TedTest

From the Ted Talk by David Puts: To find your perfect mate, think like an evolutionist

Unscramble the Blue Letters

Hi there. I could be wrong, but I think this talk may have the dctontsiiin of being the one talk in this series that ends with oagsrm. (Laughter) But let's not get ahead of ourselves. (leutahgr) Have you ever thought about the fact that you're here, alive on this penlat because every one of your ancestors rceuedorpd? Every one, in an uenobrkn chain, all the way back to the first life on this planet, over three and a half billion years ago. That's a lot of reproducing. And for the past billion yraes, your ancestors reproduced sexually. So sex is a pretty big deal. But you probably knew that. But let's talk about haumn mating. Why does human mating take the fomrs that it does? Why are we attracted to certain people? Why do we sometimes form long-term romantic relationships? Why do we sometimes cheat? Now I don't mean why consciously do we do these things. I don't mean what happens in the brian to cause it. I mean, why did we evolve these feelings and these behaviors? In other words, how did the uinerdylng brain sretrtuucs and brain chemistry contribute to our ancestors' reproductive success so that those traits got passed on into the present generation while others didn't. Answering evolutionary qeiosntus like this is like being a crime scene investigator, we're left with the evidence, and we have to try to establish what happened. So let's go back six or seven moliiln years ago to our early ancestors. This is right after the split between our lienage and the lineage that would eventually give rise to chimpanzees. Now these were small brained apes, they waelkd on two legs, and males probably fought each other for mating opportunities. We know this because males fight for mates in all of our closest living relatives, chimpanzees, orangutans, gorillas. And because males are larger than females when they fight for mates. And the fossil record indicates that our male atncrsoes were larger than females. So males tend to be larger, more mlsacuur, stronger, more physically aggressive, when they fight for mates. Our species has all the hallmarks of a species that's experienced an evolutionary history of male figtnhig for mates. For example, men have, on average, 60 prnceet more muscle mass, and 75 percent more ueppr body muscle mass, and those differences in musculature tlsnraate into large sex differences in strength. The average man is segrnotr than 99.9% of women. These are data on hand strength, which is a good predictor of overall upper body strength, on over 600 men and women. And as you can see, there's a large sex difference. And in fact, not one of almost 400 women had as strong of a hand strength as the average man. So, men can open jars. (Laughter) And move furniture or at least two things that we're good for. Who cares, right? The answer is that men care. Men, especially young men, seem really concerned about figuring out who's the toughest or strongest, or the most physically floabrmide, and sometimes they devise elaborate ways for determining this. From early development, boys and men are more physically agsseigvre than girls and women all over the wolrd, and this aggression sometimes rusetls in violence. Men have a virtual monopoly on same-sex homicides. In other wodrs, men are vastly more likely to kill each other than women are to kill each other. These are data from every society from every time period in history for which data were available when the authors compiled them, on proportion of same-sex homicides that are male killing male. And as you can see, the percentage is always close to 100%. On average, 95% of same-sex homicides are committed by males, and itapmlnotry, these don't include war killings, which would bring the percentages even closer to 100%. And from what evidence that we have, a dominance among men translates into mating and reproductive opportunities. So we're a species that's experienced an evolutionary history in which our male ancestors won mating opportunities through the use or threat of force. In that regard, our apple has not fallen far from the evolutionary tree. But in other ways, human mating and reproduction are profoundly different from what we see in our close relatives, and they've changed a lot since our early ancestors. For example, males in canpizhmees, orangutans and gorillas, spend time and effort competing for mates, but don't spend much time with individual females and don't provide resources. They don't provide food for their offspring. So that's a big change. Although most human sceiiteos allow polygamous marriage, that is one man married to more than one woman, even within polygamous societies, most marriages are monogamous. And in the average hunter-gatherer society, almost 80% of meairrd women are monogamous, so that's different. And, importantly, men pivorde resources for their mates and offspring. So how did we get there? Well, in species where males fghit each other for mates, dominant males indicated by the larger, dekrar male symbols here, tend to have more mating opportunities, and hence more offspring. And subordinate males tend to have fewer mating opneirtptoius and are more likely to fail to reproduce. So this sets up an interesting situation, because for subordinate males, it would be advantageous to aetpmtt monogamy rather than winning lots of mating opportunities. One mate is better than none. The poblrem is that in general, subordinate males cannot defend females from dominant males, and besides, females tend to perfer mating with dominant males for the genetic benefits, poiundcrg stronger, hieeltahr offspring. So what changed all of this was probably several tnorniiatss hnpniepag together around the same time. By about two and a half million years ago, we had started to ipractorone more meat into our diet. We know this from various lines of evidence, including - this is cool - stnoe tool cut makrs on animal bones dated to 2.5 million years ago. That's cool. I love this stuff! And then by about 2 million years ago, brain size really started to increase, and with that came a lgenhtnenig of the juvenile period, so now kids became both really coslty and costly for a long period of time. And this made male provisioning both possible and necessary. Possible because it's much eaesir to bring back calories, protein, fats, in the form of meat than trying to do that by transporting plant foods, and necessary because kids became so energetically costly that iiuiddnavl females would have had trouble providing resources for themselves and their offspring. And when we look at medron hunter-gatherer societies, that's what we see. These are aggregate data across several hunter-gatherer societies on net daily calories. Are you bringing in more calories than you consume, through foraging, or are you consuming more than you bring in? And the green bars are net daily caloric surplus, in other words, bringing in more than you consume. And the red bars are a deficit, so you're cnsouimng more than you bring in. And you'll notice that men from about 20 years of age to 60 years of age are operating at a daily caloric surplus. They bring in, generally through hunting, more calories than they can consume, and these calories are distributed. If it's lgrae game, it's gelrnealy distributed equally to everybody in the village or camp. Smaller