum I got out of this
class was 24 children.

51:43.768 --> 51:46.438
I think it was a Chinese
student, I don't totally

51:46.442 --> 51:48.912
remember,
and that 24 was only two sets

51:48.907 --> 51:51.197
of twins,
so there were 22 separate

51:51.199 --> 51:55.049
successful pregnancies,
two of which produce twins,

51:55.048 --> 51:58.388
24 children,
one woman.

51:58.389 --> 52:02.869
Even--forget this--independent
of this calculation which I've

52:02.871 --> 52:05.861
just sort of sketched for you at
the--

52:05.860 --> 52:09.140
even before the calculation was
done and the person who did the

52:09.137 --> 52:13.767
calculation knew about it--
this is not--here is

52:13.771 --> 52:22.921
the--Norway in an earlier set of
women which is this set,

52:22.920 --> 52:25.690
and a later set of women,
and this is the number of

52:25.688 --> 52:29.518
children that the women have,
and the percentage--the per

52:29.516 --> 52:32.406
1,000 of women that have that
number.

52:32.409 --> 52:40.119
In the late 1880s the most
common number from Norway--

52:40.119 --> 52:43.299
again we're talking Norway
1890, we're not talking about

52:43.298 --> 52:46.868
anything very primitive,
is 10 children.

52:46.869 --> 52:51.509
The mode for Norway was 10
children and it goes out to 18,

52:51.512 --> 52:55.262
which was the record that
someone here knew.

52:55.260 --> 52:57.680
There were--of course if you
had a bigger assembly you get an

52:57.679 --> 52:58.929
occasional of something more.

52:58.929 --> 53:01.879
Student:  The world's
record it's 69 children.

53:01.880 --> 53:02.900
Prof: What does it say?

53:02.900 --> 53:06.210
Good for him--what--that's
something special;

53:06.210 --> 53:07.890
does it say anything about it?

53:07.889 --> 53:09.959
Student:  She has--
Student:  Sixteen sets

53:09.958 --> 53:12.118
of twins, seven sets of
triplets, and four sets of

53:12.117 --> 53:12.777
quadruplets.

53:12.780 --> 53:16.330
Prof: Okay so it
was--what was the total number

53:16.333 --> 53:18.483
of--yeah so--okay I was wrong.

53:18.480 --> 53:24.890
Send me--both of you send me
the reference for that because

53:24.887 --> 53:27.537
next year I'll use it.

53:27.539 --> 53:29.759
Now, just as long as I've got
this slide up there,

53:29.755 --> 53:30.655
look what changes.

53:30.659 --> 53:35.369
We go from 40 years later,
not a huge fraction of time;

53:35.369 --> 53:38.129
we're going to talk about this
later in the class.

53:38.130 --> 53:41.940
It goes from the mode being 10
children to the mode being 2

53:41.936 --> 53:42.656
children.

53:42.659 --> 53:47.409
Something drastic happens in
between these two in 40 years,

53:47.407 --> 53:50.107
and this is common over Europe.

53:50.110 --> 53:53.200
This is just one data set and
we're going to talk about that a

53:53.204 --> 53:54.274
since it's up here.

53:54.268 --> 53:57.788
In this period of time that
we're talking about women had

53:57.793 --> 54:01.393
this very un--
in the mode there's a very

54:01.385 --> 54:06.555
large number of children and
they far exceeded what's

54:06.556 --> 54:09.436
calculated as the maximum.

54:09.440 --> 54:13.110
Let's see okay,
the answer is that the

54:13.112 --> 54:16.292
biological limit is very high.

54:16.289 --> 54:22.059
I'll say 24,
you say 69, and we have to read

54:22.063 --> 54:23.813
that stuff.

54:23.809 --> 54:27.349
In a human population,
and continuing for any length

54:27.353 --> 54:30.693
of time, the highest
well-documented fertility is

54:30.690 --> 54:33.470
that of the Hutterites in the
1920s.

54:33.469 --> 54:35.379
Anybody hear of Hutterites?

