Practice English Speaking&Listening with: 2. Behavioral Evolution

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Stanford University 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 requirement same unit so take

whichever one makes your life easier

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 because I'm

substituting it for bio 43 which I don't

want to take my dad used to make me read

books about human behavior and biology

is punishment that doesn't make any

sense I know one of the TAS so I figured

that guarantees me an A okay guys it's

in your current one I really liked

because I want to be a filmmaker after

college EA interdisciplinary what else

my first grade teacher is making me

atomic fat and 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 a correct answer and my

favorite why have you taken this course

yes okay

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 a null frosh dorm and I date a

biologist let's see there was also the

question on there of the thing on the

board look more like an A or B and just

to really facilitate that when 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

when for entity interdependent however

one finding that has come up over and

over is that far more females are

interested in peace than males males

more interested in justice okay 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 meeting okay

there was one question here that was

carefully signed and something

approaching calligraphy it was so

beautiful and was otherwise blank for

years running the course 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 okay so we start off I keep telling

Hennessy about this but nothing gets

done okay we start off we start off if I

can open this which is something you

could do if you have a certain type of

training if you're some osteology store

whatever you smokes 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're 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 tree leaving only the

skull and this one has a penis shortly

before leading leaping out of the tree

and leading leaving a skull so all you

know is this is an adult female an adult

male and if you've got the right tools

there you could 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

and see 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 okay 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 describe some

species doing something absolutely

amazing and unlikely and go like this

the giraffe the giraffe has a long neck

and it obviously has to a big heart to

pump all that blood up there and you

lock up a whole bunch of biomechanics

people with you know 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 like desert rodents that drink once

every three months and another bunch of

folks have done math and figured out

like 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 juris unless they add

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 a 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 giraffes 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

whatever's in your kidney what's the

optimal behavior strategy

something all of us as soon as we got

like some kids sibling learn how to do

the optimal strategy in tic-tac-toe and

so that you could never lose and it's

totally boring but that's the case of

thinking about 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 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 isn't the

inventor of that there was another guy

Alfred Russel Wallace the two of them

and for some reason Wallace has gotten

screwed historically in 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 soundbite that's

got to be gotten rid of all of this is

not about survival of the most adapted

it's about reproduction of 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 their modern parlance a

mutation from that you could begin to

get actual large changes in what a

population looks like okay 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 won't come from this Darwinian

tradition into thinking about behavior

is you do the exact same thing there are


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 incendiaries issue there as to how

genetic and that's not the same thing as

saying how genetically determined how

genetic behavior is okay so that's going

to be a 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 and you'll sit around

and saying well what would a female

chimpanzee want to do at this point to

optimize the number of copies of regimes

in the next generation

what would this brine shrimp want to do

to deal with this environmental stressor

what would this you know cherry tree do

they're not planning they are not

conscious they are 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 L of

evolution and reducing the optimal they

want to do this this is just going to be

a shorthand throughout

once you get past the Apes nobody is

wanting to do any of these optimization

things so just getting that's a

terminology out of the way okay 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 some

thing 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 it's dawn on the savanna and you

see there's a whole bunch of 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

were looking at one of the Magnificent

things of the natural world which is the

migration of zebras throughout East

Africa a herd of two million of them

migrated around following a cyclic apat

urn 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 in 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 in 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 end

entered 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 mine

kinder and throws himself into the river

where immediately the Crocs get beat he

busy eating them up and the other two

million wildebeest could tiptoe around

the other way across the river and

everybody's fine and you're then saying

why'd this guy do this why did this guy

fling himself into the river and we

would always 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 Wynn Edwards

hyphenated Wynn 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

Wynn Edwards in group selection that

would be the term selection for the good

of groups for the selection for the good

of a species win Edward and group

selection I'm sure the guy did all sorts

of other useful things and anyone who

really is has any depth to them would

find out they're 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 jumps in the river

and finally when you look at them long

enough instead of the camera crew

showing up for three-minute when you

study 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 this

guy's been pushed from behind because

all the other ones are saying yeah get

the old guy on the river sacrificing

himself I asked 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 this


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 new species of

the group but to maximize 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 its self 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 the chicken is an