iemts can be brought back to individual family, but this contrasts with what's going on with women, in their reproductive years, they're operating at a dliay ciroalc deficit. gitoetasn, lactation, carrying babies, are eletmrexy costly energetically and limit one's ability to forage efficiently. So male pnoiioirnsvg, both possible through hunting, and necessary. And this change had profound iatmpcs on human miantg and reproduction. In a sense, it tepipd the balance for fealmes. So now it was sometimes worth mating with a subordinate male, even if he may not possess the best genes, if he provided resources. And this is baboon pornography. (Laughter) I probably should have warned you there'd be monkey porn. This is from PlayBaboon Magazine. arglhit, I'm going to stop with the jokes. This is a female baboon in estrus, so her genitals are seowlln, and this happens in a lot of primate species. Females' appearance changes over the cycle, and becomes more attractive and this initces male competition for females during the fertile part of the cycle, with dnaimnot males tending to monopolize copulations, clsoer to ovulation. Well. We don't look like this. And you knew that. But what you might not know is that women's attractiveness does chagne over the cycle. My lab, and others, have swohn that women's faces, voices, even odors, are more attractive to men during the fertile part of the cycle. But these changes are extremely slbtue. And compared to other primates, the evidence indicates that we've evolved to suppress cues to ovtulaoin. That in a sense, ovulation is concealed in humans. But think about what impact this would have. This would mean that dominant males would not be able to monopolize coatnplouis near ovulation. It would protect the pair bond from invasion by a dominant male. So that a male in a pair would have more confidence that he was the father of the offspring. The couple is having sex throughout the cycle. And this is unique to human mating, we don't see it in many other primates. We have sex throughout the cycle. And so this would essentially increase a male's confidence in ptnertiay, because a dominant or some other male wouldn't be able to target the female and bully their way in at the fertile point in the cylce. And this would have ianmtrpot implications for parental investment, in particular, males providing resources for their offspring. Because across speecis, when maels provide resources for offspring, they target those resources toward their own biological offspring, and they avoid investing in the offspring of unrelated males. And so the evolution of male care for offspring and investing in rsecueors and offspring, pair bonding, and concealed ovulation, went very much hand-in-hand over our eotvuloin. We have also evolved a specialized psychology for foirmng long-term ritamnoc rhnitpiolseas with the pistiobsliy of investing in opfsnfrig together. We fall in love. All around the world, people prefer mates who are kind and generous and capable and willing to care for mates and offspring. In one of the largest cross-cultural sedtuis of human mate preferences ever conducted, covering 33 countries shown in red here, the single most important mate choice criterion to both men and wmoen, was mutual love and attraction. But as you also know, people are not always perfectly faithful to their mates. And in particular, women sometimes face a tradeoff between good genes and investment. Women sometimes find themselves in relationships with men who may be cnriag providers, but may not possess the best quality genes for offspring making them strong and healthy. And several features of women's mating psychology seem to have evolevd, in part, to resolve this trade off. And I mean, reictnruig genes, if you will, from outside of the long-term relationship. For example, women have more seaxul faanistes about men other than their long-term partner, during the fertile part of the cycle, and that's particularly true if the long-term partner has physical signs of being lower in genetic quality, like he's less physically artticavte. I think that's interesting. (Laughter) That's why I'm talking about it, I hope you do too. And women's mate pecefrneres similarly change over the cycle so that they prefer more dominant, more masculine males during the flritee part of the cycle. These are results of a study that I conducted on women's preferences for men's veicos. And I used ctepmuor sfwatroe to manipulate recordings of men's voices to make them sound either more masculine or more dominant, or more subordinate, more feminine. And I had women rate them on how attractive would this man be for a short-term, purely sexual relationship, and for a long-term committed relationship? And I also got information about where women were in their cycles. Were they in the fertile or non-fertile part of the cycle? These were all women not taking hormonal contraception. And what I found was that women preferred a more masculine, dominant-sounding voice, siflaplceciy in the fertile point of the cycle, and only for a sexual relationship versus a long-term cmttmeiod relationship. Now, this sounds like science fiction, but it's science, fact. Because this result has been shown lots of times across a variety of domains from women's preferences for men's voices, that this result was replicated by another lab. Women's preferences for men's faces, bodies, odors, and even behavior. Well, I said that we would get to orgasm. (Laughter) And we're there. I just want to strat by saying I'm for it. (Laughter) I'm pro-orgasm. I think more people should have more orgasms. But from a snfiitceic perspective, women's orgasm is especially fascinating because there's eevndcie indicating that it increases the probability that conception will result from an act of sex. There's evidence that it brings sperm up through the female reproductive tract and toward the egg. And think about what the ioitncplmias here could be. If women were more likely to have orgasms with some men than others, then this could be a mechanism by which they choose, not cuosonsicly, to be fertilized by some males and not others. And wouldn't you picdert that women would be more likely to have orgasms with males of high genetic quality? And in fact, a study by my lab published just a couple of years ago found that women reported more orgasms, earlier teimd orgasms, that is, they were easier to achieve, they aecehivd them more quickly, when they were having sex when their mate was more masculine and more dominant, and what's interesting is that this was true only for their orgasms from sexual intercourse, but not from other partnered sexual behaviors. I'll let you use your imagination what those might be. So we've seen that thinking like an eiolnuistovt can enable us to predict things about ourselves that we did not already know, and would not likely have guessed for a long time. We didn't know that women's mate preferences changed over the cycle. Until evolutionary thinking led us to that discovery. So that's one point that I want to make. But we've also seen how evolutionary thinking can clarify and unite dseivre parts of the human experience, and help us understand the best and the worst of ourselves, from violence and aggression and infidelity to men's care for their children, sexual attraction, sexual pleasure, and even the strength and fragility of romantic love. Thank you. (Applause)