54:35.380 --> 54:37.660
It's a Christian religious sect
that are an--

54:37.659 --> 54:42.339
what's called an anabaptist
sect that originated in Europe,

54:42.340 --> 54:45.640
migrates here,
they're in the upper mid-West

54:45.635 --> 54:49.385
in North Dakota and going on
over into Canada,

54:49.389 --> 54:54.609
and they're very successful in
both economic ways and in

54:54.610 --> 54:56.320
population ways.

54:56.320 --> 54:59.580
They marry fairly early,
not extremely early but fairly

54:59.577 --> 55:00.057
early.

55:00.059 --> 55:02.529
They have a good diet,
they're farmers and very

55:02.525 --> 55:04.935
productive farmers,
and they have good medical

55:04.936 --> 55:05.416
care.

55:05.420 --> 55:09.740
They engage in sex regularly;
they're supposed too,

55:09.735 --> 55:14.455
and their religion forbids
contraception or abortion.

55:14.460 --> 55:16.350
Not only do they have--they
obey these rules.

55:16.349 --> 55:20.409
Many people have those rules in
the books but this is a very

55:20.409 --> 55:23.299
religious group and they obey
the rules.

55:23.300 --> 55:26.980
Their, what we call total
fertility rate,

55:26.980 --> 55:30.990
which at this moment you can
consider the average number of

55:30.994 --> 55:34.874
children that a woman in that
society would have was 12.4

55:34.869 --> 55:35.769
children.

55:35.768 --> 55:39.348
Nothing--that's high--you think
that's high, I saw someone

55:39.346 --> 55:42.856
blanch here, as an average,
but nothing like the 24 or 60

55:42.860 --> 55:44.680
that we're talking about.

55:44.679 --> 55:48.139
This is the highest human
population that we have

55:48.139 --> 55:52.179
documented, can have that,
and it's nowhere near any kind

55:52.175 --> 55:54.405
of calculation for a limit.

55:54.409 --> 55:57.889
The most usual limit,
and you see a lot of cultures

55:57.889 --> 56:01.369
in at least some part of the
history where the--

56:01.369 --> 56:06.449
eight is current cultures were
or historical cultures where

56:06.447 --> 56:09.947
eight is kind of a maintained
average.

56:09.949 --> 56:11.589
In the colonial United States,
for instance,

56:11.590 --> 56:15.280
for a short time when the
frontier was wide open they had

56:15.282 --> 56:18.452
a fertility rate of eight
children per women,

56:18.449 --> 56:23.019
but as soon as the frontier
would close in a region the

56:23.019 --> 56:25.389
fertility rate would drop.

56:25.389 --> 56:27.729
It's clearly land availability
had something to do with it.

56:27.730 --> 56:29.730
There's good data for
Massachusetts,

56:29.728 --> 56:32.468
Concord Massachusetts,
very good demographic data

56:32.469 --> 56:33.039
there.

56:33.039 --> 56:35.879
People had these high birth
rates until the frontier closed.

56:35.880 --> 56:39.800
What did the frontier mean in
1600s in Massachusetts?

56:39.800 --> 56:42.670
It meant like Springfield,
these were people living in

56:42.670 --> 56:44.030
Plymouth,
and Concord,

56:44.032 --> 56:46.532
and Lexington,
right near the coast and the

56:46.527 --> 56:49.847
frontier was Springfield,
and as soon as--if they had a

56:49.847 --> 56:52.697
lot of children,
the children would have to move

56:52.702 --> 56:56.432
out to Springfield or somewhere
which is 100 miles or something

56:56.425 --> 56:59.185
like that and that was beyond
the frontier.

56:59.190 --> 57:03.070
As soon as the children had to
move more than a day's horse

57:03.074 --> 57:05.624
ride away the fertility rate
drops,

57:05.619 --> 57:07.419
so there's something about
having the support of your

57:07.422 --> 57:09.362
children,
really having a group that

57:09.364 --> 57:10.834
increases the fertility.

57:10.829 --> 57:14.329
As soon as the children will
have to disperse and not anymore

57:14.331 --> 57:16.491
be of some sort of support to
you,

57:16.489 --> 57:20.799
or some part of your group,
fertility comes back down.

57:20.800 --> 57:27.140
No society really has ever come
close to the biological limit.

