Stanford University.
The often asked question, what's the difference between Bio 150,
Bio 250, and-- is it Hum Bio 160?
No difference.
It's exactly the same.
So like the same requirements, same unit.
So take whichever one makes your life easiest.
Let's see.
Any other procedural stuff?
Well, the answers are back from Monday's questionnaire.
And a variety of interesting answers.
Not surprisingly, given the size of a group.
Why have you taken this course?
Really want to know about animal behavior, but willing to deal
with humans.
[LAUGHTER]
Because I'm substituting it Bio 43, which I don't want to take.
My dad used to make me read books about human behavior
and biology as punishment.
[LAUGHTER]
That doesn't make any sense.
I know one of the TAs, so I figure
that guarantees me an A. OK, guys, that's in your court.
One I really liked, because I want
to be a filmmaker after college.
Yay, interdisciplinary.
What else?
My first grade teacher is making me.
Tom McFadden told me to.
I'm a hyper-oxygenated dilettante.
I wanted to, somewhat correctly pointing out,
why have you taken this class?
I haven't taken it yet.
A number of people reporting that,
in fact, that was the correct answer.
And my favorite, why have you taken this course?
Yes.
[LAUGHTER]
OK.
Relevant background, relevant background.
I'm human, I'm human and I often behave.
I'm human and I have biology.
19 years of being confused about human behavior.
Not really, sort of.
Seeing crazy behavior as an RA in an all frosh dorm.
And I date a biologist.
Let's see.
There was also the question on there of,
did the thing on the board look more like an A or a B.
And just to really facilitate that one,
I forgot to put the A and the B up.
But that taps into a cognitive something or other,
which maybe I'll get back to at some point.
Telephone numbers.
Reading them off, accuracy dramatically
tanked as soon as the three number,
four number motif went down the tubes.
And when it came back briefly, accuracy
came back a little bit.
Finally, let's see.
All of you guys conform to a standard frequent gender
difference.
Which is everybody was roughly equally-- by gender-- roughly
equally likely to see dependent as the opposite of independent.
A small minority went for interdependent.
However, one finding that has come up over and over
is that far more females are interested in peace than males,
males are more interested in justice.
OK, have you taken the bio core.
Quote, no way Jose.
Somebody pointing out quite correctly,
don't settle for peace or justice.
Then of course, there was the person
who responded to that question by writing those words are just
symbols.
Need to know assumed meaning.
[LAUGHTER]
OK.
There was one questionnaire that was carefully
signed in something approaching calligraphy,
it was so beautiful.
And was otherwise blank.
For years running, the subject that most people really
want to hear, and most people really don't want to hear,
is about the biology of religiosity.
And for 22 years running now, Stanford students
are more interested in depression than sex.
[LAUGHTER]
OK.
So we start off.
I keep telling Hennessy about this, but nothing gets done.
We start off.
We start off, if I can open this--
which is something you can do if you have
a certain type of training.
If you're some osteologist, or whatever these folks are
called.
If you are presented those two skulls
and told this one's a female, this one's
a male, you can begin to figure out stuff like how heavy,
how large the body was of that individual, what
diseases they had, had they undergone malnutrition,
had they given birth, a lot of times, a few times,
were they bipedal.
All sorts of stuff you could figure out
from just looking at these skulls.
What today's lecture, and Friday's, is about
is the fact that with the right tools under your belt,
you could look at these two skulls
and know that information.
You are a field biologist, and you've discovered this brand
new species.
And you see that this one nurses an infant
shortly before leaping out of the tree,
leaving only the skull.
And this one has a penis, shortly
before leaping out of the tree and leaving a skull.
So all you know is this is an adult female and an adult male.
And if you've got the right tools there,
you can figure out who's more likely to cheat on the other.
Is the female more likely to mess around, or is the male?
How high are the levels of aggression?
Does the female tend to have twins, or one kid at a time?
Do females choose males because they have good parenting
skills, or because they're big, hunky guys?
What levels of differences in life expectancy?
Do they live the same length of time?
You would be able to tell whether they have the same life
expectancy or if there's a big discrepancy between the two.
All sorts of stuff like that, merely
by applying a certain piece of logic
that dominates all of this.
OK, so you're back reading those Time Life nature
books back when, and there was always a style of thing
you would go through.
Which is they'd describe some species
doing something absolutely amazing and unlikely,
and it goes like this.
The giraffe, the giraffe has a long neck,
and it obviously has to have a big heart
to pump all that blood up there.
And you lock up a whole bunch of biomechanics people
with slide rules, and out they come out with this prediction
as to how big the giraffe heart should be
and how thick the walls.
And you go and you measure a giraffe heart,
and it's exactly what the equations predicted.
And you say, isn't nature amazing?
Or you read about some desert rodents that drink once
every three months, and another bunch of folks
have done math and figured out how many miles long
the renal tubules have to be.
And somebody goes and studies it,
and it's exactly as you expect it.
Isn't nature wonderful?
No, nature isn't wonderful.
You couldn't have giraffes unless they
had hearts that were that big.
You couldn't have rodents living in the desert
unless they had kidneys that worked in a certain way.
There is an inevitable logic about how organisms function,
how organisms are built, how organisms
have evolved solving this problem of optimizing
the solution.
And what the next two lectures are about is,
you can take the same exact principles
and apply them to thinking about the evolution of behavior.
The same sort of logic where, just
as you could sit there and, with logical principles,
come to the point of saying, a giraffe's heart
is going to be this big.
You can go through a different realm of logic built
around evolutionary principles and figure out all sorts
of aspects of social behavior.
And we already know what's involved in, say, optimizing.
What's the optimal number of whatevers in your kidney.
What's the optimal behavior strategy or something.
All of us, as soon as we got some kid sibling,
learned how to do the optimal strategy in tic-tac-toe.
So that you could never lose, and it's totally boring.
But that's a case of figuring out the optimal solution
to behavior, reaching what is called the Nash equilibrium.
And actually, I have no idea what I just said.
But I like making reference to Nash,
because it makes me feel quantitative or something.
So that is called the Nash equilibrium.
The Nash equilibrium, and what the entire point here is,
the same sort of process of figuring out
what are the rules of optimizing tic-tac-toe behavior
can be built upon the principles of evolution
to figure out all sorts of realms
of optimized social behavior.
And broadly, this is a field that's known as sociobiology,
emerging in the late 1970s-- mid 1970s or so.
And by the late 1980s, giving birth
to another discipline known as evolutionary psychology.
The notion that you cannot understand behavior,
and you cannot understand internal psychological states,
outside the context of evolution had something to do with
sculpting those behaviors and those psyches.
So to start off with that, basic song and dance about Darwin.
Just to make sure we're up to speed on this.
Darwin, just to get some things out of the way.
Darwin did not discover evolution.
People knew about evolution long before that.
Darwin came up with the notion of a mechanism
for evolution, natural selection.
And in fact, Darwin is the inventor of that.
There was another guy, Alfred Russel Wallace,
the two of them.
And, for some reason, Wallace has gotten screwed historically
and Darwin gets much more attention.
But starting off with a Darwinian view of how evolution
works.
First thing being that there is evolution.
Traits in populations change over time.
Traits can change enough that, in fact, you
will get speciation.
New species will form.
And the logic of Darwinian evolution
is built on just a few couple of very reasonable steps.
First one is that there are traits that are heritable.
Traits that could be passed on one generation to the next.
Traits that we now can translate,
in our modern parlance, into traits that are genetic.
And we will see, soon, how that's totally not correct
to have said that.
But traits that are heritable.
The next thing is that there is variability among those traits.
There's different ways in which this trait can occur,
and they're all heritable.
The next critical thing.
Some versions of those traits are more adaptive than others.
Some versions work better for you.
For example, giraffe who wind up with hearts
the size of, like, a tomato, that's not an optimal version.
Amid the range of variability, some
will carry with them more fitness, more adaptiveness,
than others.
And that translates into another sound bite
that's got to be gotten rid of.
All of this is not about survival of the most adapted.
It's about reproduction, something we will
come to over and over again.
It's about the number of copies of genes you
leave in the next generation.
So you've got to have traits that are heritable.
There's got to be variability in them.
Some of those traits are more adaptive than others.
Some of those traits make it more
likely that that organism passes on copies of its genes
into the next generation.
And throw those three pieces together, and what you will get
is evolution in populations.
Changing frequencies of traits.
And when you throw in one additional piece, which
is every now and then the possibility
to have a random introduction of a new type of trait
in there-- modern parlance, a mutation-- from that,
you can begin to get actual large changes in what
a population looks like.
OK, so these are the basic building blocks of Darwin.
And it is easy to apply it to giraffes' hearts
and kidneys of desert rats, and everything we think about
in the world of physiology, anatomy,
in the context of evolution.
So how do you apply it to behavior?
And the basic notion, for folks who've
come from this Darwinian tradition
into thinking about behavior, is you do the exact same thing.
There are behaviors that are heritable, types, traits,
classes of behaviors.
They come with a certain degree of variation among individuals.
Some versions of them are more adaptive than others.
Over time, the more adaptive versions
will become more commonplace.
