Sex and Violence Among the Apes 
Sex and Violence Among the Apes
by Yale / Robert Wyman
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Lecture Description


Chimpanzee males compete for position in a dominance hierarchy; status often depends on support from other members, including females, of the group. High-ranking males have much greater sexual access to females in estrus. Males control females by physical violence and intimidation. Chimpanzees also engage in purposeful raids to kill members of other chimpanzee groups. This inter-group violence can help explain intra-group violence. To fend off attack from other groups, males must remain in groups and that requires males to compete for mating opportunities within the community. Competition for the scarce resource, eggs, leads to male-male violence and male coercion of females. If the alpha male monopolized all reproductive potential, then evolution would push non-dominant males to either fight continually for dominance or to leave the group and find females elsewhere. The chimpanzee solution is to allow all males some, though very unequal, reproductive possibility.



Reading assignment:


Peterson, Dale and Richard Wrangham. Demonic Males: Apes and the Origins of Human Violence, chapters 10 and 11



De Waal, Frans. "Bonobo Sex and Society." Scientific American (March 1995), pp. 82-88



De Waal, Frans. Chimpanzee Politics: Power and Sex among Apes, chapters 2 and 4



De Waal, Frans. Our Inner Ape, pp. 75-79




Transcript



January 15, 2009



Professor Robert Wyman: How many of you saw The New York Times yesterday morning? What did you see?



Student: The girls who had been splashed with acid by the Taliban on the way to school.



Professor Robert Wyman: Yes, so the front and center story in The Times is--let me get my pointer. So this girl--so in Afghanistan one of the ways of suppressing women is to keep them from getting any education. When these girls go to school--because, you'll learn a lot about that in the course of why they want to go to school and why their parents want them to go to school. They go to school and three guys came up on a motorcycle--a motor scooter and they just ask the girls, "Are you going to school?" They're walking to school in the morning, and the girls said, "Yes." Threw acid in their faces, and this story is about that kind of thing happening right now in Afghanistan. When this happened, the girl--everybody was of course very scared but the parents--one set of parents that were quoted here said, "You must go to school even if you're killed." That going to school is more important than their lives in these communities and you'll understand a lot later why.



Now one other notable thing happened--so that's quite amazing. I talked about it on Tuesday and Wednesday morning up comes The New York Times story. This happens every year. I think there's a spy in the class. The next thing is a student said she loved the lecture, but what did she love about it? She loved the dung beetles, and so she sent me her own personal picture of dung beetles, here, and she waxed a little bit poetic about them. "I have to let you know that dung beetles are among my favorite animals. The best part is watching the males agonize over rolling the ball over to the hole while the female rides relaxed, just planting her eggs inside it. The ultimate feminism, if you ask me." Now the student wants to remain anonymous, so that you all don't think that she's a little kinky maybe; nothing wrong with that. This is--we're very liberal minded here in this class.



Now how many of you were not here last time? A few of you, so I should give a very short summary of what went on last time. I was describing the basic biology of how the social organization of the species is organized around their sex and reproductive function. For virtually all species of higher then single cell organisms, the female puts a lot of--makes big eggs, a lot of investment; she doesn't make that many eggs. They're rare and expensive. The male sperm is very tiny; he can make a huge amount of them, and so they are plentiful and very cheap. Males then, given the excess of sperm, that males can inseminate many females.



The males then must compete for the females, and they have two mechanisms, either sperm competition where the sexual system is polygamous, promiscuous, and many males will mate with the same female; the same female will mate with many males, and then the sperms themselves will compete by a whole variety of mechanisms to see which sperm will fertilize the egg. The other male strategy is to physically fight with other males to gain control of the female or to compete in some other way like displaying your--the peacock with this enormous tail displaying, 'I've got a more beautiful tail than you do,' or we talked about birds dancing. The males dance for a long time and display their mental ability to dance coordinatedly and their beauty and stamina to the females. Then the females choose.



The females also have two strategies. Obviously this is a great simplification. The females also have two strategies, one is to get resources from the male, as in the dung beetle. The dung balls are full of nitrogen which is very rare, and so they feed this to the female, and the female then can produce more eggs in it, which is evolutionarily very good for both the male and the female.



Or the female wants to choose the male with the best genes; in some ways the males have to display what are the best genes, and best just means those that are successful reproductively. Sometimes bigger is better; sometimes smaller is better; sometimes fast is better; sometimes slow is better; better does not mean anything and fitness--the word fitness, which you've heard, does not mean anything other than 'leaves more offspring.' It can be any kind of phenotype you can imagine, any kind of body type, any kind of ability or the opposite. In some ecological situations being fat is good, and other times being skinny is good. The females either watch the male's display, watch the peacock's tail, or observe the end of fighting between the males; that one male becomes dominant then the female is happy to copulate with that male.



When males fight, the males tend to get large because that helps them in the fight. Evolution makes them larger, and they get larger than the females, and once they're larger than the females, they can start coercing the females. And that's really the origin of--the biological origin of--a lot of male/female violence. Males can either--to gain access to female--they can either fight with other males which can be very difficult and you're liable to get damaged or killed, or just coerce a female who's smaller and less strong, and so you get male coercion of females.



In primates, it's the last sort of--in primates and the great apes--we are all great apes--in particular, this tendency toward male violence onto females is carried to--is most prominent. The reason is, we invest enormously in our young. We spend a very long time with the young, taking care of them, and therefore, the females who do most of the investment can't have very many young; they can't have them very rapidly.



In the great apes, aside from humans, which we'll talk about next time as an exception, it takes five to ten years. The females don't have a second--they have a child--a baby, then they wait five to ten years before having a baby again, so eggs are very difficult to come by. In a group of chimps, maybe one egg a year is available for fertilization, and the males compete like crazy by every possible mechanism, including a lot of violence, to get access to that single egg.



