Prof: Now I've been
describing the intimate
relationship between sex and
violence within the chimpanzee
social system.
 
This lecture,
and forever after,
we shift our focus to humans,
and we want to ask what's
stayed pretty much the same and
what has changed.
Today I'm going to discuss two
topics, one: war in humans which
hasn't changed all that much,
you can certainly see a
continuity.
 
Then I'm going to talk about
fecundity in humans,
how many children we bear
compared to chimpanzees and
you'll see there's a very big
difference there.
The most obvious similarity and
one that gets the public quite
excited is the similarity in--
 
violent death has always been
very important aspect for humans
especially--
well all the time,
but I'm going to talk now about
what's called 'primitive times,'
and this is data from a tribe
that's in Paraguay in South
America in the period just
before it had real contact with
Western people.
 
So it has nothing to do with
modernity;
this is apparently the way they
lived for time immemorial.
What this table does is list
the number of deaths by age,
putting them in different age
groups.
Here are just children or we
would call them infants almost,
0 to 3 years.
 
You can notice there's a
significant amount of death;
this is all illnesses;
that's communicable diseases
and all kinds of other diseases;
that's the percentage of deaths
from that,
and then there's other causes:
congenital, degenerative,
accidents some,
but here's violence--
various forms of violence.
56% of infants from 0 to 3 died
because of violence.
Here is children age 4 to 14
and again we see that all
illnesses, about 15%,
accidents.
Violence 74%.
 
Now adults during--this is a 45
year period, the number of years
in the periods are not equal,
and here is illness 28%,
not insignificant;
accident, not insignificant,
but the various forms of
violent deaths:
46%, and it's only when you get
over 60 years of age--
so in each of those three age
categories violent deaths have
been the dominant form of death.
 
It's separated by males and
females, males/females total,
and that's true for males and
for females, I'm showing you the
sum totals.
 
It's only even after age 60
violent death is still the
dominant cause,
a third of deaths,
but it's the only age at which
it isn't --
at least half of the deaths,
only when you get that old.
It's quite striking how
significant violent death is in
human demography.
 
Several things should be
noticed there,
that communicable diseases are
less important for
hunter/gatherers;
these are very primitive
hunter/gatherers,
the Ache.
One of your readings is from
their own description of the way
they live and the dangers that
they face--
that communicable diseases are
less important because the
population density is so low.
 
Later we'll see--and so
diseases just don't get to pass
around.
 
We'll see later that the
influence of diseases rises
drastically,
especially among infants,
when the population density
gets high enough so that people
pass around--
disease is quite common.
Another thing you may notice
from this,
that more individuals die in
the first 3 years of infancy,
131 deaths than in the 45 years
of adulthood 126 deaths.
So deaths in infancy are
50--per year are 15 times as
common as deaths in adulthood.
 
Of 383 people who are cataloged
here, only seven people died of
old age.
 
All of them had other really
identifiable causes.
Given this background of the
significance of violence,
and this includes more than
just war,
but does not include deaths
from animals--
being eaten by animals which is
considered an accident.
Defining war,
going back to--we talked a lot
about chimp--
you might call chimp war and
now talk about human wars,
let's take a definition of war
as the intentional killing of
members of one group by members
of another group.
 
The killing is done because
they are members of a group not
because of any prior or
particular conflict between
individuals.
 
It's a group thing that
determines that the two sides
that they're going to kill each
other.
The human social system in
primitive times and in some
politically correct circles,
you're not supposed to use the
word 'primitive,' but I use it
in its original sense of living
closer to the way humans did
millions-- thousands--many
thousands or millions of years
ago.
It's an early form of being
human.
During that time we lived in
small tribal groups and they're
multi-male groups,
(again we talked about most
mammal's solitary males) with
strong male bonding,
competition for status,
lots of inter-group conflict,
competition for females and
violence against females.
Everything that we know says
that humans have lived in
communities with those
characteristics since as far
back as we can --
know, and that is the same
description you would apply to
chimpanzees.
The archeological data shows
that through early farming times
we lived in these small
dispersed settlements,
and the average size seemed to
be in the same range as current
chimpanzees, about 40
individuals.
Size of communities range but
when you dig up these--the
archeologists dig up these old
settlement they're in that
ballpark.
 
The anthropologists studying
currently alive people again
find that the smallest organized
group of humans is a politically
autonomous group consisting of
20 to 50 individuals with a head
man.
 
They call this--the proper
anthropological term is a band,
again, basically the same size
as a chimp community.
Among chimpanzees,
as I've described to you,
inter-group violence is a
hit-and-run affair.
With a small group of chimps
from one community,
patrol their boundary;
they detect an isolated
individual, a very small group,
or even better,
a single individual in another
community, and then they attack.
Anthropologists tell us that
primitive warfare has exactly
the same characteristics.
 
Among current primitive groups
the commonest form of combat is
called raids and ambushes,
and communities are constantly
engaging in this hit and run--
these hit and run raids on each
other and they spring ambushes
to catch lone members of the
other group.
 
I lived for a while among
headhunters in Borneo.
Presumably they weren't
headhunters anymore at that
time,
and it was perfectly acceptable
for them to go out and find a
child from a neighboring
community--
same tribe, same everything,
but the neighboring community--
playing by the river,
catch him and take off his
skull and they had their
attics--
were decorated with skulls.
None of this was big--that
whole community fighting that
whole community,
but little raids finding
individuals,
didn't matter if it was child,
adult,
nothing mattered like that.
You can draw many similarities
between the chimp organization
of this lethal raiding and human
warfare.
How does one think about this?
 
Well there are two
possibilities.
Either whatever you think of
the chimp warfare and the causes
of it you have to think that a
lot of that is still causing
human warfare,
or you can say as many utopians
do,
that they're different.
That human--human warfare has
nothing to do with chimp
warfare.
 
One of the ways to prove or
disprove that would be to look
in history,
as far as we can tell,
and if it has different causes,
what you have to assume is,
we know for sure that this is
what chimps do,
and we presume that their
ancestors some millions of years
ago before we split--
did that, but we don't really
know that,
but we presume it's true that
chimps did that and then
sometime in human history we
have to find a period where we
stopped doing it.
Then at a later period we
started doing it again but now
for a totally different set of
reasons than for the chimp
reasons.
 
