3. Behavioral Evolution II

Transcription for the video titled "3. Behavioral Evolution II".


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Intro (00:00)

Stanford University. >> Okay. Let's get going. Various announcements, procedural things. A number of people want more information about grading and what the exams are like all of that. I think I mentioned one-third of the points will come from the midterm, two-thirds from the final. In terms of the style of the midterm, the midterm is heavily going to be about making sure you got down all the factoids from the first half of the course that you've got the basics of each of our proverbial buckets. The second half, the final, is all going to be about integration, thinking across the different categories. So just a sense of that. Readings, readings, as they are coming out, the books are not required until the second half of the course. The handout on Monday, I think, said which chapters of the Zebra book you should read. We will shortly get to you which chapters of the Chaos book you should read as well. The readings that are being posted on the course works, the downloads of various published papers, those are required. Clear on those whether this is a paper you should read all of, this is one you should read the abstract of. Even if you read all of, do not read it in some obsessive detail-oriented way. The goal is probably to be able to say in one or two paragraphs why this paper has something pertinent to say about the topic they fell into. You're not sitting there having to memorize techniques, middle names of the authors, how many animals, anything like that. In terms of that, it probably makes sense to read those after the first lecture of whatever block there is. Hopefully, if I get organized, I'll be able to get you the list of the readings further in advance than one week in advance. Nonetheless, you should probably hold off reading it until after the lecture occurs. Let's see, what else? People wanted to get a sense of how long things were going to go. As we'll see today, the evolution lecture topic will cover two classes. Molecular Genetics, which is what we'll pick up on Monday. I'm guessing one to one and a half. Behavior Genetics following that. One to one and a half. Ethology one. Neurobiology and equinology will have one week devoted to intro to the topics. Again, that's one word. This is so important for everybody to be up to speed. Rather than these being in catch-up sections that week, the whole week Monday, Wednesday Friday, we devoted to that with the TA's teaching it. The following week, three more lectures, more advanced ones. And depending on proximity to the midterm, there may be a half lecture in there on statistics. Or maybe not. So it's going to depend on keeping on schedule. This is a rough approximation. The midterm is going to be a Monday night. You will be responsible for material up to the previous Wednesday. And there will be lots of review stuff. Take a look at the extended notes being posted. What else? Okay. I think that covers most of the procedural stuff. All of this stuff will get posted as well. So picking up on the other day, what was happening the other day? Number one, the trouncing of Darwin, inventing evolution. Trouncing of survival of the fittest. Probably most importantly, trouncing of behavior for the good of the species. Group selection type arguments. What we saw was number one, the rationale for the whole thing. There is a vicious, unfightable logic to why hearts have to be the size. They are in kidneys. They have the filtration rates they have to have in order to solve the challenges of leaving as many copies of your genes in the next generation. And making sense of the evolution of hearts and kidneys and things like that could be the world of bioengineers and biomechanics folks with an underlying logic that it's got to be something that increases the number of copies of genes that you leave.

Deep Dive Into Animal And Human Reproduction And Relationship Behaviors

Explanation Hard Knocks (04:04)

And the whole rationale for Wednesday's lecture today is applying the same sort of logic to behavior. The whole world of just as you can optimize sort of the way one's neck how long it is if you're a giraffe, you can optimize behavioral strategies. And again, also throwing in a caveat, no animal is sitting there, maybe with the exception of some other apes, sitting there consciously strategizing along those lines when saying, so what would you as this dandelion want to do at that point with this ecological challenge personifying just to make things easier? Okay, what we've then barreled into were the three major building blocks we're thinking about the evolution of behavior in the framework of contemporary evolutionary thinking, number one, individual selection, passing on as many copies of your own gene to the next generation as possible by way of your own reproducing. The individual selection, a chicken is an egg's way to make another egg, I've now rehearsed that so I've got that down right. The whole notion of behavior as just being this epi phenomenon in order to do what's needed to get another copy of the genes into the next generation. Building block number two. Some of the time, the best way to increase the number of genes you pass on to the next generation is to help your relatives do so. Following that logic of Mendelian relatedness and people in the catch up section I know went over issues of why is it that you share half your genes with a full sibling, a quarter with a half sibling, etc. So sometimes the way to maximize is by helping out a relative to do so with again constrained by this vicious mathematical logic of it depends on how related you are to the relative. And thus you will gladly lay down your life for one identical twin, two full siblings, eight cousins, off you go. So the whole notion there of insight into why social animals the galaxy over are so obsessed with kinship and relatedness the whole world of who counts as an us who counts as a them in terms of cooperative behaviors playing out along lines of relatedness. Finally, we saw the third piece, which was reciprocal altruism, you scratch my back, I'll scratch yours, many hands make the task less scratchy or whatever. And what you see in those cases there is a whole world in which you don't have to be related to have cooperation. And we saw all the domains of that bringing in the formalization, biomechanics person figuring out how strong a leg bone has to be, a game theorist figuring out within the realm of social behavior, when you cooperate when you don't what sort of strategies, game theory of seeing the prisoners dilemma as the building block of that entire field and seeing all the strategies worked out by mathematicians and economists and diplomats and seeing which ones optimize under what circumstance and then going and look in the real world and seeing there's all sorts of animals out there that have evolved optimization strategies of when to cooperate and when to defect. And what we'll get to as a huge, huge issue by the time we get to the lectures on aggression, cooperation, etc. is, well, that's great when you've got a cooperative system going. How do they ever start? How do you jumpstart cooperation and systems, the evolution of cooperation, that's something we will get to in great detail down the line. Finally, what we shifted to was now saying, great, we've got all these principles in hand here on our big three building blocks and all of that. How would it be applied to making sense of animal behavior out in the real world? And we left with the example starting someplace there. Yes, that's it. That's it. Of us marching through, know one individual factoid about some species or other species, know that there's a big difference between the genders in size or there isn't, know that there's not high levels of aggression in males, know that females always give birth. Whatever those traits are as we marched through, using these ideas about individual selection, kin selection, reciprocal altruism, you could march through and logically infer what the social behavior of this particular species was going to be like. And you would be right. We saw, for example, in tournament species, tournament species where you have high levels of aggression among males, male-male competition for access to females. As a result, males tend to be a lot bigger than females. They are being selected for muscle mass, secondary sexual characteristics, plumage, big shark, canines for slashing the other guy, bringing up this issue of, in a tournament species, who does the male want to mate with? What sort of female are males interested in mating with?

Single births & paternal investment (09:00)

The answer being, anyone who will mate with them, because there's like no cost involved. All that's involved is no parental behavior. None of that, the cost of sperm, and literally people analyze the relative cost of sperm versus eggs in tournament species. Males are dramatically unchoosey as to who they mate with. In tournament species, males have dramatic variability in reproductive success, 5% accounting for 95% of the mate eggs. And female choice in the tournament species, what does a female want out of a male? She certainly is not going to get good fatherhood out of the guy. All she wants are good genes, because that's all she can hope for from the guy. A whole world of female selectivity for markers of good genes. And as we'll see in the sexual behavior lectures, a whole world of males trying to fake out females across the animal world suggesting they got better genes than they actually do. So we will come to that. Then, tournament species, do you see female abandonment of kids? Absolutely not, because there's nobody else who's going to take care of them. Coupled with that, you see single births among those species, low level, high levels of aggression amongst the males, low levels of parenting, and males tend to live a lot shorter than females. And what we saw at the other end, the pair bonded species was a completely different picture. Males are being careful who they're mating with, because the wiring there is, you mate, you take care of the kids. High levels of male parenting, females are thus able to abandon them, females can have multiple births, males are selected to be as close to females as a male can be. So there's not a big difference in size, there's not a big difference in secondary sexual characteristics, there's not high levels of aggression, there's not big differences in lifespan. Who does a female want to mate with? Someone who is going to be a competent father, thus the whole world of pair bonded species were males caught with rituals of coming up with food and coming up with things of that sort. So the most striking thing about that was, again, going back to the two skulls I brought in, you could know nothing more about that species other than this is an adult female, this is an adult male, and working through the same logic, you know a huge amount about the private lives of this species and who's messing around with who in the bushes, and that's nearly by applying these principles. And likewise saying, here's a picture of a pair in this species, and you can't tell which one is who by gender that tells you a whole world of predictability at the other end. So a first example of how much explanatory power you can get out of this. And on the website I will find all sorts of appropriate pictures of tournament and pair bonding species for you to look at. Okay, so a first realm of looking at animal behavior and seeing how once we got these principles in hand, individual selection, kin selection, reciprocal altruism, suddenly an awful lot of stuff makes sense. Next domain where that's the case. And this is one that has had a real challenge to the who isn't nature benign animals, behavior that go to the species viewpoint. This one domain probably proves an individual selection framework more than anything else out there. Okay, back to our inevitable National Geographic specials, and somewhere at the end of whatever the special is about whatever species, at some point they usually get some narrator with some deep, power tone voice coming at that stage, and say something like, man is the only species that kills for pleasure. Man is the only and look at how wonderful and benign these rose bushes are. They don't kill. They don't have war. Only humans do it. And what occurred by about the mid 70s or so was enough field workers from a different species reporting, hey, wait a second, we're not the only species that kills. And we will see plenty of domains where that makes sense in the lectures to come, but one particular version really, really demanded some three thinking about animal behavior, which was as follows. What is one of the universals, whether you start with us and go all the way down to slime molds, it's babies are cute. Everybody likes babies. Babies are adorable.