One anecdote about the relationship of sociology and sexuality has to do with orangutans, who are the most distantly related of the great apes from us. They are just--they are very clever, like all the great apes, and they use all kinds of ways of being attractive to a male and vice versa. One of the ways they use, like we do, is intellectual brilliance. I think Yale students are evolved especially to use intellectual brilliance to be attractive. My college girlfriend, I fell, I guess, in love with her, because she could do the Latin and I couldn't. I was hopeless. She was--I was just stunned at how well--how good--how well she did it.



Anyway, in 1978 a graduate student from Stanford went to the orangutan research station in Borneo and his job was language. They--a lot of people want to show how close or how different great apes are from humans, so language is a special human ability. But the great apes have a certain degree of it and he wanted to find out how much. He taught an adult female named Rinnie sign language and the guy's name was Gary Shapiro, Rinnie was his mate. It turns out she was a brilliant student, she really should have been at Yale, but she was stuck in Borneo and didn't have the money to come here. Gary just could not believe how fast Rinnie learned the language, and so he was just glowing and he loved Rinnie, and his research project. He was going to get famous, probably being to teach more language than anyone else has ever taught to an ape.



Rinnie took all this attention quite personally. She thought there was something going on between the two of them; it wasn't all intellectual. She waited for Gary and nothing happened, so one day she took the dominant role, as I've heard Yale girls sometimes do, and she took Gary by the hand and did the obvious things to try to seduce him.



There's Gary, what is he going to do? Well he wasn't very up for this, like many Yale guys that I've heard of, and so Gary just pushed her away not thinking an awful lot about it, but being a scientist, he hadn't read his literature. He does not know that there is no wrath like the wrath of woman scorned. Thereafter, she lost all interest in signing, would not cooperate in the lessons, ruined his PhD thesis project. So let that be a warning guys.



We've talked about--we talked last time about orangutans--of the great apes, those five species, including us--we talked about the rape that orangutans do; we talked about the infanticide that gorillas do, and now we come to chimpanzees who have yet another system. Again, always coping with this idea of the rarity of female eggs. Unlike the orangutan and the gorilla, the males are not solitary. The standard--the most common, there is no standard; there are millions of species and they do millions of different things. The most standard mammal thing is for the males in some way to fight with each other and they push other males away and one male gets one or several females. There are exceptions to this but that's the most common sort of way. Chimpanzees don't do this.



They live in a group of males, and in fact the males that are born into a group stay with the group, so this a male group that genetically has been staying together for as far back as one can tell. Males basically never transfer groups; they never leave a group, so these are basically a long line, one family set of males. Within that community--let's see, I think I have some slides of this. Ah, that's a picture of the orangutan that fell in love with the grad student. We'll come to Jane Goodall in a minute.



Given that there are males together, what they do then is compete for dominance and a lot of that is physical fighting. Their dominance position gives them access to food and to females. When a chimp wants to move up in the dominance hierarchy, he may go through a long period where they're sort of jockeying in various ways, and I'll describe some of the jockeying going on. Largely big displays, beating the chest, if there's anything around, shaking branches, stomping on the ground, hollering, but they don't fight. But eventually, if in fact a reversal of dominance position is going to take place, a real fight almost always does occur, not always successfully.



Jane Goodall describes one of these, Sherry--and they give names to each of the chimps--Sherry, a younger male, was moving up in the hierarchy, an aggressive young male. You know some of those. He had beat out some of the lower ranking young males, but the next one on his list was named Satan. You can tell from the name this was not a wise move. Satan was not the Alpha male, but was higher than Sherry. They had a huge fight.



When it was over, Sherry was bleeding from bad wounds on his shoulder, both hands, his back, his head, and one leg. Sherry escaped and ran away screaming loudly. This was apparently such a bad experience that Sherry never again attempted to dominate any other male. He had been whipped, and he learned whatever his instincts may or may not have been about aggression, he learned that's not his game; he never tried this again.



They do a lot of threats and displays as--prior to these fights--but if there's going to be a real reversal, there's usually a fight and the fight's can get very severe. In the wild, the loser just runs away and they don't carry the fight to the death, and by the end of the lecture you should understand why they don't want to kill each other. In a zoo, when the chimps are in captivity, the males can't escape and then that proximity leads to a prolongation of the violence and sometimes to death.



Frans de Waal, who you'll do some reading from him; he describes one fight where the loser had an ear gone, the other ear torn, his hands and feet badly mauled with several bones exposed, and some fingers and toes missing. A gash stretched from one shoulder to the opposite hip, and toes were missing, and this guy was really beat up. They took him to a human type hospital and tried to fix him up. It didn't work; he died. Within a group the fights basically never end in death. In captivity they do end in death; that's within-group fighting.



This finding your place in the dominance hierarchy is a very serious business. You can either win and go up or you can lose and stay and either die or get badly physically damaged or be relegated to a low place. Humans call dominance hierarchy 'status,' and when I use dominance, think status. We don't always use the word here but think--one of the other things if you want to compare chimps and humans, think of the various things that humans do for status.



Chimps live in groups of about 40 individuals, with a dozen or so adult males, approximately the same number of females, and, as with orangutans that I've described to you, the female they have a big range, 15 square kilometers, 40 square kilometers, something like that and they wander about this. The females, when they have a young, are usually fairly isolated, not necessarily, not all the time, but mostly they're by themselves with their young. It's a very stable group that always stays together. As I told you last time, the mother is never out of either touch, or sight, or hearing of their young for five or more--five to ten years.



The males, on the other hand, wander around also but they bond together. They travel together and they are very often in parties, and they go around searching for food and patrolling the borders of the territory. They also of course visit the females, go around see which females--what the sexual status of females is and I showed you a slide last time of a male smelling a female's sexual secretions to figure out what status she's in. This looks like something that I've already talked about here. Is this repeating? All right, so I don't remember whether I did this.



