Toxoplasmosis is a parasitic infection found in the feces of cats and other animals, and it s been around for a really long time. It s found a way to get into the brains of animals and humans, and in doing so, it s changed the way we think about fear and attraction. In this episode, we talk to neuroscientist and animal behaviorist Dr. Robert Krieger about the cat parasite, Toxoplasma gondii, and how it got into our bodies and brains. And how it s changing our perception of the world and the things we can do to make us more attractive to other animals and things we don t want to be attracted to them. Plus, we learn about how a parasite can rewire an animal s brain to reprogram its neural wiring to make them less afraid of predators. This episode was produced by Alex Blumberg and edited by Annie-Rose Strasser. Music by Ian Dorsch and Mark Phillips. Additional music by Zapsplat and Matthew Boll. Art: Mackenzie Moore. Music: Hayden Coplen. Editor: Steven Kanter. Editor: Patrick Muldowney. Cover art by Ian McKirdy. The theme song is by Ian Somerhalder. Our ad music is by Haley Shaw, courtesy of Epitaph Records, and our ad music was written and produced by Matthew Boll, and additional selections were produced by Robert Kucharski. Additional music was done by Mark Hollands and Mark Boll, with additional engineering by Matthew McElveen. and John Rocha. Thank you, and the rest is by Mark McElroy for the music used in this episode was written, edited by John Chamberlain, and edited, and provided by Ian Meegan, and Matthew Korte, and his band is . and the music was produced and produced for this episode is by Bobby Lord, and is by Jeff Perla. , and the production was edited by Jeff Graham. for use in the music is , and is a postcode is by in this eponymous author, and by , with permission by . Thank you is a copyright of , edited by ? by Brian Stellare, on this episode and , in association with permission by Rachel Ward, by David Schwartze .
00:00:39.000Well, it was just fascinating to me that, literally, I mean, what is the number that you estimate in Americans alone that might have been infected?
00:00:48.000I think it's on the order of, I'm not sure with Americans, but worldwide, it's something like 50% of humans is the best guess.
00:00:59.000For people who've never heard of this, would you mind explaining what this parasite is and how it affects rats and then cats and then people?
00:01:07.000So it's this protozoan parasite, Toxoplasma gondii, and it's got one of these weird parasitic lifestyles.
00:01:15.000The only place on earth where it could reproduce sexually is in the gut of a cat.
00:01:21.000I don't know why there are people who know this, but so it reproduces there, comes out in the cat feces, feces are eaten by rodents, and now Toxo's evolutionary challenge is to get that rodent into a cat's stomach.
00:01:35.000So what Toxo has evolved is this ability, it slowly migrates to the brain of rodents and basically wipes out the innate fear that rodents have of cat smells.
00:01:49.000Like, you take a lab rat who's been like the descendant of lab rats for like a thousand years and they've never seen a cat and put like a little puddle of cat pee in its cage and the rat's going to go on the other side of the cage.
00:02:01.000Just hardwired, instinctual aversion to cat pheromones and then put toxin in a rat and it loses that aversion.
00:02:10.000And in fact, in a subset of rats, they like the smell.
00:02:13.000So, out in the natural setting, you now go and approach a cat, and soon the rodents inside the cat's stomach, and Toxo is completed its life cycle.
00:02:24.000Well, I'd heard that it was a subset of rats that actually are gravitated towards it, because I'd heard it actually rewires them sexually, right?
00:02:32.000Yes, that's actually work that we did in my lab, that it...
00:02:37.000Basically crosses some of the circuitry in the brain and the hypothalamus so that cat pheromones that used to be activating every alarm circuit in your limbic system and these rodents now instead sort of taps into sexual arousal pathways.
00:02:54.000And in male rats, when they smell cat pheromones, they increase testosterone production.
00:03:01.000So TOXO has just figured out the most brilliant way of doing it.
00:03:08.000Is there any understanding at all of the mechanism of how a parasite can figure out how to rewire an animal's sexual reward system, the fear of predators?
00:03:22.000Well, that's something my lab spent a bunch of years on, trying to figure out...
00:03:28.000I mean, you look at some of these parasites, this taps into this whole world of behavioral manipulation of hosts by parasites, and it turns out They've evolved unbelievably brilliant mechanisms for manipulating hosts for their own benefit.
00:03:44.000You get rabies, you get a rabid dog, and what that's about is a virus that has affected the nervous system of that dog so that it's now rabid and more likely to bite somebody with viral Particles in its saliva,
00:04:00.000which it now passes on to the next individual.
00:04:03.000Like, you take 10,000 neuroscientists and stick them in a convention on the neurobiology of aggression, and rabies knows more about the neural wiring of aggression than we do.
00:04:15.000And toxo knows, quotation marks, something about fear and aversion and the neurobiology of attraction.
00:04:24.000Part of what it seems to involve is toxo, somewhere along the way, has picked up a gene that is pertinent to the dopamine system.
00:04:39.000There's no protozoan parasite for buoy mirrors that's had any use for this stuff, except it's part of how toxo seems to be manipulating the reward system in rodents.
00:04:51.000And then, a couple years ago, there's a paper showing that in chimpanzees, toxo makes you less afraid of the smell of leopards.
00:05:01.000So, this appears to be a parasite that just has evolved like this spectacular insight into fear circuitry and attraction circuitry, and it's all for its own benefit to wind up in a cat's gut.
00:05:15.000So specifically cats, do the chimpanzees still have aversions to snakes and other things that can kill them?
00:06:04.000As far as I know, the chimp study has only been with big cat urine, but the rodent studies, exactly that, showing it's a fair specificity.
