 In San Francisco, we know that design is in the air we breathe. It's such a big part of the culture that we live in. And design clearly plays such an important role in the human body. That's one of my big takeaways from Nathan's book. So on that note, I thought it would be pretty fun to kick off our conversation and learn a little bit about Nathan's design preferences in other parts of his life, just to kind of warm us up a little. So Nathan, I'm gonna give you a few design options to choose from, and I just want you to choose one based on just your first reaction to it. So when it comes to cars, do you prefer the design of a VW Beetle or a Tesla? Well, I could never afford a Tesla. So I'm assuming we're talking sky's the limit here. I would definitely go for the Tesla though. I'm a futurist in some sense, so I have to go with the Tesla. Good enough. What about phones? Samsung or iPhone? iPhone. Dogs. Corgi or French Bulldog? So my own dog is a half pug and half Bijan Frise. So what's the answer to this then? I guess a Corgi Bulldog mix would be close to what I have. All right, this is gonna get tough. Cities, New York or San Francisco? Okay, I love living in New York and I love visiting San Francisco. Good answer, good answer. Libraries, reading, do you like to read on a Kindle or some kind of e-book or some kind of hard cover book? I go with the hard book. Excellent. Almost exclusively. I will use a e-book when there's no other choice, but I have a room and an office full of books that I've read or that I plan to read, which is your to-do list, your to-read list, your books never get smaller. I add books to it more than I read them but I prefer the physical books. And now let's get into a little bit about the human body. We're gonna learn a little bit more as we talk but in terms of design, do you have a preference for the eye or the nose? Probably the eye. Okay, and we're gonna learn more about the eye. Yeah, the eye. The knee or the ankle? The human knee and the human ankle are, well you'll, we'll talk about that. I guess the knee because I haven't ever broken my knee but I've certainly broken my ankle. All right, so on that note, now that we've gotten a little bit into some design here, if the human body is so wonderful and you do tell us in your book how wonderful it is, why would you decide to write about the flaws? So that's the most common question I get is, why did I write a book all about imperfections in the human body? Do I think the human body is ugly and gross and terrible and non-functioning and, no I don't, first of all, I absolutely don't. But the human body does have a past, right? It has a history and the signs of that past and the marks of that history are found in our bodies. And so when you think of the body as a product of evolutionary forces and evolutionary time, you don't expect perfection. But we do have this idea that we, that organisms should be perfectly adapted and humans are the pinnacle of creation. There's various sort of flavors to this, misconception and I think flaws and imperfections, glitches are a really interesting way to probe our past and our history because they're very informative and I hope we get there tonight with our conversation. Most of it really ends with a happy story, with a happy ending because here we are. I mean, the vast majority of species never succeed, ultimately. Usually evolutionary dead ends is where most species go. A few are lucky enough to leave descendants and we're the result of a long legacy of a species struggling for survival and winning by a hair's width in some cases. But so I think our flaws really are a testament to our greatness in many ways. And I hope we can explore some of that even tonight but no, I don't think the human body is horrible. I just think it has a past. All right, so let's take one of the design flaws that you write about. Let's start with our eyes. Why would we wanna do over when it comes to the way that our eyes are designed? Yeah, do over would be great. So the human eye is a product of about a billion years of evolution and it began as light sensing patch of skin on the outer surface of an organism, pigments. First, the first pigmented patch and it sort of migrated inwards like this. It started as a depression and then an invagination and then a cavity. And our retina is basically oriented backwards, right? The photoreceptor cells are oriented as if the light were coming from behind. And actually a microphone is the best analogy here. So if this is the hot end of the mic right here and this is say the backend, our retina is oriented so that the photoreceptor cells are pointing this way but the light is coming in this way. So the light is coming at the retina like this and the photoreceptor cells in the back, right? So the light has to move its way through this tissue and then hit the photoreceptor cells. Now, one thing is clear, we've done a good job of adapting to that design but there's no way you would design it that way to begin with. Like so if you could have a do over you would flip this around and the light would come in the proper way. And there are consequences to this faulty design as it were. One of them being a detached retina is much more common when you have blood vessels and other tissue here and the light, since here you have more tissue than you need, right? So it's thicker and it's easier, more easily detached. There are examples of an eye very similar to ours that is oriented correctly and that's the cephalopod eye. So that's a octopi and squids. They have an eye that's much more intelligently designed if I can throw that word around. It is oriented, very similar to ours is the camera like eye is what that is. It's different than the insect eye and crustaceans and so forth. Where you have a lens concentrating the light onto a retina, everything's fine but they have their photoreceptor cells oriented the proper way, if you will. So if we could have a do over in our eye we would avoid retinal detachment. There's a couple of other things wrong with the eye as I write in the book. Number one, I see a lot of corrective lenses out there which is a sign that our eyes often don't work very well and part of that problem is the eye becomes too long in most individuals and it is the majority. So I think 40% people have myopia in Europe and North America, it's up to 75% in Asia so the majority of the human population have need corrective lenses to see at distance. So what kind of design is that? If the majority need that. Now we now know a little bit about why that's the case. Part of it is it's an artifact of our modern living and we spend most of our childhood indoors. So we're not focusing on distance objects for most of the day, every day. And there have been studies in three different countries now that have shown that actually children who spend a lot more time outdoors need glasses a lot less. And in fact, hunter gatherer tribes myopia is down around 10%. 10% still high though, by the way. Can you imagine an eagle not being able to see very well at distance? If you're a bird of prey, there is a 0% chance that you have poor distance vision because you wouldn't survive a day or two with that. But I think that's a testament to us actually that we have the ability to survive and thrive even with poor vision. And some of the answer is right in this room I see all these corrective lenses but even before those were invented in the 1600s what did we do if you had poor vision? You did something else, right? There were other ways to contribute. We had this very complex social structure and division of labor. Some people were hunters and they needed great vision but some people were homesteaders. Some people were gatherers. Some people were shamans. Some people had social knowledge and wisdom. And there were just 100 ways that you can contribute and some of them required excellent vision and some of them didn't. So the story of us in our poor eyes, again it's a happy story in the end, right? Like aren't you glad that your body doesn't have to be perfect for you to be a contributing wonderful member of our species? I mean I certainly have a lot of imperfections in my own but I'm glad I'm not put to that test day in and day out. And in fact my vision was very, very terrible. And the ultimate I think example of what we do with our human errors is I use the advance that I got after I wrote this book to pay a doctor to shoot lasers in my eyes. And now I see well. So we overcome our imperfections with technology, with helping each other with various other ways. We don't have to have perfect bodies in order to be contributing valuable human beings. And I think that's the story of our past is we really liberated ourselves by having a complex social structure and with empathy and social cohesion and all of that. We need to rediscover some of that but I think it is ultimately a happy story. When it comes to our sinuses I think there's something equally fascinating there about how we're designed and has led to some of the things that we deal with that I didn't realize until I read your book many other species never deal with. Right, so if you just, anybody here had a head cold? Anybody have a head cold right now? You know the average adult human being gets between three and four head colds a year. If you're a, children get about twice that. Other animals don't deal with that. Not nearly as much as we do. And sinus infections especially are almost unheard of in other creatures including our closest relatives. So why don't chimpanzees get colds? Why, maybe you have pets I assume? Do you find them with sniffling and sneezing regularly three or four times a year? I mean if your dog is sneezing and you take them to the vet, it's very unusual for other creatures to have what we consider the common cold. And for a while we used to chalk it up to just population