Infanticide hierarchies are about reducing aggression (13:12)

You want to take care of babies. Your eyes dilate as soon as you're around them. And a long standing notion that what infants, what babies, what baby features are about, among other things are means to reduce aggression. And we will see in the etheology lecture something about that. That was the standard sound bite forever. And suddenly you got field biologists coming back from studying various species saying something's up there because in my species, I see individuals murdering kids all the time. Whoa, what's up with that infanticide within a species? Suddenly, not only are humans not the only species that kills, we're like not the only one who goes and kills adorable little Disney infants. Suddenly, all sorts of species popping up where there was infanticide. And the huge challenge then became to make sense of this. This first emerged in the 1970s, studies of lander monkeys in India by someone named Sarah Herdie reporting this, soon it was reported among the lion, some other species as well. And the first obvious response to this was, wait, this can't be because I watch all the wildlife specials. There's something growing. Oh, there's some sort of psychopathology going on. This is not a normal population. This is not a normal population because they live close to humans. There's some disturbance. There's a toxic waste dump somewhere. They're not a normal species because you've got the wrong color socks on as the observer, whatever it is. This is not normal. This is pathological behavior. But long enough time goes by and it becomes clear in all sorts of species, individuals kill infants. So what is this about? You start to look closely and there's patterns. There are patterns to it. The first one being that tends to be adult males who kill infants. The next being, you look closely and it's not random who kills who. It's males killing infants who are most likely to be the offspring of, you guessed it, individual selection, most likely to be the offspring of other males. So this began to be seen in these species that had infanticide. It was male infanticide of offspring who were most likely to be the offspring of other males. But more patterns popped up at that time, which is, well, why don't you see that in any social species where you have competition? And what wound up being clear after a while is there's only a certain pattern that you see in species that have competitive infanticide, which is the average interbirth interval among females is longer than the average tenure of a high ranking male. What? Here's what that means. That means you're some low ranking guy. You've been working out in the gym for years on end. You're finally in a position to boot out the alpha male and take over the whole group. And damn, every single female in the group has a newborn who they're going to be nursing for the next two and a half years. So they're not going to be ovulating and they're not going to be ovulating for about three years. And you're likely to be alpha for only a year and a half or so. Where the length of time on average that you are going to be able to be reproductively active is shorter than the length of time that females and your species nurse kids and thus are not ovulating. And suddenly you have this brutally clear logic that makes perfect sense from everything on Monday, which is go and kill the kids. Go and kill the kids for two reasons. Number one, by killing the offspring of some other male, you are decreasing that individual's reproductive success. This competition is leaving as many copies of your genes, et cetera. Number two, by killing an offspring, the female by stopping nursing will soon be ovulating. And thus you see this pattern in langer monkeys, vervet monkeys, pattice monkeys, lions, mountain gorillas and such where it's always the structure. Competitive and fantasized, a male takes over a breeding group and goes about systematically trying to kill the infants. So we've got an enormous violation there of behavior for the good of the species and baby animals are cute and suppress aggression and all that sort of thing. The clearest demonstration of that is to look at the fact that one of the species where this goes on by this vicious sort of logic of competition, this is one of the species on earth that is as close to extinction as possible. As close to extinction as you can get, mountain gorillas. There's maybe 600, 700 of them are left and these are just like stunning animals and they are disappearing because of habitat degradation and human presence and civil war sweeping through there and all that sort of stuff. Also, they are facing, I think, inevitable extinction in a decade or two because every now and then a male mountain gorilla will systematically go and kill the infants around in a group by this logic.

No Kin Selection? (18:16)

You can't ask for a much better demonstration of animals not behaving for the good of the species or the group, this individual selection strategy. So immediately we start applying some rules to this. Well, when's a circumstance that a male would come into a group and boot out the previous reproductive male and take over and where he wouldn't be all that fast to try to kill all the infants in the group? One would a male take over a group and not be all that thrilled to do this competitive and fantasized strategy? Any guesses? Yeah, part two, individual selection, kin selection, kin selection, you don't see the competitive and fantasized if the males replacing are close relatives by exactly that logic. So then you begin to see some more elegant stuff going on. In some cases, in a bunch of species, instead of males killing infants, what happens is the presence of a new male causes females to miscarry, pregnant females to miscarry. One version of this, and this is seen in wild horses, the new male in there harasses pregnant females to the point of the miscarrying. Same exact logic again. In a whole bunch of rodent species, you see something far more elegant. The new male shows up, and if you were a pregnant female, the smell of a new male causes you to miscarry a litter. And the biology that is completely worked out going from the olfactory signaling, and we're going to hear tons about olfactory signaling in weeks to come, going from the olfactory system to release of a stress hormone that disrupts uterine maturation and you abort. Olfaction induced abortion. What's up with the female with that? Why is that a strategy for her to leave as many copies of her own genes in the next generation? If this guy is around, she's got a choice at that point, a choice again metaphorically. She has a choice at that point. Either she can go through the rest of the metabolic costs of pregnancy, give birth to these kids, and then they get killed, or at least she can take the lesser of two evils. He spontaneously aborts at that point, and soon after, she is ovulating and has a chance again to pass on copies of her own genes. And this is the whole world of you put a male hamster in with a female who's just had babies and he goes and eats the kids. Oh, it's psychopathological. It's not psychopathological.

Mbornings come last (20:52)

Male hamsters are migratory. If there are kids there, they're not likely to have been mine. That's the logical thing. Females having been selected for if there is the smell of a new male, miscarry. And the same logic again extending the smell of a new male, unless he's a close relative of the previous male. You see the exact same thing playing out there. Now all of this of course is very sort of male biased in terms of this. These are females sort of making the best of a bad situation. You're some female langer monkey and some new male has come in and his intent on being infanticidal. And you've read evolutionary biology also. What do you want to do to maximize copies of your own genes in the next generation? Well, you've got this kid here who you're trying to protect. Would you protect that child to the point of your being killed? Probably not. And you don't see females doing that. Under what circumstance would a female be most motivated to defend her child to the point of her being seriously injured? Older females. Older females who are less likely to have another child after that. You're on the scene there and who else from day one would be most willing to get injured in order to protect the kid, the maternal grandmother, who has no reproductive potential at that point. And what you see in these langer monkeys, the females will defend, not to the point of serious injury. The older the mother is, the more strenuously she defends and the grandmothers defend even more. Following the same logic here playing out in that way. But you also have another option which is to do something much more clever. And this is not in the world after you've given birth, but the world of when you are pregnant. Because even in these species that have the competitive infanticide, the new male is also perfectly happy to harass a pregnant female. What have females evolved in a number of primate species? One of the great all-time ways of manipulating males. So you're this pregnant langer monkey and in comes this new male and you know you're going to go through like six more weeks of pregnancy and they're going to be enormously costly and the damn guys get to kill your kids as soon as they were born and what can you do and all of that. And you come up with something very clever physiologically. You go into what is called pseudo-estris. Estris being the term for when female primates are ovulating or sexually receptive are in heat and most primate species give external signs of when they're ovulating there's engorgement of all sorts of tissues around the vagina and rear end and stuff. And humans don't do but they have some of the physiological residues of water retention for example. So you've got all these external signs of I am ovulating except you're not ovulating because you're pregnant. You are pseudo-ovulating. You are going through a pseudo-estris. You generate the picture of it. So what happens at that point with this new guy who's just shown up and here's this like four month pregnant female who nonetheless looks like she's going through estris. Well these guys sit there then and say well well that's kind of nice and they go and mate with her and you know like two and a half weeks later she gives birth and you know what the guy is going to do. He's going to sit there and say what's the gestation period in my species. I'd say like five months or something. I've been here three weeks and already she's given birth. Whoa what a guy. What a guy. And they fall for it. They fall for it every time.

