This is the opening lecture of the course entitled Human Behavioral Biology delivered by Stanford professor Robert Sapolsky. This presentation happened on March 29, 2010. Below is the full transcript of the lecture.
Robert Sapolsky – Stanford professor
This is BIO 150, isn’t it? OK, just wanted to make sure.
So we start off with a scenario. 40 year-old guy — quiet, suburban life. Married 15 years, two kids, 3.5 dogs. Everything’s standard. Everything’s going wonderfully. And one day out of nowhere, he punches somebody in the face at work. Totally bizarre, out of character. The guy is standing there by the water cooler and makes some comment on some baseball team, takes exception to it, punches him in the face. Utterly strange. Things are quiet.
Three months later, his wife of 15 years happy marriage discovers he’s having an affair with a 16-year-old checkout kid down at the Safeway. Really weird.
Then three months after that, he absconds with all the money at work, embezzles it, disappears, and is never seen again.
Three possibilities. First one, this guy is a truly deep creep. Second, he is having the most immature midlife crisis you could ever imagine. Third possibility, he has a mutation in one gene in his head.
And what we will be seeing is this is exactly the profile that you get in a certain neurological disease where it’s one gene that’s out of whack. First demonstration of that.
OK, just to get a sense of who’s here, how many of you think there is a genetic influence on sexual orientation? OK, how many think it is possible for prenatal events to influence your political opinions 30 years later? OK, how many think that there is a valid way of using biology to understand who’s religious and who isn’t? Not quite as many hands there.
OK, as long as we’re in that terrain, how many people believe in God? How many people believe in souls? How many people believe in evil? How many people believe in free will? That’s going to change.
Oh, I might as well ask. Is there anybody in this room who actually does believe in evolution? Just wanted to make sure. See what we’re dealing with here.
OK, how many think that there is a genetic influence and that there is a basic biological difference, sex difference, in levels of aggression? How many think there’s biological basis of sex differences in intelligence?
OK, who thinks it’s all explained by nature? Who thinks it’s all explained by nurture? Who thinks there’s a magnificent, fascinating, nuanced interaction between nature and nurture?
Yay. OK, well everybody’s going to get an A+ then. You already have the course under control.
So we start off trying to find something in common. Look at these four events here — or not, in terms of being scraped out there. But these are four circumstances that have something surprising in common. Having your period. Having a brain tumor. Eating a lot of junk food. Taking anabolic steroids. Those of you who are not oriented to with, that’s the ones that build up your muscles like testosterone derivatives. OK, these all have something in common — having your period, having a brain tumor, eating a lot of junk food, and taking a lot of anabolic steroids.
Anybody want to fathom a guess what’s the commonality amongst the four of them? Yeah.
Hormones. Good. OK, we’re off and running with hormones. Good. Even more specific than that. Something they all have in common.
Oh, come on, somebody want to guess? I see these brief movements of hands there as people change their mind.
OK, it all has to do with hormones. They all have hormones in common, I say, trying to facilitate somebody making the next guess. Oh, come on. They all have something. OK, we got to get out of here at some point. These all have four things in common. All of these have been used successfully in courts of law to explain the behavior of a murderer.
In the first case, a number of cases where the fact that a woman was having her period at the time of killing someone was part of what a jury said led them to exonerate the person. A literature showing that a disproportionate share of female aggression comes around the time of menses.
Next one, there is an area of the brain you will know so much about over the next three months called the amygdale that has something to do with aggression and has something to do with fear. And you get a brain tumor there, and in a number of cases, you get someone who is uncontrollably violent. And this has also been used successfully in a court of law.
Junk food, any of you who are San Francisco history buffs will know 20 years ago, 30 years ago that Dan White, a disappointed office seeker, assassinated the mayor of San Francisco along with Harvey Milk. And as part of his remarkably successful defense for a double murderer that led to a remarkably short jail sentence, was the famed Twinkie defense. The argument that his addiction to junk food caused wild fluctuations in his blood sugar levels, which caused him to do that.
Finally, anabolic steroids. Any number of cases of people having uncontrolled violence arguing because they were weight lifters and a wildly abusive range of taking this stuff had something to do with violence.
Put all four of these together, and we get the first of the two points of this entire course. Which is, sometimes the stuff that’s going on in your body can dramatically influence what goes on in your brain.
Second critical point, tonight, when you’ve settled back down, and you’re ready to go to sleep, and you’re nice and relaxed, and your heart’s beating nice and slow, think the following thought. You know, that heart isn’t going to beat forever. Think about your lips turning blue after. Think about the blood flow slowing down. Think about your feet and your toes getting cold. And at that point, you will probably be increasing the rate at which that heart beats. And you will have just seen the second key thing in this course, which is sometimes what’s going on in your head will affect every single outpost in your body.
And what this course is about is the intertwining, the interconnections between your physiology and your behavior — the underlying emotions, thoughts, memories, all of that, and the capacity of each to deeply influence the other under all sorts of circumstances.