00:06:12.000The rodents lose a little bit of their general skittishness.
00:06:18.000They get a little bit disinhibited behaviorally.
00:06:20.000So just in general, they're out more and more exploratory, more likely to get eaten.
00:06:25.000But the most selective lasering effect is they're not scared anymore of cat pheromones.
00:06:31.000Now, what's fascinating to me is that I've also read that there was a disproportionate amount of successful soccer teams that are in countries with high rates of infestation of toxoplasma.
00:06:45.000Okay, that one's new to me, but that sounds like exactly the sort of epidemiological studies that are popping up about humans.
00:06:58.000There's two branches of interesting stuff with Toxo in humans.
00:07:02.000One is a literature that's been around for quite some time showing that Toxo seems to increase the risk of schizophrenia.
00:07:11.000There's a higher rate of schizophrenia of individuals who have antibodies against Toxo.
00:07:18.000In other words, sometime in the past, their body was Dealing with it, who had cats growing up, whose mother had cats during pregnancy, and like anybody who gets pregnant knows you immediately get all anxious about cat litter boxes because of the possibility of toxoplasmosis.
00:07:37.000It can attack the fetal nervous system, do all sorts of damage, and a subtle version of it seems to be a sleeper effect of increasing the risk of schizophrenia.
00:07:48.000The other realm is toxo-infected humans get subtle changes in personality, neuropsychological profiles.
00:08:01.000If you're toxo-infected, you're more likely to die in a car accident involving reckless speeding.
00:08:09.000If you're toxinfected and clinically depressed for the same severity of depression, you're more likely to impulsively kill yourself.
00:08:18.000In other words, toxo is doing something kind of similar.
00:08:21.000If you're a rat, one of the hardest wired scary things in the universe out there is the smell of a cat.
00:08:27.000If you're a human, it's hurtling through space really fast, jumping out of windows and Toxo seems to blunt a lot of those effects there.
00:08:39.000In the speech that I saw you give, you were talking about your time working in a hospital and that there was a disproportionate amount of motorcycle victims.
00:08:49.000This was actually something I heard from a clinician.
00:08:54.000An old sort of parasitology, infectious disease doctor, who sort of, when I was first telling him about this sort of emerging toxin story, he had like one of these bolts of memory saying, my God, I remember back when I was a resident,
00:09:10.000there was this old doctor saying, you know, if you're ever harvesting organs from an accident victim, I don't know why, I don't know why, but if it's from somebody who was in a motorcycle accident, make sure you check to see if they have toxoplasmosis.
00:09:25.000I don't know why, but there's a high rate of that that you find in organs from people who were killed driving motorcycles recklessly.
00:09:35.000Totally anecdotal, n equals 1 kind of thing, but nonetheless, this was a guy who studies infectious disease and toxoplasmosis and had not heard about sort of the behavioral findings before and that out of the recesses of his memory.
00:09:51.000So what initially seemed like, okay, this is a parasite that's very selectively developed this life cycle between cat stomachs and rodent brains and completing its life cycle.
00:10:03.000And weird, when it gets into humans, it has some behavioral effects also.
00:10:07.000That's just kind of evolutionary spillover.
00:10:10.000But then you see if it's doing something similar between chimps and leopards, Suggesting that that life cycle manipulation has been selected for in primates as well.
00:10:25.000And for me the strangest thing is the certainty with which there's a gazillion viruses and bacteria and god knows what else out there that manipulate host behavior in ways we just haven't figured out yet.
00:10:39.000Or we just haven't discovered the particular...
00:10:47.000It seems to have less severe effects on neuropsychological profiles of women.
00:10:53.000Again, the literature on this is pretty scanty in humans, but it seems to have some similar effects but not as extreme.
00:11:01.000However, the story now gets a little bit more complicated, and this is actually this fabulous scientist, Ajay Vyas, who's my postdoc, who's now a professor in Singapore, who's continued to study this.
00:11:14.000Okay, so normally, one of the things animals have evolved to be really good at is picking up signals that somebody else is unhealthy.
00:13:14.000Other than, again, pure anecdotalism, that one elderly doc somewhere back when saying, watch it when you're getting organs from, like, people killed in motorcycle accidents.
00:13:34.000I suspect they do, and sort of in the clinical world of people who worry about toxo, toxo, pregnancy, scary, alarms going off.
00:13:45.000Toxo, anything else, after an acute period of infection...
00:13:48.000You have a latent toxoplasma infection.
00:13:52.000In other words, the agreed-upon sort of notion there is, toxo has gone latent, it's formed sort of these cysts that are inert, and you've got nothing to worry about then.
00:14:04.000But the whole notion that meanwhile, up in the nervous system, there's effects happening there, you know, infectious disease people are thinking about Inflammation outside in the body there.
00:14:15.000For them, chronic toxinfection is not something you worry about a whole lot.
00:14:20.000But if it's having behavioral effects up there in the nervous system, maybe it is something to worry about.
00:14:27.000Well, to me, it's unfathomable how this little thing figures out how to hijack a whole body, a whole biological system, and work it to its own It's very hard for me to grasp.
00:14:45.000Well, if you think of it in terms of, oh, I don't know, Toxo has had, like, 100,000 more generations to evolve its ways of exploiting mammals, and mammals have had ways of fighting it off.
00:15:02.000What's most remarkable is it turns out this is like a whole world of parasites that do bizarre manipulative things to their hosts.
00:15:09.000Most of it's not in the realm of mammals.
00:15:12.000Instead, There's like some parasitic something or other that gets into barnacles and takes over their reproductive system so that the barnacle digs a hole for them, not the barnacle, but the parasite to lay eggs into.