egg's way of making another egg okay

ignore that sometimes what the guy said

is sometimes a chicken is an egg's way

of making another egg all this behavior

stuff and all this animus or a 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 about is

maximizing 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 and 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


that carry no adaptive value but for

some random bizarro 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 and male moose and they

use that for fighting off predators or

fighting whether the male that would be

natural selection sexual selection might

account for the fact that like the

antlers or green paisley patterns all

over for that

and for some reason that looks cool the

female moose mooses 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 that traits

those traits will also become more


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 than

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 the 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 2m 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 rule of sexual selection

to have more of whatever those traits

are that are attractive

so this first building block it's not

group selection is 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's another way of

accomplishing the same thing that you

just did with the individual selection

as follows one of the things that could

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 a hundred percent 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

okay so the closer a relative is to you

the more copies of G the more genes they

share in common with you so suddenly

you've got this issue you're an

identical twin and you're 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 forego reproducing to make it

possible for your identical twin to do

so because on a 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 to 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 like witty

geneticists of all time a guy named Hall

Dane who apparently once a nabarro 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 one-eighth with each

of them and it winds up being a whole

org 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 the 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 you

know one identical twin to have civil

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 and animal

behavior of animals being obsessed with

kinship animals being fully aware of who

is related to who and 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

and 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

and Xenia I believe and what they did

was a whole bunch of these vervet

monkeys were sitting around and they the

researchers had made really high-quality

Riccar recordings of various

vocalizations from the monkeys over time

so they had the sound of each animal

giving alarm call giving a friendly

gesture call giving or whatever and what

they would then do is hide a microphone

inside some bushes and play the sound of

one of the infant's from the group

giving an alarm call so what is the

mother of that infant - 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


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 that came out in these studies so

you've got two females each of whom has

a kid a daughter or whatever and female

a and female B and one day female a does

something absolutely rotten - 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 this will see

all sorts of other species can do this

also there's that caveat again all sorts

of other species

want to figure out who their cousins and

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

it'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 eight 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

often 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 for going to help

relatives as a function of degree

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 and things animals like forgo

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 cost B C can damage

a but it costs a and you get the right

distribution of

with one of those traits in a population

and you will reach a rock-scissors-paper

equilibrium where nobody is doing

anything rotten to each other great

example totally cool example that got

published some years ago by a guy named

Brendan Bohannon 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 third one the

good thing going for it is that it

didn't have the bad thing was it didn't

have poison the 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

strengths each one of those has a

vulnerability they're like no pokemons

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 to see who's the one who can

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


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 and 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're 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


to 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 this opens up the

third building block of all of this

which is reciprocal altruism cooperation

altruistic behavior among non relatives

but undergoing very strict sort of

constraints of it's got to be

reciprocated with all sorts of rules

like that so what does that look like so

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 got

to be smart animals they got to be

social they got to be smart why don't

have to be smart because they have to

remember this is the guy who like 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 to 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's the

part that actually fruits so you want to

be in the fruiting part because that's

the part that actually reproduce

is in the stock is doing all the work

there and what you see is attempts at

cheating attempts at one of these

strains trying to disproportionally 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

live social beast but it can occur in

all sorts of systems so what it's built

around is reciprocal cooperation and

intrinsic in that is another motivation

going on there not just to involve a

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 there is a

test that's used in evolutionary

psychology where you're 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 like really

complex and in 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 is supposed to

get rewarded and instead they get


a cheater in that case and amid these

convoluted stories people are much

better seventy five percent to twenty

five are much better at detecting when

cheating has gone on in the story then

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 the 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 and reciprocal and

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 like 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 blocks

sort of the fruit fly of game theory is

a game called the prisoner's dilemma

prisoner's dilemma of sort of cutting

two is already going to really tails two

individuals or prisoners and they escape

and they're both captured and they're

interrogated separately and if 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

word 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


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 stab and the other

guy in the back you cheat and they

cooperate you have exploited them you

have taken advantage of them isn't that


that's the highest payoff in prisoner

dilemma games second-highest payoff you

both cooperate third highest payoff

which is beginning to not Canada's two

payoff but in a lot of the games is set

up as 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

is 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 and later in the course we are