57:27.139 --> 57:31.149
Before we talked about how
culture pushes up the birth

57:31.153 --> 57:33.653
rate,
but now we see that something

57:33.648 --> 57:37.698
is pushing down the birth rate,
that we're coming to an

57:37.704 --> 57:39.364
intermediate level.

57:39.360 --> 57:44.840
What's going on is again fairly
straightforward and simple.

57:44.840 --> 57:52.240
That it was this slide that I
want--here is again fairly

57:52.237 --> 57:54.117
recent data.

57:54.119 --> 57:58.069
Chinese women interviewed in
1981, but referring to their

57:58.072 --> 58:02.172
pregnancies which had been
sometime in the past and it says

58:02.166 --> 58:06.466
it tried to gather data on what
was the birth interval of your

58:06.472 --> 58:09.652
children and how many of them
survived?

58:09.650 --> 58:13.920
If the birth interval was less
than two years 45% of the

58:13.918 --> 58:15.158
children died.

58:15.159 --> 58:20.779
If it was between two and three
years, 34% of the children died.

58:20.780 --> 58:26.340
If it was more than three
years, only 19% of the children

58:26.335 --> 58:27.025
died.

58:27.030 --> 58:31.160
In every culture and every time
and place where we have data

58:31.164 --> 58:35.234
like this it's very clear that
if the birth interval is too

58:35.228 --> 58:38.818
small,
the children just don't survive.

58:38.820 --> 58:44.390
What's going on with pushing
down the fertility rate is that

58:44.393 --> 58:46.513
it--
especially in situations of

58:46.507 --> 58:48.797
poverty where resources are not
great,

58:48.800 --> 58:51.440
women are not especially
healthy, there's no--

58:51.440 --> 58:56.030
any kind of medicine available,
that if the child does not get

58:56.032 --> 58:59.312
a lot of resources,
which a large case is milk from

58:59.311 --> 59:01.091
the mother is the primary
thing--

59:01.090 --> 59:05.890
in China there's no dairy
products at this time in this

59:05.887 --> 59:07.217
social class.

59:07.219 --> 59:09.879
It's largely food directly from
the mother;

59:09.880 --> 59:12.570
the children are just going to
die.

59:12.570 --> 59:17.120
The reason that fertility is
pushed up from below,

59:17.119 --> 59:22.879
is pushed down is not to reduce
total number of children but to

59:22.876 --> 59:25.936
maximize surviving fertility.

59:25.940 --> 59:28.550
What people aim is not to just
keep popping them out and having

59:28.547 --> 59:29.007
them die.

59:29.010 --> 59:33.950
What people aim at and cultures
have learned to accommodate to

59:33.952 --> 59:36.952
is to maximize surviving
fertility.

59:36.949 --> 59:39.929
Not total fertility,
which is just being born,

59:39.929 --> 59:44.439
but maximizing the number of
children that are going to stay

59:44.440 --> 59:48.030
alive to become adult
reproducing members of the

59:48.032 --> 59:48.952
society.

59:48.949 --> 59:55.639
Now people have many mechanisms
for limiting the birth rate.

59:55.639 --> 1:00:00.879
One that is often quite
conscious is breastfeeding;

1:00:00.880 --> 1:00:03.960
it's a very standard method
across many cultures.

1:00:03.960 --> 1:00:08.320
You've all heard of this,
lactation amenorrhea,

1:00:08.320 --> 1:00:14.300
and many, many cultures don't
leave--

1:00:14.300 --> 1:00:16.560
I mean in our culture a woman
can breastfeed a little bit or

1:00:16.563 --> 1:00:18.163
long,
it's totally up to the

1:00:18.157 --> 1:00:18.857
individual.

1:00:18.860 --> 1:00:22.990
Many cultures are very strict
rules about this.

1:00:22.989 --> 1:00:26.069
You must breastfeed for at
least--and there's a certain

1:00:26.070 --> 1:00:27.040
period of time.

1:00:27.039 --> 1:00:31.699
Among the !Kung of Southwest
Africa, which these people speak

1:00:31.702 --> 1:00:35.512
this click language,
they've got all these--you've

1:00:35.510 --> 1:00:36.910
heard of them.