00:15:37.000There's this wasp that gets into cockroaches and takes over his nervous system.
00:15:44.000I'm fascinated by parasites, beyond, but it's so confusing to me how something, I mean obviously you're dealing with hundreds of thousands of generations for it to get to this point.
00:15:55.000This current state, but how something evolves to be so effective.
00:16:41.000Oxytocin makes you more trusting and expressive and generous and...
00:16:46.000And economic games and oxytocin has all these pro-social effects within a species.
00:16:52.000But then it turns out that this hormone that has spent the last, I don't know, 100 million years having mothers and infants connect to each other emotionally, when you and your beloved dog sit there and stare into each other's eyes,
00:17:10.000And if you pump up oxytocin levels in your dog, it will stare at you longer, and you will stare longer back and secrete more oxytocin.
00:17:19.000This is like an ancient, ancient hormone having to do with mother-infant bonding, and in 20,000 years, which is like a blink of an eye evolutionarily, suddenly we're doing this weird oxytocin-tango thing with another species.
00:17:34.000Another species who we feed and take care of and they, like, manipulate us wildly into, like, getting them, like, good dessert treat bones and stuff like that.
00:17:46.000And they, in turn, do all sorts of wondrous stuff for our self-esteem because they, like, lick us unconditionally.
00:17:56.000Just 20,000 years, and you've hijacked this ancient neuroendocrinology about parental behavior, and now it's got to do with this weird symbiotic thing.
00:18:08.000We and wolves worked out somewhere back when.
00:18:10.000Does it have any effect on friendship?
00:18:14.000Like human beings staring at each other?
00:18:37.000And if you have one particular variant that's associated with oxytocin having less effective of an oomph in your nervous system, that's associated with less stable relationships.
00:18:51.000So, you know, none of this stuff is deterministic.
00:18:54.000Your sex life and your romantic life is not being determined by this one gene, like nothing remotely resembling that, but that's just part of the mix in there.
00:19:04.000I was just wondering if that mix applies to, like, platonic friendships, like male bonding and stuff.
00:19:10.000When guys are out having a good time, if they're also getting a good juice of oxytocin.
00:19:15.000My guess is when you have your basic pathetic male sociality, which is like you talk about sports for five minutes with some guy and as a result you're willing to give up your life for him because this is male, male body, I bet that's got something to do with oxytocin.
00:20:13.000Okay, so another way of stating that is over and over in life we come to splits in the road where we've got temptations and we've got impulses and we've got yeah go for it right now you know you want it and The frontal cortex is critical at that juncture as to whether we do the inane,
00:20:35.000impulsive, self-indulgent thing that we may perhaps regret for the rest of our lives, or if you tough it out and do the right thing.
00:20:43.000What your frontal cortex does at critical junctures is one of the most consequential pieces in neurobiology we've got.
00:20:51.000So you ask what kind of things affect how well your frontal cortex is working in that one second where you have to decide if that person is holding a cell phone or a handgun and do you pull a trigger?
00:21:05.000Or in that one second where you decide do you take this thing and run or does temptation get resisted?
00:21:13.000So what sort of biological things affect what your frontal cortex is doing?
00:22:09.000There's just biological forces shaping what we're doing to an incredible extent.
00:22:14.000And it's the exact same story about any other part of the brain, but this is just like one of the most Of agency and free will and volition, whether or not I'm going to resist this temptation or not, by age five, for example, a kid's socioeconomic status is already a predictor of how much frontal development there is in this part of the brain.
00:22:37.000Because if you've been foolish enough in this country to choose the wrong parents to get born into there, and you're being raised in poverty, on the average, your stress hormone levels are higher.
00:22:48.000And as a result of that, on the average, your frontal cortex is thinner and not developing as fast.
00:22:54.000And on the average, already at age five, you're not as good as on average at the hold out, relieve me, you're going to be glad you held out for this long-term reward thing.
00:23:06.000Now, does toxo have an effect on the frontal cortex?
00:23:10.000Almost certainly, that's a hot area of research.
00:23:15.000We were originally hoping to see that, oh, toxo was just going to laser in on just some key parts of the brain that are absolutely essential to its behavioral effects.
00:23:26.000It seems to wind up more widespread, so that sort of makes it a tougher story, but in some ways, Sort of impulsive behavior is either due to a stronger biology of impulsiveness, which has much to do with the limbic system,
00:23:44.000or a weaker biology of, hold on a second, are you sure this is such a great idea?
00:23:50.000The hold on a second, is this such a great idea is the realm of the frontal cortex.
00:23:55.000So that could very readily be half of the equation right there.
00:24:56.000But it's this completely, well, it's basically the explanation for why adolescents are adolescent.
00:25:03.000They have a brain that's going full blast, especially the dopamine system with reward and sensation.
00:25:11.000Seeking a novelty, seeking anticipation, and a frontal cortex that's like half-baked at that point and is not very good at controlling impulses.
00:25:21.000That's why adolescents are the way they are.
00:25:25.000So, two sort of really interesting implications with that.
00:25:29.000First one is sort of in the kind of big picture legal implications realm.
00:25:36.000This fact that the frontal cortex is not fully developed until you're in your mid-20s was implicitly the main driving force around the Supreme Court some years ago saying you can't execute somebody for a crime they did before age 18. And you can't put him behind bars for the rest of life without a chance of parole because their frontal cortex isn't quite there yet.
00:26:00.000Of course, the flaw with that thinking is the presumption that magically on the very morning of your 18th birthday, you suddenly have a spanking new frontal cortex that has memorized all those Sunday morning sermons and can get you to do the right thing.
