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  • Stanford University.

  • The often asked question, what's the difference between Bio 150,

  • Bio 250, and-- is it Hum Bio 160?

  • No difference.

  • It's exactly the same.

  • So like the same requirements, same unit.

  • So take whichever one makes your life easiest.

  • Let's see.

  • Any other procedural stuff?

  • Well, the answers are back from Monday's questionnaire.

  • And a variety of interesting answers.

  • Not surprisingly, given the size of a group.

  • Why have you taken this course?

  • Really want to know about animal behavior, but willing to deal

  • with humans.

  • [LAUGHTER]

  • Because I'm substituting it Bio 43, which I don't want to take.

  • My dad used to make me read books about human behavior

  • and biology as punishment.

  • [LAUGHTER]

  • That doesn't make any sense.

  • I know one of the TAs, so I figure

  • that guarantees me an A. OK, guys, that's in your court.

  • One I really liked, because I want

  • to be a filmmaker after college.

  • Yay, interdisciplinary.

  • What else?

  • My first grade teacher is making me.

  • Tom McFadden told me to.

  • I'm a hyper-oxygenated dilettante.

  • I wanted to, somewhat correctly pointing out,

  • why have you taken this class?

  • I haven't taken it yet.

  • A number of people reporting that,

  • in fact, that was the correct answer.

  • And my favorite, why have you taken this course?

  • Yes.

  • [LAUGHTER]

  • OK.

  • Relevant background, relevant background.

  • I'm human, I'm human and I often behave.

  • I'm human and I have biology.

  • 19 years of being confused about human behavior.

  • Not really, sort of.

  • Seeing crazy behavior as an RA in an all frosh dorm.

  • And I date a biologist.

  • Let's see.

  • There was also the question on there of,

  • did the thing on the board look more like an A or a B.

  • And just to really facilitate that one,

  • I forgot to put the A and the B up.

  • But that taps into a cognitive something or other,

  • which maybe I'll get back to at some point.

  • Telephone numbers.

  • Reading them off, accuracy dramatically

  • tanked as soon as the three number,

  • four number motif went down the tubes.

  • And when it came back briefly, accuracy

  • came back a little bit.

  • Finally, let's see.

  • All of you guys conform to a standard frequent gender

  • difference.

  • Which is everybody was roughly equally-- by gender-- roughly

  • equally likely to see dependent as the opposite of independent.

  • A small minority went for interdependent.

  • However, one finding that has come up over and over

  • is that far more females are interested in peace than males,

  • males are more interested in justice.

  • OK, have you taken the bio core.

  • Quote, no way Jose.

  • Somebody pointing out quite correctly,

  • don't settle for peace or justice.

  • Then of course, there was the person

  • who responded to that question by writing those words are just

  • symbols.

  • Need to know assumed meaning.

  • [LAUGHTER]

  • OK.

  • There was one questionnaire that was carefully

  • signed in something approaching calligraphy,

  • it was so beautiful.

  • And was otherwise blank.

  • For years running, the subject that most people really

  • want to hear, and most people really don't want to hear,

  • is about the biology of religiosity.

  • And for 22 years running now, Stanford students

  • are more interested in depression than sex.

  • [LAUGHTER]

  • OK.

  • So we start off.

  • I keep telling Hennessy about this, but nothing gets done.

  • We start off.

  • We start off, if I can open this--

  • which is something you can do if you have

  • a certain type of training.

  • If you're some osteologist, or whatever these folks are

  • called.

  • If you are presented those two skulls

  • and told this one's a female, this one's

  • a male, you can begin to figure out stuff like how heavy,

  • how large the body was of that individual, what

  • diseases they had, had they undergone malnutrition,

  • had they given birth, a lot of times, a few times,

  • were they bipedal.

  • All sorts of stuff you could figure out

  • from just looking at these skulls.

  • What today's lecture, and Friday's, is about

  • is the fact that with the right tools under your belt,

  • you could look at these two skulls

  • and know that information.

  • You are a field biologist, and you've discovered this brand

  • new species.

  • And you see that this one nurses an infant

  • shortly before leaping out of the tree,

  • leaving only the skull.

  • And this one has a penis, shortly

  • before leaping out of the tree and leaving a skull.

  • So all you know is this is an adult female and an adult male.

  • And if you've got the right tools there,

  • you can figure out who's more likely to cheat on the other.

  • Is the female more likely to mess around, or is the male?

  • How high are the levels of aggression?

  • Does the female tend to have twins, or one kid at a time?

  • Do females choose males because they have good parenting

  • skills, or because they're big, hunky guys?

  • What levels of differences in life expectancy?

  • Do they live the same length of time?

  • You would be able to tell whether they have the same life

  • expectancy or if there's a big discrepancy between the two.

  • All sorts of stuff like that, merely

  • by applying a certain piece of logic

  • that dominates all of this.

  • OK, so you're back reading those Time Life nature

  • books back when, and there was always a style of thing

  • you would go through.