The females are usually quite promiscuous with their sex partners. In the community followed by Jane Goodall, in each estrus cycle, each female had at least one bout of intercourse with every male in the group. Did I--I did do this yesterday. Forget this; I don't know how this happens.



How do the males do their--operate in their dominance hierarchy? It's not all violence. One aspect is violence but they also make friends with other males. Single males cannot be successful; it's a very, very social situation. These animals are very clever; they know each other individually; they know each other's propensities, which ones are dominant, which ones are not, which ones are smart, which ones are not, which ones they can fool, which ones they can't fool, and so on. So they do a lot of social manipulation to try to get allies in their dominance fights.



In these friend relations you mostly see it as a grooming thing. Males and females spend a lot of time with each other grooming, and what is grooming? Chimps, like all kinds of other animals are infested with parasites, which can carry diseases and be very dangerous, so they have to get rid of them. So one chimp will sit there and the other chimp will come by and spread the fur very carefully and then if there's an insect--it's good for the person from whom they take the insect because that insect is no longer-going to parasitize them--and it's good for them, they get a little bit of protein. They spend hours and hours doing this. Males to males, males and females with each other, and females to females; everybody does it with everyone else, and one of the things that the observers do is count how much time each individual spends grooming the other. The person--the chimp who's being groomed has this wonderful expression on their face, they're clearly enjoying this; it's like a nice massage.



The purpose of this friendliness or one of the purposes is to help the males when they engage in dominance fights. Jane Goodall describes one of these: Goliath, one of the males that we'll talk about later. Late one evening he arrives in camp all by himself, and he seems a little on edge. Every so often he stands upright and stares back at the direction from which he had come. He seems nervous and startles at every sound. Six minutes later, three adult males appear on one of the trails, and one is the high-ranking Hugh. They pause, they seem him; they pause, their hair on end, then abruptly they charge down toward Goliath but he--in the time that they were sort of waiting, he then has disappeared quietly into the forest.



For the next five minutes these three big guys thrash around the underbrush, they're looking for him, but he has successfully escaped. He is afraid, obviously one against three, he's afraid. The next morning Hugh returns to camp with two companions. A few minutes later Goliath--Goliath the one that had run away before--charges down, dragging a huge branch, that's one of their display kinds of things, and then he runs straight at Hugh and attacks him. The guy that ran away last time, one against three is still one against three, but now he's the attacker; very strange. It's not until the battle is already in progress where they're grappling and hitting each other, that it becomes obvious why he has done that.



There's a--the dominant male, one of the very--not the Alpha but one of the strong dominant males is a very big one called David Graybeard, and while this fight has just begun, David Graybeard appears from the undergrowth and he gives a display, and whoa and gives some pant hoots and he's clearly on Hugh's side, and had obviously been with Hugh just before Hugh came in, so now he had an ally and then the outcome of the fight was very different. Suddenly Goliath leaps right onto Hugh, grabbing his hair and shoulder, pounding on his back with both feet, and Hugh gives up and he manages to pull away and runs off screaming and defeated. The guy that was--I think I got the names right, the guy who was scared last night, when he has an ally, is now the winner.



The females are almost as good as males in the dominance coalitions against each other. Their behavior to arrange these coalitions is extremely complex and manipulative as I've said. They spend huge amounts of their time trying to organize these coalitions, and then as soon as there is--so several males will be in a coalition, one of them will get to be Alpha, almost immediately after they become Alpha, the other two go out and form other coalitions to try to displace him.



We have some of our faculty members like that. Last night I was reading a book about renaissance intrigue, and it was amazing how some of the big dukes, like the Medicis and the Sforza, and then you have some of these smaller guys, and then you have the Pope who's got his own army, and there's this constantly floating crap game of who's going to be allies with who and as soon as someone gets--one of these principalities gets to be dominant, the coalition rearranges and everyone else goes against him. You can read the history of Europe in the nineteenth century where there's all this balance of power stuff or you can read the newspaper today, and it's all balance of power where they're shifting alliances and we--Japan and Germany were our great enemies, now they're their our great allies, and et cetera. Russia was an ally in World War I and II, and then they were an enemy, and then they were an ally again, now maybe be an enemy again. It's--it really doesn't read terribly differently.



The purpose of all this fighting for status is of course to gain access to females. There's some degree of food, and we'll talk about whether food is a real scarce item for them or not, it's usually not a scarce item, but access to females--I think I mentioned this last time is dependent on the status of males. It's not simply size and aggressiveness at all that determines dominance but how good a social manipulator the individuals are, especially females. If a male has not been nice to the female, which means sharing food with them. They go and hunt Colubus monkeys, and if they catch a monkey how much of the meat gets shared, how much grooming they do, and if the male is boorish, the other chimps will simply shun him. They just--when he comes up and tries to start some kind of friendly interaction, they just turn their back on him and walk away. He's shunned and isolated.



The point is, no matter how strong, physically strong and violent a single male is, he can never be Alpha without the support of the community. It really is, not quite democratic, but has aspects of a democratic choice, and that the male must have the consent of the community before he can become dominant. This social acceptance, the value of your peers, and your social status is really the deciding factor in who will be dominant and therefore who will pass on their genes into the next generation.



Now going back to the females, when the sex behavior of chimpanzees was first being observed, the observers were quite struck with the obvious promiscuity of the females. The females just didn't seem to care who mated them. We discussed that last time, in each mating cycle a female will be mated by every single male in the troop, in Jane Goodall's troop, sometimes not quite so extremely. That was kind of surprising given the theory that I've described to you, that females should want something from the males. They should want to choose either the male with the best genes, or the male who's giving them the biggest gift, or something and this just sort of compliance under any circumstance, it was obvious that that's what they were observing but it didn't make any sense.