density but our farm animals don't deal with that either and they have worse population density than we do. So what is it? Well it turns out our sinus cavities are very poorly designed. So the largest sinus cavities are here behind your cheekbones. They're called the maxillary sinus and they're the largest ones. Well what do the sinus cavities do? They warm the air, they humidify the air but they also have mucus membranes and a flow, a steady flow of mucus that traps all the dust and particles and allergens and infectious particles, whatever. Well that's great and there's a steady flow and it collects in the throat actually and you have to clear your throat every so often, everybody has to, every so often, that's that mucus collecting back there and then you swallow it down to your stomach where it's safe with the acid baths sort of kills everything and everything's fine. Well the drainage of the maxillary sinuses, the largest sinus cavities is at the top of the chamber. Not the bottom where a plumber would put it, right? But have you ever seen a shower where you walk in and the drain is like halfway up the wall? Of course not, it doesn't work. Gravity can't help you when the drain is at the top and so what you have to do is work against gravity every second of every day to push the mucus up with these little cilia, little hair like projections and most of the time it's okay if there's not a lot of dust, not a lot of particles, you can sort of keep it going but it doesn't take much to overwhelm that system because you get no help from gravity and then it pools, excuse me, it pools and it festers and you get an infection that way and that's why we get the common cold and sinus infections so much more often. You will find however that you get some relief when you lay down, right? A lot of people, especially with sinus infections you get some relief because you can get a little bit more drainage. The problem is the drainage pipes are also very skinny, way skinnier than they need be and way skinnier than we find in other creatures. So the sinus cavities really need a whole scale redesign if you ask me. So that's the sad part of the story but the interesting part is how we got that way in the first place. So why do we have this really horrible design and why don't our cousins have it? The chimpanzees, the orangutans, gorillas, they don't have this and we do. Well, so the earliest mammals descended from reptiles as they were were largely dependent on their sense of smell. That was their chief sense for getting around and so most mammals are snouted, right? So think of your dog, but lots kangaroos, whatever lots, most mammals are snouted because they use their sense of smell much more than we do. Like I don't know if you know this, your dog identifies you by your smell much more than by your physical presentation. Well, in the origin of primates that evolution into primates and then again into apes we reduced our reliance on smell and increased our reliance on vision. So we're much more vision dominated creatures. Well, when you're going to vision you don't need this big snout with all these huge sinus cavities to concentrate the air and the olfactory receptors and you're not really using smell anymore. So now this big snout is in the way of your vision. We brought our eyes to the front so we could have this binocular three-dimensional vision and the snouts in the way. So we reduced the snout, right? And we just mushed it all into our face to get it out of the way since we didn't need it anymore. And when you shmush something up like that it might end up in a nice arrangement, it might not. What orangutans did, which is much more clever, is they just ditched. We have six pairs of cavities. The paranesial ones, depending on how you count, they just ditched those all together. So they have fewer, so more room for the fewer that they have. Chimpanzees, the drainage is sort of in the middle whereas ours is in the top so it's a little better and it's wider. And they also spend more time on all fours. So it's more sort of in line with their posture. Ours is the worst. We get the worst end of this deal when it comes to the nasal cavities and that's why we get all the cold and sinus infections we get. But why did evolution tolerate that? Why didn't natural selection fix this problem? Because you don't die of the cold very often, right? How often does it kill you to have a sinus infection? You might feel like you wanna die but you really don't die of it very often so you don't take that trait with you. And that's the cold lesson that we get from this is that evolution does not shape us to be healthy, to be happy, to be comfortable, just to survive and to survive and reproduce. That's about it. And I think we find that most of the time we're not very comfortable. And that's the story of our flaws. You mentioned animals that walk on all fours. And of course we don't but we have some trade-offs that we've made to get to stand upright. Talk to us about that. Well, yeah, so we certainly have quadripetal ancestors. So we have ancestors that ambled about on four legs like chimpanzees and grills do. And then we transition to upright walking. That happened really, really, really quickly. In terms of evolutionary time, the blink of an eye. Where if we trace our ancestors back it's like fully quadripetal to upright walking but still able to swing in trees so they were sort of joint arboreal and terrestrial, but they were definitely upright walkers very quickly. Well, anything you do fast, you don't do well, right? So we evolved, we adapted I should say to upright walking in a very short amount of time. I think if it had been a slower process we probably would have gotten it better. But if you want some examples of the poor design anybody here ever had lower back pain? I usually, usually if there's one person in the audience I can get a hand up. Yeah, our lower backs are, it's this weird S shape that we've adapted to have. And you have these discs, these vertebral discs in between each vertebra. And they, they're discs of cartilage that are there to absorb impact and sort of lubricate the joint. Well, they're really better designed as if they were resisting the weight going downwards as if we were on all fours, but we're not. So they slip out, they slip forward. And that's called a herniated disc or a slipped disc. There's no veterinarian has ever reported a slip disc in a chimpanzee or a gorilla, right? They have a backbone that matches their posture. We have a backbone that's sort of been bent to fit our current posture, right? But the overall structure really, if it had been more J-shaped it would be perfect for a quadripetal animal. So we just sort of bent the lower part into this S. And an engineer would design a straight. I mean, have you, when you see a robot I mean, do you see this nice S-shaped curve? No, of course not, it's ridiculous. You would have a straight and it would be more in the middle. Now we can't do that because we have some organs that we had to deal with but you would have a straight, pretty much straight structure there in our back. That would be the best way to design a bipedal creature. So the back, I think is the worst but our knees, our ankles, I mean, your ankles are a mess. You have all these joint, these bones in here that you don't need. You don't need all those, it's like seven bones in your ankle plus the bones in the top of your foot and the two leg bones, they all crunch together in this little space. And your ankle really only has like about that much movement to it and it's strong, but it's not very flexible. So it's actually a very poor joint for what it has to do. And of course it has this giant Achilles tendon in the back which is the most important part of the ankle is also the most vulnerable. I mean, it's just sitting there on the back. Once, if you cut someone's Achilles tendon, they can't walk. Absolutely nothing will never use that joint again and there's no way to fix that without surgery. So why would you put your most important structure in the most vulnerable position possible? But evolution is not a designer. Gotta ask this one, do we have tails? We sort of do. We have the stump of a tail, right? And the curious part is, so the tailbone, the coccyx as it's called, it doesn't even have the same number of bones in each one of us. Isn't that weird? It's not like there's an absolute number that we all have. Some people have three, some people have four, some people have five. It depends on fusion and whether or not they fused or not. And that just goes to show you how superfluous this is. And you can get cancer in your tailbone and you can bruise your tailbone. You can have lots of things happen to it. One thing that will never happen though is that you'll miss it if it's gone. So people have had coccygectomies. It'll have it removed usually for cancer but there's other times when tailbone has been removed and there's no long-term side effects. There's no problem with sitting, standing, or continents or anything like that. What we do have in the stump of a tail is completely pointless. It does bear some weight when you're sitting but if it's gone, you wouldn't miss it. Interestingly, you do also have some muscles that attach to it on one side and then attach to nothing on the other. So if you did have a tail, you could flex it. That's what I think is interesting. So we have some of the apparatus to manipulate a tail that we don't have anymore. Now, I actually don't write a lot about that kind of stuff in the book because there's not that much of a downside to that. It's just sort of vestigial. It's left over. But if you get cancer of your tailbone, you would disagree with what I just said. That seems like a pretty big downside. But it's sort of left over. So evolution really didn't finish the job of getting rid of this