00:26:13.000But at least the courts have implicitly recognized that brain maturation Parentheses, frontal cortex is such that adolescent impulse control is not what you see in adults.
00:26:28.000The other issue that sort of fascinates me on a neurobiological level, you know, most of your cortex is doing just fine by the time you're three, four, five years old.
00:26:39.000And there's the frontal cortex taking another like 20 years to get there.
00:27:26.000Because by definition, if this is the last part of the brain to wire up, it's the part of the brain that's most sculpted by experience and environment and least constrained by genes.
00:27:38.000And this is the part of the brain that does social appropriate context learning.
00:27:47.000Like every society, every culture on earth, you think about it, every culture on earth celebrates some types of murder and is horrified and punishes other types.
00:27:58.000Some get medals, some get damnation, some get like simply that one.
00:28:04.000Every culture has some sort of strictures against lying, yet in some circumstances expect you to have socially appropriate lying.
00:28:12.000In certain circumstances of protection or so on.
00:28:17.000And every culture does this differently.
00:28:19.000Every culture has culture-specific mores and situational ethics and things like that.
00:28:24.000And that's like fancy, complicated stuff that takes a long time to learn.
00:28:29.000That's what you're doing as an adolescent, as a young adult.
00:28:32.000You're learning all the subtleties of appropriate behavior.
00:28:35.000That's your frontal cortex, learning not just how to get you to do the right thing when it's a harder thing to do, but all those complexities of what actually counts as the right thing.
00:28:46.000And all the things that make us human above all the other primates.
00:28:51.000Because we're the species that in some cultures can say we strongly believe in monogamy and build our theologies around that, yet at the same time have incredibly high rates of people failing to remain monogamous,
00:29:07.000yet condemn that we have cultures where you're not supposed to lie, yet at some point you have to learn Okay, it's okay to lie in a circumstance of, so tell us, are you harboring those refugees in your attic?
00:29:26.000Situational ethics like that, it takes a very Strong frontal cortex to keep you from lying in certain tempting circumstances.
00:29:35.000But once you decide you're going to lie, it takes a strong frontal cortex to do it right, to do it effectively, because you've got to regulate your voice and your facial expressions and where your eyes are looking.
00:29:48.000Whoa, so this is a part of the brain that's got to incorporate your society's rules as to when it's okay to lie, and in fact this sort of thing that we view as heroic, but when it's not okay to lie, but once you decide you're going to lie, how to do it effectively.
00:30:04.000This is like complicated neurobiology.
00:30:08.000It can't just come with a genetic program that wires it up.
00:30:11.000It's got to be totally sculpted by learning all those subtleties.
00:30:46.000But it's just implicitly a different thing.
00:30:48.000Like a monkey could do a delayed gratification task where it's got to wait a couple of minutes for the reward.
00:30:57.000And it's the exact same neurobiology as us doing delayed gratification.
00:31:02.000Except we do delayed gratification like you study hard to get a good SAT score, to get into a good college, to get into a good grad school, to get a good job, to get into the nursing home of your choice.
00:31:13.000We do delayed gratification that takes 60 years.
00:31:16.000Depending on your theology, we do delayed gratification where the reward's not going to come, supposedly, until the afterlife.
00:31:24.000So, like, yeah, a monkey can have its frontal cortex do delayed gratification for it.
00:31:39.000So, essentially, maybe even some religious rules or some ethical guidelines that we follow could almost be like a scaffolding for the frontal cortex.
00:32:24.000That you start getting fancier, cortex that does more abstract stuff, and it's not till you get to mammals that you start seeing the first hints of frontal cortex.
00:32:34.000So, you know, recently evolved, the last 50 to 100 million years.
00:32:39.000So, in other words, the frontal cortex is like spanking new, and it's not till you get to primates that you get a big frontal cortex, and it's particularly large in apes, and then proportionally it's particularly large or complexly wired in us.
00:32:54.000Now, I know you spend a lot of time studying baboons, and I listened to that Radiolab podcast that you did where this baboon, do you call it a troop?
00:33:09.000And that these baboons became accustomed to eating this human garbage and the unprecedented change in their behavior when the males, the dominant males, got sick from tuberculosis.
00:33:44.000Of, like, you go back to the same animals and you camp under the same tree, and this is in a national park in East Africa.
00:33:51.000And you go back to the same animals and sort of the particular area I've focused my work on over the years is stress and health and what stress does to the brain and with the baboons it was trying to make sense of What does your social rank and your personality and your patterns of social affiliation have to do with which baboons have the rotten cholesterol levels,
00:34:16.000which baboons have the high blood pressure, who's healthy, who's not?
00:34:19.000So these are animals where you'd go do your basic Jane Goodall scene of just like...
00:34:48.000Just working that the last time I was out, I had a portable electric cardiogram machine for looking at cardiovascular, cardiac function in these guys.
00:34:56.000So you keep them there for a day, you do various tests, and then you let them go back to their buddies, and then you have a sense of How is their bodily function, their health, their diseases, their stress physiology related to aspects of behavior?
00:35:13.000For the first 10 years out there, I thought what I had learned was if you want to be a healthy baboon with a minimal number of stress-related diseases and you get a choice in the matter, you want to be high-ranking.
00:35:26.000It took me about 25 years, and almost certainly that had to do with my having to grow up a little bit on my own, to realize that there's much more interesting stuff going on.
00:35:36.000If you've got a choice between being a high-ranking baboon or a baboon with a lot of stable affiliative relationships, translated into English, friends, friends are going to be even better for your health.
00:35:56.000How often are you playing with infants?
00:35:58.000Turns out that's much more of a buffer for good health than simply what your dominance rank is.