Finally, they observed more--the chimps were obviously not terribly easy to observe and over a lifetime so you know what's going on, and the story is this, that when chimps are young, either males or female, the juveniles are under the domination of their mothers and the females meet with each other every so often, so any female can dominate any young independent of sex. You really, if you just looked at the social behavior, you wouldn't be able to distinguish a boy infant and a girl infant. I'll give you some reading, about human societies, many what we call 'primitive human societies' have the same thing, that even the words for a young boy is the same as for a girl, that they're not distinguished, only at some sort of puberty right do the boy--do the biological boys become socially constructed boys, in a sense.



In chimpanzees--so when they're little the females dominate them, but of course the males start growing big and in adolescence they start to get up to the same size of the female, and then what happens is that these young males come and start attacking the females for no obvious external reason. When this first happens the female is still bigger and she swats him away and he runs off screaming, but as he gets bigger, he comes back and seems to sort of choose one female at a time starting up on--there's some mild dominance hierarchy among females, not very strong but a little bit there. He goes and just gratuitously attacks one female after another and keeps doing it: pushes her, punches her, bites her, pulls the hair, and she fights back, but eventually he's big enough to cow her and he becomes dominant to that female.



Then he goes to the next, and the next, and the next and eventually as they go through adolescence, the young males become dominant to each female. Then, that's not the end of it, that every so often thereafter, they again gratuitously attack the females for no particularly obvious reason. Let me describe to you one--read to you one of the descriptions of these kind of dominance attacks. This is one of the people in--studying in Jane Goodall's group in Gombe in Tanzania and this is--she is recollecting: "Nearly 20 years ago I spent a morning dashing up and down the hills of Gombe trying to keep up with an energetic young female. On her rear end she sported this small bright pink swelling, characteristic of the early stages of estrus." She was just coming into her fertile period and really wasn't particularly fertile at that time. "For some hours our run through the park was conducted in quiet--quietly, but then suddenly a chorus of male chimpanzee pant hoots shattered the tranquility of the forest.



My female rushed forward to join the males. She greeted each of them, bowing and then turning to present her swelling rear end for inspection." You know, 'hey guys get interested in me.' She's young and a little inexperienced, she thought they would be real hot-to-trot, but didn't turn out, and the males examined her kind of perfunctorily and they saw she wasn't really ready yet, and so they resumed grooming one another and showing no interest in this young female.



The scientist here, the anthropologist was rather surprised by this indifference to a potential mate. Then she under--she sorted of recalled and there's--well, her swelling is really pretty small so far so she' not ready, so she realized it. It would be a week or two before she was really going to be fertile. Then they'll be really interested. She was sort of watching this, the males basically grooming each other, ignoring this female, and then boom all of a sudden they attacked.



"The attack came without warning. One of the males charged toward us," the anthropologist was with the female, "One of the males charged toward us hair on end, looking twice as large as my small female and enraged. As he rushed by he picked her up, hurled her to ground, and pummeled her. She cringed and screamed. He ran off, rejoining the other male's seconds later as if nothing had happened." He attacks this one and then nothing happened. It was not so easy for the female to return to normal. She whimpered and darted about, darted nervous glances at her attacker and he--she was worried he was going to just charge at her again. The primatologist continues that in the years that followed she saw many such assaults like this.



What's the purpose of this? These attacks do not end in sex, so they're not rape. What happens is the male establishes a dominance over the female. She's afraid of him--as I told you they of course know each other individually and remember over many, many years and so these attacks during adolescence when they establish their dominance, and then the continual reminders that they're dominant and they can coerce them at any minute is what the purpose of this is.



So when she does come into estrus and all the males are around and there's only a very short window of opportunity when he may--she may be alone, the other males are fighting or not paying attention for a moment--remember he only needs 15 seconds, remember I described that last time for a bout of intercourse--he has 15 seconds before the other males are going to come and interrupt him. The last thing he wants is for her to resist. She has to be compliant in that very short time, sort of a like a private in an army, don't ask questions do whatever you're told immediately, and this prior violence the purpose of this prior violence is to cow the females into submission at that moment when they need this submission. That is the chimp system. It's--to our eyes it's not a very pretty kind of system and you can think how much of that we still do something similar and that's up to you to decide.



We've described now three other great apes, aside from us, and there's the fourth great ape species which you probably have heard of, called Bonobos, and for a long time--they're very similar to the chimps. I showed you last time the evolutionary tree. They split off from chimps and Bonobos have split off very recently, so they're still very much the same. The Bonobos are a little bit smaller; the difference in size between males and females is not so great.



Their behavior is enormously different. There's almost no violence in a Bonobo troop. The various Bonobo troops don't get into violent attacks with each other. What they do is have sex a lot, that anything that comes--anything that in a chimpanzee would elicit violence--competition for food, competition for females, whatever--they have sex, and somehow that diffuses it.



They do everything you can dream of--somehow there's something wrong. Anyway, what happens is, males or females may initiate the sex bout. They often do it face to face which is not a usual animal sort of thing, and the picture that I had, and I don't know where they--why they're not being pulled up--is first a male and a female copulating, sort of face to face and what you'd recognize immediately what was going on, and they seem happy about that. Then I have another slide of two females going at it, and what they do is they stand face to face and rub their genital regions together. Of course what do the primatologists call that? Genital-genital rubbing, perfectly neutral. Now the locals where these Bonobos live they are much--they understand better, and so what do the locals call it? Hoka, hoka. So there's a long picture of hoka, hoka. In previous years I had--I won't tell you this story, very interesting story--afterwards.



The question is--there's essentially no dominance of the males over the females, or very little dominance of the males over the females. You don't see this violent theme happening. You read about this, there's several readings on Bonobos because I don't have time in the lecture to talk so much about them, but it seems that what's going on is -- Bonobos live one side of the Congo River and chimpanzees the other side, and on the side where Bonobos are, there are also gorillas and so they compete for the same food source. I'm sorry, on the side where the chimps are they're also--have I got this right? Gorillas--and so they compete for the food source, there's not that much food so the chimps have to forage pretty much alone, the females get isolated, and therefore they're subject to male dominance.