The strategy of trying to
figure out this question is then
to go back in history and gather
the archaeological and the
anthropological--
whatever data we can gather,
and try to find out:
has there been a period in
human history where we were
not--
did not have this
inter-communal violence.
The people who believe that war
has different causes --
they think agriculture started
it because land becomes valuable
or private property of some
sort,
people wanted to get each
other's private property,
or governments,
modern state governments,
or very commonly you'll hear
that it has something to do with
modernity,
that civilization has somehow
corrupted the pure nature of
early humans who were wonderful
human beings and didn't go to
war.
What was the situation for
prehistoric humans?
We can go back to the
Neanderthals,
which are a sister subspecies,
and these guys as you know--
heavy musculature,
robust bones--they were
obviously strong characters.
 
When you take--study their
graveyards, 40% of Neanderthal
skeletons have head injuries.
 
How does one attribute that?
 
Either they were very clumsy
and accident prone and always
somehow managed to fall on their
head--
so far as we know they didn't
climb trees very much and hang
upside down and fall,
or there was a lot of club
wielding and head bashing going
on.
Homo sapiens,
not Neanderthals,
the earliest human burials that
haven't just decayed away are
about 20,000 to 35,000 years ago
and when you dig them up what do
you find?
 
Spear points embedded in the
bones, cranial fractures,
scalping marks,
and so forth.
These burial grounds are found
wherever archeologists look.
Some of the most prominent ones
are Italy, France,
Egypt, Czechoslovakia because
that's where archeologists have
had access to dig.
 
At a 13,000 year old cemetery
in Sudan, over 40% of the
skeletons had spear or arrow
points embedded in them.
The wounds--there were children
buried there--the wounds found
from the children in the
cemetery were all execution
shots in the head or the neck.
 
They were just bashed to death
in the head or the neck.
This was not like one burial
from one horrific incident,
it was used over several
generations.
It was a continuing cemetery,
and many of the adults showed
not only the wounds that caused
their death but many prior
wounds,
bone cracks and skull cracks
that had healed,
so you can see both a wound
from some prior conflict which
had healed and the new wound
which caused the death at this
moment.
Individuals had gotten into a
lot of conflict:
one skeleton had 20 different
wounds.
That means bone cracks that you
could still see 13,000 years
later, and soft tissue injury we
just don't have any way of
knowing about.
 
When you get to modern times,
still prehistoric,
meaning before we have any
written records--
before anything you'd call
civilization--
things get a little stylized,
that clearly culture is
advancing.
 
There's a middle Stone Age cave
in Germany, only 5,000 to 10,000
years old, where there are two
caches of skulls,
just the skulls are there.
 
They're neatly arranged like
eggs in a basket,
and they are the disembodied
heads of men,
women, and children with
multiple heads--
multiple holes not by axes into
their skulls.
I don't have--they didn't show
a picture of that,
but this is a modern version of
it.
This is actually from Thailand;
this is the way skulls can get
arranged.
 
This--that picture has a
totally different kind of
purpose.
 
How many of you remember ice
man?
The guy that got unfrozen from
the Alps;
you're all aware of this.
 
In 1991, one of the glaciers in
the Alps disgorged this Stone
Age man who had died they think
5,300 years ago.
As at least a good number of
you know, he had a lot of press
and he was called the ice man.
 
Since it took 5,300 years for
him to come down the mountain,
he must have died pretty high
up in some high point of the
pass in the mountain,
so it was just assumed that he
died--
froze to death--while trying to
cross the Alps and got encased
in the ice and 5,000 years later
came down.
 
For ten years academic opinion
said that, and then they finally
got around to taking a CAT scan
of the body.
Guess what they found?
 
A two centimeter flint
arrowhead had ripped through his
scapula and lodged six
centimeters deep into his
shoulder.
 
He had been shot from behind by
an arrow and he died of internal
bleeding.
 
Again, a violent death.
 
You come to even more recent
times,
a Native American settlement,
American Indians from about
1325 A.D.,
so almost 200 years before they
have any contact with
westerners,
and this contains the remains
of 500 men, women,
and children.
 
This is not a great picture,
but again,
what you see that these victims
had been scalped,
mutilated, and then something a
little unique,
left exposed for a few months
to scavengers before being
buried,
again, as a form of punishment,
disrespect, or whatever.
 
For the victim you not only
slaughter them,
mutilate them,
maybe mutilate and then
slaughter them,
and then you leave the
scavengers to chew on them and
then finally they get buried.
In short, archeology documents
warfare in every well-studied
region for the past 10,000
years, which is when we have
very good records.
 
That's what you can dig up.
 
The other thing is to look at
currently primitive human beings
and ask how many of them are
truly peaceful.
The anthropologists now take
over from the archeologists.
What the anthropologists find
is that 90% to 95% of known
societies have been involved in
war that we can document.
One sample of 50 societies,
45 engaged in war frequently;
4 did not engage in war because
they had recently been driven
into isolated refuges by
warfare.
Have any of you been to the
Aymara Indians in Lake Titicaca
in Peru?
 
It's a big tourist spot.
 
There's an island in the middle
of Lake Titicaca,
and they're very peaceful
people, they live on reeds,
they don't have anybody to
fight.
They were pushed off the
mainland by war and they've just
been isolated,
so that's one of the groups
that's-- well we haven't seen
them get into any wars but they
have no possibility of it.
 
One which is called 'peaceful,'
the Moonachie,
which live actually in the
Sierra Nevada Mountains of
California they say--
we'll call them peaceful
because they only rarely go to
war.
In another study 66% of
primitive societies went to war
every year,
75% at least every two years,
and up to 90% went to war at
least once every five years,
so the evidence is mounting up
that so called primitive humans
are not a terribly peaceful lot.
 
The Dani tribes of New Guinea
had seven full battles and nine
raids in one five and a half
month period.
Some anthropologists was
sitting there for five and half
months and that's the number
that he counted.
One Yanomamo Village,
that's in Venezuela,
was raided 25 times in 15
months.
In the U.S. West,
86% of the Indian tribes went
raiding or had to resist raids
at least once a year.
Now you come to groups that are
usually peaceful,
so there's a group in Malaysia
called the Semais and they were
recruited so--
but during World War II,
as you know,
the Japanese took Malaysia,
and the British incited a sort
of guerilla movement against the
Japanese;
so they were retained as scouts
by the British to fight.
 