00:36:05.000So these baboons, they started eating food from a resort, and it changed their behavior to the point where they were no longer getting up very early and foraging.
00:36:15.000They knew when the food was coming, so they just wandered down to this dump.
00:36:19.000And then they would basically essentially fight over dominance of the dump.
00:36:22.000And a few strong, powerful males had control over that until they got sick.
00:36:27.000So this was the troop next door to mine that had this tourist lodge in their territory and thus had a garbage dump.
00:36:35.000National parks everywhere have this issue of having a controlled wild animal's access.
00:36:39.000So this garbage dump troop, as you said, had taken to basically just living in the trees above the dump, waddled down each morning just in time for the food junk leftovers from the lodge to be dumped there.
00:36:52.000And I did a few studies on this troop.
00:37:06.000They got tooth decay, they got different parasites in their stomachs.
00:37:10.000So they're just fine living off of the good life there of throwing out desserts from this tourist lodge.
00:37:17.000And in my troupe, a couple of kilometers away, I don't know how this works, but in some baboon way, some of my males got word Of this feasting going on up there.
00:37:32.000But it evolved that in the mornings, about half the males from my troop would pick up and run those couple of kilometers to go punch it out with the guys there to get access to some of this garbage.
00:37:44.000The key thing was that it wasn't random which of my baboons would go over there.
00:37:49.000So you're a guy from like an outside troop and you show up at this garbage dump and there's 80 baboons like feasting there and you're an outsider.
00:37:58.000No one from my troop would like dream of going near the garbage unless he's a big aggressive guy.
00:38:05.000The other thing is, morning is when baboons do most of their socializing stuff.
00:38:09.000They sit around and they groom and they gossip before they go out and they do the day's foraging.
00:38:14.000So, if you're willing to pick up and instead spend each morning fighting with strangers over garbage, that means you're not very socially affiliated.
00:38:23.000So, in other words, the males from my troop who were going to eat the garbage were the most aggressively socially affiliated guys.
00:38:31.000So this is going on for a couple of years, and then there turns out to be a tuberculosis outbreak among the baboons over there because there was tubercular meat in the lodge.
00:38:43.000A meat inspector who's being bribed and all sorts of horrifying things.
00:38:49.000And, you know, a human gets tuberculosis and they can sit around and write thousand-page novels about it for the next ten years while they slowly waste away.
00:38:58.000TB kills other primates, like, over the course of weeks.
00:39:01.000It's like wildfire in non-human primates.
00:39:04.000So there's an outbreak of TB from the infected meat in this lodge dump, and it basically kills all the baboons in that troop, and it kills all of my baboons who had been going over there every morning for food.
00:39:18.000So now what you have is half the number of males as usual.
00:39:22.000So you got a two to one female to male ratio, which is pretty atypical for a baboon troop.
00:39:27.000And the key thing is the baboons who are left are the nice guys.
00:39:38.000You find somebody smaller and weaker to take it out on.
00:39:41.000They weren't dumping on weaker animals.
00:39:44.000They weren't having displaced aggression.
00:39:45.000And it turned into, just to be technical here, like a much nicer troop.
00:39:52.000They had much higher rates of grooming, less aggression, more sitting in contact.
00:39:58.000Male baboons would groom each other, which you don't see male baboons grooming each other in this troop.
00:40:03.000So, in and of itself, that's totally fascinating.
00:40:05.000So, okay, you get rid of 50% of the males who are the jerks, and you have a commune there going on.
00:40:12.000What was most interesting, the thing that just flattened me, was 10 years later, the troop is still like that.
00:40:21.000Ten years later, all the males who were there during the TB outbreak, who survived it and ushered in sort of the commune, they're long gone.
00:40:33.000Male baboons pick up at puberty, they leave their home troop, and they go wandering and join some adult troop somewhere else and spend the rest of their life there hanging up the hierarchy.
00:40:44.000In other words, By ten years later, all the males in this troop, who were still being less aggressive and more socially affiliative, they had all grown up someplace else in some other troop and transferred as adolescents into this troop and somehow or other learned,
00:41:01.000even though they grew up in the normal big bad baboon world out there, somehow they learned, we don't do crap like that here.
00:41:18.000Once these new males show up, for them, they're less subject to resident males dumping on them because there's less of this displacement aggression.
00:41:28.000Females who are getting dumped on less by males and thus are much more relaxed.
00:41:32.000Lower stress hormone levels are more willing to be affiliated with them.
00:41:37.000You're some new adolescent male, and you show up in your typical baboon troop, and it's like 80 days on the average before some female grooms you.
00:41:45.000In this troop, it was like three days.
00:41:49.000Because everybody's much more relaxed because no one's being miserable to each other.
00:41:53.000And it turns out you take a jerky adolescent male, because these guys were just as jerky as any transfer males were to any of the neighboring troops, and you treat them nicer and they kind of calm down over the next six months.
00:42:08.000Literally, what you had, what social anthropologists would be forced to define as cultural transmission, non-genetic transmission of a style of behavior from one generation to the next.
00:42:22.000This was culture being transmitted, a culture of high affiliation and less aggression.
00:42:28.000And these baboons are essentially living a natural life.
00:42:33.000Out in the Serengeti in East Africa and just going about normal baboon life.
00:42:39.000For me, what was most striking about this is baboons are as high rates of aggression as you find in any non-human primate.
00:42:49.000Male dominance, highly hierarchical structured societies since the early sixties.
00:42:56.000They've not just metaphorically, but they've literally been the textbook example of primates evolved for aggression and male dominance and hierarchy and stratification and all it took was one generation of a radically So,
00:43:18.000in a sense, what we see in human beings, we see big differences in cultures, in the way people are treated, the way women are treated, the way they cohabitate with each other, whatever community they live in.