And every now and then, you can have mutations
that introduce new variability.
Totally logical, absolutely unassailable.
And what we're going to spend an insane amount of time
in this class on is one simple assumption
in there, which is that certain behaviors are heritable.
That certain behaviors have genetic components.
And as you'll see, this one is just
going to run through every lecture wrestling
with that issue there.
This is a big incendiary issue there as to how genetic--
and that's not the same thing as saying
how genetically determined-- how genetic behavior is.
So that's going to be an issue we come back to again
and again.
So now, transitioning into how you would apply
these Darwinian principles.
First thing before starting, a caveat.
You're going to wind up, in order to think about all
of this most efficiently, hopefully do some personifying.
Personifying as in, you'll sit around saying, well,
what would a female chimpanzee want
to do at this point to optimize the number of copies
of her genes in the next generation?
What would this brine shrimp want
to do to deal with this environmental stressor?
What would this cherry tree do?
They're not planning.
They're not conscious.
They're not taking classes in evolutionary biology.
What would this organism want to do
is just a shorthand for something sculpted
by the sort of exigencies of evolution,
and reducing the optimal.
They want to do this.
This is just going to be a short hand throughout.
Once you get past the apes, nobody
is wanting to do any of these optimization things.
So just getting that sort of terminology out of the way.
OK, so we start off with what's the first building
block of applying Darwinian principles to behavior.
Something that is absolutely critical to emphasize,
because the first thing we all need to do
is unlearn something we all learned back when on all those
National Geographic specials and that would consistently
teach us something about this aspect of evolution,
and would always teach it to us wrong.
Here's the scenario.
So you're watching, and there's this wildlife documentary.
It's dawn on the savanna.
And you see, there's a whole bunch lions
on top of some big old dead thing.
Some buffalo, or something.
And they're chewing away and having a fine time.
So something happens at that point,
which is, they have to deal with how they divvy up the food.
Or let me give you another example.
Another standard, sort of endless vignette
that comes up in these films.
Once again, now, you're back on the savanna.
It's not dawn this time, but you are
looking at one of the magnificent things
of the natural world, which is the migration of zebras
throughout East Africa.
A herd of 2 million of them migrate around, following
a cyclical pattern of rains.
So they're always going where the grass is greener.
So you've got this wonderful herd of 2 million wildebeest,
and there's a problem.
Which is, there's some great field right in front of them
full of grass, and bummer, there's
a river in between them and the next field.
And especially a bummer, a river teeming with crocodiles
just ready to grab them.
So what are the wildebeest going to do?
And according to the National Geographic type
specials we would get, out would come a solution.
There's all the wildebeest hemming and hawing
in this agitated state by the edge of the river.
And suddenly, from the back of the crowd,
comes this elderly wildebeest who pushes his way up
to the front, stands on the edge of the river
and says, I sacrifice myself for you,
meine kinder, and throws himself into the river--
[LAUGHTER]
--where immediately, the crocs get busy eating him up.
And the other two million wildebeest
could tiptoe around the other way across the river,
and everybody is fine.
And you're then saying, why'd this guy do this?
Why did this guy fling himself into the river?
And we would get the answer at that point.
The answer that is permeated as, like, the worst urban myth
of evolution.
Whatever.
Why did he do that?
Because animals behave for the good of the species.
This is the notion that has to be completely trashed right
now.
Animals behaving for the good of the species
really came to the forefront, a guy in the early 60s named
Wynne-Edwards.
Hyphenated, Wynne-Edwards.
Some hyphenated Brit zoologist, who pushed most strongly
this notion of that animals behave
for the good of the species.
He is reviled throughout every textbook, Wynne-Edwards
and group selection.
That would be the term, selection
for the good of groups, for the selection
for the good of the species.
Wynne-Edwards and group selection.
I'm sure the guy did all sorts of other useful things.
And anyone who really has any depth to them would find out.
But all I know is that the guy is the one who
came up with group selection.
Animals behave for the good of the species.
This isn't the case at all.
Animals behave for passing on as many copies of their genes
as possible.
And what we'll see is, when you start
looking at the nuances of that, sometimes it
may look like behaving for the good of the species.
But it really isn't the case.
So animals behave in order to maximize
the number of copies of genes they
leave in the next generation.
Remember, not survival of the fittest,
reproduction of the fittest.
So first thing you need to do is go back to that vignette
and saying, so what's up with the wildebeest there?
And what's up with the elderly guy who jumps in the river?
And finally, when you look at them long enough
instead of the camera crew showing up for three minutes,
when you studied this closely enough,
you see something that wasn't apparent at first.
Which is, this elderly wildebeest
is not fighting his way through the crowd.
This guy is being pushed from behind.
[LAUGHTER]
This guy is being pushed from behind,
because all the other ones are saying,
yeah, get the old guy on the river.
Sacrificing himself, my ass.
This guy is getting pushed in by everybody else.
He is not sacrificing himself for the good of the species.
He does not like the idea of this whatsoever.
So he gets pushed in because the old, weak guy.
None of this group selection stuff.
What came in by the '70s as a replacement,
a way to think about this, is this notion of animals,
including us, behaving not for the good of the species
or of the group, but to maximize the number of copies of genes
left in the next generation.
And what you see is three ways in which this could occur.
Three building blocks.
The first one being known as individual selection.
The first one, built around the notion
that sometimes the behavior of an animal
is meant to optimize the number of copies of its genes
that it leaves in the next generation
by itself reproducing.
The drive to reproduce, the drive
to leave more copies of one's genes.
This was once summarized really sort of tersely as,
sometimes a chicken is an egg's way of making another chicken.
No, that's backwards.
Sometimes a chicken is an egg's way of making another egg.
OK, ignore that.
What the guy said is, sometimes a chicken is an egg's way
of making another egg.
All this behavior stuff, and all this animate social
interaction, is just an epiphenomenon
to get more copies of the genes into the next generation.
Individual selection, a subset of way of thinking about this
is selfish genes.
What behavior is about is maximizing
the number of copies of genes in the next generation.
And sometimes the best way to do it, sometimes
the way that animals maximize, is to get as many copies
by way of reproducing themselves.
It's not quite equivalent to The Selfish Gene,
but for our purposes, individual selection.
And this can play out in a number of realms.
And bringing in sort of a big dichotomy
in thinking about evolutionary pressures, Darwin
and the theory of natural selection.
What natural selection is about is
processes bringing about an organism who is more adaptive,
what we just went through.
Darwin soon recognized there was a second realm of selection,
which he called sexual selection.
And what that one's about is, this
is selecting for traits that have
no value whatsoever in terms of survival or anything like that.
Traits that carry no adaptive value,
but for some random, bizarre reason, the opposite sex
likes folks who look this way.
So they get to leave more copies of their genes.
And suddenly, you could have natural selection bringing
about big, sharp antlers in male moose,
and they use that for fighting off predators or fighting
with a male.
That would be natural selection.
Sexual selection might account for the fact
that the antlers are green, paisley patterns all
over for that.
And for some reason, that looks cool.
The female moose is, and what you wind up
getting as a mechanism for sexual selection
is, as long as individuals prefer to mate with individuals
with some completely arbitrary traits,
those traits will also become more common.
So this dichotomy of natural selection
for traits driven by traits that really do
aid leaving copies of genes outside the realm of just
sheer sexual preference, sexual selection.
And sometimes they can go in absolutely opposite directions.
You can get some species where the female fish
prefer male fish that have very bright coloration.
And that's advantageous, then, to have the bright coloration
by means of sexual selection.
But the bright coloration makes you
more likely to get predated by some other fish.
Natural selection pushing against bright coloration
in males.
Very often, you've got the two going against each other,
having to balance.
So how would that be applied in this realm
of individual selection?
This first building block.
Sometimes an egg-- damn.
Sometimes a chicken is an egg's way of making another egg.
Sometimes what behavior is about is one individual trying
to maximize the number of copies of their genes
in the next generation.
A natural selection manifestation of it
being, you're good at running away from predators.
Selection for speed, for certain types of muscle metabolism,
for certain sets of sensory systems that will tell you
there's somebody scary around.
That would be the realm of that.
Individual selection, selecting the realm of sexual selection
to have more of whatever those traits that are attractive.
So this first building block, it's not group selection.
It's not behaving for the good of the species.
It's behaving to maximize the number of copies of one's genes
in the next generation.
And the most straightforward way is
to behave in a way to maximize the number of times
you reproduce yourself.
Second building block, which is, there
is another way of accomplishing the same thing that you just
did with individual selection, as follows.
One of the things that can be relied upon in life
is that you are related to your relatives.
And what you get is, the more closely related you are,
the more genes you share in common with them.
On a statistical level, identical twins
share 100% of their genes.
Full siblings, 50%.
Half siblings, 25%.
This is exactly something that's going
to be covered in the catch up section this week.
If you're not comfortable with this stuff, this sort of thing
will be reviewed in more detail.
OK, so the closer a relative is to you,
the more genes they share in common with you.
So suddenly, you've got this issue.
You're an identical twin and your identical sibling
has the same genes that you do.