Stupian fathering? (24:29)

Females by having these pseudo-estris things the males are not infanticidal afterward when the female gives birth. So this whole world that initially makes no sense at all. Oh my god animals killing members of their own species even babies making vicious logic when applying issues of individual selection and the qualifications by wave kin selection. Next example another one with a similar flavor and yeah. What is the definition of the male that didn't figure out that it was his children. Yep and I think probably the most technical Darwinian way of explaining that is the well-known propensity of blood flow to either go to male brains or penises. They just get impulsive at that point. They don't stop to think and get the gynecology textbook that you know there no doubt is an advantage for the tiny subset of male langer monkeys who can actually like be like prudent at that point and think through the logic. It works with males. They fall for it. Suggesting that a lot of what's going on there is not a conscious cognitive strategy and this is sort of not a facetious answer run by the end of next week.

Animals recognising Other Individuals (25:44)

We get to looking at how do animals recognize individuals with a lot of species. There's not a cognitive strategy. You're not able to sit there and figure out wait a second this isn't making any sense. I mean like if not the logic we're figuring out but who haven't achieved the flavor of the males that for any reason what do they figure out and just feel like they do after three weeks and seven or five months. I think what it is is that there's not a whole lot of males there who could make sense or who have been selected for making sense of the fact that mating has something to do with babies down at the other end of things. I think there's not been much selection for being able to cognitively do that or to have some sort of rule if I mate with this individual any time she produces a baby I'm going to be unaggressive to the baby unless it's within this sort of time span. I think that's a little too much to have asked to evolve into sort of a primate system. The males fall for it. Another version with a lot of the same logic and this became clear studies of baboons savannah baboons in the early 60s which is you would have some male who male is having attention with another adult male and they are about to have some sort of clear fight and one guy is obviously low ranking and he's going to get trounced and here comes the big high ranking male and this guy is terrified and what does he do he looks around frantically and grabs a baby and holds a two's chest. 1950s National Geographic special. Why is he doing that? Because infants are comforting because babies are cute and everybody becomes less aggressive when there's a baby around because oh my god who would attack somebody holding an infant? What if the infant's injured? Okay so that's the old version. So applying some contemporary interpretations what do you wind up seeing along comes the threatening male, the subordinate male grabs an infant and holds it and what you only begin to see after a while of studying individuals is it's not random which infant he grabs and you know exactly what's going to come next, very similar theme to the competitive infanticide when males are doing kidnapping like this and that is something that's going to be a little too much. So if you look at the term like this and that is the term used they're not randomly grabbing kids, they're grabbing kids who are likely to be the offspring of that male and it is very clear at that point mess with me and your kids going to get it and it's clearly not being played out in any sort of conscious level like that but what you see is it's not random and it comes with the sort of qualifiers that show you even more how the system is working. So you've got some guy who's a big high ranking male and is obviously fathered all sorts of kids in this troop and you're about to trowse this smaller guy who grabs one of the kids who's more likely to be his than yours, logical competitive strategy of essentially black male.

Males, Kids and Reproductive Success; Females and Competition (28:42)

So you've got a big high ranking male who's dominating everybody else except he only joined the troop two weeks ago. In other words there's not been enough time for him to have kids yet when he's threatening lower ranking guys they're less likely to kidnap against him than kidnap against the high ranking male with a long residency. So you've got to find even more interesting which throws you into this world of well are these guys consciously thinking about this or do they just smell that that kid's that kid is that guy's kid and do they just know in primate they're thinking about it and the way to realize that is when they screw up and make a mistake and this one sort of years ago I was watching some baboons and there was this low ranking guy he was actually middle ranking and this high ranking guy was coming at him he was a middle ranking guy who critically was on his way down he used to be a high ranking guy he was aging and other words he used to be reproductively active and other words there's some of his kids around in the troop. So he's sitting there and here comes this terrifying high ranking male who's coming at him and our guy gets all agitated and nervous and looks around and he grabs a kid and it's likely to be his kid he's grabbed his own kid. Oh my god you're sitting there saying I'm never going to get a damn thesis out of this these animals just ruined all the theoretical models he's grabbing the wrong kid so he's holding the kid there and you're sitting there and you could see the guys about five steps away and he just that one tosses the kid clear just as he's attacked you will see they act as if they have made a mistake they are consciously working around something like this so this whole notion of coercive black male and kidnapping again it only makes sense once you begin to see these structures of individual selection can selection reciprocal altruism. Another example and this one makes perfect sense instantly you look at the world of female primates and lots of different species and there's ranking systems there's a hierarchy and what's the hierarchy built around you get a rank one below that of your mother you inherit your rank. Your mom is the alpha female you're her first daughter so you're number two and as soon as she has another daughter your kid sister is number three until you have a first daughter who pushes your kid sister down one step in other words dominance hierarchies among the females are entirely opportunistic whoa how can you explain that part part number two kin selection dominant systems and all sorts of social species are built around the nepotism of related this so that makes sense. Next one next interesting notion here which is one of those choices one of those choices that are not conscious choices but you're about to get pregnant and you have a choice as whatever species you are do you want to have a male or a female or do you want to have a litter of males or females or do you want to have a litter that's predominant male or predominantly female and it comes down to an issue now of two things which is how much does it cost to have a female versus a male during pregnancy and what are the reproductive probabilities of having a male versus a female back to this issue you are in a big tournament species and as we saw there's high degrees of male variability in reproductive success five percent of the guys are accounting for 95 percent of the meetings so you sit there and what you've got is a rule that if you go for a son like 90 percent of sons running around there are never going to reproduce and you hit the jackpot and you have the five percent at the very top and each of them are good are like father 30 different kids going for males in a tournament species is a big gamble it's a risky move going for a female however there is no female primate out there who has 420 kids because she lays eggs like a salmon most females there unless they have some fertility problem they all have something roughly one to five kids or so over the course of the life of an old world primate so female variability is way down in other words what's a conservative strategy to pass on copies of your genes have a daughter what's a riskier strategy have a son and what that immediately predicts is two things number one you look in dominance hierarchy and the prediction is that females who are high ranking should show more of a tendency towards having sons than daughters and females who are low ranking exactly the opposite and that's what you see in a bunch of primate species that have this sort of structure next prediction you should then predict that when ecological circumstances get tough when times are tough you want to go for the offspring that costs less a female fetus is less calorically demanding than a male fetus male fetuses cost more to bring the term than females do the prediction should be during times of ecological pressure the percentage of females being born should increase and as a measure of the fact that males are more expensive as fetuses something like 53% of fertilizations and humans are males about a 53 to 47% ratio and over the course of pregnancy the cost the increased metabolic vulnerability of male fetuses are such that by the time birth comes around it's around 51 49 and it's not until adolescence that it flips over to the typical pattern of female dominance you've got to have more male fetuses to start off with because they are more expensive more vulnerable so this prediction during times of ecological duress you should get a bias towards more females being born the 50/50 ratio skewing in that direction and that's precisely what you wind up seeing and you see all sorts of examples of this in humans for example during periods of famine food deprivation the ratio of birth skew towards females what you also see is a measure of that is among humans a boy