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've 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 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

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 a

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 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 explain 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 computer 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's 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


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 its clear-cut in

its play it's not some probabilistic

thing and 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 dis advantageous 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 okay 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 over there um where are you

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 like rebel group in Colombia and

she fled okay what that does is 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 a first

building block of optimizing the


like optimizing giraffe hearts first

piece you don't believe behave for the

good of the species individual selection

passing on as many copies of your own

genes as possible sometime a chicken is

an egg's way of making another egg he

says triumphantly building block number

two Ken 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 at piece 3 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 five

minute break but you promise you will

come back if you go out and everyone

will wander off 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 the 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 outcomes tit for

tat tit for tat drives all the others

into extinction

however there is a vulnerability in

tit-for-tat which is

okay 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's sheet and

this one cooperates or 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 a

hundred percent perfect

what if there's the possibility of a

mistake being made of sending the wrong


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 defected

defection so what happens as a result

this individual forget it

okay what happens as a result the

individual who cooperated but somehow

the message got through is cheating they

don't know something got lost in the

wires between them and translation the

other individual is 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

and when I was a kid there was like one

of these like thriller books I remember

reading where there's a glitch in the

system and at

I mean scary Soviet Union launched a

missile that knows the United States the

United States by accident launched a

missile a nuclear weapon where they

didn't mean to some cockroach

you know chewed through the wire

someplace or other and the missile went

off and wound up being destroying Moscow

and oh my god we had a cooperative

system of mutually sort of 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 sort of thermonuclear wasteland

the Soviet Union was allowed to destroy

New York okay 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 assumes 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

ways 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 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 see-sawing things

what forgiving tit for tat does is we'll

have a rule for example that if we

seesaw 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

reestablish cooperation after the signal

error came in and that one as soon as

you introduced the possibility of signal

error that one outcompetes tit for tat I

guess it makes perfect sense it's a

great way of solving that problem

so that was terrific tit for tat that

the ability 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

C songs all that's a whole world of

optimizing how soon you are forgiving

nonetheless the general theme being

forgiving tit for tat outcompete stood

for tab 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 tat er 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 and they're going to

keep stabbing in your back forgiving tit

for tat is vulnerable to exploitation

playing against individual players that

don't have forgiveness in it 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

forgiven clear nice initially you were

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 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 either the first two types

of payoffs I do the same thing again and

the other part of course is and if I

have if I play my strategy and I lose

one of the two bottom the two bottom

outcomes I switched 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 you know 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 Pablo

goes along just fine with this and as

long as Pablo continues whenever they

switch over to a forgiving tit for tat

pavlovo out-compete them because Pavlov

exploits what they then emerged was just

zillions of people studying all sorts of

games like this there's other ones

ultimatum game as a trust game but 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

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

sociobiology stuff formal patterns of

optimizing behavior and they say whoa

does this apply to the behavior of real

organisms is 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 and 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 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 of that that systems were

things like mutually assured destruction

doesn't work because you're really

willing to set it off that the

advantages of math is this whole world

of people working on it mathematicians

and more strategist 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 and

all this stuff started to go and study

animals out in the wild and see were

there any examples where this happened


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 about 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 this throat sac thing and they

go back to the nest and they discord 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

altruism each female comes in

discouraged the disc gorges the blood

and feeds everybody's babies and they'll

all feed each other's babies and

everything is terrific and they have

this blood vampire commune going there

and they have reached in my state of

stable cooperation now make the bats

think that one of the females is

cheating on them outcomes 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 which stickleback

fish can do a tit-for-tat strategy

here's what you do you have a

stickleback fish in your in your fish

tank and you make the fish you make him

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 then in

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's

just he doesn't get tired thank God I

don't get tired and they're just going

at it on 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 he sees

that one moving forward and which is

fortunate because he's also seeing

another fish coming from that way and he

say they're saying this is great I don't

know who this guy is but wow what a team

we are doubles this is great he's in

there and the think it's funny how those

two guys are so synchronized the whoa

we're holding him off 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 work together every years