00:43:33.000There's differences in the way we behave.
00:43:35.000But with most primates, would you essentially say, Most chimpanzees or most bonobos that you can kind of uniformly say, bonobos behave this way, chimpanzees behave this way.
00:43:45.000Is this the only time you've ever seen a complete variation of the standard behavior of a primate?
00:43:52.000As far as I know, this is the only example of something like this that's been seen.
00:43:59.000Other ecological extremes, and you get some radical shifts.
00:44:03.000But in lots of ways, this is the biggest cultural shift that anyone has seen in sort of the social milieu of a baboon troop.
00:44:13.000And for me, what the biggest take-home message of that is, exactly what you just honed in on.
00:44:18.000Ooh, these guys are textbook examples of the inevitability of stratification and aggression and all that.
00:44:24.000And no, it turns out it's not inevitable.
00:44:26.000It can suddenly flip with some unique circumstances and be transmitted multigenerationally.
00:44:33.000Anyone who could look at humans and say that there's certain inevitabilities to some of the most unpalatable things we do, they don't have a leg to stand on.
00:44:42.000If baboons have the behavioral sort of flexibility, plasticity, built into them just lurking for a unique situation like this, And suddenly, six months of a different cultural style, and you adopt it and pass it on,
00:44:59.000again, you don't have a leg to stand on to say that certain of the worst things about human culture and behavior is inevitable.
00:45:05.000We vary so wildly from continent to continent that we've kind of gotten used to it, but to see it in In another kind of primate and to see that circumstances can change the way they behave and literally change their entire community to the point where decades later,
00:45:23.000it's like 20 years later, they're still the same, right?
00:45:33.000Did it evolve back to normal baboon behavior?
00:45:37.000It basically ended when the troops sort of moved into the vacuum created by the TB outbreak and the neighboring troop moved into the lodge area and they kind of disintegrated as a troop.
00:45:49.000A lot of them got habituated enough to the humans there to represent the danger.
00:45:53.000Game Park Rangers had to kill about half of them.
00:45:56.000So the troupe basically does not exist anymore, but it went for about 20 years.
00:46:52.000In 1914, all it took was about four hours of British and German troops fraternizing from across the lines while they were supposedly doing nothing more than Retrieving dead bodies from no man's land between the trenches and before it was over with,
00:47:07.000they were praying together and having Christmas dinner together and playing soccer together and exchanging addresses to meet after the war and where they held out for days at some of those points until officers had to show up and threaten to shoot these guys unless they went back to trying to kill each other.
00:47:26.000These days, there's entire travel agencies that are devoted to Vietnam veterans going to Vietnam, going back for reconciliation ceremonies, or going back to foundations that literally build bridges across rivers,
00:47:51.000What if that could have been conceived of in like 1970?
00:47:55.000Yeah, humans have an astonishing capacity to change.
00:47:58.000It's so fascinating when you consider all of the variables that cause a person to be who they are, to behave who they are, and then them interacting with all these other people who share variables and have unique variables and that there's so many different factors What makes a community,
00:48:19.000It's pretty mind-boggling when you consider all the variables.
00:48:24.000It's utterly mind-boggling, and just to really get sort of provocative at this point, what one does with all that complexity And with all the biology we haven't discovered yet, and all those gaping sort of holes of explanations to where that behavior comes from,
00:48:47.000And all free will is, is the biology we haven't discovered yet.
00:48:52.000Yeah, Sam Harris broke my brain talking about free will once where I really believed it was real until he started explaining to me determinism and all the different variables.
00:49:02.000There is a little bit of something that we have where you're talking about the frontal cortex that allows you to resist things.
00:49:08.000But why is yours the way it is is the big question, right?
00:49:11.000Yeah, and if some of it had to do with how stressed your mother was when you were a fetus.
00:49:22.000Okay, just on the level of sensory stuff going on, just the sensory cues we're getting in the world and how that's influencing our behavior, put up a pair of eyes, a poster with just showing a pair of eyes on a bus stop,
00:49:43.000Display a pair of eyes on a computer screen and people become more generous in online economic games because it's tapping into being watched.
00:49:53.000Stick somebody in a room with smelly garbage and they become more socially conservative on questionnaires they're filling out because something just feels viscerally disgusting and that biases us towards deciding that something that's different is different and wrong.
00:50:10.000People don't become more conservative about economic issues or geopolitical stuff.
00:50:15.000They're just more likely to decide that thems who do something different from you, it's not just different, it's wrong because something just feels kind of disgusting because there's smelly garbage in the room.
00:50:28.000One very influential study looking at 5,000 judicial decisions over the course of a year in a parole board system, and the single biggest predictor of what decision a judge was going to make if they gave somebody parole or sent them back to the slammer was how many hours it had been since the judge had eaten a meal.
00:50:48.000Because when you get higher glucose levels in your bloodstream, your frontal cortex works better because it's a real expensive part of the brain.
00:50:56.000And when you're hungry, you feel less sympathy.
00:51:00.000People become less generous in economic games and how much would you contribute to this?
00:51:05.000And what sort of a judge has to do there in a situation, anytime we judge, is do this difficult frontal task of trying to view the world from somebody else's perspective.
00:51:18.000They're hypoglycemic, you haven't eaten in four hours, and it's more likely that your frontal cortex, in effect, is going to say, screw that, that's too hard, the guy's rotten, send him back to jail.
00:51:27.000And what's most amazing is, if you had gotten one of those judges two seconds after they made that decision, that could most be predicted by the effects of glucose on brain metabolism, and asked them, so, why do you make that decision?