Human Sex Ratios (34:43)

giving birth to a boy statistically decreases the body weight is likely to decrease the body weight of the next offspring it's expensive having one of those males and what you wind up getting then is fluctuation as a function of your dominance rank if you're high ranking it's almost always worth the gamble to go for one of those high risk high payoff boys if you're low ranking go for the far more conservative female you've got this fluctuation around this 50/50 ratio and this was something worked out by one of these sort of founding figures this sort of modern evolutionary thinking a guy named robert trivers in the 1970s sex ratio fluctuation as a function of social context and people have gone and looked and it's precisely this you get an interesting bit of conservatism in this though which is there's some circumstance where it makes perfect sense for you to have a gazillion daughters because that's the time to do it and at some point you're having a gazillion daughters and everybody else having gazillion daughters and suddenly males become really valuable because there's not a whole lot of them around so the logical thing to do then is to switch over and start having males and everything else being equal after a while with a with a predominance of males it's going to make sense to switch over to females you have density dependent selection you will always have oscillating around 50% whichever sex is in the smaller number that one is immediately more preferable poor ecological conditions pushes you this way dominance rank push you one way or the other but in any of those circumstances you have an oscillation around the mean whichever is more common is less desirable so sex ratio fluctuation more stuff role of kinship for example in vervet monkeys we talked about that the other day play the sound and infant alarm call and the mother gets all agitated and everyone else looks at the mother they know that she is the mother sort of demonstrating the mother sort of demonstration of the weariness of kinship there now another very interesting social structure to some species which is we've seen all of these tournament species you have one high ranking male mating with lots of females and all that sort of stuff and polygon the systems what about polyandry circumstances where a female is mating with multiple males what about circumstances of stable polyandry where you get in effect the inverse of a harem you get a single breeding female with a number of males and what is seen with a very very high predominance is when polyandry occurs you get a type which is

Delphic Polyandry (37:22)

called a delphic polyandry and the second I tell what it is it will make perfect wonderful sense okay two male lions sharing a pride that's like not what you're supposed to see it's one male lion and mousa mufasa and his brother gets pushed out of there and like that's not what you see when you study Disney lions is supposed to be only one male is the breeder in the pride and occasionally you see these prides where instead there are two males how can they pull that off they should be doing competitive and fantasize all of that who are the two males yes you guessed it somewhere up there before it'll be two brothers when you see cases of two male lions sharing a pride or flip the other way when you see a pride being willing to tolerate two males in there instead of one very very high likelihood that they are brothers this technical term a delphic polyandry and you wind up seeing one totally wild example of this in humans as I went over the other day looking at our humans tournament species they pair bonding were somewhere stuck in between were terribly confused what you see is most cultures traditionally allow polygamy but most people are not actually polygamous all of that and somewhere in there you got asked the same question hey is there any polyandry going on with the other ones? there is one wild cultural example of this and this is seen in traditional Tibetan society and there you get a delphic polyandry you have the following structure in rural areas a woman will marry a man and in the process she will marry him along with all of his brothers all of his brothers she marries the entire lot of them it is the delphic polyandry and you see that and like it's down to the point where her father is a little bit more and there is a woman will marry a man and in the process she will marry him along with all of his brothers all of his brothers she marries the entire lot of them it is the delphic polyandry and you see that and like it's down to the point where here's this woman with her husband and his younger brother and his younger brother all the way down to this infant that she's holding who's the youngest brother who's now one of her husband's and that's what you see what's the explanation for this this is a pattern that you build with her mother? a pattern that you get in agriculturally very impoverished areas where you got a problem you've got five sons or whatever and with a pattern of land inheritance where you would otherwise split up the land amongst the five sons that's going to put each of them below subsistence level what you need to do is have a way in which they remain as one reproductive unit so you don't split up the land you see this a delphic polyandry a woman marrying this whole bunch of brothers and it's in circumstances where it's trying to keep the small farm plots from being broken up but again the logic there is the same as you see in lions with two brothers sharing a prod what else now somewhere in there you begin to get in a realization that not only do you have males competing with males for reproductive success and females with females but there's intersectional competition how could this be? how could a planet that comes up with valentines they have intersectional competition what is obvious is the reproductive interests of any given individual may not be exactly the same as the individual she or he mates with what would be an example of this here you have a species in which males are migratory it's a tournament species a male shows up during a mating season lots of aggression lots of secondary sexual whatever and he mates with a female and she has kids they have parented an offspring and they've shared their genes and increased their reproductive success except this being the species this guy is going to pack up and leave the next day in other words he has no investment in the future reproductive health of that female whereas she sure does she would be delighted for this offspring to thrive and prosper but perhaps not at the cost of her future reproduction what we see here is between the male and the female different reproductive strategies and this opens up a whole bizarre world of intersectional competition here's one really bizarre manifestation of this basic Mendelian genetics those of you who got the catch up this week should have a vague sense of this by now hardy Weinberg ratios you've got one parent has one genotype just

2 lovers have bad offspring (41:20)

to distinguish the parents and changes the colors they're all in the same way changes the colors they're all of that what is it that isn't bothered with from day one when you learn these sorts of things when you're making it doesn't matter which one is the male and which is the female which is the father and which is the mother this is just one of them contributes this profile one that what pops out the other side basic Mendelian genetics when making sense of pedigrees it doesn't matter which parent is contributing the homozygotic profile the heterozyg it doesn't matter which parent but then there's a whole world of genetic traits where in fact it does matter which parent it comes from because the same combination of alleles will function differently whether it came from the mother or from the father and this was a field that sort of emerged in the early 1990s and these are called imprinted genes imprinted genes these are genes where for our purposes to define them these are genes which have different manifestations different phenotypic consequences and different genes that work differently depending on which parent they came from Mendel rolling in his grave this is not how it's supposed to work this obscure world of imprinted genes violates this they work differently depending on which parent you get it from shadowing when we get to the ethology lecture the word imprinting is going to come up again in a totally different sense this is a purely molecular term right now okay so you get imprinted genes imprinted genes people began to figure this out in the 90s that wait a second we've got a completely different profile in these individuals with a mutation and a particular disease here we have these two very different diseases and they turn out to have the exact same mutation in the same gene what's up with that if you get that gene from this parent you get this disease if you get it from that parent you get that disease totally boggling making no sense at all first thing to have to be solved what's a mechanism for actually making a gene work differently depending on which parent it comes from for those who care about these sorts of details that's a biochemical process called methylation you methylate the gene in one parent's genome and not the other don't worry about the details the main way is there is a genetic mechanism for making genes work differently depending on which parent it comes from so okay we know how to do it why should this happen why does this make any sense and it took a while and people began to see patterns to this and finally this was put together by an evolutionary biologist at Harvard named David Hagg in the early 90s who came up with the unifying theory which explains it all and it's very cool here's what you see you begin to look at imprinted genes and for our purposes the way we can describe them as this is a gene where if you get it from one parent it does what it's supposed to do if you get it from another parent it's silenced it never works it's methylated into silence these are imprinted genes so he began to notice something when you look at imprinted genes where they are active if they come from

Hormones doing to drive fetal growth (45:25)

the father they all tend to be genes that promote fetal growth they're all genes that increase fetal metabolism they're all genes that make for a thicker uterus they're all genes driven by hormones coming out of the fetus they're all genes that push for greater fetal development and then you look at the imprinted genes coming from the female and they're all genes that tend to slow down fetal development what have we got here we've got that intersectional competition played out precisely there you've got this male hamster who's going to make never be seen again because he's in this category and what does he want he could care less what happens to the future reproductive success of this female he wants this offspring of his to survive the male imprinted genes push for greater amounts of fetal growth and the female one saying well that would be great if this kid survives but I also have a future reproductive life to think about her imprinted genes tend to counter it what would this look like one of the imprinted genes first one's identified which comes from active from the male codes for a protein called insulin like growth factor who cares what insulin like growth factor does what's clear from the name is it's a growth factor it's one of those things that make fetuses grow more it promotes fetal growth and then meanwhile the female hamster has a cognate an opposing imprinted gene what's that one for that codes the gene for the insulin like growth factor receptor and what her version does is make for a less responsive receptor the male is pushing for more of the insulin like growth factor she gets a receptor that's not as responsive and you literally have this co-evolutionary arms race there of male imprinted genes evolving to push for more and more fetal growth female ones pushing for less and less fetal growth and you see that coming out most apparently when you see mutations in some of these genes for example another pair of imprinted genes one from the father one from the mother and what you see there is the mother's version the father's version promotes invasion placental invasion into the uterus and that's actually the term that gynecologists use invasion of the fetus into the uterine wall it promotes more of that the female version slows it down so what if you have a disease where the male gene relevant to this is mutated and knocked out of action you solely have the female input which is decreasing fetal implantation into the uterus what if you got then you've