I'm sorry this was later--this
was--they've--they were scouts
to fight the guerilla insurgency
by supposed communists.
Eventually some of the
guerillas killed a few of the
Semais,
a few of their kinsmen,
and then even though they had
never been known to be warlike
they become extremely warlike.
 
One Semai veteran recalled,
"We killed,
killed, killed,
the Malays would rob the
corpses, but we did not want
anything.
We thought only of killing.
 
Wah!
 
Truly we were drunk with
blood."
It sounds like their culture,
like many cultures,
have repressed the killing
instinct,
or killing propensity for one
reason or another,
and then when the cultural
controls came off,
boom, the instinct just roars
up, totally full blown,
almost instantaneously.
 
We've seen that in so many
cases.
In Yugoslavia recently where
people lived together for a very
long time in moderate harmony,
all of a sudden,
bang, they start killing each
other.
The Germans in the 19--before
the Depression in the 1920s--
were among the most civilized
people on earth in science,
and education,
boom, they become savages
almost immediately.
 
I think the indication is
there's something inside of us
ready to pop out.
 
Culture can repress it,
but demagogues know how to
stick their finger into
populations and pull out that
us/them and vilify the
"them"
and bring us right back to
chimpanzee days.
You all know Yale has a center
for study of the Cambodian
genocide,
where now one group of people,
the Cambodians,
sort of split into two and the
slaughter was terrible.
 
How many of you have seen the
movie The Killing Fields?
How many of you know about the
Cambodian genocide?
Again, most of you,
but not all of you;
it's one of the most recent,
most horrific kinds of killing.
This killing is--can be--what
basically happens is that one
group does not consider another
group humans,
and if you look in primitive
languages,
very often the word for human
is the same as the word for
their group whatever their group
is.
In the American Indians that
was also a common kind of
phenomenon.
 
There's a good report from
March 18,1690 in Salmon Falls,
New Hampshire,
where a girl named Mercy Short
lived.
 
They were raided by the Abenaki
Indians;
that was at that time 1690,
a real frontier town.
Mercy saw them kill her parents
and three of her brothers and
sisters.
 
She was taken to--on a long
winter march to Canada,
and the captors sort of dragged
her up to Canada.
During that March she saw a
five year old boy chopped to
bits,
a young girl scalped,
and was forced to watch with
her hands tied as another fellow
captive was stripped,
bound to a stake,
and tortured with fire,
after which the Abenaki
"danced about him and at
every turn,
they did with their knives cut
collops of his flesh,
from his naked limbs,
and throw them with his blood
into his face.
 
Remember this is someone who is
already a captive with his hands
tied so there's no immediate
threat.
It's a clear sign of just not
considering these out-group
individuals as humans.
 
All chimpanzees have one set of
morals toward an in-group,
and as I've told you,
that in the wild the male/male
conflicts never result in death
nor do the male/female conflicts
within a group,
but in an out-group if possible
they always result in death.
 
Now what does one think of this?
 
There's a very interesting
story from early America,
it's actually Amerigo Vespucci,
after whom America is named,
and you know Columbus
discovered America in 1492.
Ten years later they were
exploring all around and
Vespucci went on a--one of the
exploration expeditions along
the coast of South America.
 
He had some interactions with
the local tribe's people and had
some interpreters on board.
 
Columbus had brought some
natives back to Europe,
and they were able to do some
kind of translation.
He was very interested in how
different they were from
Europeans.
 
"Their marriages are not
with one woman but with as many
as they like,
and without much ceremony,
meaning they just get married
very causally and we have known
someone who had ten women
married to him.
They are a very prolific
people, , but they have no heirs
because they hold no
property."
Even childbirth is without
pain, "Women in parturition
do not use any ceremony as ours
do.
They eat everything,
go on the same day to the
fields and wash themselves;
it seems that they hardly feel
their parturition."
 
Parturition--giving birth--now
you can see that what he's
dealing with in the 1500s,
the late renaissance attitude,
political science theory.
 
What is it that causes wars
between societies,
which they had lots of back
then.
One of the issues is original
sin, these are very religious
people, and what was the major
punishment for Eve's eating of
the apple?
 
Pain in childbirth,
severe pain in childbirth;
here were some people that had
no pain in childbirth,
and he waxes poetic about that.
 
Were they absolved of original
sin?
That's the kind of issue that's
in his mind.
He also says,
"They are people who lived
many years,
and according to their
succession, we have known many
men who have four generations
living."
 
So that's about 80 years--what
is he referring to here?
Again, from the Bible;
the span of life,
what's the span of life?
 
70 years, very hard to fit four
generations into that,
so again, he's reflecting that
these are not people like
European people.
 
He goes on with all the wonders
of their civilization,
or their un-civilization
whatever you want to call it.
But, he says,
"They are a warlike
people,
and when they fight they do so
very cruelly,
and that side which is lord of
the battlefield bury their own
dead,
but the enemy dead they cut up
and eat.
One of their men confessed to
me that he had eaten the flesh
of more than 200 bodies."
 
Continuing, Vespucci talking,
"The most astonishing
thing about their wars and
cruelty is that we could find no
reason for them,
since they have no property or
lords,
or kings, or desire for
plunder, or lust to rule,
which seems to me to be the
causes of war and
disorder."
Again straight late renaissance
theory and political science
theory.
 
"When we asked them to
tell us the cause of the war and
disorder they could give no
other reason except that this
war began among them a long time
ago and they wish to avenge the
death of their ancestors."
 
It's a very interesting
passage, the Indians--
Vespucci's idea is that
original sin is what causes this
and then political--
the sins that humans do have
the lust for power,
etc., is what causes all these
wars and none of that fits these
South American Indians.
The same message,
that -- it's not obvious what
the cause of these wars is,
comes from modern anthropology,
so the Yanomamo of Venezuela
and Brazil who are very violent
people,
there was a book called The
Fierce People that describes
them.
They're very, very warlike.
 
They're in that border between
Venezuela and Brazil;
they're involved in almost
constant warfare and yet what
are they after?
 
Yanomamo villages are
surrounded by abundant
unoccupied territory.
 
They're just not settlement,
to settlement,
to settlement,
there's plenty of space in
which they could expand.
 