1:00:36.909 --> 1:00:39.849
Mothers keep the infant with
them at all times,

1:00:39.849 --> 1:00:42.979
they nurse all day,
at intervals separated by only

1:00:42.981 --> 1:00:43.941
15 minutes.

1:00:43.940 --> 1:00:46.870
Bonnie how would you like to
have that all day long?

1:00:46.869 --> 1:00:49.639
Nurse every 15 minutes the
child;

1:00:49.639 --> 1:00:53.209
they sleep next to the mother,
and have access to her breast

1:00:53.211 --> 1:00:56.721
all night long and the nursing
continues until the child is

1:00:56.722 --> 1:00:58.542
more than three years old.

1:00:58.539 --> 1:01:02.049
By that mechanism,
primarily by the lactation

1:01:02.050 --> 1:01:06.920
amenorrhea, the birth interval
among !Kung is four years which

1:01:06.918 --> 1:01:10.108
fits--is beyond this survival
issue.

1:01:10.110 --> 1:01:15.660
This is the kind of--I talked
about Nomads and people that

1:01:15.659 --> 1:01:19.029
have--
fairly conscious--they're

1:01:19.025 --> 1:01:25.125
probably are aware that this is
limiting the births and it's

1:01:25.130 --> 1:01:28.650
something that they want to do.

1:01:28.650 --> 1:01:33.210
When the women go foraging they
carry their children--

1:01:33.210 --> 1:01:35.970
again the !Kung,
they carry their children with

1:01:35.969 --> 1:01:39.569
them until their four years old
and while carrying the infant

1:01:39.570 --> 1:01:42.210
she walks up to 12 miles round
trip to--

1:01:42.210 --> 1:01:46.280
it takes 6 miles to go out and
find some food and come back;

1:01:46.280 --> 1:01:50.060
12 miles round trip and then in
addition to that she carries

1:01:50.059 --> 1:01:51.789
loads of 15 to 35 pounds.

1:01:51.789 --> 1:01:55.469
Here's a woman who--being a
hunter gatherer is probably

1:01:55.465 --> 1:01:59.175
fairly healthy,
she's carrying an infant on her

1:01:59.177 --> 1:02:02.107
back,
walking around 12 miles,

1:02:02.110 --> 1:02:07.050
and coming back with a load of
35 pounds of food.

1:02:07.050 --> 1:02:10.570
It's quite a feat and it's
clear that they can't--

1:02:10.570 --> 1:02:12.260
they're not going to have a
second infant,

1:02:12.260 --> 1:02:14.790
one on the back,
one of the hip,

1:02:14.789 --> 1:02:18.219
this is not a way of improving
survival.

1:02:18.219 --> 1:02:22.529
That's--lactation is one
mechanism.

1:02:22.530 --> 1:02:28.560
There's many taboos on sexual
relations, especially after

1:02:28.557 --> 1:02:29.417
birth.

1:02:29.420 --> 1:02:32.270
In many cultures,
as I said, a prescribed period

1:02:32.271 --> 1:02:33.061
of nursing.

1:02:33.059 --> 1:02:37.319
There's also a post-partum
taboo against having sexual

1:02:37.317 --> 1:02:41.327
relations, and again,
another obvious mechanism for

1:02:41.333 --> 1:02:42.783
birth spacing.

1:02:42.780 --> 1:02:48.090
If you--again this gets to the
degree of consciousness of these

1:02:48.092 --> 1:02:48.952
methods.

1:02:48.949 --> 1:02:52.609
If you ask a member of a
society that has a taboo they

1:02:52.610 --> 1:02:56.690
report for instance that sex at
that time is very dangerous,

1:02:56.686 --> 1:02:58.616
a life and death matter.

1:02:58.619 --> 1:03:01.819
It is dangerous to mix the
man's blood with the woman's,

1:03:01.820 --> 1:03:04.790
and the man's blood is
transmitted through semen.

1:03:04.789 --> 1:03:08.089
It's a bodily fluid and they
don't totally--the biology is

1:03:08.088 --> 1:03:09.128
not very strong.

1:03:09.130 --> 1:03:12.730
Their course at Yale was
terrible--we'll talk a lot

1:03:12.731 --> 1:03:14.841
about--
not a lot--some,

1:03:14.844 --> 1:03:19.334
about what pre--pre-education
people believe about

1:03:19.331 --> 1:03:22.171
reproduction and everything.