In the Bonobos territory there's more--a greater food density so the females can stay together and forage as a party. As you will read, there's female power; the females stay together, and if a male comes and tries to dominant one of the females, her sisters support her and beat the male off. So in evolution they've sort of given up trying that trick, and now everybody copulates with everybody else. What do we call that when there's this great promiscuity? What's the form of competition going on? Sperm competition, and so one of the ways that the Bonobos evolve is that they're--in evolution the testes get bigger and bigger, and so you measure the ratio of testes size in a Bonobo which has a lot of sperm competition to chimpanzees which have a lot less, very little because they fight--the males fight each other, and what you find is that as a fraction of total body size, the Bonobo testes are much larger than the chimpanzee testes.



We've seen four different models of male/female relationships: the rape in orangutans, infanticide in gorillas, battering in chimps, and total promiscuity in Bonobos. One of the questions that you can ask is which one most resembles the human condition? Well it turns out that if you do the statistics, in human's, rape is relatively rare. Of course we all know that it happens, but it's not a frequent event. Infanticide, which you'll see happens very frequently, but not against the will of the mother. The males, unrelated males, killing the infants of other females is a very, very rare event in humans, again it happens, but it's quite rare.



The common form of male/female human violence, what do we call it? Battering, right. Battering is extremely common almost all over the earth and for as far back in history as we know. Various studies have been done in different places. In Punjab in North India, 75% of scheduled cast women, that's lower caste women, reported being beaten frequently by their husbands. There's an agreement there, 75% of the men report beating their wives. In Bangladesh 47% of the women report having been beaten. A study of ten countries ranging from Japan to Ethiopia showed that in most sites between 30% and 56% of ever partnered women, had experienced both physical and sexual violence.



Of course these are almost certainly, whenever you collect statistics on something that is not exactly appreciated in the society, you're getting a very low report. These are certainly under reports because people don't want to report it, but also when you ask about not just casual, a little bit of violence, but, 'Have you been severely beaten,' in a society where 75% of the women are beaten frequently, the standard for what they're going to call severe is going to be very high. If you used our understanding of male/female battering the numbers would clearly be much, much higher.



What's interesting is there's a fair amount of collusion between the males and the females in this beating, this battering. Both--in the culture--both the men and the women feel that it is the husband's right to beat the woman, and it's justified. It's the woman's due. She should be beaten, and they talk about this quite openly; 40% to 80% again in different surveys, 40% to 80% of wives agree that a beating is justified if a wife neglects household chores or is disobedient. Again, disobedient probably has a much more minor meaning--disobedience worth a beating would not be even considered disobedience by us maybe, probably very minor.



Severe beating is almost uniformly justified and condoned for many reasons, including for example, a husband--a woman disobeying her husband's orders. If a husband gives a woman a direct order and she does not follow it, she gets beaten. It's her duty to obey her husband and they describe it--the women talking to each other and talking to investigators describe it as selfish when she follows what she wants to do, which of course there is always conflict between what Person A wants to do and Person B, then they said, 'I was selfish, I deserved a beating. Or they say that of another woman, 'She was selfish and she deserves a beating.'



In the U.S. of course we haven't escaped this, this has now become--it was hush hush for a very long time, but now it's fairly open because of the feminist movement, and the numbers are something like 50% of U.S. women will be physically abused by the men with whom they live, so again this is partner violence. Six million will be really battered and that's way more than rape, and auto accidents, and muggings, and every other kind of mishap put together.



Battering seems to be both the chimpanzee mode of violence, it's not the orangutan, it's not the ape, and it's certainly not--not the orangutan, not the gorilla, and certainly not the Bonobo, but humans seems to engage in the same kind of violence as chimpanzees. The most wonderful quote that I have describing this is from a Palestinian woman and she says, "Men have small brains. If you feed them, cook for them, and clean for them, maybe then they will not beat you." That's a great tag.



Okay, so now I've spun a nice story for you, the way chimpanzee's social organization around sex and reproduction. I don't know if any of you have noticed there's something really wrong with the story. Wrong, incomplete, incorrect, anybody think of anything? What have I described to you? I've described to you on the first hand that these males fight with each other their whole lives. A male, he has not much else to do, than feed and think about his part in the dominance. In the whole year there's going to be one or two females ready to be inseminated, and what do they do the whole rest of the year? They're fighting for dominance, and finally you get to have an Alpha male, and most of the time he's in strong control and really can control all the other males. That's the naked ape kind of story which you've heard.



Wait a minute, what else have I also told you? Every time the female comes into estrus she does it with everybody. Those two stories don't jibe with each other. There's some contradictory thing going on there, and that's the next part of the whole story that we have to figure out. Why, since the Alpha male could easily win when there's a really strong Alpha male--could easily keep all the other males away from the females, it's only a couple of weeks that she's at all fertile, and he's spent the whole year being boss. Why doesn't he keep the other males away and get all the sexual activity for himself? It's an interesting--it's a surprising thing and it tells you that something is missing from the story.



This is where Jane Goodall comes in; she's responsible for almost everything about chimpanzees and the whole field of primatology. She's a real hero of mine. I'm angry that Yale has never given her an honorary degree even though she lives right here in Connecticut. It's really--that's shameful. What's her story?--Just a little bit of personal interest: she was 23 years old in 1960 and she--in her biography, she always loved watching animals. She would go into the hen house and just sit there and her mother couldn't find her, and then look where the hens are, well that's where Jane is. She's not from a family that was sort of education bound. She had not been to a university; she had no particular career, but she was invited to visit a friend in Africa and--in a lot of England, at that time, Africa is sort of a very romantic kind of place, because every young person wants to go and see Africa.