Napoleon Chagnon,
who you may have heard of,
the anthropologist who studies
the Yanomamo,
believes that the fighting
between them was apparently
motivated only by desires to
exact revenge and capture women.
We seem to have come across
this before,
but again, just as in
chimpanzees, in primitive
warfare females are killed as
often as they are captured and
most of these primitive tribes,
as well as modern people's,
have difficulty getting food,
not as a cause of war but as a
result of war.
 
Things get so disrupted by war,
that's the reason they have
trouble getting food.
 
All of this is archeological
and anthropological,
studying times or peoples who
don't have really any writing
system.
 
So in a sense it's prehistoric.
 
Once we come to writing,
the record of violence flows
hot and heavy.
 
The first account of the
exploits of mortals is our
military histories.
 
The earliest writing of the
Chinese, of the Greeks,
of the Romans,
are concerned with wars and
warrior kings.
 
Most Mayan hieroglyphic texts
are devoted to the genealogies,
biographies,
and military exploits of the
Mayan kings.
 
The earliest Egyptian
hieroglyphics record the
victories of Egypt's first
Pharaoh's.
The first secular literature
written in cuneiform recounts
the adventures of the warrior
king, Gilgamesh.
The early and extreme
warlikeness of the earliest
civilizations is laid out in the
Bible.
You just read the Bible and you
get the whole message I'm giving
you.
 
The earliest written part of
the Old Testament,
Exodus, recounts the brutal
Hebrew conquest of Canaan.
Numbers 31:7-18,
The Israelites get the Ten
Commandments.
 
Thou shalt not kill.
 
And then they go off to conquer
Canaan with lots and lots of
killing.
 
They waged war against the
Midianites as the Lord--
this is one of my favorite
passages: "They waged war
against the Midianites as the
Lord had commanded Moses and
killed every male among them,
but the Israelites kept the
women of the Midianites with
their children as
captives."
 
When Moses learned about this,
the captains came back,
thumped their chests,
we've had a great victory;
we've killed all the men and
here we have the women and
children as captives,
Moses becomes angry:
"So you've spared all the
women,
why they are the very ones who
prompted the unfaithfulness of
the Israelites toward the Lord.
 
Slay therefore every male child
and every woman who has had
intercourse with a man,
but you may spare and keep for
yourselves all girls who have
had no intercourse with a
man."
 
An echo of the chimpanzees who,
when a female tries to transfer
if she has children she's a
goner,
if she's young,
presumably a virgin,
then she will probably be
allowed to transfer.
After the fall of Jericho the
Israelites,
quote, "Put to the sword
all living creatures of the
city,
men, women, young and old,
as well as oxen,
sheep and asses."
Next they attacked Ai,
"there fell that day a
total of 12,000 men and women,
the entire population of
Ai."
 
The clear thing,
it's quite striking how this
comes so soon after the Ten
Commandments,
that what's clearly going on
is, just as chimps--
is an in-group,
and clearly the Ten
Commandments is --
intended for the in-group,
'thou shalt not kill,' straight
chimpanzee.
However, out-groups,
if you don't kill them all
you're not obeying God's
commandments.
In very modern times atrocities
continue with no lessening of
the horrific nature of it
compared to chimps or early
human beings,
and I'll describe one famous
event to you which--
how many of you know about the
rape of Nanking?
 
Again, not all of you,
all of you should know these
things that I refer to are very
important things.
This is during World War II in
I think it was 1937.
The Japanese were trying to
conquer China,
and it was a big place and they
were getting rather frustrated
because--
in Japan it's a small place,
in China it's a huge place,
and it's not an easy thing to
do.
 
But they captured a city called
Nanking, south of the Yangtze
River.
 
In short order,
the Japanese slaughtered
350,000 people.
 
The total population of Nanking
at the time was only about
650,000 and several hundred
thousand had already fled.
In short, they basically killed
every Chinese that they could
find, just like the Bible
stories, or the chimpanzee
stories.
 
A Japanese newspaper reporter
watched Chinese prisoners being
bayoneted on the top of the city
wall.
"One by one,
prisoners fell down into the
outside of the wall,
blood splattered everywhere,
the chilling atmosphere made
one's hair stand on end and
limbs tremble with fear."
 
This reporter is talking only
from Japanese and we'll see,
Nazi sources because it's
possible the Chinese sources may
be exaggerated or something,
but the belief is that neither
the Japanese nor the Nazi
sources would exaggerate.
Another Japanese military
correspondent,
even more constrained,
described another locale where
the murders were by
samurai-style decapitations.
"Those in the second row
were forced to dump the severed
bodies into the river before
they themselves were beheaded.
The killing went on nonstop
from morning until night,
but they were only able to kill
2,000 persons that way.
The next day,
tired of killing in this
fashion, they set up machine
guns.
So great was the slaughter that
the Japanese general complained
that he could not find ditches
deep enough to bury the enormous
pile of corpses."
 
Tens of thousands of Chinese
women were raped,
often in schools and nunneries,
thousands more were put into
sexual slavery,
forced into prostitution,
and referred to in Japanese as
public toilets,
the women forced into
prostitutions.
Many soldiers went beyond rape
to disembowel women,
slice off their breasts,
nail them alive to walls.
Fathers were forced to rape
their daughters and sons their
mothers;
not only did live burials,
castration, and the carving of
organs and roasting of people
become routine,
but more diabolical tortures
were practiced like hanging
people from their tongues on
iron hooks,
or burying people to their
waists and watch them being torn
apart by German Shepherds.
So sickening was the spectacle
that even the Nazi's in the city
were horrified.
 
When the Japanese took
Singapore, right after Pearl
Harbor, they shot and
decapitated another 20,000
Chinese.
 
That was just a modern example
to show you that whatever this
is in humans that makes us want
to kill members of another
group,
it is totally unfettered by
anything that you might call
control or civilization,
when it breaks out the violence
is just incredible.
The bottom line is that war
seems to be characteristic of
almost all, and possibly all
human societies at all times in
our history.
 
There is no example,
no period which we can find
out,
where there's a discontinuity
between the chimpanzee behavior
and our current behavior,
and so again,
I think whatever you think of
what's causing the chimpanzee
war,
you probably have to consider
very much the same explanation
for human war.
 