structure but it probably would have given enough time. Not because it causes us harm but because, and this is another theme of the book, we do have a sort of use it or lose it approach to anatomy, not for the reasons that Lamarck thought about in the 18th century but for the reasons of we're always getting hit by mutations that destroy things. And if it's not important, it'll go away for that reason. And we're gonna talk more about mutations. It's gonna be really interesting. Something many of us are obsessed with today in our culture is diet and our diets. And after reading your book, I actually thought that may be for good reason. So you share how animals are better designed for eating in some ways in terms of the nutrients than humans, how so? Ooh, so there's a lot of reasons here. So at some point you're gonna have to cut me off because I could talk about this for hours. In fact, actually in some ways that I could have written a whole book about that. So there's a couple of ways. First of all, just in a basic sense, we don't eat any of the food we were evolved to eat. The modern human diet right now does not at all resemble what our ancestors ate during the time that they were evolving. So obviously our deep ancestors are all strict vegetarians because most of our closest relatives are all vegetarians. We clearly made a transition into incorporating meat in our diet, but it started with bone marrow. We were scavengers at first before we were hunters. So if you really want a paleo diet, here's what you gotta do. Leaves, a lot of leaves, sticks, bone marrow, raw, of course. Worms and roots. Not roots like potatoes and turnips and nice things like that, but roots, like roots. So that was the paleo diet at that point, right? So we got very, very, very good at extracting calories from really, really nasty uncomfortable food. And we would have to spend probably three to five hours chewing every day because the food was so tough and so fibrous. And in fact, you can see this in fossils where their jaw muscles were three, four, five times the size of ours. And of course, the way that they articulated into the skeleton was totally different. So we don't do that anymore, but what we did with the advent of agriculture, well first hunting, so then you had windfalls of meat separated by long periods of drought. So we were basically built for feast or famine. So you'd go weeks with very little food and these sticks and leaves and things and then you'd get a carcass and you'd have a ton of food all at once. So we're built to pack on the pounds. Every time you, so basically every rich meal that you ever eat, your body thinks, ooh, this is it. We're not gonna eat like this again for weeks. So put it all on, pack it all in and we gain weight very, very easily. And then we lose it very difficultly. So that's one problem is just metabolic. And by the way, the foods that we eat, like I said, were nowhere on our diet. And with the invention of agriculture, we all went towards staples and different, agriculture was invented at least seven times, maybe nine times, different places around the world, oddly right around in the same window of time. But in the Americas and Africa and Middle East, it's weird, it was all happening around the same time. But all of them, all of them developed their agriculture around starchy cereals. So rice, grain, corn, millets, whatever. And this high carbohydrate diet was just never part of our past. So we've just never been able to deal with this carbohydrate-based diet. It's just very, very unnatural in terms of our physiology. We're much better with high volume, high fiber, high protein, low carb. That's much more of a natural diet for us. So that's the first thing. We're just wrong all off the bat. 75% of our calories are from carbohydrates in a sort of typical diet. And that's true in the East and the West. That was never the case. If we got 20% of our calories, that was a good day back in the day from carbs. It would have been from fruits. If you got lucky, you found some fruits. So that's one problem. The other problem is that when you grow up, so to speak, evolutionarily, in the salad bowl of the rainforest in Africa, there's a lot of vitamins and other nutritious things that are sort of just served up for you. And your body sort of fails to make it for itself. So vitamin C, for example, most other animals make it for themselves. They have no need for it in your diet. You don't have to give oranges to your dog and cat, right? They don't need citrus fruits. They don't need any vitamin C in their diet whatsoever. But the molecule that's called vitamin C is just as important to them as it is for you. They just make it themselves in their liver, like we should, but we don't. No primates do actually. And that's why primates are very restricted to certain parts of the world. Primates never lived in Europe, for example, until Neanderthals and then we did because there's no vitamin C there. And we got scurvy when we did that, right? I mean, scurvy was a major public health problem for human beings, and I assume Neanderthals as well. So we don't make vitamin C. We don't absorb vitamin B12. That's another weird one. So vitamin B12 is only found from animal products. That's, if you're a vegan and you're vegans in the room, I assume there are. This is San Francisco after all. So that's like the one vitamin you have to sort of think about how you're gonna get it if you're a vegan. Most of the soy milks and almond milks have a little supplement. You don't need a ton of it, but it really does not come from plant sources at all. But what about all those herbivore animals? I mean, most animals are actually herbivores and they don't have vitamin B12 problems. Horses, cows, hippos, they don't need meat in their diet, but yet they don't have vitamin B12 deficiency like we would. Do you know why? They have bacteria in their intestines that make vitamin B12 for them and they absorb it that way. Well, why can't we do that? This is where it gets weird. We do have those bacteria in our intestines and they do make vitamin B12 for us, but we don't absorb it. The reason why is we only absorb vitamin B12 in our small intestine and those critters are in our large intestine, which comes later in the flow of gastrointestinal traffic. So you literally create vitamin B12 in your stomach or in your intestines and send it to the toilet instead of absorbing it. So it's another bad design. And how was that ever allowed, this bad plumbing? How was it ever allowed? Well, because we were starting to eat meat and then we just got lazy about absorbing this B12 because it was being absorbed, or sorry, it was being served up to us in our diet in the bone marrow and the other things we were eating. So our body just got lazy. And that's really the story of our diet is our body got lazy and we're stuck with it now. So we have to do these little tricks. We have to supplement. But the only thing I can say for sure that I know about a healthy diet is reduce sugar and carbs as much as you can. It's hard though. A really low carb diet is quite difficult because from rice to quinoa to corn to bread and all the other pasta, potatoes, it's everywhere. You have a great quote in your book and you referred to it a couple of times on this topic, which is people don't eat too much because they can. They eat too much because they were designed to. Yeah, yeah, because it's this feast or famine kind of history that we had. You wanted to capture every calorie you had available to you at that moment because it could be weeks before you ate like that again. And we feel hunger. We feel intense hunger. But actually, Jared Diamond writes about how he spends times with Hunter Gather tribes in New Guinea and they would go a couple of days without food and it's just part of their, they know that that's how it is. In fact, he tells the story where he was moving. He hired a bunch of workers to move a camp from this one to the other and he was gonna have provisions waiting for them at the end of the trip, food and water. And they got there after 18 hours of hauling like beasts of burden, all this stuff. And he was with them and they got there and the food wasn't gonna be there till the next day. And he thought they were gonna kill him. He was like, they're gonna murder me right now. They've done all this work all day. And when he told them, he goes, guys, I'm sorry, the food's not gonna be here tomorrow. They're like, yeah, it's fine. And they went to bed. I mean, can you imagine telling your own children if anybody here has children? Oh, you're not gonna eat tonight. Tomorrow, well, maybe we'll get something. I mean, you would revolt. So we actually can't handle long periods without eating. It's just not comfortable. Because we're designed to try to get every calorie we can. So two more I wanna ask you about around diet. One is vitamin D. And you actually, I believe, have done some research on vitamin D. Yeah, I have. I've done, what's weird is vitamin D keeps popping up in my life various ways. In my research life, it was working on a gene family in my lab, how it was regulated. And vitamin D seemed to be important. My doctor just recently told me I'm deficient in vitamin D. I'd really take pains to eat a varied diet with lots of different things in it because I think that's the healthiest way to live. So I was quite offended that I needed vitamin D in my diet. And it turns out, though, that vitamin D is just one of these weird things where we're not very good at absorbing it. It's like calcium. So you start off your life pretty good at absorbing calcium. Infants absorb 60 to 70% of the calcium they get that they bring in, I should say. But by adulthood, it's 20 or 25% on a good day. And by sort of the third age, when you're a senior citizen, you're lucky if you get 10% of the calcium you take in. So you