Discussion On Lactogen Expression, Pregnancy, And Group Selection

Invasive placental crawling (48:09)

got a disease where fertilized eggs don't implant on the other side suppose there's a mutation in the female part of this pairing and as a result all you have is the male input driving for more and more aggressive fetal invasion what do you have you wind up with one of the all-time bad cancers you don't want to get choreocarcinoma a cancer of the uterus because it's growing completely out of control being prompted by the fetus when you take out each of the voices through mutation you see that normally you're having this tilting this balancing of competition between males pushing for more fetal growth at the expense of the future reproductive success of the female females trying to slow it down all of the imprinted genes show this amazingly people now have even identified imprinted genes that don't work until after birth and they work in the brain and what do they do the male derived one does things like make for infants that suckle more ooh get more calories out of mom and the fetal version tends to blunt some of the suckling reflexes it's all built around the strategy of males and females do not necessarily have exactly overlapping reproductive strategies so another version

Lactogen expression and pregnancy bonding (49:30)

of it is one male gene which is pushing towards expression of a fetal enzyme fetal lactogen and what that does is it makes it easier for the fetus to grab sugar out of the bloodstream from the mother and the mother tries to counter it and if she's not very effective at doing it or if she's rather over effective you get pregnancy hypoglycemia pregnancy diabetes suddenly this is mom having a fight with her offspring over how much calories they're going to get the offspring being driven by an imprinted gene from the father totally cool totally interesting there should be a problem lurking here though which is this is a pattern you only see in tournament species you got a pair bonding species and there's no reason why a male should be saying something like ooh I want to ruin her future reproductive success at the cost of her giving birth on a pair bonding bowl and I wanted to give birth to a child the size of an elephant who's going to survive and who cares about her future their pair bonding they're in it together for the rest of time you don't find imprinted genes in pair bonding species you find imprinted genes in tournament species and thus we get back to that same issue the other day looking at tournament versus pair where do humans fall into this and what we've already seen is if humans can come up with choreocarcinomas and things like that we have imprinted genes same punchline again as the other day in terms of number of genes we have put somewhere in between tournament and pair bonding species again we are terribly confused okay let's take a five minute break and we will pick up with more examples okay let's get going again two good questions just now one is where does homosexuality fit into all of this and where it fits in is about 30 minutes worth of the sexual behavior lecture sometime in mid-May it is a challenge for some of this thinking the second good question was am I capable of speaking louder I will try I mumble okay pushing on so we've just brought in this whole bizarre unexpected world of trashing the hallmark cards of intersectional competition another example of it a really interesting one this was work done by a guy named William Rice at Santa Cruz over some years looking at a number of different fly species female flies are polyandrous they mate with a lot of different males and your male who just made it with a female and what you would like more than anything in order to pass on copies of your own genes is like not have some other guy in pregnancy some other male fly guy who's intimidating you not have some other guy do it and suddenly what you see is this interesting world where because of the mating frequency of the females she will have sperm from a number of different males inside her at the same time and suddenly we get this very strange world a whole field of research of sperm competition sperm competition of relay teams and gold medals and all of that of sperm competing with the sperm from other males and what you see is in fly species the sperm of males make toxins that kill the sperm of other males whoa that's very elegant that's very elegant because in part requires you to come up with the toxin it is in toxic to yourself you can solve that all sorts of molecular tricks for doing that but this makes wonderful sense you increase the likelihood of you the sperm reaching the gold line and killing the other guys and all of that except there is a problem for the females which is these toxins that the male sperm release aren't such a hot deal for the females health and what Rice did were these really interesting studies I won't go into the details of that in large part because I still don't understand what the guy did but he was able to somehow take populations of male and female flies and he would hold the females so that they could not evolve in response to whatever was going on with the males male male competition for reproduction while he held constant the female female competition the females were not evolving the males were and what he saw over the course of 30 generations was this male male sperm competition was such that the male sperm were making such powerful toxins that they were shortening the life expectancies of the females whoa that's not smart whoa that makes perfect sense house flies are not your parabondings swans dying in each other's arms for life sort of organisms it's a classic case of the male only has an investment in the current reproductive bout and if he can wipe out the competitor sperm and the female bummer the female has now got all sorts of rotting necrotic lesions in her vagina this is not a very reproductively effective female fly down the line what do I care I'm off to the next pile like how dung after that you have that same structure there but this is a bummer for the females the males left to their own competition will evolve more and more toxic sperm which exacts more and more

Themes (55:16)

of a price on the future reproductive success of the females now rice flips things and now he takes these populations and he holds the male evolution constant and allows the females to evolve and over the course of 30 generations they have evolved means of detoxifying the sperm so here we have male male competition inadvertently being played out in an intersectional realm as well where again this co-evolutionary arms race totally bizarre sperm killing each other and sperm damaging the female and that makes no sense if you do for the good of the species again very logical in the context of these models these models of evolution okay final example and here's one that will become very relevant way down the line when we're looking at things like the biology of aggression so you've got these social primates and lots of social mammals you've got this pattern which is one of the genders picks up around puberty and moves to another group it's to avoid inbreeding and everybody having six fingers and tails if you're a species that doesn't have a tail and is perfectly logical and what you need is just some sort of pattern is that the females or the males of the species which disperse no one among the primates has ever found a good rule for which primates species have female exogamy or male exogamy which gender leaves of puberty but there's variability in chimps it's the females who leave at puberty in gorillas it's the females who leave at puberty in baboons macaques a few other old world monkeys it's the males who leave at puberty with a very critical implication you've got baboons baboons you've got the troop and you look at the adult males and adult females in there the adult females grew up in that group the adult males grew up someplace else and emigrated into here at puberty in other words among the adult females in this group they're all relatives among the males there's no relatives meanwhile next door with the chimps it's the females who have left at puberty you look at the mature animals in a group and it's the males who are there with all the relatives who have been there all their life and the females who have no relatives so asking a question comparing baboons and chimps which of those species has higher levels of male male aggression within the group? baboons yeah because they're all brothers and brothers at arms in the chimp group there and none of the adult males in baboon troops are typically related to each other very high levels of intramail aggression intergroup so which species on a certain level has put us to shame when it comes to the invention of warfare of fighting between groups chimps because you've got bunches of males who cooperate because they're relatives and what you wind up seeing with chimps and we will eventually get to this is you see things that are now termed border patrols where a bunch of males from a group will patrol the edge of their territory if they encounter a male from the group over there they will attack they will kill him as documented by jane goodall taken to an extreme the males of one group will eradicate another group and if the rule is I am killing this guy we are killing this guy not because we don't like to look on his face but because he is a member of that group this is the united nations definition of genocide chimps have not only come up with organized warfare between groups they have come up with a chimp version of genocide what's the driving force on that one of the truly scary things on this planet which is when all the males living next door are getting along with each other because when they do they suddenly start looking over at this side organized males driven by female exogamy and chimps is where the warfare pattern comes from and as you can guess when we get to thinking about the biology of aggression with humans we are suddenly in this world of taking non-relatives who are military recruits and convincing them to pseudo kinship themselves into being a band of brothers increasing a sense of kinship there chimps do this all on their own so now making sense of which primate species have high levels of male male aggression within group versus between group between group or ones where it's the females who leave the puberty all these guys have been together since they were terrorizing other kids in kindergarten they are an organized group against each other you get intergroup organized conflict in primates that have female exogamy females leaving a puberty okay so we've now worked our way through a bunch of examples here and how to apply individual selection, kin selection that sort of thing a fourth branch has come into the field in the last decade or so and this is one that has had a lot of controversy in part because what is built around is mistaken by a lot of folks as being an outdated concept but in part because what it is actually implying is very controversial in some realms and this is this business of group selection somehow sneaking back in the back door there and becoming relevant to the evolution of social behavior group selection you remember Wednesday all the will to beast there and the elderly will to beast pushes his way forward and he distributes his bank account and then leaps into the river and the crocs and all of that and that makes no sense at all because animals don't behave for the good of the species individual selection he got pushed in nonetheless a notion of group selection has come back into thinking but it occurs only under a couple of specialized circumstances the version that we just trashed which was the