The amount of death--I showed
you one example from one tribe,
the Ache in South America,
and any one tribe's experience
may or may not be
characteristic.
This is from a book,
Lawrence Keeley,
War Before Civilization,
which traces a lot of the
information I've been giving
you,
and what he does is,
he collects all the data that
anybody's ever collected,
so that he sort of can get some
idea of the percentages of
deaths by war.
This is percent of deaths from
warfare--
this is males,
and this is everybody together,
and these are different tribes
at different tribes for whom we
have data.
 
You'll see that the
numbers--the male numbers go up
to 50% or 60% of male deaths are
from these wars,
and the deaths of everybody
which is this,
is somewhat smaller,
a fifth or a sixth,
15% to 20% of deaths,
but going up of course to 40%
of deaths.
 
The point he's trying to make
with this graph is,
here's primitive warfare,
these darkly colored bands,
what he calls primitive
warfare, and the white bands are
so called civilizations and he
calls civilizations anything
that has a state,
like the Aztecs had a state in
one of these it is Aztecs.
 
From the data that one has we
are--
even though we think of World
War II and all of these current
and incredible wars and all our
technology devoted to war--
what's happening is that we
have much--
many, many more people die then
did in the past but the
population of humans has grown
so much that the percentage is
not so huge,
and that wars are less frequent.
Rather than having raids almost
continuously as in a lot of
primitive warfare,
we have wars every 15 or 20
years or so in general between
any two groups fighting each
other.
 
What he shows,
again, from the data that has
large and unknown error bars--
the civilized warfare which is
the Aztecs,
France in the nineteenth
century with Napoleonic War,
the 1870 War,
Western Europe in the
seventeenth century lots and
lots of wars in the 1600s,
U.S.
and Europe in the twentieth
century,
World War I and World War II
and so forth,
that as far as he can tell the
fraction of all deaths that is
caused by war is decreasing.
 
One possible very nice way of
looking at human history is that
humans have some sort of a
propensity,
call it an instinct if you
like, to identify an in-group
and everyone else is out-groups.
 
These in groups can be
nationality, they can be
religion, they can be color of
skin, they can be language.
Language is a big source of
conflict in Canada and Belgium,
all kinds of places;
almost anything will do.
It can be Yale versus Harvard,
or Berkeley College versus
Calhoun College,
and Red Sox,
the Red Sox fans.
 
The English who are generally
very civilized,
get into a soccer stadium and
they start killing each other.
Humans have this enormous
desire to identify in-group and
out-group.
 
We even now pay to advertise a
company,
because anything that looks
like a group membership symbol,
humans love that,
and will pay a lot to have a
hat or a name of some team,
or even some company on them.
We have very different morals
towards the in-group and the
out-group.
 
It seems that that's what's
still going on in us,
that as time--we have that
still.
But as time goes on,
because of increased
communication and increased
education, probably what we
consider the in-group grows.
 
First it was your little
village, a little hamlet of 40
people,
and then maybe organized into
some sort of a tribe of 1,000
people and gradually it grows.
If you read the history of
Europe there are all these
little cities,
say Greece with city-states,
a whole city could be
considered one family,
with a lot of divisions within
it.
Renaissance Italy you have the
Medici's and the Pazzi killing
each other, families within
cities, but gradually it grows.
You get nation states,
and as they grow,
the wars get less because
people within say France don't
generally have wars with each
other,
but France will have a huge war
with Germany.
The group that people consider
"us"
gets larger,
the frequency of war goes down,
but since you have so many
people fighting so many people,
the war causes more and more
deaths.
Possibly, this is optimistic,
that as we become more
interconnected and we consider
more people "us,"
and fewer people
"them,"
that gradually this behavior
will disappear.
But that's just guess work.
 
Now Keeley, who gathered a lot
of this data,
he has his own summary.
 
Again, in frustration about not
really understanding …
what these wars are all about,
he does not accept any idea
that there's any biology
involved.
He says, since he can
occasionally find some group
that hasn't been to war for 20
years or something like that,
then it can't be biology.
 
The view of biology that many
social sciences have is sort of
that --….--if it's
biology, it's a knee jerk
reflex.
 
If you're not--if your nervous
system is not impaired,
every time I hit your knee with
a hammer your knee will kick out
and there's no volition.
 
They say if we ever see a human
not doing some behavior,
that behavior cannot be
instinctual.
Of course that was disproven in
around 1910 by Pavlov,
you all know about Pavlov?
 
He takes an instinct as basic
as eating,
and a dog sees a piece of meat
and starts salivating,
and then very rapidly he rings
a bell a minute before the dog
sees the meat and the dog starts
salivating to the bell.
Since 1910 at least we've known
that even the most basic
behavior can be controlled by
something with as small a brain
as a dog,
even though one would never say
the dog does not have an eating
instinct,
does not have a salivating
instinct,
of course they do and yet dogs
can control it.
I tell a story about my dog,
so a smallish white Samoyed,
and I'm at work all day.
 
I work long hours and so she's
at home all day and by the time
I come home she's a little
frustrated.
She's been cooped up,
and I'm a little frustrated.
So what happens:
I get down on my hands and
knees and I growl at her.
 
She immediately picks up the
cue, she's snarling back at me,
and then I swat her one,
a gentle swat but she gets--
she snips back at my hand and
we go at it.
We have a great time.
 
Unfortunately my dog has died,
but we had a great time and in
the course of these she's
snapping--
she's aroused,
her hair is standing on end,
her tail is straight up,
her fangs are showed,
and she's snapping away at me
and I get,
maybe--we do 20 minutes or so
maybe--
at least 50 to 100 bites where
she actually wins.
I win, I smack her,
she wins and--so what that
means over the years I've had
many tens of thousands of times
where she's grabbed me and all
that,
and guess what,
not once in all those many
thousands of bites has she ever
pierced my skin.
All right, this is a peaceful
house dog;
she doesn't know anything about
killing.
No, not true.
 
In the morning I take her out
running in the woods,
I don't know if she takes me or
I take her,
and if she sees a bird or a
squirrel,
she's off and she comes back
with a dead bird in her mouth,
clearly killed,
she clearly bit through their
skin--
very, very proud,
walking there with a dead
squirrel.
Here's an animal and I love her
dearly,
but her brain is not very big,
and she can get into the depths
of real instinctual responses
and yet her brain is clever
enough to be able to control it
and not--
and to kill the squirrel but
not to kill me or not even break
through my skin.
 