just have to take all these pills and really just to get enough calcium. You have it, you just don't absorb it. You don't absorb any calcium unless you have vitamin D. And then we have trouble absorbing the vitamin D. It's like there's two ways to become calcium deficient. One, like that's poor design just there. But vitamin D is weird because we can make it ourselves. We actually don't need it in our diet at all as long as you get enough sunlight. You can activate one of the precursor molecules. There's three steps, by the way, in this biochemical activation of vitamin D. Sunlight in the skin and then there's a step in the liver and then there's a step in the kidney. And you need all three steps and then you get fully active vitamin D. I mean, that's just obnoxious anyway. But we can do it. The problem is for most of our history, we had to deal with if you got a lot of sunlight, you were subjected to skin cancer and also folate destruction because folate gets destroyed by sunlight in your skin. So it's like you had this push pull between being deficient in folate and doing deficient in vitamin D. And you had to get the right amount of sunlight for that balance without knowing what's going on, right? I mean, humans had no idea about any of this, right? And they're also trying not to get skin cancer. And so that's all in the mix. And then when we migrated out of tropical regions into more temperate climates, it's even worse because what do you do? You put clothes on, right? You have to. You have to survive Europe or Asia, Central Asia and on up. You have to wear, and we use skins from other animals, ironically, because they have no trouble with this. They activated in their fur. We ditched our fur, right? So other animals, mammals, I mean, use their fur to activate vitamin D in the sun, which can't give them skin cancer or folate reduction. Right, so other animals have it great. So we lost our hair and made us vulnerable to vitamin D deficiency. And then we covered our skin with the skin of other animals, which probably had vitamin D in it. We can't absorb it that way. It's just really funny. But if you look in the fossil record of ancient humans, especially when they migrated out of Africa, you see rickets and osteoporosis like crazy. So these are not modern scourges. We were dealing with brittle bones. So if you have vitamin D deficient as a youngster, when your bones are still growing, that gives you rickets. And if you become vitamin D or calcium deficient as an older person, it's osteoporosis. Either way, what happens is you steal the calcium from your bones because it's absolutely critical for other functions in your body. It's bad design. I don't know what else to call it. All right, so we knew we'd get here sooner or later. Let's talk genome. What do you think, in 100 words or less? What's the human genome and how does it work? Well, it's a full complement of our genetic material. So all of your DNA put together, you call that your genome. You'll find different scientists put different numbers on this and about how much of it is junk. And by the way, the term junk DNA was used for a while and then it fell out of fashion, but now it's back. I think it's back because there's certainly huge stretches of DNA that we know have no important function. We know this because they're purely parasitic repetitive DNA that is good at nothing but copying itself. And when you're fighting a battle against something whose only function is to copy itself, that's a losing battle. I mean, so there's one repeat called the ALU repeat that you have more than a million copies of in your genome. And all it is is a short stretch, about 300 base pairs long of DNA that split off of something that once functioned and you have a million copies of it in your genome. And you very dutifully, responsibly copy it and proofread it and send it all to all the cells of your body and it does nothing. And luckily it has quieted down. So it stopped copying and spreading. So it settled down at about a million copies, luckily. But it's caused a lot of damage along the way because when it copies itself, it spits out of the chromosome copies and then jumps back in randomly, which means it can cause mutations, it can cause cancer, it can cause all kinds of problems and it certainly has. There's no way to know, but I'm sure that number is in the millions of people, of human beings who have died because of a genetic condition caused by a jumping aloe element. So this parasitic DNA does cost us things. It does cost our survival, hurts our survival. And aloe is just one of them. We have tons of these. Interestingly, we're finding that through the genius of evolution, we'll say you do sometimes get functions from some of these. So a paper just came out about six weeks ago now that found there's a key step in embryonic development that requires one of these repetitive pieces of DNA. And it has a lot of us rethinking a little bit about how we talk about it. But to be clear, most of it doesn't do that. And most of it's not important, has these functions. That line one repeat that's important in embryonic development probably is a fluke. But when I write a book where I talk about junk DNA and I put these numbers to all this, I am aware that I could look very foolish in a certain number of years when we discover functions for some of this, I'm aware, but I know that we're certainly not gonna discover functions for most of it. I mean, unless you're gonna describe, so the word function is often debated as well. I mean, unless you think the function of cars is to fill junkyards, which maybe it is. I don't know. There are people who run junkyards who I think find that an important function of cars. But I think that it's a pretty safe assumption more than half of our genome is that we could live without and we would live better without. I think I'm still confident saying 75% is useless. Nathan, there's something in your book you write about where you say we have alligators in the gene pool. What's that about? Yeah, so that's what I was talking about before about the parasitic pieces of DNA. So some DNA is just repetitive nonsense. It doesn't have any function, but it doesn't hurt you either. It's just repetitive. So all your centromeres or telomeres, some of these other things like, they're sort of repetitive, not really hurting anything. But there are also these parasitic pieces of DNA that will copy themselves very aggressively. So they jump, so what one copy jumps out of the genome makes more copies of itself than jumps back in and it does cause damage when it does that. It'll destroy genes. And in fact, there are several genetic diseases that can be traced to some of these jumping parasitic pieces of DNA. But one thing I end that chapter with, each chapter has what's called a coda, where I sort of take a different spin on the topic. Pardon me. And the coda for that chapter is interesting because we had one very happy accident with one of these jumping pieces of parasitic DNA. So we have what's called trichromic vision, meaning we have three kinds of color receptors, three kinds of cones, whereas most other mammals only have two. So that's why you may have heard that your dog and your cat don't see as rich of colors as you have, as you can see. And that's true because they only have two kinds of cones, whereas we have three. Well, the way we got that third one essentially was from one of these jumping pieces of DNA that jumped into the gene, jumped back out again and grabbed the gene with it, duplicated, and then they both jumped back in. So it is occasionally a way that evolution can use for these creative happy accidents. And the ability to see, to have three cones and therefore see a much richer palette of colors had enormous advantage to our primate ancestors because ripening fruit are in this spectrum where that third cone really helps to figure a spot in a forest of mostly green and brown, you see a little bit of red, a little bit of yellow, that's a nice ripe fruit that you're gonna wanna eat. And most of our ancestors, of course, did eat fruit. So it was at kind of the right place, right time. And that's what's great about evolution. It's just constantly random, trying all different things and then the right combination happens in the right place and boom, you can see this nice ripening fruit or you can drink milk in adulthood, which is another story. I don't tell in the book, but I love that story. It's in the next book. So along with our diets, it looks like animals beat us out quite a bit, especially when it comes to sex. What about that? Tell us about that. Let's start with fertility rights. Yeah, so we're very inefficient at making more of ourselves and you would think that that's the one thing that evolution would get right. And I know it's kind of hard to picture us being bad at reproducing since there's eight billion of us now on every continent. But actually, we teetered on the brink of extinction. Now we're in the brink of extinction, I guess. But for several times in our past, we have teetered on the brink of extinction. And at least part of why is that we're actually very inefficient with reproduction. At every stage of reproduction, from the making of sperm and egg all the way to the growing up of a healthy child, every step along the way, we have some really peculiar inefficiencies that most animals don't deal with. First of all, we don't reach maturity till very late in adolescence. 