00:51:40.000And they're going to, like, be quoting, like, Enlightenment-age philosophers or something, And that's just like rationalization, running to catch up with the biology that's just rumbling underneath the surface there and influencing our behaviors.
00:52:07.000If nothing else, like what people have known for decades when we're stressed, our learning and memory doesn't work that well.
00:52:15.000Then people learned we're more likely to be anxious and learn to be afraid of things we don't need to be afraid of.
00:52:21.000And then we learned we're more likely to have horrible judgment and have our frontal cortex not work very well.
00:52:27.000And the newest realm of that is when you're stressed, you're less empathic.
00:52:33.000Because it takes a lot of work to try to view the world from somebody else's perspective and worry about their worries instead of your own problems.
00:52:42.000And if you're in a defensive or worried position, you're most likely to lash out, you're most likely to protect yourself quickly.
00:52:49.000Yep, and quite literally a part of the brain that's involved in empathy doesn't work as well when stress hormone levels are elevated.
00:52:56.000Now, what about the frontal cortex and actual damage?
00:53:01.000Like damage from car accidents or head trauma?
00:53:10.000You massively damage somebody's frontal cortex and They will know the difference between right and wrong, yet they still cannot regulate their behavior on the most fundamental level.
00:53:24.000Famous neurological patient in the 1840s, Phineas Gage, he had part of his frontal cortex destroyed, and he was a foreman of a railroad construction line, had a problem with some dynamite, somebody did something wrong, had a 13-foot metal rod,
00:53:40.000Shot up one of his eyes and out the top of his head and took his frontal cortex with it, landing about 50 feet away.
00:53:46.000And Gage, who was the sobrietest, devout, reliable, he was the foreman there, turns into this disinhibited, crass, sexually abusive bully afterward who never was able to hold a job again for years afterward because you had taken out his frontal cortex.
00:54:04.000And you damage the frontal cortex, and you get dysregulation of volitional behavior, which is once again a way of saying people know what their optimal behavior is, the difference between right and wrong, and yet they can't regulate their behavior.
00:54:21.000Something like, depending on which study you look at, something like 25 to 50% of the men on death row in this country have a history of concussive head trauma to the front of their heads.
00:54:35.000And that's a world of, like, volitional control is not that volitional.
00:54:43.000Well, that seems to go contrary to the idea of a lobotomy, then.
00:54:46.000Okay, a lobotomy was just, that's great, that lobotomy was just, like, savaging about the front third of the brain.
00:54:54.000It was getting the frontal, but it was also getting limbic.
00:54:59.000Well, by the time it really got developed, the guy, like one of science's amazing ironies, the guy, a Portuguese neurologist named Agas Moniz, who developed leucotomies, is what they were originally called, got the Nobel Prize in Physiology and Medicine for this wonderful technique.
00:55:16.000And then when it hit America as a sort of psychiatric intervention, good American know-how and Can-do spirit decided to get a sort of assembly line approach to it.
00:55:27.000A guy named Walter Freeman pioneered sort of rapid, like, wham-bam frontal lobotomies where you would insert an eye pick An ice pick, rather, behind somebody's eyeball, go up through the optic cavity there,
00:55:43.000and go in there and just scoop around, and there you go.
00:55:47.000He had instructional films in the 50s for how you could do a frontal lobotomy on one person every umpteen minutes and just go through an entire hospital's worth of psychiatric patients in one devoted afternoon of Calvinist ethics.
00:56:06.000So the neurobiology of what you were disconnecting there was virtually random other than you were just making a mess of the front part of the brain.
00:56:16.000So frontal damage instead is a much more selective issue.
00:56:20.000Do you shudder when you think about the fact that that was just not even a hundred years ago?
00:56:27.000You know, go to a medical school library and go eight floors down to the sub-sub basement and, like, go read some of these journals from, like, 19-aught, whatever.
00:56:43.000The things they didn't know then, my God, the damage they could have done then, the damage as to the causes of disease, the causes of psychiatric disorders, my God, some of the things they were doing then.
00:56:57.000And if you've got a shred of capacity for self-reflection, you then have to sit there and say, well, a hundred years from now, they're going to be looking at our level of knowledge and they'll be saying the same exact thing.
00:57:10.000What do you think would be the big one?
00:57:12.000Do you think it would be antidepressants?
00:57:14.000Do you think it would be painkillers that they're handing out?
00:57:16.000What do you think would be the big one that people would be freaking out about today?
00:57:19.000I think about what we think about in the future.
00:57:23.000I think it's overwhelmingly going to be, my God, that quaint, medieval, destructive belief they held onto then about human agency and free will.
00:57:39.000Who had brains that couldn't regulate their own behavior.
00:57:43.000They punished people who, because of toxin exposure or stress during adolescence, wound up with brains that couldn't control this or that at particular junctures.
00:57:52.000And they used words like justice back then.
00:57:55.000Wow, I can't believe the stuff they did.
00:57:58.000It was practically like gangs of, like, gorgeous peasants getting burning torches and going and burning down to whatever's around the medieval castle, in terms of senses of the word justice applying to what biology has to do with behavior.
00:58:14.000There's so few people that share this idea that you're having.
00:58:18.000Obviously, your sense of it is so much more educated than the average person.
00:58:22.000And you understand all the mechanisms behind all these particular behavioral problems that people have, and all these different things can affect the way human beings operate.
00:58:31.000But most people are not aware of this.
00:58:36.000If you had a guess, it might be that 90% of people haven't really considered all the factors that lead to someone having a brain that would put them in these impulsive, terrible decision-making situations.