Selection (01:00:59)

version of marlin per okay how many of you guys know who marlin perkins was it's come to that marlin perkins how many guys know what does mutual of omaha does that still exist mutual of omaha's wild kingdom is that still a television program? yes no when you were young did that exist is it still sponsored by mutual of omaha they still do that's great okay because that one has been going for decades and decades and you know it was always you know they'd have they'd somehow always have to segue the mutual of omaha in there during the commercials building and it's like you know just as rhinos will mate on for hours on end you want fire insurance for your home or some such thing but in its original couple of decades it was hosted by a guy named marlin perkins and marlin perkins taught most of america their evolutionary biology marlin perkins is the guy who taught everybody behaving for the good of the species and that sort of thing the first version of group selection that got trashed in the 60s was marlin perkins group selection the group selection that's sneaking back into the field is very different two different versions first one something you will get in various populations you've got a population of something or others and some bio geographic event occurs which causes a subset of them to get isolated from everybody else a land bridge disappears or somebody drops a lake there who knows what but something isolates a small subset of the population so these guys go about reproducing by their standards and these guys go about reproducing by their standards and what's going to be a characteristic very soon of the smaller population they're going to be more inbred than this population simply because they're smaller they're going to have a higher degree of relatedness among individuals so now we throw our second piece of our three building blocks throw in kin selection and what that immediately predicts is levels of cooperation will be higher in this group than in this group because the higher degree of relatedness that's great and that's great because once we see how cooperative systems have a larger payoff you will get a crystallization so that everybody the second or third cousins are eventually going to have to be just as cooperative as the siblings are with each other you are going to fix a trait of cooperation in that population at a high rate so notice here in this case we have a high degree of cooperation driven by kin selection whereas these guys are going about their usual savage in each other's throats business bio geographic event reverses and these guys get reincorporated into the main population and they're so different by then that they get a different color and what you've got then is here in the large population here is a nucleus of animals who are cooperating and here is the huge unwashed mass of the ones who are not and everything we know about reciprocal altruism all of that means that these guys are going to start out competing these guys and the model that is used is cooperation will have to crystallize outward animals will have to join in in these cooperative patterns because these guys will out compete them what do we have this is called a founder effect this is a small population that thanks to being inbred has fixated some trait that's advantageous with the evolution here moves faster than in here because of the smaller population with the inbreeding some adaptive trade comes in there they get reinduced into the main population and this founder driven trade quickly spreads throughout the population and what you get here is if the same thing is occurring in the realm of behavior reciprocal cooperative behavior somewhere in here you have a transition from this being a kin selection phenomenon to this being a reciprocal altruism phenomenon so that stands as one of the models out there for how do you jumpstart cooperation in non-relative populations you use inbred founder populations to drive it there and just to have a metaphor all you need to do think about in some city there's some occupation some mercantile something or other that there's a gazillion of them and

Getting the jumpstart (01:05:20)

all sorts of people work in that and there's a subgroup of people there who work in this who are all related and as a result they do something cooperative and kin selective they make low interest loans to each other and as a result they're more successful at business and they get incorporated into here and what you then have is this economic force that everybody else has to join in to this cooperative business of trusting each other or low interest loans or I trust you like a sibling you don't have to pay me a phone next week used to be that only siblings trust each other like siblings but a force there for more cooperation a driving force of inbred kin selection initially so that's one way in which people are thinking about group selection and here you now have this group out competing this because of this trade and people actually use terms like crystallization the trade of cooperation will crystallize outward and fix in the whole population so that's one version of it and this is one again we will come back to this is one of the ways to jump start cooperation in a world in which there is no reciprocal altruism because you see the problem with that we all have learned to tit for tat is the best one except forgiving tit for tat might be better except Pavlov might even be better and all of those who built around this one requirement though which is somebody has to make the first move of being cooperative that's got to jump start the system and what we all know is in a system that doesn't go along with the rules of can't we all sing kumbaya what happens is the first one in the first round who does something cooperative is some schmuck who's one step behind everybody else for the rest

Group selection Takes Off (01:07:10)

of time there's no way to get these cooperative systems to evolve initially we'll see there are ways and this is one of those have it driven initially by kin selection and then throw it into the general population so that's one version of where group selection is crept back in another version is sort of the more generalized form of it and it could be illustrated okay the following example you've got chickens you've got chickens with an array of traits and you can see there's two types of chickens one chicken is super aggressive and beats on everybody else and she lays lots of eggs another chicken far more pacific and introspective and less aggressive and has fewer eggs so now you take any one of the high aggression females and one of the low aggression guys and put them together and who's going to leave more copies of routines the high aggression female and then you have a whole group of the high aggression females and a whole group of the low aggression females what's going to happen in the high aggression females they're also aggressive that they all injure each other into lower fertility rates all of that and suddenly you have this very important world in which a can dominate b but where groups of b dominate groups of a and it's in that realm that you suddenly get a push towards group selection selection selection on that level a world of any individual being out competed because of a trait but as a collective and bringing in that word not randomly as a collective and the collectivist future of chicken low ranking chickens to throw off their chains once you have a group of them the same traits that could be dis advantageous on an individual dyadic level as a group out competes the others and when you do that you've suddenly got group selection in a classical form where these animals because of their traits they are not behaving for the good of a group but the very traits their dis advantageous individually are advantageous as a group and it's another way of thinking about this if you indiscriminately make low interest loans to everybody on earth you are very readily falling into this category if you are part of a group that makes low interest loans to each other suddenly you out compete the other fascinating book evolutionary biologist named David Sloan Wilson who's been the main person pushing for this idea for decades has a very broad range of intellectual interests including religious history and a number of years ago he published a book called Darwin's Cathedral and he analyzed the birth of clusters of new religions over time as examples of founder effects and group selection type properties and he wound up in great detail

Analysis Of Multi-Level Selection And Evolutionary Psychology

Multi-level Selection (01:10:23)

analyzing Calvin and the starts of Calvinism and Calvin and his sidekick Hobbes and Zurich in the 17th century whenever it was the Calvinism started of analyzing how there were all sorts of these little religions popping up there in these little city states and what it was about Calvinism in I think it was Zurich that took off where they established some of these inbred cooperative patterns and then beat the pants off of all the other city states and soon all of central Europe was Calvinist really interesting book in that regard so back has come this whole possibility of group selection and out of that has come the more broad way of thinking about it now which is multi-level selection a very important concept here which is sometimes selection occurs entirely on the level of a single gene in other words have a gene with bad enough of mutation and it doesn't matter how many great other genes he got going for you selection will be decided entirely on the basis of one gene as we saw on our principles from the other day much more common selection at the level of the individual an aggregation of the genotype playing out in terms of phenotype all the different traits there but what this introduces is some circumstances where selection is at the group level and there's never at the level of how an individual's trait plays out individually in a group it's how this trait played out individually emerges as a group behavior that you get group selection and this marks this great piece that's come between this David Sloan Wilson and the guy is probably the most towering figure in this whole field this guy E.O. Wilson Edward O. Wilson at Harvard who David Sloan Wilson spent years not getting along with each other because Wilson Wilson is very strongly individual selectionist model guy and thus he hated group selection David Sloan Wilson the other way around each of them were endlessly invited to the wrong parties because of the same shared last name and also to social awkwardness there in the last few years I don't know what happened I don't know if they arranged marriages between their grandchildren or something but they arranged some sort of truth and Wilson Wilson published a paper last year basically saying whoa you know what some of the time I'm right and some of the time he's right and isn't that great and can we all get along and delineating circumstances where individual selection individual selection can selection reciprocal altruism is going to dominate circumstances where selection is going to get played out of the group level they love each other now they have formed a new language they share burial customs and this sort of constitutes a great resolution yeah depending on the circumstances the most important thing in evolution might be a single gene a single organism or a single group and the power of a group and aggregate traits that work lousy in the individual is