1:03:22.170 --> 1:03:28.510
If man's blood gets into the
woman through his semen then it

1:03:28.509 --> 1:03:33.169
also gets into her milk,
and then the man's blood goes

1:03:33.166 --> 1:03:36.916
back into the baby through the
mother's milk and this is poison

1:03:36.920 --> 1:03:37.890
for the baby.

1:03:37.889 --> 1:03:43.959
That's their version of why
they shouldn't--why they have

1:03:43.960 --> 1:03:45.370
this taboo.

1:03:45.369 --> 1:03:47.319
We see this in the evolution of
cultures,

1:03:47.320 --> 1:03:49.100
I mean just as we evolve
biologically,

1:03:49.099 --> 1:03:52.869
of course evolve culturally,
that cultures may--

1:03:52.869 --> 1:03:56.769
will pick up a behavioral
pattern for who knows what

1:03:56.766 --> 1:03:59.166
reason,
and they may have no clue what

1:03:59.172 --> 1:04:01.922
it's 'real' as we see it,
it's 'real' purpose is,

1:04:01.916 --> 1:04:04.996
in this case to space births
apart they have some kind of

1:04:05.003 --> 1:04:08.143
cultural story about it and it
doesn't matter whether that

1:04:08.143 --> 1:04:10.683
cultural story has any degree of
reality.

1:04:10.679 --> 1:04:13.639
If they've picked up a cultural
norm that works,

1:04:13.635 --> 1:04:16.965
the society is still here,
and that gets passed on.

1:04:16.969 --> 1:04:22.779
If that cultural practice does
not work, not only reproduction,

1:04:22.775 --> 1:04:26.705
all sorts of ways,
that society is gone.

1:04:26.710 --> 1:04:31.760
This post-partum abstinence is
a major issue,

1:04:31.760 --> 1:04:34.860
especially in Africa now.

1:04:34.860 --> 1:04:40.170
The abstinence is up to three
years which is--that's sort of

1:04:40.170 --> 1:04:42.780
the mode of this in Africa.

1:04:42.780 --> 1:04:46.890
In addition to limit births,
there's another thing which

1:04:46.889 --> 1:04:50.029
again is a population limitation
issue,

1:04:50.030 --> 1:04:52.100
because we've talked about
individual family limitation

1:04:52.097 --> 1:04:53.897
issues,
trying to keep the kid alive.

1:04:53.900 --> 1:04:58.190
If the village is resource
limited they may have mechanisms

1:04:58.186 --> 1:05:02.766
for keeping the whole population
of the whole village down,

1:05:02.768 --> 1:05:06.098
and so in Africa especially,
they have a thing called

1:05:06.099 --> 1:05:07.509
terminal abstinence.

1:05:07.510 --> 1:05:10.780
That means at a certain point
in life the culture demands that

1:05:10.782 --> 1:05:12.662
you stop having sexual
relations.

1:05:12.659 --> 1:05:16.709
Very often this is when your
daughter has her first child.

1:05:16.710 --> 1:05:19.700
After that you're a
grandmother, and you're not

1:05:19.699 --> 1:05:21.779
supposed to reproduce anymore.

1:05:21.780 --> 1:05:25.110
It's interesting what--to
prevent--they perceive it as

1:05:25.110 --> 1:05:28.880
preventing conflicts between
their duties as mother and their

1:05:28.882 --> 1:05:31.892
duties as grandmother,
so a grandmother is supposed to

1:05:31.891 --> 1:05:33.161
help raise the grandchildren.

1:05:33.159 --> 1:05:36.909
And there's a lot of biological
theory about why do humans,

1:05:36.909 --> 1:05:41.819
somewhat unique among animals,
why don't we just die --

1:05:41.820 --> 1:05:43.550
females especially after their
fertile period,

1:05:43.550 --> 1:05:45.930
there's no reason for you to
evolutionarily stay alive,

1:05:45.929 --> 1:05:49.979
most animals they don't have a
post-menopausal period.