I think the idea is a lot of
people think when you've
described biological basis for
behavior that it's inevitable.
The human species were lost,
we're never going to change,
but that's nonsense.
 
Humans are like chimpanzees,
we're quite intelligent,
and we are capable--we have
instinct,
I believe that we have
instincts for sure,
you'll see it come out in the
most horrible ways and in some
good ways,
but it's not that difficult to
control.
 
My dog can do it,
you guys can do it.
The other issue which--these
are good topics for discussion
in the sections--
is, some people also say when I
describe duck rape or orangutan
rape,
that some of--my describing it
and saying that animals do it
I'm justifying it.
 
There's this whole thing now
that what's natural is good and
what animals do is natural and
therefore it's good,
and it slops over to foods and
everything.
This whole idea of natural law,
that you can tell from nature
what is good and what is bad is
not to be taken seriously.
That finishes that topic,
and I think you've had enough
violence.
 
I want to skip--switch to the
opposite side now.
Demography is,
of course, births and deaths;
those are the two main things
in demography.
We have been talking about one
of the main causes of human
death on one side,
and we find that there is a
clear continuity between
chimpanzees and humans.
Now let's talk about the other
side, births and there
surprisingly,
humans are drastically
different from chimpanzees.
 
How do we know this?
 
Chimpanzees were never very
successful demographically.
At their peak there may have
been two million chimpanzees.
A very small Chinese city is
two million individuals,
and now because of the rise of
humans they're taking over their
territory,
the guess is they've been
reduced to about 100,000;
5% of their peak population.
They are restricted to central
Africa;
they have never spread beyond
central Africa.
Humans, on the other hand as
you know, number in the
billions;
we've spread to the farthest
corners of the earth from the
ice cap around the North Pole to
the hottest desert and jungle.
 
There are tens of thousands of
times as many people,
humans, as there are
chimpanzees, and humans have
become absolutely dominant
basically everywhere on earth.
From a demographic point of
view, maybe the first question
we should ask,
why are there so many humans
and so few chimps?
 
What is the secret of our
demographic success?
Let me give you a clue about
the time scale.
We separated from chimps about
six million years ago,
and I've shown you--this is
another version of the
deaths--don't worry about it.
 
Remember this--the family tree
here,
and here is the split point
where humans branched off from
chimps and bonobos and its
ballpark six million years ago
that we split off.
 
The population size,
what is believed,
that the population size of
all--the group that became these
three species was only about
50,000 individuals at this split
point.
 
That comes from the genetics,
the variation in genetics.
This small group branched off
and started behaving--evolving
quite differently.
 
What happens when you have a
small group to begin with of
50,000 breeding individuals,
then a small group breaks off
and they may further subdivide
into smaller groups that may not
come much in contact with each
other,
you have inbreeding,
and inbreeding causes a lot of
genetic problems,
but it also allows evolution to
go very rapidly.
 
For mutation,
if it is beneficial it appears,
it can spread to a small
population very rapidly whereas
it's extremely difficult for it
to spread into a large
population.
 
The tinyness of the number of
our human ancestors allowed a
rather rapid evolution away from
the other groups who were also
evolving of course because they
were also in small groups.
That--at the split you start
going down this pathway and it's
shown here as a single line,
but as all of you know from the
newspaper,
there are many,
many species splitting off at
different times with different
characteristics all in the
humanoid,
hominid line and by chance all
of those other species went
extinct except one.
 
That's another characteristic:
if you're a small group then
it's very easy to go extinct.
 
And all of the--we know 20,30
other humanoid species,
and all went extinct except
one.
The genus Homo,
which is the group of species
in which we sit,
originates about two and a half
million years ago,
and they start calling
skeletons Homo sapiens
about a half a million years
ago,
but even though they're Homo
sapiens their brains are,
at that time,
significantly smaller than ours
are now,
and anatomically modern humans
date only from about 100,000 to
150,000 years ago.
 
All during this period the
number of humans was clearly
very small.
 
It's very humbling to realize
that with a small group that's
evolving rapidly,
which means it's not yet
mastered it's environment
because you don't--
once you have optimized your
relationship to your environment
evolution slows down,
but if we're evolving rapidly
that means we haven't yet
mastered it.
So a small group struggling in
its environment,
very likely to go extinct;
most of our sibling species
went extinct,
and I think with a very small
role of the dice differently the
line towards humans could easily
have gone extinct.
 
It seems that about 100,000
years ago there was a bottleneck
in the growth of human species,
and the humans living at that
time,
a small group,
were the ancestors to all
current human beings.
There was a small population of
about 2,000 to 10,000 they
believe,
and that the total human
population,
from 2,000 to 10,000 of humans
living in Africa and
interbreeding.
There may have been other human
populations somewhere else that
disappeared.
 
We don't know,
and the numbers 2,000 to 10,000
some research puts them a few
times higher,
we don't really know,
but again a very small number.
We know from that period that
there was no substantial
population growth,
so that means the average
number of surviving children was
two or maybe teensy weensy bit
higher then two,
so that meant when you have on
average two children per couple,
that means that most lineages
have died out,
that most individuals who were
living at that time of this
small number now leave no
descendants at all.
 
If you trace back,
the genetics suggest that all
current humans,
all races all over the world
are the descendants of a single
human female.
That every other line,
from the time when she was
alive has died out,
and similarly for males,
we are all the descendants of a
single human male.
All other lines have died out,
and those two didn't have to
live at the same time.
 
In fact, almost certainly did
not live at the same time;
it's just the randomness of
lines dying out and the genetics
tells us that we know the rate
at which DNA mutates and
diverges and so we--
and we know the range of a
variation in current humans so
we just sort of narrowed that
back and it goes back to this--
what did I say 100,000 years
ago.
 
That's the genetic Eve and the
genetic Adam that the newspapers
just love this story but it's
just a common result of --
a population that doesn't have
a lot of surviving children--
lines are going to die out.
 
You can read that the royal
houses of Europe is where you're
all exposed to it.
 
Look how few generations the
royal houses last before they
don't have any heirs,
and that's in modern--these are
the richest people at their time
and have all the food and
protection and everything that
they want and they can't stay
going for more than a few
generations.
In primitive times,
the rate of extinction of lines
was great.
 