00:58:50.000Well, what gives me a little bit of sort of optimism is most people, though, at least in the West, have done that in a couple of realms.
00:59:00.000Like 500 years ago, if you had an epileptic seizure, the smartest, most reflective, most compassionate, like...
00:59:10.000Middle Ages bleeding heart liberals even would have had an explanation for what caused an epileptic seizure, which is you were demonically possessed and the therapeutic intervention was to burn you at the stake.
00:59:21.000And now instead we're, I don't know, a century or two into having a mindset where instead we make a biological statement.
00:59:33.000Oh, he's not demonically possessed, he's got something screwy with his potassium channels in his brain, and once he gets synchronized outbursts every now and then, he has a seizure disorder.
00:59:42.000Like, it's taken us about 500 years to do that one, to go from, this is a blasphemous behavior where we know the intervention, which is to burn somebody at the stake, to saying, oh, it's a biological problem.
00:59:56.000And we even recognize constraints with it.
00:59:59.000If somebody has uncontrolled epilepsy that's treatment resistant, they may not be able to get a driver's license.
01:00:06.000But you don't sit there and say, yeah, let's have a burning of the driver's licenses and the epileptics.
01:00:12.000It's about damn time they got what they were...
01:00:14.000No, it's a realm where words like evil or soul or punishment or justice is totally irrelevant.
01:00:37.000Most of the time, obviously if someone's behind the wheel and they have a seizure and someone dies, but we don't think of it as someone doing something.
01:00:44.000We think of it as they lost control of their body, like literally, and they're piloting a car, unfortunately, and that's what happens, versus someone committing a crime.
01:00:53.000500 years ago, if an epileptic during a seizure with their limbs flailing struck someone, that would have been assault and battery.
01:01:02.000Who told them to go, like, sleep with Satan?
01:01:07.000And it's like, it's a ridiculous mindset now.
01:01:10.000There's large parts of the developing world that still has exactly that view of epilepsy, but at least in the West, like, that's an unrecognizably different mindset.
01:01:19.000No, no, that was not, they didn't choose to do that.
01:01:22.000That was something screwy with their biology.
01:01:25.000Like, we've gotten to that, so, I don't know, maybe another 500 years and we're going to be able to do that with...
01:01:32.000Maybe half the juries in this country are capable of doing the same thing of saying, it's not him, it's his disease.
01:01:39.000When you have somebody with paranoid schizophrenia who in a delusional state does something violent, maybe, I don't know, half of teachers in the country are able to incorporate, no, this kid isn't lazy, that's not why they're not learning to read.
01:01:53.000They have this thing called dyslexia, meaning there's abnormalities, macromalities in their cortex and the part having to do with it.
01:02:02.000So, you know, we're making a little bit of progress, but...
01:02:08.000Well, optimistic in 500-year time spans.
01:02:12.000I mean, you think it's kind of playing out in the right direction, just very slowly.
01:02:16.000Like, when you see these, like, political debates and people on television talking about crime and punishment and none of these factors being discussed, is it incredibly frustrating?
01:02:31.000They will look back at us and say, my God!
01:02:35.000The things they thought then, the damage they did then, and all we can do at this point, given that we don't know a whole lot of the biology, and look at most of this stuff that we've learned about the frontal cortex or oxytocin or genes,
01:02:51.000and we've learned all of it in the last 50 years, in the last 20 years, in the last five years.
01:02:57.000If you look at the distribution of when these papers were published, All we could do in the meantime is simply have a hell of a lot of humility before we think we understand what the cause is of the behavior, especially a behavior that we judge harshly,
01:03:15.000because the odds are we haven't a clue what the actual biology is of what's going on there, and we fill in those attributional yawning vacuums This invention that we call volition and free will.
01:03:29.000Has anyone ever used Toxo for an excuse or for a defense, for a crime?
01:03:45.000Severe perimenstrual syndrome has been used successfully in courts of law to mitigate sentencing of women who committed violent crimes around the time of their period.
01:03:56.000Having certain variants on genes, this one gene, which unfortunately this variant has gotten the horrible term, the warrior gene, has been used successfully in a couple of courts of law to mitigate sentencing.
01:04:11.000It's a gene called MAO alpha, monoamine oxidase alpha.
01:04:17.000It's got something to do with neurochemistry and something to do with the neurochemistry of aggression.
01:04:23.000The gene comes in a couple of different versions, and one particular variant is associated with high rates of antisocial aggression in humans.
01:04:33.000If, and only if, the human was abused during childhood.
01:04:38.000In other words, the gene is determining absolutely zero, you're getting a gene-environment interaction.
01:04:45.000The absence of an abusive childhood, having this gene variant, has zero impact on this behavior.
01:04:50.000So, like, ridiculously simplified pseudo-scientific interpretations, findings like these, have sort of led even to courts of law saying, oh, well, has that genetic variant, that's inevitably So is this similar in a way to,
01:05:05.000I believe it was India, they used fMRI to determine someone's knowledge of a murder and they convicted the woman and made her guilty of it?
01:05:14.000No Lie MRI is the name of the company in the United States that purports to have the technology well enough that they can tell if you're lying or not.
01:05:22.000But from what I understand, it was just functional knowledge of the crime, which could have been imparted In defending, or trying to put together a defense, because you obviously have a lot invested in this crime, because you might go to jail for the rest of your life for it.
01:05:57.000I think it was in a court in Italy, where just sentencing was decreased because the defense made an argument afterwards saying, well, genetically predisposed.
01:06:49.000Oh no, my son the scientist is like being convicted of murder.
01:06:54.000So it's essentially in these less informed areas where these things have passed, like the fMRI thing in India and this in Italy, the warrior gene thing.