Individual selection, you will be just as successful
as passing on copies of your genes into the next generation
if you forgo reproducing to make it
possible for your identical twin to do so.
Because on the level of just sheer numbers
of copies of genes in the next generation,
they are equivalent.
And sometimes, you will thus get behavior which really decreases
the reproductive success of an individual
in order to enhance the success of a relative.
But you've got a constraint there,
which is, all of your relatives don't
share all your genes with you.
They have differing degrees of relatedness.
And what that winds up producing is another factor,
another observation.
One of the great, witty geneticists of all time, a guy
named Haldane who, apparently, once in a bar
was trying to explain this principle to somebody
and came up and said, I will gladly
lay down my life for two brothers or eight cousins.
And that's the math of the relatedness.
You passing on one copy of your genes
to the next generation is, from the sheer mathematics of just
how evolution is going to play out over the generations,
is exactly equivalent as giving up your life for eight cousins
to be able to each pass on a copy of their genes.
Because you share 1/8 with each of them,
and it winds up being a whole [INAUDIBLE].
And it's that math.
And out of that, you get something that
makes perfect sense instantly.
Which is, evolution selects for organisms cooperating
with their relatives.
Something along those lines.
And thus we have this second building block
known as kin selection.
Inclusive fitness.
Kin selection.
First building block, individual selection, passing on copies
of your own genes as a way to maximize future success.
Second version, helping out relatives.
Helping out relatives in terms of increasing
their reproductive success with this vicious mathematical
logic, which is one identical twin
to have two full siblings, eight cousins, and so on,
as a function of degree of relatedness.
And what this begins to explain is a whole world
in animal behavior of animals being obsessed with kinship.
Animals being fully aware of who is related to who in what
sorts of ways.
Animals being utterly aware of you
cooperate with relatives, but as a function of how
closely related they are.
Animals put us in Social Anthropology, in kinship terms,
and could you marry the daughter of your uncle's third wife
or whatever, to shame in terms of how
much a lot of social animals deal with relatedness.
So inclusive fitness, kin selection.
Here would be evidence for it.
Here's one example.
Very cool study done some years back by a couple, Seyfarth
and Cheney, University of Pennsylvania,
looking at vervet monkeys.
And these were vervet monkeys out in Tanzania, I believe.
What they did was, a whole bunch of these vervet monkeys
were sitting around.
And they, the researchers, had made really high quality
recording recordings of various vocalizations
from the monkeys over time.
So they had the sound of each animal giving an alarm call,
giving a friendly gesture call, giving a whatever.
And what they would then do is hide a microphone
inside some bushes and play the sound of one of the infants
from the group giving an alarm call.
So what does the mother of that infant do?
She instantly gets agitated and looks over at the bush.
That's her child, all of that.
How to know that everyone else in that vervet group
understands kin selection, what does everybody else do?
They all look at the mother.
That's whoever's mother, what is she going to do next?
They understand the relatedness, and they understand
what the response will be.
All the other vervets look at the mother at that point.
Whoa, I'm sure glad that's not my kid giving an alarm
call from the bushes.
They understand kinship.
Another version of that came out in these studies.
So you've got two females, each of whom has a kid, a daughter,
whatever.
And female A and female B. And one day, female A
does something absolutely rotten to female B.
And later that day, the child of female B
is more likely than chance to do something rotten
to the child of female A. They're
keeping track of not only revenge,
but not revenge on the individual who
did something miserable to you, but displaced by one
degree of reproduction.
Keeping track of kinship.
Animals can do this.
All sorts of primate species can do this.
And as we'll see, all sorts of other species can do this also.
There is that caveat again.
All sorts of other species want to figure out
who their cousins-- they don't want to figure out.
Evolution has sculpted an ability
to optimize behavior along lines of relatedness
in all sorts of species.
So how would natural selection play out
in this realm of kin selection, I will lay down
my life for eight cousins.
And that's just sort of obvious there by now.
How would sexual selection play out in this realm.
I am willing to expend great amounts of energy
to convince people that my sibling is incredibly hot.
And with any chance, then passing
on more copies of genes.
That would be inclusive fitness, kin selection in both cases.
Decreasing your own reproductive potential
by way of being killed by a predator to save the 8 cousins,
or having to spend so much time haranguing about your sibling.
Doings that, in order to increase
the reproductive success of relatives,
where you were willing to give up more energy
and potential on your part, the more closely related
the individual is.
So you throw those two pieces together,
and you're suddenly off and running
with explaining a lot of animal behavior.
Individual selection, none of this
for the good of the species.
Maximizing the number of copies of your own genes.
And the easiest way, the most straightforward,
is you yourself maximizing reproduction.
Foundation number two the whole thing, kin selection.
Sometimes the best way of leaving more copies of genes
in the next generation is using up
your own reproductive potential foregoing
to help relatives as a function of degree of relatedness.
OK, that's great.
So now the third piece, the third final building block
of making sense of social behavior in the context
of real contemporary evolutionary theory,
the third block here.
Which is, you look at animals and they're not all just
competing with non-relatives.
Animals forego competition at certain points.
Animals would have the potential to be
aggressive to other animals, and they will forego doing so.
And there's one circumstance in which that can happen,
where you get what is called a rock-paper-scissors scenario.
You've got animals A, B, and C. A has a means of damaging B,
but it costs A. B has a means of damaging C,
but it costs B. C can damage A, but it
costs A. You get the right distribution of individuals
with one of those traits in a population,
and you will reach a rock-scissors-paper equilibrium
where nobody's doing anything rotten to each other.
Great example, totally cool example that got
published some years ago by a guy named Brendan Bohannan, who
was assistant professor in the department here at the time.
He was studying something or other about bacteria
showing a rock-paper-scissors circumstance.
You had three different types, three different versions,
of this bacteria in this colony he had made.
The first one could generate a poison, but it cost.
It had to put the effort into making that poison
and protecting itself from that poison, all of that.
The second type was vulnerable to the poison.
It happened to have some transporter on its membrane
that took up the poison, and that was bad news.
But it had an advantage, which is the rest of the time,
that transporter took up more food.
The third one, the good thing going
for it is that it didn't have-- the bad thing
was, it didn't have poison.
A good thing going for it was it didn't
have to spend energy on a poison,
and it didn't have that transporter.
So each one of those has a strength, each one of those
has a vulnerability.
They're like, I don't know, Pokemon or something.
And you put them all together there,
and you get a rock-paper-scissors scenario
where you get equilibrium, where they are not
attacking each other.
Because note, if I am A and I destroy B,
B's no longer wiping out C, who's
the one who could damage me.
It's got to come to an equilibrium state.
So you can get the evolution of stalemates like that,
and that's quite frequently seen.
And note here, this was the evolution
of stalemates not in chimps, not in cetaceans, but in bacteria.
What we're going to see is bacterial behavior,
to the extent that this is sort of a metaphor for behavior.
Behavior of all sorts of unlikely species
are subject to these same rules of passing
on copies of your genes.
These three different strains of bacteria
are competing with each other.
None of them are behaving for the good of the species there
of the three of them.
So rock-paper-scissors is very cool,
and you get versions of that in humans.
That's been sort of studied quantitatively, all of that.
But that's not real cooperation.
That's merely everybody realizing
we have to cut back on the competition.
We have to cut back on the aggression.
Because every time I damage whoever,
I am more vulnerable in another realm.
That's a stalemate.
That's a truce.
But you look at animals, and in all sorts of realms,
it's not just rock-paper-scissors stalemates
they're reaching.
They actually cooperate with each other.
And you look close enough, and you see they're not relatives.
They're not relatives, yet you get
all sorts of altruistic behavior,
and you've got it under a whole bunch of domains.
Because this brings up the question,
why should you ever be cooperative
with another individual if you are a social animal.
At every possibility, you should stab them in the back
and be selfish.
And the reason why that isn't a good idea
is, there's all sorts of circumstances where
many hands make the task light.
Or whatever that is, cooperation can have synergistic benefits.
And you see that with species that
are cooperative hunters, where they are not necessarily
relatives.
They will chase one, chasing an animal
while the other is getting ready to cut a corner on it.
Cooperative behavior, and they increase the likelihood
of them getting a kill.
Another example of this.
Research by a guy named Mark Hauser
at Harvard looking at rhesus monkeys.
And what he showed was, he would put these monkeys
in a situation where they had access to food.
They had access to food under one circumstance,
where they could reach for it and take it in and share it
with another monkey.
Under the other circumstance, it required two monkeys
to get the food in there.
And what he showed was clear cut reciprocity.
Monkeys who were sharing with this guy
were more likely to get shared back with
and got more cooperation when it was a task where two of them
had to work together to get the food.
One alone wasn't enough.
Many hands make the task lighter under all sorts
of circumstances.
Cooperation has a strong evolutionary payoff,
even among non-relatives, with a condition.
Which is, you're not putting more into it
than you are getting.
That is reciprocal.
And ' opens up the third building block of all of this,
which is reciprocal altruism.
Cooperation, altruistic behavior among non-relatives,
but undergoing very strict constraints of,
it's gotta be reciprocated with all sorts of rules like that.