About 50,000 years ago--we're
going to spend a few million
years in Africa,
then about 50,000 years ago a
group of humans migrated out of
Africa.
Again, the numbers and the
times, some people say it was as
late as 25,000 years ago that
they migrated out.
Then amazing things happened,
once they burst out on the rest
of the world,
they spread everywhere.
Humans are found everywhere on
the Eurasian continent,
that's from Siberia to Spain by
about 20,000 years ago,
and then from Siberia they
crossing the Bering Strait,
which was a land bridge at that
time,
and expanded into the Americas
and reached the very tip of
South America by 10,000 years
ago.
In 40,000 years which is a
blink of an eye in evolutionary
terms, humans spread everywhere
on earth, an incredible
population explosion.
 
This is the first and greatest
explosion, a population
explosion of humans.
 
You should note that something
was making us superior at that
time, and clearly it has nothing
to do with modern technology.
All of this fantastic expansion
even pre-dates the invention of
agriculture and most of what we
consider civilization starts
with agriculture.
 
What is the main difference
that has allowed this story that
humans have done this and chimps
have done this?
Well you ask,
what is the reproductive rate
of chimpanzees?
 
Well I've told you that a chimp
mother has one young every five
to eight years,
so at that rate it's going to
be very hard to increase at any
great speed.
Human females have babies much
more frequently,
it's quite possible to have a
baby every year,
or every year and a half,
or two years,
and this is common--my brother
was born 20 months apart from
me.
 
How many of you have siblings
less than two years apart?
Most of you.
 
So humans are quite capable of
doing something that chimps just
cannot do.
 
They have a rate of
reproduction of about four or
five times slower than we do.
 
The mothers,
the chimp mothers cannot take
care of more than one young at a
time.
They will have a young that's
clinging to them and then
perhaps an adolescent son or
daughter with them but they'll
never--
you never see two infants at a
time,
whereas, humans can easily take
care of two infants at a time.
 
Twins in chimps?
 
I have never heard--read
anything about chimps occurring
in--twins occurring in chimps,
and I don't know whether they
ever do.
 
It may be just that we don't
have enough observation that
maybe occasionally chimp twins
do happen, but it's not been
reported that I've seen.
 
Anybody take a--
Student:  Not about
twins, I was just going to ask
if that's regulated by hormones
completely.
 
Like you would say that
lactation stops--
Prof: Yes.
 
Student:  But it's a
chimp is nursing a baby for five
years?
 
Prof: They're nursing
them for a long time.
I don't recall what the number
is, but there's many behavioral
mechanisms.
 
So in nursing,
the actual physical stimulation
of the nipple releases hormones,
Oxytocin, which prevents
ovulation again,
and that can be prolonged for
quite a period of time but is
not absolute,
so there are other behavioral
mechanisms,
other internal hormonal
mechanisms which ensure this and
in chimpanzees we--
it's very hard to capture a
chimp and do the physiology and
experiment,
so we basically probably don't
know most of the answer to that
question.
 
The--a major difference --
between humans and chimps is a
tremendous increase in human
fecundity.
Now in demography we use the
word--fecundity means the
ability to have children.
 
Fertility means the number of
children you actually have,
and that comes from French
usage and French use the word
sort of oppositely to the way we
do and demography was born in
France.
 
When I say fertility I don't
mean the ability to have
children,
that's fecundity,
but I mean the number of
children that any given set of
women actually have.
 
We have to ask ourselves what
evolutionary factors allowed
this change in fecundity.
 
What limited chimp population,
what limited chimp fecundity?
Well in primate evolution the
main factor is the time that
brain development takes.
 
A body that's capable of
walking and chewing and so forth
can develop rather rapidly in
all kinds of animals,
develop in a very short time
scale and are immediately
capable of doing those things,
but if you're going to have a
species with a big brain,
that's a slow process.
In all the higher brain--the
bigger brain primates,
the slow thing is brain
development.
In order to not have to carry
this baby like for--
until the brain is mature at
age 13 or something--
they say we don't really
progress beyond adolescents--
so in humans and great apes the
baby is born with physically
somewhat mature but the brain is
still growing enormously.
Really there's post-natal
development of the brain,
so even at the nine months of
pregnancy, we're not at the end
of the period of brain
development.
The brain is nowhere near its
final size or complexity.
That limits the rate at which
one can have childbirth and
because the infant is born in
chimps and in humans,
is born incapable of taking
care of itself,
the mother has to stay with the
child and take care of it.
In chimps the mother stays
exclusively with her infant for
several years.
 
The chimps get very little,
as I mentioned,
very little in the way of
resources from the males.
They mostly watch and they
do--they don't come in contact
with males all that much,
they and their young forage by
themselves,
and etc., etc.,
and the males are just
patrolling.
They see them every so often
and the males protect the
boundaries.
 
In terms of taking care of the
young the males basically have
no role whatsoever.
 
As a result of this need to
have intense care of the young,
and no help from anyone,
sometimes other females will
help,
but basically no help at all,
the period in which the mother
has to devote herself
exclusively to that one young is
quite prolonged.
Now in humans,
males do play some more
intimate part in child rearing.
 
Not anywhere near as much as a
female but they do bring
resources.
 
In general, in most human
societies over time,
males are responsible for
bringing some resources to the
female on a rather continuing
basis.
We don't really know how this
evolved because these things you
can't really tell these things
from fossils.
What we know is that
Africa--the chimps started in
the jungle and then Africa
started drying out and so some
subset of the chimps,
maybe pushed out by stronger
individuals or clever
individuals,
were pushed into this drying
out grasslands where there was
less cover and less fruiting
trees.
Dry land doesn't produce the
big fruiting trees that chimps
depend on.
 
As a difference between chimps
and bonobos, when there's a
lesser food density the
population has to spread out.
That if an individual is going
to find any food they're not
going to find enough for a large
group,
so individual females would
have to go forage quite
separately.
 
You can speculate further that
as the females spread out,
the dominant males could no
longer keep watch over and
control over these females,
they were just too far spread
geographically.
 
While in chimps--while the male
or female may go off for a short
time period,
in what's called a consortship
and there may be matings at that
time,
there's no lasting,
no continuing relationship
between any particular male and
a female.
Chimpanzees,
as I mentioned,
are male bonded and they spend
more time with each other,
male to male,
than the males do with the
females.
 