Two Behaviors that Many Species Do, But Humans Have Unique Reasons for Doing (01:12:41)

going to be really important down the line when thinking about aggression and stopping aggression and things of that sort okay so all of this is great this multi-level selection now showing sort of a fancier more sophisticated way of thinking about individual kin reciprocal circumstances where it works circumstances where this is the most interesting thing so that's great so now we begin to look for a first pass where humans fit into this we've already seen in terms of all of these traits tournament versus pair bonding we're somewhere in between in terms of imprinted genes we're somewhere in between these are specifics how do we begin for a first pass to think about humans human behavior fitting into these frameworks two problems or two issues that are all will touch on at this point the first one is there's this temptation as soon as you think along these lines to discover oh isn't that interesting langer monkeys will have infanticide male langer monkeys will kill the kids of some other male human males do that sometimes oh langer monkeys might be an interesting evolutionary model for where infanticide will be behavior came from in humans oh isn't this interesting dominance is passed along by males we do that isn't it interesting kidnapping somehow occurs and before you know it you have a world in which people are saying well damsel flies do something that look like rape so how we've got a damsel fly model of human behavior in that realm and two things are happening there one is taking the traits a small number of traits in some other species and inflating the relevance that has for understanding us the other dangers is somewhere creeping below the surfaces you see it happens in other species it's kind of natural it's kind of inevitable this is a whole world in which people have run off with how this applies to humans in a completely distorted way we are unique as a species as is every other species we are unique by applying the same evolutionary rules that every other species has that's the commonality not the outcome the other challenge is constantly going to be that you get all these great predictive models and then humans go and screw it up by having quirks and idiosyncrasies and personalities and stuff like that all I can say in that realm is back to Wednesday if making sense of which lions are going to go to the scary speaker and the bushes there revolves in some part around personalities humans by the time you get to us blindly assuming these models apply is going to be very sort of unshaky very shaky okay so just the first pass at how one will

Why Figuring Out How These Models Apply to Humans Will Be Difficult (01:15:38)

have to be cautious for the rest of the course and applying all these models now far more critically is looking at what are the criticisms that have been brought against this whole framework this framework of social behavior has evolved to maximize number of copies of genes driven by kin during my reciprocal altruism group selection is a rare trait but when it does it follows the properties this is how you explain all the behavior know these four or five rules and not only can you look at two skulls of different sizes but you can explain all the behavior and all the human behavior and it's all biology and eventually as E.O.

Social psychology crisis and dynamics. (01:16:24)

Wilson said in this landmark book of his in 1975 social biology eventually all of the social sciences will be under the wing of evolutionary biology no surprise the social scientists were not very pleased with that proclamation at that point but this was this notion that this was going to explain everything so what are the criticisms that have been leveled at the style of thinking as we see there are a lot of them all of the stuff we've been thinking about this basic notion of applying the Darwinian rules as to why giraffe have to have hearts of certain size to behavior there's three features that are coming through for out the first one is the notion of heritability of traits because what we've been discussing throughout the last lecture or so is there's heritability of the tendency to kidnap infants at the right strategic time there's heritability of the tendency to decide that you like males with big fancy plumage and long canines as opposed there's heritability to deciding that your daughter should be highest ranking of the true brother of that one's heritability an assumption of heritable behavioral traits runs through every single one of these discussions the next thing that runs throughout all of them is the notion of adaptiveness if some trait has emerged out of the evolutionary merc if some trait has been selected for selection implies adaptiveness the notion that everything you see has an adaptive explanation for why it's emerged evolutionarily the third principle which is not explicitly stated in this field very often but is implicit to everything about it is these processes of evolutionary change are gradual at every generation if by getting into some better behavioral strategy for playing prisoner's dilemma you leave 1% more copies of your genes and everybody else come back in 100 zillion generations and that trait will have spread all of this is played on generation after generation so that evolutionary change is occurring in gradual incremental steps so what do you do

Three assumptions in Evolutionary Psychology. (01:18:27)

with these three starting points the first one an awful lot of the next two weeks will be looking at how other disciplines look at the issue of how do you figure out when a behavior is genetic and one of the first things we'll learn is how that phrase means absolutely nothing whatsoever maybe a better way of stating it is how do you figure out when a behavioral trait has a genetic influence and as we'll see even the safer way of saying it is how do you figure out in which environment a certain behavior has a particular genetic influence how do other disciplines go about saying oh it's genetic it's genetic in this field among this sort of sociobiological thinking what you do is an inverse style of proof you say okay if a trait has a genetic component you would expect it to be heritable along these lines if it's more adaptive it will increase its frequency all of that and look that explains where competitive infanticide has come from show me a more explanatory model show me a model that is more predictive and until you can show me one I'm assuming this trait has some heritability and we'll see how by next week the more molecular people rip this view to shreds tell me when you're talking about heritability of some behavior show me the damn gene show me the sequence of DNA show me how that produces the behavior this is where this field ends saying oh we can inferentially sort of decide there's a genetic influence as we'll see by next week this one piece is the main thing attacked by a number of other fields next piece the adaptiveness the notion that everything that has evolved has evolved under the scalpel of evolutionary demand for optimization all of that and the critics of this view call this the adaptationist fallacy the notion that everything is there for a good reason and what they often do in terms of making fun of that is that oh you look at people who do this kind of evolutionary biology with this adaptationist emphasis and it's one big just so story why do giraffe have hearts with thick muscles and here's the story I make up and if my story is better than yours I get tenure and you don't why is it the zebra's got stripes why is it that males kill infants in the species or whatever that everything is adaptive and what you need to do now is come up with the story to explain why it's adaptive and if it fits in those principles of individual and group etc then you

Adaptionism. (01:21:03)

win you've got the best just so story and what is constantly brought as a sort of criticism of that is show me experimental evidence that is adaptive and by the time we get to looking at the field of ethology you'll see a whole way in which people do that show me that it's possible to disprove it okay tell me a just so story where if that were the case that would prove that this is not what's going on you've got to have the rules of science it can't just be you observe something and come up with the best story and you can see that there's a lot of evidence that's going on with the best story and you win but what's most striking sort of terms of criticizing this is some domains in which there are traits that have not evolved because they are adaptive they've just evolved because they are excess baggage and this is brought in a whole sort of criticism of the field now some of the time when you begin to see it's kind of hard to see where the adaptiveness is it's because it's a more subtle feature of it for example you can look at squid and someone who is enamored with fish and how cool and aerodynamic aqua dynamic fish are and all of that will point out that squid are pretty lousy swimmers compared to all sorts of fish they're pretty lousy swimmers compared to fish but they're pretty great swimmers for something starting out evolutionarily as a mollusk this adaptiveness has to be in the context of where it came from where it got to okay so that is a qualifier nonetheless even factoring that in of hidden features of acid and features of adaptation evolutionary history there's lots of traits that are simply not adaptive and one of the most effective critics of this whole view Stephen J. Gould introduced a term about 30 years ago that summarized this view Gould was a paleontologist at Harvard and I was thinking we'll come in a whole lot in next week's lectures he teamed up with another guy a molecular geneticist at Harvard named Richard Lewenten and critiquing a lot of this they came up with a term saying an awful lot of traits have evolved that exist not because they're adaptive but because they're spandrels so at that point everybody in the field had to go and run to their dictionary because Gould and Lewenten were all being snottie and coming up with fancy high-falutian culture terms because it turns out spandrel is a term from architecture so immediately they already one points off of everyone else for being all cultured and stuff but a spandrel is you got some medieval So, at that point, everybody in the field had to go and run to their dictionary because Gould and Lewinton were all being snottie and coming up with fancy high-falutin culture terms, because it turns out spandrel is a term from architecture. So, immediately they already won points off of everyone else for being all cultured and stuff, but spandrel is you've got some medieval building, remarkably enough, that's a medieval building. It's a nice medieval building. What you get is you have these arches that there winds up being a space between arches, that there's space between arches just because you can't build arches next to each other without there being like the space here. This is solid brick or Lego blocks or whatever. So, you have these arches and there's a space in between and you got the space. It's not there for any good reason. It's there because you can't put two arches next to each other without coming up with this triangular space. And the architectural term for those triangles are spandrels. And spandrels in architecture is something that forms between two arches. And as Gould and Lewinton use the term, a spandrel is some trait that occurs simply as the unavoidable outcome of some other traits that are being selected for. You can't put two arches together without getting some sort of triangular shape in between.