So what does that look like.
You're going to see reciprocal altruism,
when would you see that.
What's the immediate thing, what sort of species
would show systems of reciprocal cooperation
among non-relatives.
They've got to be smart animals.
They've got to be social.
They've got to be smart.
Why do they have to be smart?
Because they have to remember, this
is the guy who owes me a favor from last Thursday.
They need to be able to recognize individuals.
They have to be long lived enough so that there's
a chance of interacting with that individual
again and establishing this reciprocity.
You would thus predict you would see
systems of reciprocal altruism only in long
lived social vertebrates.
But you see the exact sorts of things in bacteria.
You see the exact sort of things in fungi.
You see that in all sorts of other realms.
You get social bacteria, colonizing bacteria.
And where what you might get are two clonal lines
that are together.
In other words, two genetically-- two lines,
each of which is, all the bacteria
have the same genetic makeup.
So think of it as one individual who's just kind of dispersed.
Another one who's just kind of dispersed.
And they've come together in something
called a fruiting body, which is how bacteria reproduce
or whatever.
And there's two parts to a fruiting body.
There's one which is the stalk, which
attaches to something or other.
And then there is the part that actually fruits.
So you want to be in the fruiting part,
because that's the part that actually reproduces,
and the stalk is doing all the work there.
And what you see is attempts at cheating.
Attempts at one of these strains trying
to disproportionately wind up in the fruiting part,
and what you also see is, the next time
around, this other strain will not cooperate with it.
Will not form a social colony.
So that's getting played off at the level of single cell
organisms forming big social colonies.
Getting played at that level.
Yes, as we will see, reciprocal altruism
works most readily in big, smart, long
lived social beasts.
But it can occur in all sorts of systems.
What it's built around is reciprocal cooperation.
And intrinsic in that it is another motivation going
on there.
Not just to involve the reciprocal relationship
with a non-relative, and many hands, and light tasks,
and all of that.
But also, whenever possible, to cheat.
To take advantage of the other individual.
And thus, another key facet of it
is to be very good at detecting when somebody
is cheating against you.
To be vigilant about cheating in what
would otherwise be a stable, reciprocal relationship.
And an awful lot of social behavior
is built around animals either trying
to get away with something or spotting somebody else
doing the same.
An example of it.
There is a test that's used in evolutionary psychology
where you are given this very complicated story,
or another version of a complicated story, where
somebody promises if you do this, you'll get this reward.
But if you do that, you're going to get this punishment.
And really complex.
And one outcome, the outcome of it
is, the person isn't supposed to get rewarded.
But the individual decides to reward them.
Spontaneous act of kindness.
In another circumstance, the person
is the individual who is supposed to get rewarded,
and instead, they get punished.
A cheater in that case.
And amid these convoluted stories,
people are much better-- 75% to 25%--
are much better at detecting when cheating has gone
on in the story than when a random act of kindness has gone
on.
We are more attuned to picking up cheating.
And remarkably, some very subtle studies
have been done with chimps showing
that chimps have the same bias.
They are much better at picking up
social interactions involving cheating than ones that
involve spontaneous altruism.
So you see here, this balance between cooperation,
reciprocal, even among non-relatives.
And that's great, but you should cheat
when you can get away with it.
But you should be vigilant against cheaters.
And what, of course, it comes down to then
is tic-tac-toe and giraffe hearts and all of that.
What is the optimal strategy in a particular social species
for a particular individual.
What is the optimal strategy.
When do you cooperate and when do you cheat.
When do you defect on the cooperative relationship
you've had.
And this introduces us to a whole world
of mathematics built around what is called game theory.
The notion that there are games, formal games, that
have mathematically optimal strategies,
or multiple strategies, multi-equilibrium.
And a whole world of research has
been built around them in terms of when to cooperate
and when to defect.
So game theory stuff.
This was starting off in a world of people
studying economics, and negotiation, and diplomacy,
and all of that.
And that was a whole world built around this logic
of when do you cooperate, when do you cheat.
And what came out of there were all sorts
of models of how to optimize behavior in terms of that.
And the building block, sort of the fruit fly of game theory,
is a game called the prisoner's dilemma.
Prisoner's dilemma, sort of cutting to-- sort of getting
rid of the details.
Two individuals are prisoners, and they escape,
and they're both captured.
And they're interrogated separately.
And both of them refuse to talk, that's great for them.
If they both squeal, they both get punished.
If one of them is able to squeal on the other one,
they get a great reward.
If the other one-- what you get formally
are four possible outcomes.
Both individuals cooperate, both individuals
cheat against each other, individual A cooperates and B
cheats, individual B cooperates and A cheats.
And what you get in prisoner's dilemma
is a formal payoff for each.
What gives you the greatest payoff, stabbing
the other guy in the back.
You cheat and they cooperate.
You have exploited them, you have taken advantage of them,
isn't that wonderful.
That's the highest payoff in prisoner dilemma games.
Second highest payoff, you both cooperate.
Third highest payoff-- which is beginning
to not count as a payoff, but in a lot of the games, this set up
is the start of punishment-- both of you
cheat on each other.
Fourth worst possible payoff is you're the sucker.
You cooperate, and the other individual
stabs you in the back.
So what the prisoner's dilemma game
is set up these circumstances where individuals will play
versions of this against each other with varying rewards
and that sort of thing, and parameters that we will
look at in a lot of detail.
And seeing when is it optimal to cooperate,
when is it optimal to cheat.
When would you do this.
So you've got examples of this, and this
was the building block.
And what anyone would say looking at this is,
it's obvious.
What you want to do is, in some way,
rationally maximize your payoff.
This whole world of Homo economists,
the notion of humans as being purely rational decision
makers.
And what you begin to see in this world of game theory is,
there is anything but that going on.
Later in the course, we're going to see
something very interesting.
People playing prisoner's dilemma games inside a brain
scanner, looking at a part of the brain that
has a lot to do with pleasure.
And what you see is, some individuals
activate that part of the brain when they have successfully
stabbed the other guy in the back.
Some individuals activate it when they have both cooperated.
And there's a big gender difference
as to which circumstance.
[LAUGHTER]
So you just guess which one is going on there.
We're going to see a number of studies
like that coming down the line.
So the question becomes, how do you
optimize prisoner dilemma play?
And what emerged at that time was
the notion of all sorts of theoretical models and stuff.
And then in the 1970s, there was an economist
at University of Michigan named Robert Axelrod who
revolutionized the entire field.
What he did was he took some paleolithic computer
and programmed in how the prisoner's dilemma would
be played.
And he could program in as if there were two players.
And he could program in what each one's strategy would be.
And what he then did was, he wrote to all of his buddies
and all of his mathematician friends and prize fighters
and theologians and serial murderers and Nobel Peace Prize
winners, and in each case, explained
what was up and saying, what strategy would you use
in a prisoner's dilemma game?
And he gets them all back, and he programs
all these different versions.
And he runs a round robin tournament.
Every strategy is paired against every other strategy
at one point or other.
And you look at what the payoff is.
You ask, which is the most optimal strategy.
And out of it, shockingly to everyone--
because this was a computer teaching us optimizing
human behavior-- out of it came one simple strategy that
always out-competed the others.
This is people sitting there, probabilistic ones
as to when to cooperate, and lunar cycles as to what to do.
The one that always won is now called tit for tat.
You start off cooperating in the very first round
with the individual.
You cooperate.
If the individual has cooperated with you in that round,
you cooperate in the next round.
And you cooperate, cooperate, as long
as the other individual cooperates.
But as soon as there is a round where the individual cheats
against you, you cheat against them the next time.
If they cheated at you that time also,
you cheat against them the next time.
If they go back to cooperating, you
go back to cooperating the next time.
You have this tit for tat strategy.
In the absence of somebody stabbing you in the back,
you will always cooperate.
And what they found was, run these hundreds
of thousands of versions of these round robin tournaments,
and tit for tat was the one that was most optimal,
to begin to use a word that is not just
going to be a metaphor.
Tit for tat always drove the other strategies
into extinction.
And what you wound up seeing is this optimized strategy.
And it was very clear why tit for tat worked so well.
Number one, it was nice.
You start off cooperating.
Number two, it retaliates if you do something crummy to it.
Number three, it is forgiving.
If you go back to cooperating.
Number four, it's clear cut in its play.
It's not some probabilistic thing.
What you get, then, with tit for tat is,
suppose you're playing three rounds with another individual.
You both cooperate the first one,
you both cooperate the next one.
You're playing tit for tat strategy,
so you cooperate on this one.
And they stab you in the back, and you can't get back at them,
because this is the last round.
What you'll see is, under lots of circumstances,
tit for tat is disadvantageous.
But what the soundbite is about it is, tit for tat
may lose the battles, but it wins all the wars.
This pattern of being nice, but being retaliatory, being
forgiving, and being clear in the rules,
drives all the other strategies into extinction.
OK, at this point my alarm just went off,
which was to remind me to ask somebody
who is wearing a life vest-- is somebody wearing a life vest?
[INAUDIBLE]
Over there.
Where are you?
She just left.
She left.
Isn't that interesting?
