Transcript: Robert Sapolsky on Behavioral Evolution at Stanford

Stanford professor Robert Sapolsky discusses Behavioral Evolution in detail at Stanford. This lecture took place on March 31, 2010. Below is the full transcript.

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Robert Sapolsky – John A. and Cynthia Fry Gunn Professor and Professor of Biology, of Neurology & Neurological Sciences, and of Neurosurgery

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. 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 as punishment. 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.

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.

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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 a person who responded to that question by writing those words are just symbols. Need to know assumed meaning.

There was one questionnaire that was carefully signed in 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.

  1. 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 is 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.

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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’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 expected. 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.