She took a job as a waitress because she wasn't trained to do anything else, and saved up enough money so she could get this steamboat passage to Kenya. She took a boat to Kenya in 1960. She met up fairly soon with Louis Leakey in the expatriate community, the English community there. Louis Leakey you may have heard of. His family has done all the paleontology, all the digging up of Lucy--I think Lucy's one of theirs, and all of the other skeletons, and sort of rewritten the history of human evolution. The idea being basically there were lots of branches that--our species just didn't grow out of chimpanzees but there were lots and lots of species floating around and all the others went extinct and what survived is us.



Here comes this young woman and she doesn't really have a job and she needs some support, and she loves Africa and she loves animals, and Leakey gets an idea that well, no one has been able to go out and see what chimpanzees do. They knew by that time they were our closest relative. They didn't really understand about Bonobos at that time, and Bonobos didn't live where he was anyway, and so he says to her, "Are you interested at all in going out and trying to observe chimpanzees?" She says, "Yes, yes, yes!" He says, "you know, they don't like humans. They run away, and if they don't run away they'll probably try to attack you. These are big, violent beasties, and you may be in physical danger." She says "Yeah, yeah, yeah I want to do it." He says, "You're an attractive young woman and…what did I say 23 or something? "There aren't going to be any men around. You're going to be living in the jungle basically by yourself. Are you sure you want to do it?" "Yeah, yeah, yeah I want to do it." He says "You know, it's going to take you ten years before you're going to be able to see anything, you have to get them accustomed to you so that you can even observe them, then you'll have to be able to watch them over long periods of time to understand their social behavior, do you really want to do it?"



Yes, she decides to do it. She later on recounts this discussion where he said it would take ten years, and she said if I had done it for only ten years I would not have seen the violence that I did eventually see. In fact, in took 25 years before she saw the events that I'm going to describe to you.



The violent events that I'm going to describe are in chimpanzee communities about once a generation. More or less like humans, if you take the time say in the West between--the Napoleonic War, the 1870 War, a little bit long from the French Franco-Prussian War, to World War I, World War II -- [humans] seem to do it more or less every generation or so, ballpark 25 years, and that's very variable and chimpanzee violence has that same sort of a character to it.



In 1962 she started observing a group of--it was a large group, much larger than is usual, there were 19 adult and adolescent males, and then along with females and the young. The main thing that they were watching was the social behavior. They weren't really interested in the physiology or that kind of stuff at the time; it was really the social behavior. They watched who was doing what with whom, and one of the things they noticed were two individuals that they considered best friends, Goliath and Jomio, and they spent a very long time grooming each other and all friendly interactions. They saw these two individual interacting over six years and it was nothing but friendly.



Gradually this large group--she had started banana feeding the group. in order to be able to see them she would put out bananas and they would come and get it and they would get used to her that way. For a long time other scientists thought she may have distorted the behavior, but it turns out everything she saw has been seen again when there was no banana feeding, so that was not a real issue. She watched this group for many years, six years or so, and then things started to change. Gradually the two groups started separating, there was sort of a northern mountain hill with a ravine and a southern mountain and hill, and one group started spending--one subset of this one big group started spending more time on the northern hill and another group on the southern hill. And the northern group was somewhat larger but not a huge difference. There were eight fully mature males in the northern group and only six in the southern group, along with three females, for instance in the southern group.



First she just--they just watched how much time they spent. They recorded everything and they started seeing the group split a little bit. Then when--but it wasn't absolute, they were still seen in each other's territory, but after a while they never saw males alone in the wrong territory; they started traveling only in groups when they were in the other territory. It was clear that they were beginning--this one group was beginning to fission into two rather separate groups.



One day six northern males, most of the males were observed traveling together in their own northern territory, but they were near the border. They were kind of patrolling what was becoming the border, and they heard calling from the south. They became silent and then moved very quickly directly to where they had heard the calling. What they saw was Godi, a southern male; he was feeding up in a tree and not doing anything in particular. He noticed them coming and he jumped down and ran away, but Humphrey, one of the northern guys, chased after him and tackled him. Then--Humphrey was big--once he had tackled him, he got on top of him, and held down his--sat on his face actually and held his hands, another one came in and held down the feet, so they basically immobilized Godi and then they started attacking him. The others--remember there's six males, two to hold him down, they attacked--ripped off his skin, gashes on the face, on the nose, on the mouth, puncture in the leg, puncture wounds in the ribs, and eventually he was beaten so badly that he was just motionless, plopped out there.



Then the attackers just left. They didn't kill him or anything, they just left, but he was so badly wounded that he died shortly thereafter anyway. Seven weeks later three northern males attacked Dee, another southern male. Dee runs up a tree and starts trying to escape by jumping from branch--from tree to tree, but these are big animals and sometimes they grab a not strong enough branch. He grabs a branch, it cracks, and he's left dangling. So they pulled him down, and the three males that had--doing the attack kept beating him, and he first huddled up and then he lay flat on the ground no longer even trying to escape.



There were females in party, at this point when he was not so much a danger anymore he was pretty motionless, they joined in, and the females then started dragging him. He was faintly squeaking as they dragged him along the ground and in the dragging the skin was torn from him and then they started biting him and flaying off his skin with their teeth, and then after he was sufficiently done they just left. He actually lived for a few months; his spine and his pelvis were protruding from outside the skin. His scrotum had shrunk to one fifth of its normal size. He died.



A whole year passes. Five males attack Goliath. Goliath is the one we talked about already, who by this time is an extremely old male with teeth worn down to the gums, so clearly not a threat to anybody, he was too old to be a threat, and Jomio, who had been his previous grooming partner, and had been watched for six years - they were buddies - and he's part of the attacking party and he attacks Goliath just like any of the others. Goliath was beaten for 20 minutes and he tries to protect his head, but eventually he's too beaten and just gives up and lies still, and in this particular case the adolescent males were along, and they watched this. They stay a safe distance away but they're watching this and they get all very excited, they hoot and holler, and jumping all around--you've probably seen kids--human kids behave that way. Then again, once Goliath was pretty much immobilized they ran in and contributed their degree of violence to this.