Exploration Of Sociobiology And Modeling In Evolution

Sociobiology and Strandvelops (01:24:56)

And throughout history of architects making spandrels, these would be artistically built up and all of that. And there would be all sorts of decorative stuff on that. So if you are an adaptationist, folly person, but everything has an adaptive purpose, you look at that and oh, there's got to be some reason why spandrels have evolved and have these elaborate secondary sexual features on spandrels, little gossamer things flying around and stuff. And there's got to be an adapt. Oh, I know because people in church will look up at it a whole lot and their necks will get sore. And when their necks stop being sore, they will decide this is the glory of God and they will increase their belief for some. That's why architects put in spandrels. No, you can't build buildings like this without spandrels happening. And just because they were there, why not let's decorate them. That's the evolution of spandrels. And in Gould and Lewenten's critique, an awful lot of stuff where the sociobiology types would sit there and say we're going to have a just so story contest now and use our principles and figure out some way in which this is actually adaptive, saying this actually wasn't selected for because it's adaptive, it was an inadvertent byproduct of something else. So here's an example that would be given. Humans have chins. Humans have chins. And certainly all humans do have chins hidden away someplace or other. Humans have chins.

Chins: Andren Loere Is Not An Athlete (01:26:25)

And weirdly, we're like the only primate that does. You look at like other apes and stuff and they have the sort of weak chins that suggest sort of immoral characters and criminology, criminality and things like that. We're the only species that has chins. And apparently there's been some like nutty adaptation of school somewhere back when trying to make sense of why it is that humans evolved chins. Why it is that human faces come to a point there and what's the adaptive advantage and you can like stab rivals or you can get crumbs from out of the corner on the floor and stuff with your chin. And until somebody figured out that there's no way that you could have a primate face that has a muzzle for shortened and a jaw at this angle. You do this and you do this and you're going to get this little spandrel thing sticking out there. Oh, there hasn't been selection for a chin because you have selection for a hominid face with a shortened muzzle. This thing pops out there and suddenly all those doctoral theses about the reproductive advantages of chins go down the tubes there. It was merely a spandrel. And Gould and Lewenton's argument is that there's lots and lots of spandrels that this emphasis, everything is adaptive, everything is the outcome of competition that's produced that an awful lot of stuff is excess baggage that merely gets carried along because the evolutionary process isn't all that efficient. You're starting with a mollusk if you want to make yourself a squid. Giving rise to another concept, another term in the field, Andre Loaf, who was a French or was a Jacobe. There were these two French molecular biology guys and they both got Nobel prizes and one of them said this and I don't remember which but I'm going to say it was Loaf, who did it because I like saying a Loaf. Andre Loaf once said that evolution is not an inventor, evolution is a tinkerer. It works with pre-existing structures and the notion that you're going to see this everywhere, you're gluing stuff together, you're duct taping this part of the pelvis to this part of the circulatory system, whatever, and you're going to have spandrels. An awful lot of what those folks go through in these whole song and dances of adaptation are merely spandrels. Evolution is not about optimizing every single trait. What comes out of that is this notion that an awful lot of this world of competition really isn't about competition. You stick with these models, the models we've been covering for the last two days and every bit of advantage is going to increase the number of copies of your genes, what's the only possible outcome you need to compete? You need to out compete. It was a critique of this whole view as being one driven very strongly by competition because all the traits there are driven by having to out reproduce the next individual, next individual. Another realm in which this has been critiqued has been by, interestingly, evolutionary biologists from the Soviet Union and where was emphasized there in Western sort of emphasis in evolutionary biology, most of evolutionary selection was about competing with other individuals. Sexual competition, competing for running away from the predator faster than the guy next to you, competing for food, all of that. If you're sitting there in the Soviet Union, you're thinking about evolutionary biology, what you're mostly thinking about is evolving the means of surviving climate demands, surviving extremes of climate, what would be categorized as abiotic rather than biotic, abiotic demands in the environment. When you look at species where most of their survival is about surviving ecological extremes and environmental extremes, you don't see a whole lot of competition, that's a world with far less.

Abiotic vs Biotic Selection (01:30:01)

Throughout the years, the Soviet evolutionary biologists tended to emphasize abiotic selection which had far less of an emphasis on competition. The final piece though, the gradualism, the gradualism is very intrinsic to this because if everything is adaptive, every little bit of advantage is worth fighting for and competition and killing each other's infants and killing each other's spurs and overdogs and all of that and every little bit is going to make for a little bit of an advantage and you will have this gradualist change. The huge challenge that came to that was from Gould and another scientist in the 80s, a notion that maybe that's not what evolution looks like. Maybe evolution is not occurring in these gradualist incremental steps, maybe what occurs instead is long periods of nothing happening and then a rapid evolutionary change and long periods of nothing happening, a rapid evolutionary change, something that they called punctuated equilibrium and the whole next lecture is going to be about this. Critical implications, the genetics of how stuff evolves turns out to fit far better the molecular genetics with these models of punctuated rapid change and stasis equilibrium punctuated change rather than these gradualist models and if that's what it looks like in these steps most of the time you're not punching it out for every one half of 1% reproductive advantage and it's all competition. Most of the time nothing's happening at all and there's periods of severe selection and then long periods in which nothing happens, a step function like that, the role of competition is reduced tremendously in thinking about evolution.

Importance of modeling (01:31:39)

So we're going to spend a ton of time looking at the punctuated equilibrium model to give away the punch line that I know you are all on the edge of your seats for, I kind of think it's right in a lot of the circumstances of evolution because it fits much better with the molecular biology. Finally, in addition to these critiques of show me the genes, everything doesn't have to be adaptive because there are spandrels and besides this is really wimpy science where science counts as making of the best story and there's no reason to think that it's gradual, there's mechanism for this as well.

Looking at Punctuated Equilibrium (01:32:16)

In addition to that there's always been a final realm of criticism of this style of thinking which has been a political critique and lots of realms of science you can't really imagine a political critique as to whether Celia on amoeba flipped this way or that way or a critique as to whether like plants should have three clover things or four clover things that there's not a political factor in that. There's a huge amount of socio-political implications that run through this entire field because it addresses issues of like how natural, how evolutionarily ancient, how evolutionary really honed, how adaptive are things like whether a species, a society has male domination or not, has strict hierarchies or not, has certain degrees of aggression, has certain patterns of sexual coercion and a whole world arguing that these things have a naturalistic grounding and adaptation versus a whole world that says that's gibberish most of the time nothing's happening and when it does a lot of it is spandrels those have very different political implications and from day one the critics of this entire world have made a point of something that initially seems kind of silly but may not be silly which is the entire founding generation of these sociobiologists were white southern males. Make of that what you will. Eale Wilson from Alabama, Robert Trivers, Irvin Devorah, a whole population of these folks the first generation of these people were all white males from the American south whereas Gould and Lewenton all of these guys were northeastern Marxists. Okay so we got kind of a major contrast here and the critique of the sociobiological view is isn't it interesting that their notion of how evolutionary evolution works just happens to emphasize the naturalness of a system that rewards them for the inequalities that we have. Isn't it interesting that their models predict the naturalness of the world in which they're the ones who benefit most from the notion that this is natural and from day one that has been a strong critique and that's not like critiquing silly a meba theories for political implications that is a very real one because the notions that this is pertinent to making sense of is rape a human psychopathology or is rape a competitive strategy is the fact that children are more likely to be killed by stepfathers than by biological fathers does that represent something about the typical socioeconomic pressures in families with step parents versus the natural biology of gene competition through competitive infanticide this has a lot of implications and from day one as this field emerged in the late 70s there was a huge political agenda that was assumed to be there sufficiently so at one lecture famous conference in 1977 where E.L. Wilson was presenting there a bunch of people rushed the stage and knocked him off the stage and dumped water on him and chanted whatever it is in German saying we will have a society of law and order.

Explanation Of The Punctuated Equilibrium Model

The Punctuated Equilibrium Model (01:35:35)

This is pretty agitated circumstance for thinking about science this was a group in Boston called science for the people which is a Marxist group at the time there and saying all this sociobiological stuff is doing is justifying a world in which it is male dominated stratified and where aggression and competition pays off and this has been highly controversial from the beginning the one counter to it and I think a lot of that was valid and I think a lot of it instead defaults into models where this is not making a whole lot of sense the one thing to be pointed out is when we see what punctuated equilibrium is about it is exactly the sort of world of evolution that produces the sort of world that a Gould or Lewington would want it to be a one which minimizes competition and favor cooperation and a whole pattern of stasis and rapid dialectical change it is exactly the world that two Marxist geneticists would say evolution should be about so I think as a first pass here seeing this stuff is dripping in social political implications so starting Monday we will look at this punctuated equilibrium taking apart this piece of the story and basically for the rest of the course examining.

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