I can't believe you

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 whew but I can't

believe that guy's cheating and the next

time you set up this scenario the next

time move the chance this stickleback

doesn't attack its own reflection there

it is tit for tiding 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 improved 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 sexes 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 is doing

all that egg and oviduct and

progesterone stuff or whatever it is and

the males just got to come up with some

sperm they're doing 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 is

paying more and 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


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


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

giraffe and when you look at this realm

it's applying the same notion the same

sort of wind tunnel of selective

optimization for behavior in this case

when did she'd want to cooperate sculpt

something that is as optimized as a

giraffes 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 sort of a very

distressing real-world beginning to

creep in there which were exceptions

first exception this was done by a guy

named Craig Packer University in a soda

looking at Lions in East Africa and 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 you know 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 four hundred

menacing lions all at once and you know

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 to use this does this or if

one time one of them cheats on you you

push that one forward the next time or

somesuch saying 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 do 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


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 is

each less of the meat and backs off

earlier or something like that maybe

there's another game going on

simultaneously and this 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 it and by the

time we get to the lectures way down the

line on aggression and cooperation what

you will 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 like spend the evening

looking up close-up pictures of naked

mole rats these are like 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 predominantly

underground in Africa and they were

discovered I think only in the 1970s or

so and for a while when zoologist got


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 a relatives

and reciprocity 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 on a wood naked mole-rats do

in terms of work but there would be a

few individuals who would just be

sitting around and there was 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 line

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 them 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 were 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


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 purse 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 you know 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 and what he could then study

was mutations how often they were

adaptive how often they spread

throughout the strategy they're of

individuals playing how often they drove

the other strategies into extinction

versus ones that broom quickly driven to

extinct in 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

okay 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

jackal some other species as well that's

clearly that's like the definition of

cooperative hunting of cooperative

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

relatives 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 altruistic system

so what we have now are our 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 into

visual 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 as a function

of how related their 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're 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 them and it flows

along those lines this is something we

will get to 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 achieve 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 got to work that

way and then you begin to see how the

real world is more complicated multiple

roles naked mole-rats stuck in plumbing

things of that sort

okay so these are the principles and

what people of the 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 okay 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 adult female what is it that you can


food in this species males are a lot

bigger than females

so 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 in somebody else's nursing and

their skulls are the exact same size

oh here's the species where there's no

difference in body size between males

and females okay so let's begin to see

just using the principles we've got in

hand already what sort of stuff we can

predict starting okay 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


in which of those species the first one

like this or the same sized ones and

which ones would you expect to see more

male aggression first one okay 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 and another

species 95% of the reproducing is

carried out by five percent of the

male's a huge variability skew and 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 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 differential reproductive

access okay so you see more variability

and 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 you

know again

skulls the same size same body size on

the left what does the female want what

sort of male is the female interested in

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 for a big healthy offspring

increasing the odds of her passing on

copies for genes in the next generation

what about in this species

what's females looking for okay 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 or

harassed and all of that and 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 the one on the

right okay so lots of male parental

behavior here so 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 yes

able to express emotions

that too okay somebody else shouted out

something that gets at the broader more

globally Oprah version okay somebody

shout it out perturb parental behavior

you want a male who's 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 that

he could be using instead on you know

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 you know choosing for paternal

behavior parental behavior or don't

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 and

these sorts of species where you get

male parental behavior not much

variability male reproductive success

low levels of regression what females

want is a competent male these are ones

where you see low degrees of sexual

dimorphism so how's the female going to

figure out that this guy is going to be

a competent parent you know 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 the male

see a nice guy as he sensitivities

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 bird 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 jeans

the next generation as possible

okay how about lifespan and which

species is there a big difference and

life expectancy is a function agender

first one here are you choosing for

males to be as close to females as

possible and unless the physiology here

you got these guys who are like 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 and 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 and body size

you get a lot of sexual dimorphism and

lifespan and 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 and

which one do you never want to give

birth to twins who gives birth to twins

the one on 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 the 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 other

right because you bailout and the male

is there taking care of them you bailout

in here and you've lost your investment

and copies your jeans for the next


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 you know three other

counties they're courting somebody else

and 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

than 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 and 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

bird 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 gettin 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