Again, same story, they didn't bother to kill him, they just went away, but he died. This continues and one after the other, and three years after the first kill, the northern males caught Sniff who was the last remaining southern male. Satan was one of the attackers, you've heard Satan before, and he grabbed him by the neck and sucked blood from his nose, he had been cut in the nose; he sucked the blood. Two males grabbed one leg each and dragged him down into a ravine and again the same thing, they beat him up, they left him to die, and he did indeed die. So Sniff was the last male in the southern group.



The females were also not spared. Madame B who was a crippled female, and her daughter Little B both were in estrus, so both were sexually ready, sexually available, but it didn't matter; they were attacked. They had a series of attacks on the females over the course of a year, and in the last attack, after she had stopped moving completely, Jomio--it was observed Jomio, the male we've seen, picked her up, slams her down, stomps on her, rolls her over and over along the slope, and then he let her go. When she tried to get up another male comes in and slams her to the ground again and beat her again until she's senseless, and she dies five days after this attack.



Eventually the southern group was totally wiped out. They saw some killing of the juveniles, of the infants, but they couldn't observe that all and the presumption is that the infants that they didn't see actually being killed, they lost their mothers, they couldn't survive so they just died in the jungle somewhere. But no individual from the southern group was ever seen again.



What happens then? Now this northern group, called the Kasakela Group, is dominant. They expand into the southern territory; now they have sort of basically twice the size territory and they sort of luxuriate in that in some sense, and it lasts all of a year. Then they come in contact with the next group to the south which is even stronger than they are. They had nine--that community had nine fully adult--fully mature males. In the next year that's--that next southern group starts attacking what was the northern group and almost destroys them, almost annihilates them. They're pushed out of their newly won territory and even north of their 'pre-war boundary' so they were worse off than they were before their two wars, and in the meantime, they were being pushed north but there was another strong community in the north pushing south, and it looked very bad for this group.



Jane Goodall and her staff by then, which had grown fairly large, was worried they had spent 20 years or 25 years studying these individuals, had all their history, it was the only group that they could really understand who the individuals were, and it really looked like they were just going to be wiped out. As it turned out, they got lucky that just at the time when it looked like her group was going to be wiped out, some of the adolescent males turned fully mature and the balance of power was re-established.



When two groups are more or less equally strong they don't engage in fights. These fights only happen when a group from one community goes and finds a single individual from the other community, and then they go and kill them, or beat them up very badly. The group that's attacking basically does not take any risks, and in the course of these three years, the northern group lost nobody and the southern group was totally wiped out. They only engage in this violence when they're sure to win.



You can read about human primitive warfare as it has very much this similar character. As soon as this group got strong enough by the luck of adolescent males becoming fully adult, what they then--the two groups would meet at the boundary, they'd scream and yell at each other and bang their chest and all this kind of stuff and--but then they'd back off and retreat into their territory, so Goodall's group was saved.



Now the question comes up, as I mentioned, does this have anything to do with the banana feeding? Did somehow Jane Goodall's treatment of these animal groups--they saw a big group in the beginning, maybe that wasn't a natural group, maybe it was two different groups that came into--that sort of joined for the purpose of getting bananas and then they reverted to their prior hostility--separateness and hostility. There's no way to really know that, and there are a whole lot of other hypothesis why this couldn't be the case, that everybody knew.



Jane Goodall had herself, before she saw this war, published a lovely book saying how peaceful chimps were, and there was all this popular literature about how humans were rogue species. We're the only ones that kill each other; we're the only ones that go to war, and we're really bad and it's modern civilization or capitalism, or imperialism, or all these cultural things that have made humans such a bad species because chimps, who are our nearest relatives, were just so wonderful. People were thinking of all kinds of reasons why what they saw was not true.



Meanwhile the Japanese, who were very, very strong in this field, and again females are really almost dominant in this field; they have the patience to go there and watch for such a long time, but there's this--even in--both in America and Japan, and England, the female researchers are some of the very best. They again, they observed a group--the Japanese were in a different part of Africa. For ten years nothing but peace, then during the second decade, so years ten to 20, all six adult males of the smaller community--they also had several communities--containing 22 members, vanished one by one. Apparently due to the aggression by males of the other two much larger neighboring communities which were dominant because of their size, size in the case meaning number of adult males.



Now in this case they didn't kill the females, but one after another the females of the annihilated community transferred with their offspring to the victorious M group and the M group also got control of K group's territory. Now the exception to this transfer of the females with the young is that the adolescent males were not allowed to--did not transfer and probably were not allowed to transfer, and they just basically stayed in the old territory and wasted away and died without their social community. All the adult males were dead, and the females had transferred to other troops and they apparently weren't allowed in.



Now is this--just sort of random violence, I mean it takes three years and there are a fair number of attacks, but it wasn't like every week they had another battle, so it was sporadic. Is this just sort of casual violence or was there some kind of planning in this? Let me cut to the chase here, so usually chimps--there are many examples of this but we only have time for one. Usually the chimpanzees, when they sleep at night, the males will get together and not like one tree and they next--they make nests up in the trees, but within a reasonable distance so they can call to each other, and they call to each other before they go to sleep, to know, 'where have you built a nest; where are we all.' They're usually fairly noisy about that.



One night, Mariko Hasegawa, a Japanese woman scientist, was observing them and she noticed and quite startlingly, there was no pant hooting. They weren't making any noise, and she had never experienced that before. She was surprised, and the next morning the troop got up and started attacking a neighboring troop. They singled out a mother and her infant and attacked and killed them. Why were they silent the previous night, which she had never seen before? It looks like not only each individual was planning but it was a group thing. No one in the group was making any noise, so this had somehow been decided as a group effort the night before.