14, 15, that's really late. That means there's 15 years that you gotta keep a creature alive before they can ever hope to contribute to the next gene pool. That's a long time. That's much longer than our closest relatives. So that in and of itself is inefficiency, because that's a lot more individuals that until recently wouldn't have made it that far because life and the wild is a lot rougher than what we experience now. So that's one problem. And then, something like two to 3% of men don't make enough sperm or sperm of high enough quality. Similar numbers of women, but women also, well, it's not just exclusively women, but there's a problem with implantation and about 10% of women have no trouble conceiving, but the embryo just sort of bounces off the uterine wall and then it doesn't lead to a pregnancy. And that's really unusual. And let me give you an example of how unusual that is. In mice, if you have a male and a female breeding pair and you vasectomize the male, so the male is infertile, but obviously nobody knows it, mice, I mean. And they copulate. The female mouse will go into the motions of pregnancy. It's a condition called pseudo-pregnancy. For several days she'll start growing out her uterine wall, she'll start doing nesting behaviors. If she has had sex, she assumes she's pregnant. That's how successful their reproduction is. They never don't get pregnant after they have sex. And that's not true for us at all, right? I mean, couples have to have tried for a year before the doctors leave and talk about infertility because we always constantly have to keep at it. Now there's some upside to that and we can talk about that if you guys want. I mean, I think it's part of what created what we think of as a family, actually. But it's definitely inefficient if the goal is reproduction. We have concealed ovulation. That's also very weird. Every other mammal, pretty much, the female and the males are very aware when they're fertile. It's visibly conspicuous. There's many other signs associated with it, but we have what's called concealed ovulation. Unless you know a lot about your anatomy and your physiology, there's really no way to know exactly when you're fertile and when you're not. That's unusual, right? And it creates a lot of inefficiencies in the system. Then we have childbirth. So childbirth in humans is, it's a nightmare, right? And I'm only vicariously saying this, but wow, it looks very uncomfortable to me. And before modern medicine, between 10 and 20% of childbirth events were tragic. They ended in tragedy rather than celebration. And sometimes tragedy on both ends, from both the maternal and the infant position. Childbirth was the most dangerous thing a woman ever did until about 10 minutes ago, really, in the history of our species. And that's unusual too. If you ever have seen nature documentaries where you see mammals giving birth, I mean, it's like they barely notice, right? I mean, there are videos, you can watch a gorilla who continues to eat and care for other children while they're giving birth. It's not a dramatic affair in most species, right? And why do we have such a hard time with childbirth? Well, the first thing that happened millions of years before we got our big brains was we got narrow hips. So our hips are much more narrow. This has to do with the evolution of bipedal walking to come back to that. And that keeps our legs in the plane, in the same plane when we're walking, that's called a striding gait like this. We don't flare our legs out. Like a chimpanzee, you ever seen a chimpanzee walk on two legs? They kind of lumber around and throw it. All right, and their center of gravity bounces back and forth like that. Well, we have a nice, smooth center of gravity that stays in the same plane and we just do this. It's called a striding gait. It's great, but the only way you can get that is by narrowing the pelvis. Well, evolution doesn't think ahead, right? So that happened first, and then we got these huge brains, these huge crania. And so you have evolution pulling in two directions. You're pulling on both ends of the rope. You want a nice narrow pelvis, but you want a big head, a big brain to do all the things that we think of as being human. So when they're pulling in both directions, the result is a really horrific childbirth. And one thing we did was we sort of accelerated gestation. So we're basically born way before we're ready. We're kind of like medium rare stakes when by the time that we emerge. And that makes us, and that's a problem too, because our infants are completely dependent on maternal and paternal care. There's no way an infant, but have you ever seen like a deer or a horse be born? They sort of shake themselves off and they're off and running, right? I mean, most animals come out fully cooked, but with humans, they're completely dependent for about 35 years. All right, so we've talked a little bit about our large heads. Let's go a little deeper. We'll talk about our brains. You know, in San Francisco, when we find a defect or inadequacy of some kind, we like to disrupt it or change it or remake it. But for now, at least, it doesn't seem like that's really possible with our brains. In fact, you kick us off by saying that we're actually genetically programmed to be bad with money, which might be comforting to some of us. Talk to us about that. No, it's true. We now live in this modern world where we have to deal with a whole bunch of different systems that just were not part of our past. And we do the best we can with these big brains. I mean, written language is one of them, right? We were definitely evolved to speak and children will speak spontaneously, right? You don't have to teach your child how to speak in a sense, right? You don't have to like say, okay, move your mouth this way and make us, right? They just will spontaneously do it and they'll mimic you and so on. But to actually get them to write and read even, that's a whole different thing. So we are built to do some things naturally with instincts and then there's other things we're not. And one of the things that we're not really designed well to do is handle money as a proxy for resources. And we make a lot of very consistent mistakes in how we handle money. And some of it comes down to what we call the problem of small math. So your brain is built to naturally, just fully naturally comprehend a couple of very small numbers, zero, one and two basically, zero, one, two and many. That's the only sort of inherent numbers that we have. We have a number sense with one and two and after that it's just many. Now we have trained ourselves to deal with big numbers, but we don't really understand them. And we make a lot of mistakes when the numbers get large. And the other problem that we have is that we always assume, it's sort of the law of large numbers and math, we assume that things will work out on a small scale. For example, if you flip 10 heads in a row, every fiber of your being says the next one's gonna be a tail, right? And you're gonna spend, you would bet any amount of money, right? But the coin doesn't know that it just flipped 10 heads, right? It is exactly 50, 50 chance the next one, the next flip. But our brains don't think like that. And so that plays out on the roulette table, for example, I mean you see like, oh it hasn't hit double zero in a while and everybody's putting their money on double zero as if that makes any difference whatsoever. And then when double zero hits everybody avoids it for a while because it's not gonna hit it again, what are the odds? The odds are the exact same. But we don't think that way. We think that everything is supposed to work out with a nice even distribution. And of course it's not. Another example is the birthday paradox, right? You guys know this story? If there's only about 25 or 30 people in the room, the odds are very, very, very good that two people will share a birthday. And you're like, how could that be? There's 365 days in a year, right? If I picked a date, 20 people odds are no will be have it. But if I don't keep that date set and I just say, in this room, I guarantee there's some shared birthdays. There's way, way enough people in here for some shared birthdays. But that doesn't make sense to us, even though the math does work out if you do it. So, and that plays out in how we hold investments in how we treat property, why we rent instead of buy certain things and vice versa. Classic story, it's like somebody has a piece of property and they're not gonna sell it until it comes back up in value. And they're paying taxes, they're paying utilities, they're losing money on it every month. But until it gets back up to the price that they bought it, they won't sell it. And that makes no sense whatsoever, right? And it's called the sunk costs fallacy. So you've spent this money out and you gotta get back. It's what kept us in Iraq for way longer. I mean, we can all debate the beginning of the war, right? But once we were in it, it was so clear that nothing good was gonna come from our sustain. But we had spent so much. So much sacrifice had gone in. It can't be for nothing. And that fallacy of sunk costs kept us there for way, way, way longer. When everybody agreed on all sides that our continued presence there was not helping, but we stayed way longer than we should have. So this plays out in our politics, our personal economics, as well as our economic system. And in fact, if you, anybody have like, if you have shares of stock, I'm not a stock market person myself, but I know probably many of you are. There's the little ticker symbols that when you put in your stock, it'll ask you what you bought it at, and then it'll tell you if it's up or down. And so you will make your decision about when you buy or sell, not on what the price is, but on what the price you paid for it two and a half years ago. The stock market doesn't care what you paid for it two and a half million years ago, sorry, two and a half years ago. I'm usually dealing with longer time scales in my work. But so two and a half years ago, it doesn't matter. Your only decision should be on whether or not you think it's gonna go up or down from where it is now, not from where it was two and a half