Somebody put me up to having to ask this person,
why are you wearing a life vest?
And apparently the answer she would give
was going to free all sorts of captives in some rebel group
in Colombia.
And she fled.
OK, what that does is--
[LAUGHTER]
I don't know what that says about reciprocal altruism.
But what that says also is, after I do a summary,
don't make a move.
We will have a five minute break.
So what do we have at this point,
we have the first building block of optimizing
the evolution of behavior, like optimizing giraffe hearts.
First piece, you don't behave for the good of the species.
Individual selection, passing on as many copies
of your own genes as possible.
Sometimes a chicken is an egg's way of making another egg,
he says triumphantly.
Building block number two, kin selection.
Some of the time, the best way to pass on copies of your genes
is by way of helping relatives.
Kin selection, with the mathematical fierceness
of degree of relatedness driving it.
Piece three, sometimes what's most advantageous
is to cooperate, even with non-relatives,
but with the rules of it has to be reciprocal
and you have to cheat when possible.
You have to be on guard against cheaters.
And as we've just seen, game theory, prisoner's dilemma,
beginning to formalize optimal strategies for that.
OK, let's take a five minute break.
But promise you will come back if you go out,
and everyone won't wander off.
Altruism [INAUDIBLE] game theory as being a form or way
to maximize that behavior in a very artificial realm,
but stay tuned.
Prisoner's dilemma as the building block
of how to do this amid lots of other types
of games that are used.
But prisoner's dilemma is the most basic one.
And that round robin tournament, that computer simulation,
Axelrod asking all his buddies to tell him
what strategy would you use, run them against each other,
and out comes tit for tat.
Tit for tat drives all the others into extinction.
However, there is a vulnerability
in tit for tat, which is-- OK, so.
We have the technical way of showing prisoner's dilemma
play.
And first round, both individuals are cooperating.
Second round, both individuals are cooperating.
Third round, this one cheats-- those are fangs.
This one cheats and this one cooperates.
So the next round, this one now cheats and this one
goes back to cooperating, and we've just
gotten through a scary thing that tit for tat solves,
and it's great.
Wonderful.
What if, though, your system is not 100% perfect.
What if there's a the possibility
of a mistake being made, of sending the wrong signal.
What if there's the possibility of noise in the communication
system.
And at some point, an individual who
does a cooperative behavior, thanks to a glitch
in the system, it is read as having been defection.
So what happens as a result?
This individual-- forget it.
OK, what happens as a result. The individual who cooperated,
but somehow the message got through as cheating,
they don't know.
Something got lost in the wires between them in translation.
The other individual was saying whoa,
that individual cheated against me.
I'm going to cheat in the next round.
So along comes the next round, and that individual
cheats against them.
This one who's cooperating, because they've
been cooperating all along.
They don't know about this error.
And they say whoa, that person just cheated against me.
I'm going to cheat in the next round.
So they cheat in the next round.
This one says whoa, they just cheated another time,
again and again and again.
And what you get is a seesaw pattern for the rest of time.
You've just wiped out 50% of the cooperation.
And what you've got is tit for tat strategies
are vulnerable to signal error.
That's something that soon came out in these studies
of Axelrod's.
When I was a kid, there was like one of these thriller
books I remember reading where there's a glitch in the system.
And at the time, the mean scary Soviet Union
launched a missile that-- no, it was the United States.
The United States, by accident, launched
a missile, a nuclear weapon, where they didn't mean to.
Some cockroach chewed through a wire some place or other.
And the missile went off, and wound up destroying Moscow.
And oh my god, we had a cooperative system
of mutually restraint of aggression, all of that.
And thanks to a signal error, a cheating signal
was accidentally sent off.
And how did the book end?
A tit for tat response.
In order to avoid thermonuclear wasteland,
the Soviet Union was allowed to destroy New York.
All right, so that shows exactly how
you could then get into a see-sawing thing,
simply by way of if the system has any vulnerability
to signal error.
So it soon became clear, as soon as Axelrod
began to introduce the possibility of signal errors,
that tit for tat didn't work as well as another strategy, one
that quickly came to the forefront.
And that one-- for some strange reason,
that's the way it's shown.
That one was called forgiving tit for tat.
What happens with forgiving tit for tat?
The usual rule, like tit for tat, if you cooperate,
if they cooperate, you always cooperate.
If they cheat against you, you punish them in the next round.
Exactly the same thing as tit for tat,
but oh no, what if there's a signal error in the system
and you've gotten caught in one of these horrible seesawing
things.
What forgiving tit for tat does is,
we'll have a rule, for example, that if we
see saw like this five times in a row,
I will forego cheating the next time.
And instead, I'll cooperate.
And that will get things back on track.
I am willing to be forgiving in one round
in order to re-establish cooperation
after the signal error came in.
And that one-- as soon as you introduce
the possibility of signal error, that one out-competes
tit for tat.
Because it makes perfect sense.
It's a great way of solving that problem.
So that was terrific.
Tit for tat with the ability to forgive,
and what you would then see is variability, how many of these
do you need to go through before you forgive,
what's the optimal number of see-sawings, all of that.
So a whole world of optimizing how soon you're forgiving.
Nonetheless, the general theme being forgiving tit
for tat out-competes tit for tat when you can have signal error.
But there is a vulnerability.
There is a vulnerability here to this one, which
is, you could be exploited.
If you're playing against, for example, a tit for tatter,
or all sorts of other strategies, where
they don't have forgiving strings of defection
and you do, what's going to happen
is you're going to keep going back to cooperating,
they're going to keep stabbing you in your back.
Forgiving tit for tat is vulnerable to exploitation
playing against individual players that
don't have forgiveness in them.
So what soon became apparent was an even better strategy, which
is you start off with a tit for tat strategy.
Which is, you are punitive, you are
retaliatory amid being forgiving, clear and nice
initially.
You are willing to punish, and you cannot be exploited in this
way.
If and only if you have gone whatever number of rounds
without the other individual ever cheating on you, if you've
gone long enough without that happening,
you switch over to forgiving tit for tat.
What is that?
That's deciding you trust somebody.
You've had enough interactions with them
that you are willing to trust them.
This is the transition from pure rational optimizing
to switching over, forgiveness coming in there protects you
from signal error.
And of course, now, a whole world of how many rounds do you
need to do this before you switch that as to what
the optimal deal with that is.
But again, this is a way of transitioning
to solve the problem of signal error,
but forgiving too readily and being taken advantage of.
Soon, another strategy appeared, which was called Pavlov.
And those of you who know Pavlovian psychology
will see that this, in fact, has nothing whatsoever to do
with Pavlovian psychology, and I don't know why they did that.
But they thought it was kind of cool.
But the rule was remember, if you
stab the other guy in the back, you get a bunch of points.
If you both cooperate, you get points, not as many.
If you both cheat, you lose some points.
If you're taken advantage of, you lose a lot of points.
So two outcomes you gain, two outcomes you lose.
In Pavlov, the simple rule is when I do something,
if I get points, if I get some degree of reward,
I do it again the next time.
If I get rewarded in either of the first two types of payoffs,
I do the same thing again.
And the other part, of course, is, if I play my strategy
and I lose one of the two bottom outcomes,
I switch to the other strategy the next time.
And what you see is that can establish very good tit
for tat stuff.
But if you sit and spend hours tonight
with a long roll of toilet paper and playing
out all the rounds of it, you will
see what Pavlov allows you to do is exploit
somebody else who is forgiving.
So Pavlov goes along just fine with this.
And as long as Pavlov continues, whenever they switch over
to a forgiving tit for tat, Pavlov
will out-compete them, because Pavlov exploits.
What then emerged was just zillions of people studying
all sorts of games like this.
There's other ones, ultimatum game, there's a trust game.
It's the same notion of business there,
which is you choose to cooperate, you choose to cheat,
what's the optimal outcome.
There are mathematically optimal outcomes that you can use,
and you run all of it against the computer,
and you get the optimization popping out the other end.
Wonderful.
So there's Axelrod and his buddies using terms
like oh, this strategy will drive
the other one into extinction.
Or this strategy works, but if you program in
that every now and then there could be a glitch,
there can be a mutation, this will be-- they're
using all this biology jargon, obviously metaphorically.
But right around this point, the biologists
look at this, who are just beginning to think
about the social biology stuff.
Formal patterns of optimizing behavior.
And they say whoa, does this apply to the behavior
of real organisms?
Because at this point, it's just economists and computer types
and diplomats learning when to optimize,
all that sort of thing.
Around the time there was a paper published,
somewhat before that.
This is a name nobody is going to know,
lost in history, a guy named Daniel Ellsberg.
Daniel Ellsberg became very famous around 1970,
by he was working in the Pentagon
and he stole thousands of pages of secret files
there, and gave it to the New York Times
showing how utterly corrupt everything that
went on behind the scenes was in getting us into Vietnam.
Major blowout, all of that.
He had spent the early part of his career perfectly happily
working in the Pentagon for the military as a game theorist.
As a game theorist coming up with optimal patterns.
And he wrote one paper called "The Optimal
Benefits of Perceived Madness".