In humans of course we still
have a lot of what they call
male/male bonding,
military units,
sport teams,
all male clubs,
football, pre-wedding parties,
watching football,
watching parties,
etc., but we've evolved in the
direction of much more
male/female interaction and
contact.
 
Female sexuality changed.
 
While chimpanzees always mate
from behind,
humans engage in frontal
copulation,
and since the face is how
humans and also chimpanzees
detect each other--
they know individuals largely
by their facial structure--
and they detect emotions,
it's a very important part of
communication to detect the
emotions and respond to each
other by facial cues--
so this face to face
interaction, especially in the
intensity of the sexual
encounter is considered a large
part of the evolution of
male/female bonding.
I forgot to show you last time,
but it's an excuse to show you
this time,
here is a bonobo engaging in
front to front sex,
male and female here,
and she's grinning.
 
She's clearly being pretty
happy about this,
and I also said I would show
you--this is two females doing
the same thing.
 
If you didn't--if I didn't tell
you it was--this was two females
you wouldn't know the
difference.
Unless you're watching you can
see that they both have their
swellings, that's how you tell
that they are two females.
I mean the guys who took the
picture obviously knew a lot
more but you can tell that--so
this is what I described--that
the locals call hoka,
hoka.
This whole evolution of
sexuality in the human line,
the clitoris has moved forward
for--
which in face-to-face
copulation probably makes it--
more female pleasure during the
act of copulation and therefore
again reinforces this bonding.
 
Another big difference and this
is not an extreme case of the
rump--that's another topic.
 
Humans do not advertise their
estrus.
Not only do we not--remember
the chimps advertise their
estrus in order to get the males
together and have the males
compete for them.
 
Humans keep it secret;
not only don't the males know
when a female is in estrus,
but the female herself does not
when she is estrus,
and for a very long time it was
believed that females are
fertile during their periods.
It was only in the 1930s that
it was found out by a Japanese
group that females are fertile
in the mid-period between their
periods,
and even further,
it was believed in the 1930s
that females are fertile a few
days before and a few days after
the middle of ovulation in the
middle of the period,
and in fact,
we now know just from about ten
years ago that the actual
fertile period always is only
precedes ovulation.
Then intercourse must take
place before ovulation.
Not only do we--do human
females not advertise to the
females,
they don't know,
and scientists,
with all our investigations,
have just now finally figured
out, we think,
when a human female is fertile.
 
This is a big,
big change.
It's such a big part;
the advertising is such a big
part of primate sexuality,
why has it disappeared in
humans?
 
It may be sort of the reverse,
that if females are out there
alone and there's carnivores,
you read about this from the
Ache, that there are lions and
tigers out there ready to eat
them,
and they need protection of
various sorts and maybe help in
finding food,
so it's important to have a
male hanging around.
A male's evolutionary purpose
is he wants to inseminate the
female,
so if he knows when a female's
having estrus,
he has to be there then to
inseminate her.
 
If he knows when she is in
estrus he also knows when she is
not in estrus,
and when she's not in estrus he
may have no evolutionary push to
stay there but go out and try to
find some other female.
 
The purpose of not showing your
estrus may be to keep the male
uncertain of when you are
fertile and therefore he has to
attend to the female all the
time,
and once he's there he might as
well help her because that will
insure that whatever infants
come along are in good shape.
If that's correct,
and certainly males and females
started spending more time
together, and they're more
dispersed;
that reduces male/male
competition.
 
Remember the male/male
competition is a result of a
group in which a lot of males
stay together.
When you're more dispersed,
male/male competition has to be
reduced.
 
It looks like in the evolution
to humans that's--
what's switching is from the
advertising which allows the
males to compete and the female
gets the male with best genes,
she's switching to wanting
resources from the male.
She's no longer interested so
much in male competition but in
whatever resources the male can
bring to her by having a male
around continually.
 
This story is rather
complicated and very
controversial and there's a very
nice reading in your packet.
It might be interesting to
consider that,
how does the male respond to
this change in strategy?
If the road to monogamy starts
going down then paternity
becomes more certain.
 
In the chimps,
where the female is copulating
with everyone,
there's no reason to be certain
of paternity at all.
 
Once it becomes clear that,
yes, this child is almost
certainly mine,
then it becomes evolutionary
advantageous for the male to
start putting resources into
this mother and child because
that insures their survival and
things start developing in a
different direction.
Where stable pairing becomes an
evolutionarily advantage,
the male putting resources into
the pair are for evolutionary
advantage.
 
It seems pretty clear that an
increase in the male
contribution to child rearing is
one of the major reasons for the
increased fertility of humans--
why humans are able to out
reproduce chimpanzees.
 
Of course, as you all are
aware, monogamy has not by any
means taken human societies
totally over and some societies
overtly sanction polygamy,
but even in our culture which
Europe and North America--
genetic testing shows that 10%
to 15% of humans do not have the
father that they're supposed to
have.
 
'Father' is usually defined as
the resident male;
he's not the father,
and that's quite a large
percentage.
 
American women report 6
different sexual partners
lifetime and males report 16
female partners,
lifetime.
 
Now one thing we know if you're
at all mathematical that the--
since it takes two to tango,
the average has to be the same
so it can't be both 6 and 16,
and who knows possibly
somewhere in between is correct,
but probably higher because
these things tend to be under
reported,
no one wants to really
say--well females certainly
don't want to say how
promiscuous they are usually and
also that's old data.
 
This is from 2001 and with the
change of sexual mores in the
Western countries,
I'm sure the numbers are
exponentially increasing.
 
What's--another thing about
this thing with respect to human
evolution is that when you're a
chimpanzee the male--
the main form of competition is
male/male fighting,
male/male status jockeying
which takes a certain amount of
intelligence to arrange
coalitions and so forth,
but basically evolution is
pushing you to be big and
violent.
 
Now the individuals disperse,
the male stays with the female,
the males starts bringing
resources, violence is
decreased.
 
The importance of that in the
male evolution decreases and the
importance of being able to
provide resources become
evolutionarily important,
so the kind of intelligence
required to find food in a
scarce environment,
to find shelter,
to protect from animals and so
forth becomes important.
 
A fair reason for the increase
in human mental capacity might
also be this shift from a
dependence on violence for
competition to a dependence on
acquisition of resources for
competition and for evolution.
 
I've run out time and so we
will continue with humans and
how they are different from
chimps next time.