years ago when you bought it. It makes no difference, but yet we still do that. We still are like, yeah, but I bought it at this so it's gotta get at least to that and it makes no sense. But it does, in a sense, like it's intuitive for us for how we think because we're used to small numbers, finite resources on the African Savannah and the Pleistocene epoch. I mean, that's really what we're designed to deal with. Nathan, you show that we're actually born to be biased and I think increasingly we're learning that. Cognitive science is pointing us in that direction. Say more about that as well in terms of our brains. Yeah, so I mean, there's different theories on exactly where different kinds of biases come from but it's very, very clear that we are biased and we have deep, deep biases. And the problem with bias is that you don't know you have it, right? And even when you do, you just can't talk yourself out of it. But this made very, very good sense in the time we were evolving, right? To make snap judgments because you didn't have time to think, well, is this the right thing in the long term? You know, you were making split-second decisions for your own survival and the survival of your family and that's not a good way to make decisions now, right? We live in such a different world now. But the other kind of biases that we have, I mean, we are designed to find patterns. This is what we do. Pattern recognition is just an automatic thing about our brains. We're always looking for patterns even when they're not there. That's why you can see faces in emblems and things in nature. Everyone can see, you know, they find Jesus in their toast and that kind of, you're always gonna find a face. We're just designed because faces is some such a key part of our social interactions. Well, it's the same thing with other kind of judgments. I mean, you make very snap judgments off of anecdotes. And anecdotes are way more powerful in convincing someone of something than data and statistics. But what is data, what are data and statistics except for large collections of anecdotes? But for some reason, thousands and thousands of people crunched into a nice data set, won't convince anybody of anything. But their uncle told them one time that they wore a seatbelt and they got trapped in a lake so you shouldn't wear your seatbelt because if you drive into a lake, you'll drown. I don't think that's ever happened that someone with a seatbelt killed anyone. But you guys know this story, right? There's always someone's uncle who won't wear a seatbelt because they heard somebody got stuck under water with the seatbelt on. The reality is they don't like wearing seatbelts, right? And so they found this story that they can attach to this thing that they already believe and want. And that's more powerful than all the data that shows that you are way safer in an accident if you're wearing a seatbelt. There's really no downside to wearing a seatbelt. But my dad did that for years. He would never wear a seatbelt because he heard a story. But stories resonate with us. Data doesn't, we're designed for narratives and people and that really convinces us of things. And I mean, in the world today, I don't think I need to convince anyone that data doesn't seem to matter anymore. But it's a really weird time we're living in. But you did mention bias, so you opened the door to this. But yeah, we have this insane ability to identify with our in-group and dehumanize the out-group. And again, in the African Savannah, at that time, it probably made really good, important social sense to have extreme reliance on an in-group and fear of an out-group. And now it's gotten us where we are, frankly. And the ability to dehumanize, I mean, it's really sick to think about it, but there were concentration camp officers who went home and were loving fathers and husbands. And they were doing monstrous things all day and they would kiss their kids gently at night. It's like, how do we reconcile that the same person can be so evil and loving at the same time? And I don't know the answer to all of this, but I know that we better figure it out, right? Because we're so close to walking down that road again. And it's clearly how we're built, right? We're definitely built to find an in-group and to support them incredibly against all opposition and to dehumanize the out-group. So inter-group contact hopefully helps with that. But by the way, this is what we see in our animal relatives. So chimpanzees have invented sort of warfare. And we see this now where you have groups that will rely on each other and they'll do raids in the middle of the night and other groups and they'll murder and all of this. And it's sort of watching, it's like watching our own history play out in modern times and in the rainforest. So I think these problems have been with us for a very long time. I wanna ask you a little bit about evolution. You've talked about it as we've talked about defects in design but what are some ways that those of us who maybe are not nearly as steeped in this as you are, how can we see how evolution is impacting our bodies? Is there anything that maybe is really ever present for us that we can kind of pay attention to or maybe that researchers are paying attention to when it comes to our design? Well, in fact, that's a big reason why I decided to write the book the way I did was, I think there's a lot to be gained by understanding our past in trying to live in sort of better harmony with the forces that shaped us. And you can do this in your diet, you can try to reduce carbohydrates and try to increase fruits and vegetables and there's different decisions you can make but it can even be deeper than that. So right now, almost everybody in this room except for the people in the back are doing something very not evolutionary and that is you're sitting in a chair. Chairs were never part of our past. In fact, this is not the best posture but it's so comfortable, right? So you're sitting in these nice chairs. But if you look at even just hunter gatherer tribes but let alone our ancestors, they squatted, they laid, they leaned, they never sat or at least not for very long. And so our bodies are now gotten used to this and we find it very comfortable but the least, the less you can sit, the better. So I'm a big fan of the standup desk which by the way takes some getting used to because you're not used to having to stand all day. You're used to sitting in chairs. But I have found, so when I switched to a standup desk I have almost no more lower back pain at all. I sleep better, but it took a while to strengthen those muscles and all that. So that's just a simple example of how we can sort of live more in concert with our past. I also do, I also try to walk and work. I don't do the treadmill desk, that's just a little too much. But I do try to like, when I take phone calls I get out of my chair and I walk. Around my office, around my house, whatever I'm doing and just try to stay active, stay moving. What I eat and when I eat it, a little bit affected by that. Yeah, I think there is a lot to gain. And I think that we're on the cusp of making some real interventions in our genetics which will be interesting to see how it plays out. But the one thing I think we can all agree on as ethically acceptable is we're gonna start curing genetic diseases, simple genetic diseases like cystic fibrosis, hemophilia, psychosellinemia, tysax disease, other sort of what we call single locus genetic diseases. And I don't think there's really any ethical problem with that. And we're gonna be very close to doing that. The questions will come beyond that. Once we pick the low hanging fruit we'll get into much deeper questions about what we're comfortable manipulating genetically. But I have good news for everyone. We are so far away from doing that it's premature not to have the conversation. It's never too early to start thinking about it but it's premature to start, I think, getting too aggressive with legislation because if you wanna say make someone taller with their genetics, we wouldn't have the first clue of what to tweak. And I guarantee the first few attempts would have horrible consequences because all the genes involved in height do lots of other things in your body. So we would have to sort all of that out. I really, even something like eye color we don't have it all figured out. We know a lot but there's just something, there's still pieces we don't know. So I think that the real designer baby issue is really decades, more than decades, probably a century away from ever even being theoretically possible. So I'm not worried about the real eugenic, the darkest things we could do with the technology. I think it's important that we pursue it now for the purpose of curing genetic diseases. What I'd like to do now is see if we have some questions out in the audience. And I believe that you all are, there's definitely a floating microphone. But if we get some hands up, I'll call on some people. I'll take the gentleman in the back and the white shirt, start there. Hi. So you talked about the past and the errors that come from it. Just wanna know what your predictions are for the future. If you think we're gonna continue evolving, how do you think we are gonna evolve? It's a good question. And if anybody didn't hear it, the question was, but what's about the future of human evolution? What do we have in store for us? Well, we are evolving still, that's for sure. We're not really sure how exactly, but anytime what you have sort of uneven reproduction, then the gene pool is changing a little bit. I mean, just from a simple sense, there are several countries, Afghanistan, Pakistan, that have really sky-high birth rates. And then you have other countries like Japan, Italy, that have very, very low birth rate. So all we know for sure is that