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