What times do you want your opponent
to think you are absolutely out of your mind
and going to do all sorts of crazy stuff,
and where they wind up cooperating
to keep you from doing that.
The advantages of madness, what's that.
That's systems where things like mutually assured destruction
doesn't work, because you are willing to set it off.
The advantages of madness.
This whole world of people working on it, mathematicians
and war strategists.
And there's the zoologists now looking at this saying whoa,
this is cool.
I wonder if animals behave that way.
And that's when people, now armed with their insights
into prisoner's dilemma and tit for tat,
all this stuff, started to go and study animals out
in the wild and see, were there any examples where
this happened.
Yes.
In all sorts of interesting realms.
First example, vampire bats.
Vampire bats, we are all set up to be creeped out
by vampire bats.
But in actuality, when you see a vampire bat drinking
the blood of some cow or something,
you are watching a mommy getting food for her babies.
Because vampire bat mothers are not actually
drinking the blood.
They're filling up this throat sack thing,
and they go back to the nest and they disgorge
the blood to feed their babies.
She's just watching out for her kids.
It happens that vampire bats have an interesting system
of reciprocal altruism, which is a whole bunch of females
will share the same nest.
Will have all their kids in there mixed in.
And these are not necessarily related,
so we've just left the world of kin selection.
They're not necessarily related, but they have
reciprocal altruists system.
Each female comes in, disgorges the blood,
and feeds everybody's babies.
And they all feed each other's babies,
and everything is terrific.
And they have this blood vampire commune going there.
And they've reached a nice state of stable cooperation.
Now, make the bats think that one of the females
is cheating on them.
Out comes that female flying off to find some blood, and instead
you net her and get a hold of her,
and take some syringe full of air
and pump up the throat sack so the throat
sack is really full and distended,
but there's no blood in there.
You've just pumped air into there.
And stick her back into the nest there.
And she's just sitting there happily,
and the other females are sitting
saying look at her, look at how much blood she's got there.
I can't believe it, because she's not feeding our kids.
She's cheating on us.
And the next time they go out to feed,
the other females don't feed her kids.
A tit for tat.
What you saw here is an exact example
of introducing signal error.
Signal error, in this case, being some grad student
pumping up the throat of some vampire bat
and showing that they're using a version of a tit for tat
strategy.
Totally amazing.
People were blown away by this.
Another example, fish.
Stickleback fish who, in the world of animals-- you know,
bats are probably not some of the brightest folks around.
But I don't think sticklebacks are within light years of them.
But stickleback fish can do a tit for tat strategy.
Here's what you do.
You have a stickleback fish in your fish tank,
and you make the fish believe that he's
being attacked by another fish.
What do you do?
You put a mirror up against the edge of the tank there.
So within a very short time-- I told you
they were not that smart.
So within a very short time, he's
lunging forward at this mirrored thing
and maintaining his territory against this guy
and barely holding on.
And that other guy is just-- he doesn't get tired.
Thank god I don't get tired.
And they're just going at it.
And now make him think he has a cooperative partner.
Put in a second mirror that's perpendicular here.
In other words, he sees his reflection there.
And every time he moves forward, the
sees that one moving forward, which is fortunate
because he's also seeing another fish coming from that way.
And he's sitting there saying, this is great.
I don't know who this guy is, but wow, what a team we are.
[LAUGHTER]
Doubles, this is great.
He's in there and the thing is, it's funny how those two
guys are so synchronized.
But whoa, we're holding them off and we're doing it.
Now make him think his cooperating partner is,
in fact, cheating on him.
Take the mirror and angle it back a little
bit so the reflection is set back some.
And what he now sees is the fish moving forward,
but not all the way up to the wall there.
The fish is hanging back there.
The fish is cheating.
And this stickleback is sitting there saying, in effect,
that son of a bitch.
I can't believe he's doing that to me.
We've worked together for years.
I can't believe he's-- oh he's pretending to go forward.
But I see he's not really doing that.
Fortunately, that guy isn't coming forward anymore, either.
Phew.
But I can't believe the guy is cheating.
And the next time you set up this scenario, the next time
there's a chance the stickleback doesn't attack
its own reflection there.
It is tit for tatting against this guy.
So here we've managed to set up one of these deals
within one fish and carrying it out forever.
One fish, ultimately with some very blistered lips.
Tit for tat, once again.
Another example.
This is the most bizarre one I can imagine, and leads
to all sorts of subjects that are going
to come many lectures from now.
But there are fish species that will change sex.
And they do it under all sorts of strategic circumstances
that suddenly begin to fit into this realm of what
we've been learning about.
And you've got one of these things called black hamlet
fish.
And they can change gender.
So you'll have a pair of them who
hang out with each other of opposite genders,
and they take turns.
They flip back and forth.
For a while, this one's female, and for a while,
this one's female.
And they go back and forth, and that's great.
But there's an inequity there, which
is that the price of reproduction
is greater for the female than for the male.
As is the case in so many species,
the female doing all that egg and ovaduct
and progesterone stuff, or whatever it is.
And the male's just got to come up with some sperm there.
Doing to reproduction as a cooperating pair,
they're not relatives.
Reciprocal altruism, maximizing each of their reproductions.
Whoever's the female in any given round
is the one who's paying more.
What you see are reciprocal relationships there
of the fish using tit for tat.
If you get one fish that begins to cheat and winds up
being a male too much of the time,
the other fish stops cooperating with them.
Again, tit for tat stuff.
So people were just blown out of the water at this point,
seeing whoa, forget rational human economic thinking,
all of that.
You go out into the wild, and bats and stickleback fish
and gender switching fish and all of that,
they're following some of the exact same strategies.
Isn't nature amazing.
No, nature isn't amazing.
It's the exact same logic as saying
a giraffe has to have a heart that's
strong enough to pump blood to the top
of the head of a giraffe.
Or else there wouldn't be a giraffe.
And when you look at this realm, it's applying the same notion.
This same sort of wind tunnel of selective optimization
for behavior-- in this case, when to cheat,
when to cooperate-- sculpts something
that is as optimized as a giraffe's heart
being the right size.
So this made perfect sense.
Wonderful.
But then people began to look a little bit closer,
and began to see the very distressing real world
beginning to creep in there.
Which were exceptions.
First exception.
This was done by a guy named Craig Packer, University
of Minnesota, looking at lions in East Africa.
What you get is, typically, prides
are a whole bunch of relatives, usually female, sisters,
nieces, all of that.
But you will sometimes get prides that
are not of close relatives.
Nonetheless, they will get reciprocal altruistic things
going on.
Lions, in this case, having the same trick as
was done on those vervet monkeys.
Researcher putting inside the bush there a speaker,
and playing the sound of like 400 menacing lions all at once.
What you're supposed to do is freak out at that point.
And all of you need to very carefully approach and see
what's going on in that bush.
So what would happen in a reciprocal system,
and everybody does this.
Or if one time, one of them cheats on you,
you push that one forward the next time.
Or some such thing.
That's what you would expect.
But what he would begin to notice
is, in a bunch of these groups, there'd be one scaredy cat
lion, one who habitually stayed behind the others
and who wasn't punished for it.
So this produced this first puzzle
that oh, sometimes animals aren't optimizing tit for tat.
Sometimes animals haven't read Robert Axelrod's landmark 1972
paper, that sort of thing.
And what you suddenly have is the real world.
What could be possible explanations?
One thing being, maybe they're not really paying attention.
Maybe they're not quite that smart.
Wait, bacteria are doing versions of tit for tat.
What else could be going on?
Oh, lions interact in other realms.
Maybe this individual is doing very reciprocal stuff,
forgiving overly altruistic stuff in some other realm
of behavior.
Maybe this lion eats less of the meat
and backs off earlier, or something like that.
Maybe there's another game going on simultaneously.
And this is introducing the real world
in which it is not just two individuals
sitting there playing prisoner's dilemma and optimizing.
You suddenly begin to get real world complexities coming
in there.
And by the time we get to the lectures,
way down the line, on aggression and cooperation,
what you'll see is things get really complicated
when you have individuals playing games simultaneously.
The rules that you apply to one psychologically
begin to dribble into the other one.
All sorts of things like that.
It will get very complicated.
So a first hint there that, in fact, everything
doesn't work perfectly along those lines.
Here's another version.
Here's one of the truly weird species out there,
something called the naked mole rat.
If you ever have nothing to do and you've
got Google Image up there, go spend the evening looking up
close up pictures of naked mole rats.
These are the weirdest things out there.
They are the closest things among the mammals
to social insects, in terms of how their colonies work.
They're totally bizarre, all of that.
But they live in these big, cooperative colonies
that are predominately underground in Africa.
And they were discovered, I think, only in the 1970s or so.
And for a while when zoologists got together,
if you were a naked mole rat person,
you were just the coolest around.
And everybody else would feel intimidated,
because you were working on the best species out there.
And you would see these big cooperative colonies,
soon shown to not necessarily be of relatives.
And reciprocity and all those sorts of rules.
But people soon began to recognize
there would be one or two animals in each colony that
weren't doing any work.
Work digging out tunnels, bookkeeping,
I don't know what naked mole rats do in terms of work.