  • Which is they'd describe some species

  • doing something absolutely amazing and unlikely,

  • and it goes like this.

  • The giraffe, the giraffe has a long neck,

  • and it obviously has to have a big heart

  • to pump all that blood up there.

  • And you lock up a whole bunch of biomechanics people

  • with slide rules, and out they come out with this prediction

  • as to how big the giraffe heart should be

  • and how thick the walls.

  • And you go and you measure a giraffe heart,

  • and it's exactly what the equations predicted.

  • And you say, isn't nature amazing?

  • Or you read about some desert rodents that drink once

  • every three months, and another bunch of folks

  • have done math and figured out how many miles long

  • the renal tubules have to be.

  • And somebody goes and studies it,

  • and it's exactly as you expect it.

  • Isn't nature wonderful?

  • No, nature isn't wonderful.

  • You couldn't have giraffes unless they

  • had hearts that were that big.

  • You couldn't have rodents living in the desert

  • unless they had kidneys that worked in a certain way.

  • There is an inevitable logic about how organisms function,

  • how organisms are built, how organisms

  • have evolved solving this problem of optimizing

  • the solution.

  • And what the next two lectures are about is,

  • you can take the same exact principles

  • and apply them to thinking about the evolution of behavior.

  • The same sort of logic where, just

  • as you could sit there and, with logical principles,

  • come to the point of saying, a giraffe's heart

  • is going to be this big.

  • You can go through a different realm of logic built

  • around evolutionary principles and figure out all sorts

  • of aspects of social behavior.

  • And we already know what's involved in, say, optimizing.

  • What's the optimal number of whatevers in your kidney.

  • What's the optimal behavior strategy or something.

  • All of us, as soon as we got some kid sibling,

  • learned how to do the optimal strategy in tic-tac-toe.

  • So that you could never lose, and it's totally boring.

  • But that's a case of figuring out the optimal solution

  • to behavior, reaching what is called the Nash equilibrium.

  • And actually, I have no idea what I just said.

  • But I like making reference to Nash,

  • because it makes me feel quantitative or something.

  • So that is called the Nash equilibrium.

  • The Nash equilibrium, and what the entire point here is,

  • the same sort of process of figuring out

  • what are the rules of optimizing tic-tac-toe behavior

  • can be built upon the principles of evolution

  • to figure out all sorts of realms

  • of optimized social behavior.

  • And broadly, this is a field that's known as sociobiology,

  • emerging in the late 1970s-- mid 1970s or so.

  • And by the late 1980s, giving birth

  • to another discipline known as evolutionary psychology.

  • The notion that you cannot understand behavior,

  • and you cannot understand internal psychological states,

  • outside the context of evolution had something to do with

  • sculpting those behaviors and those psyches.

  • So to start off with that, basic song and dance about Darwin.

  • Just to make sure we're up to speed on this.

  • Darwin, just to get some things out of the way.

  • Darwin did not discover evolution.

  • People knew about evolution long before that.

  • Darwin came up with the notion of a mechanism

  • for evolution, natural selection.

  • And in fact, Darwin is the inventor of that.

  • There was another guy, Alfred Russel Wallace,

  • the two of them.

  • And, for some reason, Wallace has gotten screwed historically

  • and Darwin gets much more attention.

  • But starting off with a Darwinian view of how evolution

  • works.

  • First thing being that there is evolution.

  • Traits in populations change over time.

  • Traits can change enough that, in fact, you

  • will get speciation.

  • New species will form.

  • And the logic of Darwinian evolution

  • is built on just a few couple of very reasonable steps.

  • First one is that there are traits that are heritable.

  • Traits that could be passed on one generation to the next.

  • Traits that we now can translate,

  • in our modern parlance, into traits that are genetic.

  • And we will see, soon, how that's totally not correct

  • to have said that.

  • But traits that are heritable.

  • The next thing is that there is variability among those traits.

  • There's different ways in which this trait can occur,

  • and they're all heritable.

  • The next critical thing.

  • Some versions of those traits are more adaptive than others.

  • Some versions work better for you.

  • For example, giraffe who wind up with hearts

  • the size of, like, a tomato, that's not an optimal version.

  • Amid the range of variability, some

  • will carry with them more fitness, more adaptiveness,

  • than others.

  • And that translates into another sound bite

  • that's got to be gotten rid of.

  • All of this is not about survival of the most adapted.

  • It's about reproduction, something we will

  • come to over and over again.

  • It's about the number of copies of genes you

  • leave in the next generation.

  • So you've got to have traits that are heritable.

  • There's got to be variability in them.

  • Some of those traits are more adaptive than others.

  • Some of those traits make it more

  • likely that that organism passes on copies of its genes

  • into the next generation.

  • And throw those three pieces together, and what you will get

  • is evolution in populations.

  • Changing frequencies of traits.

  • And when you throw in one additional piece, which

  • is every now and then the possibility