Pakistan is contributing more to the future gene pool than Japan is. What that means is anybody's guess. But in a generation from now, I'm sure that will flip and change and around. So I don't know where we're headed. I don't know if anybody does. But one thing that is clear is that we have largely escaped natural selection, at least the worst parts of natural selection, because the vast majority of individuals that are born now live to reproductive age. Almost everybody that is born right now lives to reproductive age, at least in the developed world. And so that brings us into a new era, and that's been true for a couple hundred years maybe. So that brings us into a new era, because that wasn't true for a long, long, long time. And for most species out there, I mean, you guys know, you have two birds that come together and they have eight hatchlings and then they go their way. Well, the population isn't growing, so most of those hatchlings don't make it. And that's basically life in the wild for most creatures, is that the vast majority of individuals do not survive. I mean, look at the oak tree. It drops thousands of acorns every year, right? And not all of them grow into oaks. I mean, the whole planet would be nothing but oaks, if even half of them did, right? So we are really in a unique place in the world where most of our individuals that are born really will live to reproductive age. And now we're choosing whether or not we want to reproduce. I mean, that's a weird thing right there. So, and those choices are changing. A lot of people are forgoing evolution. And in fact, we're doing really anti-Darwinian things. I mean, I have two children and they're adopted. That's the least Darwinian thing you can do, right? I mean, all of my energy is in somebody else's biological children and I wouldn't change a thing. So, you know, we're in a weird phase of cultural evolution sort of taking over, but I see nothing but upside with most of it. I don't know where we're headed. I think we're gonna fix a lot of the sort of simple maladies. I broke my ankle once and I would have been a cripple for life 100 years ago, but now I have no symptoms. So I think it's a good time to be alive. But I also think that, and I write about this in the book, for the first time ever, you can think of about 10 ways that our species could do away with itself, right? And all of you right now can think, 100 years from now, you can imagine a cataclysm, right? It's not like weird science fiction to think how we could all destroy the planet in 100 years time. But none of those, or let me say it the other way, every single one of those is a problem of our own making, every one. None of you thought of a scenario of a new competitor out competing for resources or a predator coming in or even an asteroid, which we probably could deal with that, every problem is our own making. So, and by the way, every problem that we face has a solution, has a scientific solution that's readily available. We just don't have the will yet right now. I mean, if we wanted to be off of carbon-based energy in this country, we could do it in 10 years. There would be some sacrifice, but we could do it easily. I put solar panels on my house and I live in New York City, right? If you can have solar panels, power, and I'm 100% off the grid now, I mean, these solutions are there. There's an onion article. By the way, has anybody else finding it hard to tell an onion article from the news right now? It's really straight. Like every time you're like, oh, there's the onion again. Oh no, he really said that on Twitter last night. No, so there's an onion article that said, scientist friendly reminder that alternative energy is here just waiting to be used, all the technology. And it's true, we are not waiting on technological innovations to solve our energy needs or any of the other problems we face is we just don't have the will. But certain people are very, very wealthy doing it the way that we have it right now. So the answer of how we're gonna be in the future is really determined on the decisions we're gonna make in the next 25 to 30 years. I, for one, am optimistic because I couldn't get out of bed if I weren't. It's optimism by default. But the main reason I'm optimistic actually is because I work with young people all day. I teach college and there's an energy and a desire to change the world that I don't remember when I was in school. So I, my generation and older, we gotta get out of the way and let these young people come in. They really, they seem to be much more social minded, so. And if not, then, I mean, we're screwed. Other hands, other questions up here in the front in blue. On your sinuses. So what about, do you recommend headstands in the winter? Headstands. Well, so you're gonna have a problem with blood flow if you do that. But you're not the first one to suggest that if you have different nasal and respiratory symptoms that short periods of inversion can work. What I, we didn't talk about this in diet, but when it comes to all these things, I'm a big, huge believer in listen to your body and do what you find helps. And I don't think that everybody will have the same answer to that. So you lay down and if that helps, if it doesn't, if you find standing on your head clears you up a little bit, one thing I do is if I feel any symptoms, starting my nasal passages, I start consuming anything with menthol, like cough drop or whatever, that just keeps it flowing as fast as it can. And I blow my nose every time I, I'm constantly blowing my nose. And I have to say, it seems like it works in the sense that it doesn't take hold. But the idea that I'm working against gravity is what I have in my mind saying, okay, so my body can't get rid of this fast enough, so I'm gonna help it. I'm gonna do the menthol to help keep things open and flowing and I'm gonna blow my nose constantly and just get it out of there, get it out of there, get it out of there. And I've had good luck with that method. But what I always say is do what you find works, but try things out. These two have been waiting for a little while. Yeah. So have you heard anything regarding synesthesia and a genetic basis for that? Synesthesia. Okay, so no is the- Can you define synesthesia first? Why don't you define what you mean by it? Because I don't think I'm thinking of the same thing. Yeah, so that's what I was thinking. I don't know, certainly don't know about a genetic basis for that. This is getting a little bit off topic of the book, but there's a lot of research on psychedelic drugs that are being sort of reintroduced into medical trials right now, which are very interesting because the psychopharmacology involved in some of these is quite promising actually when it comes to addiction and major depressive disorder. And those do have a genetic basis. And so what I would like to see, because my background way back was actually in pharmacology. So I think a lot about drugs and receptors. And I think about the tiny differences that we have from individuals, mental illness is the best example of this. If anybody here struggle with mental illness or you know someone that has, the doctors are sort of like, well, let's try this. And then let's try this. And let's try this. And we really are very bad at matching up what are generally very good tools with the right patients. And then you hit the right combination and it seems to work. To me, it has to be genetic. There has to be like a version of the receptor that and then that person that matches up very well. So I would guess maybe that's a work there, but is that enough hand waving for everyone? How about one more? I think I wanted to ask about the mental illness issue. And that is as an evolutionary phenomenon, you don't see it amongst other animals, right? Hallucinations, visually hearing voices, whatever the mental aberrations are. Is there anything you can say about? Well, so, yeah. So the question was about major mental illness and its existence in other animals and evolutionary. So there's a couple of things I could say about this. You're right, I'm not sure that we know much about many of the major mental illnesses in other creatures, other animals. We definitely know about anxiety disorders and depression even and other mental disorders along that axis in other animals. And there does seem to be common psychopharmacologies. So the neurochemistry that's involved. What's interesting to me is that if you overlay that, but also with what we now consider the neurodiversity spectrum, so this is sometimes called the autism spectrum. But if you think about it in a much bigger sense as a personality spectrum, I've read some things that I find very convincing that it's part of our evolutionary toolkit to have a lot of variety in our species. I mean, first of all, evolution and biology are diversity creating machines, right? I mean, two individuals can come together and have a billion children and none will be identical. We really are very good at mixing up our genetic deck and creating new genetic combinations. And I think personality types, some of which we now classify as mental illness are probably within that. Not that it was any specific type necessarily gave an advantage, but we're just always creating this diversity because diversity is our bulwark against an uncertain future. So as a species, every species does this, every generation, we try to, that's why we have sexual recombination instead of just asexual reproduction. Asexual reproduction is way more efficient because every individual can reproduce. Sexual reproduction is very inefficient, but what it does is create diversity. And diversity means that you're always having new combinations of things because whatever's around the corner, someone in this species is gonna be able to deal with it and survive. And I think that same principle