But there would be a few individuals who
would just be sitting around.
And they were these big old naked mole rats.
They were much bigger than the other ones,
and they were scarfing up food left and right.
There goes Robert Axelrod down the drain.
There goes all that optimization,
because no one would be punishing these guys.
What's the deal?
And it took enough watching these animals long enough
to see this notion of oh, there's
another game going on in which they
play a more important role.
And it is sort of dribbling across.
When the rainy season comes, these big naked mole rats
go up and turn around and they plug the entry to the tunnels
then.
[LAUGHTER]
That's what they do.
And suddenly, these guys who have
been sitting around doing no work whatsoever all year
and eating tons of stuff, they suddenly have to now stick
their rear ends out for the coyotes to be around
or whatever it is that predates them.
What we have is role diversification.
Real animals, real organisms, are not just
playing one formal prisoner's dilemma game against each other
at the same time.
And by the time we, again, get to the later lectures
on aggression, cooperation, all of that,
we will not only see that things get much more complicated when
you're playing simultaneous games,
when you're playing a game against one individual
while you're playing against another one,
and then against triangular circumstances.
How play differs if you know how many rounds
you are playing against the individual versus
if you have no idea.
How play differs if, when you are
about to play against someone, you
get to find out what their behavior has
been in the previous trials with other individuals.
In other words, if somebody shows up with a reputation,
we'll see this is a much more complicated world
of playing out these games.
A much more realistic one.
So we begin to see a first pass at all this optimization stuff,
and how great that all is.
One final interesting addition to this game theory world
of thinking about behavior like that, which came from a guy
named James Holland, who apparently-- might
have a different first name.
But Holland, apparently, as an interesting piece in history,
he's the person first person to ever get
a PhD in Computer Sciences.
Which I think was in the late 50s, University of Michigan.
Apparently, there are realms of computer programmers
who worship this guy.
And he, like a lot of other folks in that business,
got interested in this game theory evolution
of optimal strategies.
And he designed ways of running all of this.
And he introduced a new ripple, which
is the possibility of a strategy suddenly changing.
The possibility of a mutation.
What he could then study was mutations,
how often they were adaptive, how often they
spread throughout the strategy there, of individuals playing.
How often they drove the other strategies
into extinction versus ones that were quickly
driven to extinction themselves.
More cases where we are getting these systems
where maybe they're not just metaphorically using terms
from biology.
Maybe they are exactly modeling the same thing.
And we will see more and more evidence for that.
OK, so reciprocal altruism.
How would that play out in the world of natural selection.
Natural selection, cooperative hunting.
And there's lots of species that have cooperative hunting.
Wild dogs, jackals, some other species as well.
Clearly, that's like the definition
of cooperative hunting, of reciprocal altruism,
if they're not relatives.
How would sexual selection play out
in the realm of reciprocal altruism?
A little bit less obvious there.
That would be if you and some non-relative
spent an insane amount of energy and time
making sure you both look really good before going to the prom.
That would be sexual selection working on reciprocal altruism
system.
So what we have now are three building blocks.
This whole trashing of it's not survival of the fittest.
It's not behaving for the good of the species.
It's not behaving for the good of the group.
But instead, these three building
blocks, the ways to optimize as many copies of your genes
in the next generation as possible.
Way number one, individual selection,
a version of selfish genes.
Sometimes a chicken is an egg's way of making another egg.
Behavior is just a way of getting copies of genes
into the next generation.
Piece number two, inclusive fitness kin selection.
That whole business, that sometimes the best
way of passing on copies is to help relatives do it.
And it's a function of how related they are.
The whole world of cooperation more among related organisms
than unrelated ones.
And as we will see way down the line, what
is very challenging in different species
is, how do you figure out who you are related to?
And humans do it in a very unique way that sets them up
for being exploited in all sorts of circumstances that
begin to explain why culture after culture, people
are really not nice to thems, and it flows along those lines.
This is something we will get to in a lot of detail.
So degree of relatedness, a lecture coming.
How do you tell who you're related to.
But that second piece, kin selection.
Third piece, reciprocal altruism.
You scratch my back and I'll scratch your back.
And whenever possible, you want to instead scratch your back,
and they want to make sure you're
not scratching your back.
Or whatever cheating counts as.
But trying to cheat, being vigilant against it,
formal games where you can optimize it, very complicated.
And can you believe it, you go out into the real world,
and you find examples of precisely that.
Optimization with tit for tat, isn't nature wonderful.
It's gotta work that way.
Then you begin to see how the real world is more complicated.
Multiple roles, naked mole rats stuck in plumbing,
things of that sort.
These are the principles.
And what people of this school of evolutionary thought
would say, armed with these sorts of principles,
you could now look at all sorts of interesting domains
of animal behavior and understand
what the behavior is going to be like by using these.
OK, we start with the first example.
Here we return to these guys.
And we have one species here, and knowing
this guy had a penis and this one nursed,
we've got an adult male and an adult female.
What is it that you can conclude?
In this species, males are a lot bigger than females.
Let's state it here as there's a big ratio of males to females.
Meanwhile in the next county, you've
discovered another species where somebody's got a penis
and somebody else is nursing.
And their skulls are the exact same size.
Oh, here's a species where there's
no difference in body size between males and females.
Let's begin to see, just using the principles
we've got in hand already, what sort of stuff we can predict.
Starting, which of those species-- in one case,
you have males being a lot bigger than females.
In one case, you've got males being the same size as females.
In which of those species, the first one like this,
or the same size ones, which ones
would you expect to see more male aggression?
First one.
OK, how come?
Their bodies are built for it.
Which begins to tell you something,
their bodies are built for it, maybe
because females have been selecting for that.
You will see higher levels of aggression
in species like this, where there's a big body size
difference, and much less of it in these guys.
Next, you now ask how much variability is there
in male reproductive success.
In one of these species, all the males
have one or two kids over their lifetime.
In another species, 95% of the reproducing
is carried out by 5% of the males.
A huge variability skew in male reproductive success.
Which species do you get the every male has
a couple of kids, and that's about it, and all equally so?
Which one?
[INAUDIBLE]
Second one.
How come?
Because these guys are being selected for aggression.
If they're fighting, there's going
to have to be something they're fighting for.
Deferential reproductive access.
OK, so you see more variability in species that look like this.
Next, females come into the equation.
What do females want?
What do females want in the species on the left
versus the one on the right?
The one on the right, again, skull's
the same size, same body size.
On the left, what does the female want?
[INAUDIBLE]
What sort of male is the female interested in?
[INAUDIBLE]
Big.
Exactly.
That's exactly the driving force on this.
How come?
Because she's not going to get anything else out of this guy.
This guy is just going to, like-- the present
is going to be some sperm.
It might as well be some good sperm, some genetically
well-endowed sperm that makes her a big healthy offspring,
increasing the odds of her passing on copies of her genes
in the next generation.
What about in this species?
What's females looking for?
[INAUDIBLE]
OK, good.
Hold on to that for a second, and let's
jump ahead a few lines.
One of the species, males have never
been known to do the slightest affiliative thing with infants.
They just get irritated and harass them and all of that.
In the other, you have soccer dads
who are doing as much raising of the kids as the females are.
In which species do you get lots of male parental behavior?
Smaller.
The one on the right.
OK.
So lots of male parental behavior here.
Somebody just gave the answer here, female choice.
What would you see in this species?
You want big, muscular guys.
You want whatever is selling that season for what
counts as a hot male, because you want your offspring
to have those traits.
And somebody else called out here,
what do females want in this category?
And what was it you said?
Good personality.
[LAUGHTER]
Good personality.
Yes.
Able to express emotions.
[LAUGHTER]
That, too.
OK, somebody else shouted out something
that gets at the broader, more globally Oprah version.
OK, somebody shouted out--
[INAUDIBLE]
--parental behavior.
You want a male who is going to be competent at raising
your children.
What is it that you want, really most deeply?
You want to get the male who is the most like a female you
can get a hold of.
You don't want some big old stupid guy
with a lot of muscle and canines who's wasting energy on stuff
like that he could be using instead on reading Goodnight
Moon or some such thing.
What you want instead is somebody
who's as close to a female as you can get to without getting
this lactation stuff.
Males are chosen who are the same size as females.
So the term given here is choosing for paternal behavior,
parental behavior.
Parental, let's just put that in there.
And that begins to explain the top line, species
in which there's a lot of sexual dimorphism.
Morphism, shapes of things.
Sexual dimorphism, big difference
in body size as a function of gender.
And in these sorts of species where
you get male parental behavior, not
much variability in male reproductive success,
low levels of aggression, and what
females want is a competent male.
These are ones where you see low degrees of sexual dimorphism.
So how's a female going to figure out
that this guy is going to be a competent parent?
Once again, we just figured out, if he looks kind of like you.
Because that suggests he hasn't wasted health and metabolism
on stupid, pointless muscles when there's
more important things in life for making sure
your kids have good values.
What else would the female want to know when she's first
considering mating with a male?
Is he a nice guy, is he sensitive,
does he express his feelings.