When they're going to attack, several males together will leave the core of their range and travel clearly purposely toward the periphery rather than just wandering around, and I'll tell you a little bit about the wandering. It really has all the aspects of being planned ahead and purposive and this is really something that they planned to do.



The purpose of this violence is not at all clear. There's contending schools about this. The most obvious one is they get more territory and therefore they get more trees, more food. They live largely on fruit and largely figs, there's a lot of figs trees in all jungles, and so they just wander around and find a fruit tree and then depending on how much fruit there is they either go up and eat themselves or they can call over someone else and say, 'Hey I found a good fruit tree.' Most of the time the chimps have no problem finding food. Jane Goodall had one of her workers follow an adult male for 50 days--never out of sight, and one of the things they noticed, did he ever go looking for food? In this 50 days, never did he try to hunt food. He would just sort of wander through the jungle, and every so often his foot would step on a rotting fruit and squish, and he would notice it and look up and there's a tree full of fruit, and climb up and eat and maybe call over some others.



She was definitely of the impression that food is not a limiting factor for that. Later, Ann Pusey, another scientist, came to the opposite conclusion, that she noticed there's some sort of dominance hierarchy among females. Those females would have more fruity trees and where they ranged, do better reproductively, and Richard Wrangham, who you'll read some of his stuff, he's a food man so there's a whole group--I'm not wildly convinced by the evidence but I'm not in the field. There's a big thought that food limitation is important.



For instance, the difference between Bonobos and chimps has been ascribed to food density and the size of the parties, and so forth. One the problems with the food idea is that they have fairly large territories, and the young, healthy adults can basically always find food. They never seem to starve to death. It's the older individuals who are quite sick and not so motile that seem to have trouble finding food, and they can get in trouble in the dry season when there's a lot less fruit. They're probably too weak to--even when they have Territory A, they're too weak to even--they just can barely search Territory A, and if you give them twice as big a territory, it may not do them any good because they just don't have the energy to go search it. I think the field is moving toward the idea that food is the important thing. The evidence that I've seen doesn't convince me yet, but again, I'm not an expert in this whatsoever.



The other purpose of course is to acquire females. I've been going on and on about how rare an egg is, and so you'd think that's the obvious reason, but then you watch them go and they kill the females, even the females in estrus, so that doesn't make a lot of sense. Although in the Japanese group, sometimes the females do transfer. The story there is quite interesting, because as you know, small groups of individuals, if they interbreed, if the group was sealed, if the males are sealed and they stay together in this one community like forever, generation after generation--if the females also stayed there, it would be an inbreeding group. Inbreeding gives big genetic problems, so all species have to have some mechanism of gene flow, and they have to get genes in from the outside and/or send their genes out.



It turns out that in chimpanzees the females have access to other troops and they go out and have intercourse when they're away. Exactly how this is done because the males watch them when they come into estrus--they must disappear before coming into estrus and have it out there. It's not really known, but now they can do the genetics and again something like half of the babies are born with fathers that are not from the troop where they are resident, and very often the adolescent females will just transfer troops altogether.



It's very interesting, when a female tries to transfer, go into another group, if she's never had a young she's almost always accepted. If she's had a young, if she's not--if she's already really in this group because she's had a young--very often attacked or even killed, or kicked out, so there's something for some reason that's not understood at all. A virgin female basically is much more acceptable for transfer then an older female and that's not really understood.



That means since the females are going to move around anyway, and biologically and socially it has to be that way, it doesn't make a lot of sense that they're doing this for--to get extra females. There's a lot of unknowns here. Let me summarize this by--the summary of the chimpanzee social system. The--come back to the question, why do the males--why does the Alpha male not dominate totally to sexuality? The reason is that these groups fight each other. A lot of--we don't really know the reason why they fight but they fight each other and the winner is always the group--so far--always the group that has the most adult males and the group that is the attacking group basically takes no casualties whatsoever, so having a lot of adult males is very important.



If an Alpha male got so aggressive that he kicked out all the other males, he wouldn't last long. The other communities would come in and annihilate him. Because of this fighting between the communities, the males have to stay together, and once the males have to stay together that means they're going to compete for females. If the competition was such that only the Alpha reproduced, then evolution would push all the other males into some other strategy, as we've seen the big and the small orangutans, and you're going to read about a whole variety of sexual strategies. You think there's heterosexual and homosexual. No, there's lots of different versions which you will read about. Evolution would push the other males to fight all the time -- if they were not reproducing they would then be pushed by evolution to either fight all the time with the Alpha male or go away and try to start their own troop, or do something. That it's not a stable situation when only one individual can reproduce and everyone else can't. The males have to compete with each other, all the males have to have some chance of fathering children. This also has many subsidiary advantages, so every male thinks he could be the father of any of the young in the troop, so they're all very protective. Once it was seen that a mother was coming back into estrus and becoming sexually interested, the Alpha male who was with her was about to start copulating with her. Her young, who did not want to--evolutionarily generally doesn't want a brother, because he wants all the resources and attention of the mother, he gets in between them, and starts fighting, and in fact he bites the scrotum of the Alpha male, this little tyke. It really clearly is sub--not even adolescent yet.



What does the Alpha male do? He stops, looks at him, bends down, very gently picks him up, takes him over h

Course Index

Course Description


This survey course introduces students to the important and basic material on human fertility, population growth, the demographic transition and population policy. Topics include: the human and environmental dimensions of population pressure, demographic history, economic and cultural causes of demographic change, environmental carrying capacity and sustainability. Political, religious and ethical issues surrounding fertility are also addressed. The lectures and readings attempt to balance theoretical and demographic scale analyzes with studies of individual humans and communities. The perspective is global with both developed and developing countries included.



Course Structure:

This Yale College course, taught on campus twice per week for 75 minutes, was recorded for Open Yale Courses in Spring 2009.

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