1:05:49.980 --> 1:05:53.930
The theoretical reason is the
grandmother effect,

1:05:53.929 --> 1:05:57.959
that as a grandmother you
support the children of your

1:05:57.956 --> 1:06:00.366
child,
and that increases their

1:06:00.369 --> 1:06:03.469
survival, and so it's
evolutionarily good.

1:06:03.469 --> 1:06:05.649
Here in these tribes in Africa,
are basically saying the same

1:06:05.646 --> 1:06:07.606
thing that if you're a
grandmother you're going to have

1:06:07.605 --> 1:06:09.815
a conflict between taking care
of your own children and taking

1:06:09.818 --> 1:06:11.268
care of your daughter's
children,

1:06:11.268 --> 1:06:16.658
and that conflict is bad so you
have to not engage in sexuality.

1:06:16.659 --> 1:06:19.909
Up to the middle of the 1900s
in Ireland,

1:06:19.909 --> 1:06:22.759
rural Ireland,
people lived in households with

1:06:22.755 --> 1:06:26.165
many members of both sexes and
several generations,

1:06:26.170 --> 1:06:28.530
big multi-family houses.

1:06:28.530 --> 1:06:31.760
The Irish believe that there
should be only one sexually

1:06:31.757 --> 1:06:35.507
active procreative couple in the
household, so they also practice

1:06:35.514 --> 1:06:37.104
grandmother abstinence.

1:06:37.099 --> 1:06:41.529
These cultural items are--they
may seem a little outlandish to

1:06:41.527 --> 1:06:44.937
us in our modern day but they
were effective.

1:06:44.940 --> 1:06:52.510
They kept that society going.

1:06:52.510 --> 1:06:57.720
Another issue is exogamy,
that just like chimpanzees,

1:06:57.719 --> 1:07:01.899
it's again in most animals,
it's the males that disperse,

1:07:01.900 --> 1:07:06.010
but in chimps and humans it's
the females that disperse.

1:07:06.010 --> 1:07:10.080
The females leave the community
at birth,

1:07:10.079 --> 1:07:13.699
to go live with the man's
family, and so she's under the

1:07:13.697 --> 1:07:17.157
control then,
in many cultures basically a

1:07:17.159 --> 1:07:22.269
slave to the son's family,
and the reproductive rules are

1:07:22.266 --> 1:07:27.746
then set by the son's family and
she has no choice in this and

1:07:27.751 --> 1:07:32.361
we'll talk about that extra--
this out marrying--remember

1:07:32.358 --> 1:07:36.008
with chimpanzees they were
hostile to the neighbors around

1:07:36.010 --> 1:07:38.640
us,
human societies are that same

1:07:38.643 --> 1:07:39.023
way.

1:07:39.018 --> 1:07:44.588
The professor in the lab next
to me is from China,

1:07:44.590 --> 1:07:47.780
a village near Shanghai,
and he describes this to me in

1:07:47.777 --> 1:07:49.327
China,
and he says my village,

1:07:49.331 --> 1:07:51.021
which have all the same name as
him,

1:07:51.018 --> 1:07:54.358
it's all a male bonded,
the males have been there

1:07:54.355 --> 1:07:56.545
forever,
they all have the same last

1:07:56.554 --> 1:07:59.754
name--they're hostile to all the
villages around them so they

1:07:59.746 --> 1:08:01.816
won't marry the village around
them.

1:08:01.820 --> 1:08:06.150
To get married they have to go
two villages away and they're

1:08:06.148 --> 1:08:07.908
still sort of enemies.

1:08:07.909 --> 1:08:10.409
In New Guinea where all over
the world that's the same

1:08:10.409 --> 1:08:11.929
problem,
you're fighting with your

1:08:11.929 --> 1:08:13.699
neighbors,
and yet you have to get wives

1:08:13.695 --> 1:08:16.905
from somewhere,
you have to exchange genetic

1:08:16.912 --> 1:08:20.272
material,
otherwise you get inbreeding

1:08:20.271 --> 1:08:25.311
and so the Mae Enga they say in
New Guinea that we marry our

1:08:25.313 --> 1:08:27.663
enemies and--
this is a great story.

1:08:27.659 --> 1:08:30.749
Time is up;
I will continue this story next

1:08:30.747 --> 1:08:31.217
time.

1:08:31.220 --> 1:08:36.000