Is he competent at being a parent.
What do you want the individual to do?
Prove to you that he can provide for the kids.
And suddenly you have a world of male birds courting the females
by bringing them worms.
Bringing them evidence that they are
able to successfully forage, they are able to get food.
Female choice is built around appearance
and behavioral competence at being
able to be a successful parent in order
to pass on as many copies of genes
to the next generation as possible.
OK, how about life span.
In which species is there a big difference in life expectancy
as a function of gender?
First one.
Here you're choosing for males to be
as close to females as possible, and thus the physiology.
Here you've got these guys who are
using huge amounts of energy to build up
all this muscle, which takes a lot more work
to keep in calories.
And you're more vulnerable in famines.
You've got these males with high testosterone,
which does bad stuff to your circulatory system.
You've got males who, thanks to all this aggression,
are getting more injuries, more likely.
In species in which you have a lot of sexual dimorphism
in body size, you get a lot of sexual dimorphism in life span.
Then you look at these guys, and it's basically
no difference by gender.
Moving on.
Considering primates that are one
of these two patterns, in which one do you always
want to give birth to twins, in which one do you never
want to give birth to twins?
Who gives birth to twins?
[INAUDIBLE]
The one of the right, of course.
How come?
Because you've got two parents on the scene.
You are not a single mother.
And you are a single mother rhesus monkey or something,
and you give birth to twins, and you do not
have the remotest chance of enough energy,
enough calories on board, to get both of them to survive.
A twin that is born in a species like this
has the same rate that it occurs in humans, about a 1% rate.
And it is almost inevitable that one of them does not survive.
Meanwhile, there's a whole world of primate species
with this profile where the females always twin.
Finally, you are the female and you
are contemplating bailing out on your kids
and disappearing, because there's
some really hot guy over there who you want to mate with.
And you are trying to figure out this strategy.
So you are going to leave and abandon your kids.
In which species do you see that behavior?
The one on the right.
The one on the right, because you bail out and the male
is there taking care of them.
You bail out in here, and you've lost your investment and copies
your genes for the next generation.
You see female cuckoldry, this great Victorian term.
You see females cheating on the fathers in this species,
but not in species like this.
Because the father is long gone and three other counties there,
courting somebody else.
And it doesn't matter, you're not
going to get any help from him.
In primate species of this profile,
you always see twinning.
And they both survive.
And what studies have shown in these species,
and we'll get to them shortly, is
after birth, in fact, the males are expending more calories
taking care of the offspring, then
the females go bail out on him and go find some other hot guy.
Which, in your species, counts as some guy
who looks even more like you than he does in terms of what
you want out of the individual.
So that.
So what have we done here?
We've just gone through applying these principles
in this logical way, and everybody
from the very first step was getting the right outcome.
And go, and these are exactly the profiles
you find in certain species.
Among social mammals, these would be referred to
as a tournament species.
A tournament species, whereas the one on the right
is referred to as a pair bonding, a monogamous species.
Because in this one, males and females
stay together, because they both have equivalent investment
in taking care of the kids.
All of that.
What you have here is this contrast
between tournament species and pair bonding species.
Tournament species, these are all the species
where you get males with big, bright plumage.
These are peacocks, these are all those birds
and fish species where the males are all brightly colored.
What are the females choosing for?
Peacock feathers does not make for a good peacock mother.
Peacock feathers are signs of being healthy enough
that you can waste lots of energy
on these big stupid pointless feathers.
That's a sign of health.
That's a sign of all I'm getting from this peacock is genes,
I might as well go for good ones.
That's the world of peacocks, that's
the world of chickens with pecking orders,
dominating like that, lots of aggression.
That's the world of primates where, as in savanna baboons,
the male is twice as big as the female.
Tournament species, where a lot of passing on of genes
is decided by male-male aggression in the context
of tournaments producing massive amounts of variability
in reproductive success.
Where males are being selected for being good at this,
so they sure are being selected for having big bodies, which
winds up meaning a shortened life
span for a bunch of reasons.
Females are choosing for that.
These are guys who are not using their energy
on parental behavior, thus you do not
want to have twins if you are a female baboon,
and you do not want to bail out on the kids
because nobody else is going to take care of them.
Go and look at a new primate species,
and see this much of a difference in skull size,
and you'd just be able to derive everything
else about its social behavior.
Meanwhile, these guys on the right, pair bonding species.
These are found among South American monkeys, marmosets,
tamarins.
You put up a picture of them, which
I will do if I ever master PowerPoint
in some subsequent lecture-- you put up
a picture of a marmoset pair, and you can't tell
who's the male and the female.
This is not the world of the mandrill baboons,
with males with big, bright, bizarre coloration on the face,
and with antlers when the females don't,
and that whole world of sexual dimorphism.
You can't tell which one is the male
and which one is the female marmoset by looking at them.
You can't tell by seeing how long they live.
You can't tell by how much they're
taking care of the kids.
You can't tell in terms of their reproductive variability.
That's a whole different world of selection.
All of the South American tamarins and marmosets,
the females always twin.
They have a higher rate of cuckoldry,
of abandoning the kids.
The males take as much care, if not more,
of the kids than the female does.
Very low levels of aggression.
Same body size, same lifespan.
All the males have low degree of variability.
How come?
Because if you're some marmoset male,
you don't want to get 47 marmoset females pregnant.
Because you are going to have to take care of all the kids.
Because as we will see way down the line in lectures
on parental behavior, the wiring there is such
is bonding with the offspring and taking care of them.
No wonder among species like these,
you have very low variability.
All the males reproduce once or twice.
This is the world of 5% of the guys accounting
for 95% of the matings.
This is totally remarkable because again,
that starting point.
You start off here, and you look at these,
and oh, you can tell if they were bipedal and were
they diseased or malnourished, simply by applying
these principles of individual selection, reciprocity,
all of that.
One factoid, you see a new primate species,
and you see one nursing and one with a penis,
and they're the same size or there's difference in the size,
and you already know all about their social system.
Very consistent across birds, across fish, across primates.
Of course, all of those, this dichotomy
between tournament species and pair bonding species.
As we will see way down the line,
among some species, types of voles, rodents,
that are famous in Hallmark cards for their pair bonding,
for their monogamy.
As we'll see, they're not quite as monogamous
as you would think.
But nonetheless, a general structure like this.
So, one asks expectedly, where do humans fit in on this one?
Where do humans fit?
And the answer is, complicatedly.
Are we a tournament species, are we a pair bonding species.
What's up with that?
What we will see is we're kind of in between.
When you look at the degree of sexual dimorphism,
we are not like baboons, but we're sure not like marmosets.
We're somewhere in the middle.
Variability is somewhere in the middle there.
I'm not going near that one.
Life span, the dimorphism in lifespan
tends to be in between.
Parental behavior and likelihood-- all of those,
you look at a number of measures.
And by next lecture, we'll be looking
at some genetics of what a monogamous species
and tournament species look like.
And we're right in the middle.
In other words, that explains like 90% of literature.
Because we're not a classic tournament species and we're
not a classic pair bonding one.
We are terribly confused in the middle there.
And everything about anthropology supports that.
Most people on the planet right now
are in a form of monogamous relationships
in a culture that demands monogamy.
An awful lot of people who are in monogamous relationships
in such cultures aren't really in monogamous relationships.
Traditionally, most cultures on this planet allowed polygamy.
Nonetheless, in most of those polygamous cultures,
the majority of individuals were pair bonded and monogamous.
You get two different versions of polygamy
in different social systems of humans.
One is economic polygamy, which is you're basically
sitting around, and the wealthiest guy in the village
is the one who can have the largest number of wives.
An enormous skew in reproductive success
that's driven by economics.
The other type is demographic.
You have a culture where, for example, you
have a warrior class.
Guys spend 10 years as warriors-- worriers, warriors,
New York City accent.
As warriors, they don't worry.
There's no anxiety.
But they eventually worry about getting a wife,
because by the time they're done being a warrior,
they're like 25.
And they marry someone who's 13, which
is what you see in a lot of traditional cultures
that follow that pattern.
And at that point, you've got a problem,
which is an awful lot of those guys have been killed
over the course of 10 years of being involved
in high levels of aggression and 10 more years of life
expectancy to catch up with you.
There's is a shortage of males.
So you see polygamy there driven by demographics,
and you see polygamy driven by economics
in other types of society.
So most cultures on this planet allow-- traditionally,
before the missionaries got them--
most cultures on this planet allow polygamy.
Nonetheless, within most polygamous cultures,
the majority of people are not polygamous.
We have one really confused, screwed up species here.
Because we are halfway in between in all sorts of these
measures.
OK, so what do we have next, which
we will pick up on Friday.
What we've just started with here
is the first case of using all these principles,
individual selection, kin selection, reciprocal altruism,
to understand all sorts of aspects of behavior.
We will then move on to seeing how
they explain other aspects of animal behavior, some ones
which, if you are behaving for the good of the species circa
1960, there's no explanation at all, because you're
doing things like killing other members of your species.
And then finally, we will see how
this applies to humans and some of the witheringly
appropriate--
For more, please visit us at stanford.edu.