applies to personality types and what we now classify as the autism spectrum disorder and also certain mental illnesses are probably within that spectrum of what I would call neurodiversity that is just part of our natural diversity. Now that doesn't necessarily mean that we shouldn't try to help and even in some cases treat these individuals, but it does mean that we should look at them as part of our tapestry of diversity. And one thing is very, very clear in biology is diversity is good and it always has been, I think the same is true politically, but maybe that's just me. Do we have time for one more question? Another hand, gentlemen in the red. If we lost our ability, make vitamin C. And we lost our ability to make B12. And we got the ability in some of us to digest milk late in life. Why didn't we, are we heading in the direction of developing the ability to process carbohydrates efficiently? So that's a great question. There's a couple of questions in there actually and we can have a long conversation about this. So the question was if we lost our ability to make certain vitamins, but then we evolved solutions to that. So that's the thing is with vitamin C, we lost our ability to make it, but it didn't cause any problems right away because the primate, the ancestor primates was living in Africa where there's citrus fruit around. So it wasn't felt. And then we have learned to make sure we incorporated this into our diet. So it's a problem that we've solved. And then the evolution of the ability to drink milk beyond weaning is an interesting one that I'm doing some work on right now. The summary of that is that we do find a way. We adapt and we use the conditions we have and find, evolution's always trying out different solutions and then you find them. So the question about carbohydrate metabolism. I don't, there's not a lot of studies on this, but since we've switched to a carbohydrate packed diet in the last 10 to 15,000 years, I'm sure some evolution along those lines has taken place. I'm sure that we are better at living with a carbohydrate rich diet than we were when we first started. But we gotta remember is that it was a gradual transition. I mean, we didn't just wake up and all of a sudden everyone's having potatoes, but we gradually cultivated and then we cultivated them to be larger and then eventually we started subsisting on this. And I think genes and genetic evolution takes time to catch up because you're waiting on random mutations to happen that give you some benefit. And then right around that same time, however, we were also sort of liberating ourselves from at least the worst parts of natural selection. So we were sort of undercutting the very profit, very process that would have helped us, right? And so now if you are not particularly good at metabolizing carbohydrates, you might have diabetes, you might be overweight, you might have whatever other problems, but you can still live a happy, fulfilling life and have children and you're not taking those genes with you because you died of it, which again, I think is a good thing by and large. And we have this history as a species of not, we're not really victims of our imperfections anymore. But in the earliest days of agriculture, we probably were still subjected to some of that. And I bet we did make some genetic progress. I don't know the work, I don't think that work's been done. And the problem is that genes don't fossilize so well. So we have some ancient genomes we don't have the ones far enough back to really answer those questions. But I think you'll find some of that work coming out that would be interesting. And why that work is important is that it might actually help us, it might identify how we can better live on a carbohydrate-based diet now. If we know what genes are involved, I'm not talking about genetic manipulations, but just ways that we can tweak our own bodies in a regular, healthy way, non-genetic way just to make better use of it. And I'm sure there are answers to that. Because like I said, plenty of creatures live that way. But to end on a happy note, one thing we found in the fossil record over the last two million years is that the idea that you don't have to be perfect to be valued by your group. We've known this for a while now. There are fossils of people with horrible injuries that lived with it for years. And there are crippling injuries and yet they lived for years. So how did they do that? Two million years ago, a hominid with a broken leg, horribly mangled leg, but yet was cared for by her group. And the old man from Dmanisi is a fossil they found with no teeth and they had weathered through, clearly had no teeth for years. How do you live with no teeth in that time period? Someone was chewing the food for him. I mean, that's a great story, isn't it? I mean, I love knowing that we've been taking care of each other for two or three million years and not relying on our bodies to be perfect. But that old man and the old woman with the broken leg was offering something else to the group. What were they offering? Probably wisdom, right? And that's what we've seen in our species is that it's sometimes called the grandmother hypothesis. So there's this idea of like, why do we have menopause? I'm going off on a tangent here, but it's very easy. My students do this to me all the time. So menopause used to be this like conundrum, biological conundrum. Why would women ever stop being able to reproduce? What's to be gained by that from her point of view? You're making fewer children than you're contributing less to the gene pool. How is this possibly a good thing? Well, what we found is that, and it is a timed event, by the way. Women don't run out of eggs or anything like that. It is a genetically timed event that menopause kicks in at a certain age. But what we found is that at a certain point, the mathematics of your reproductive success switch late in life to where actually caring for your children and your children's children gives you more payoff than just simply creating more of them, which will then compete against each other. That's the idea. That's why it's called the grandmother hypothesis, which matches up nice culturally with our experience of grandmothers being doting and all of this kind of thing. But what we're finding is that there's a couple of other species now where we find that they do this. Menopause has been discovered in killer whales and right whales. So you have these older women, and what do they do? They lead the hunting pack because they know where the fish are found. It seals usually. They know where to find them. So it's this social knowledge that they've accumulated over their life. It's no longer are they needed to create more whales. They're needed to pass their wisdom on. And so I think what that tells us as a creature with menopause is that the women are the reservoirs of social knowledge, the older women. So we should be electing them to office, shouldn't we? Yeah. Ha ha ha ha. Ha ha ha. Ha ha ha. Ha ha ha. We had a chance. We had a chance to elect a grandmother. So Nathan, we're in a library. So I see this place as such a fantastic resource with so many great branches. If there were one or two or maybe three books or a couple other resources that you could point us to if we wanted to kind of build on some of what you've taught us tonight, where would you point us? That's a great question. So one of the first books that got me turned on to thinking this way and reading and writing about these kinds of things is The Third Chimpanzee by Jared Diamond. It's an excellent book, if you've heard of it. Actually almost any of his books. And I don't always agree with everything he writes, by the way. And I hope that no one feels that they must agree with everything I say either. Some of this stuff is conjecture and I go out on a limb here and there and I try to identify it when I am. But The Third Chimpanzee, I definitely recommend that book. That's a good one to check out. Who else would I recommend reading right now? If you want to know about the CRISPR technology that's and the problems and perils of it, Jennifer Dudna, who's out at Berkeley, her book on that. She's one of the discoverers of this but she writes a lot about the, what it means for our society to have this tool now, to be able to edit genomes at will. So that's a book I really recommend to anybody read to understand what's going on right now. I just did a book review of a book called The Equations of Life. I really recommend that about how physics explains a lot of why biology worked out the way it did and things that I've been teaching for years I have to rethink how I present it because some of this stuff I just assumed, oh, it's arbitrary, DNA. We could have had any other molecule could have been the repository of genetic information. No, actually there's a lot of constraints and it's probably was inevitable that we would land on DNA. And actually if we find extraterrestrial life it might look a lot more like us than we thought. That used to be the trope of science fiction. They always make it like humanoid but really it could be totally different and it's probably actually gonna be pretty recognizable because nature lands on the same solutions over and over on this planet because they make the most sense and the physics underneath it is actually quite simple. So really complex things can be explained by really, really simple equations. So I recommend that book. If you think a lot about reason and consciousness and free will, Kenneth Miller has a book out this year on that which is really good summary of the field. Oh, there's one that just... Well, anyway, you asked for three, that's three. Thank you so much. What a pleasure it has been to talk to you and his book is phenomenal. I encourage you to read it. Thank you. All right, thank you, Gail. Thanks.