Open Cloze

Hi there. I could be wrong, but I think this talk may have the ___________ of being the one talk in this series that ends with ______. (Laughter) But let's not get ahead of ourselves. (________) Have you ever thought about the fact that you're here, alive on this ______ because every one of your ancestors __________? Every one, in an ________ chain, all the way back to the first life on this planet, over three and a half billion years ago. That's a lot of reproducing. And for the past billion _____, your ancestors reproduced sexually. So sex is a pretty big deal. But you probably knew that. But let's talk about _____ mating. Why does human mating take the _____ that it does? Why are we attracted to certain people? Why do we sometimes form long-term romantic relationships? Why do we sometimes cheat? Now I don't mean why consciously do we do these things. I don't mean what happens in the _____ to cause it. I mean, why did we evolve these feelings and these behaviors? In other words, how did the __________ brain __________ and brain chemistry contribute to our ancestors' reproductive success so that those traits got passed on into the present generation while others didn't. Answering evolutionary _________ like this is like being a crime scene investigator, we're left with the evidence, and we have to try to establish what happened. So let's go back six or seven _______ years ago to our early ancestors. This is right after the split between our _______ and the lineage that would eventually give rise to chimpanzees. Now these were small brained apes, they ______ on two legs, and males probably fought each other for mating opportunities. We know this because males fight for mates in all of our closest living relatives, chimpanzees, orangutans, gorillas. And because males are larger than females when they fight for mates. And the fossil record indicates that our male _________ were larger than females. So males tend to be larger, more ________, stronger, more physically aggressive, when they fight for mates. Our species has all the hallmarks of a species that's experienced an evolutionary history of male ________ for mates. For example, men have, on average, 60 _______ more muscle mass, and 75 percent more _____ body muscle mass, and those differences in musculature _________ into large sex differences in strength. The average man is ________ than 99.9% of women. These are data on hand strength, which is a good predictor of overall upper body strength, on over 600 men and women. And as you can see, there's a large sex difference. And in fact, not one of almost 400 women had as strong of a hand strength as the average man. So, men can open jars. (Laughter) And move furniture or at least two things that we're good for. Who cares, right? The answer is that men care. Men, especially young men, seem really concerned about figuring out who's the toughest or strongest, or the most physically __________, and sometimes they devise elaborate ways for determining this. From early development, boys and men are more physically __________ than girls and women all over the _____, and this aggression sometimes _______ in violence. Men have a virtual monopoly on same-sex homicides. In other _____, men are vastly more likely to kill each other than women are to kill each other. These are data from every society from every time period in history for which data were available when the authors compiled them, on proportion of same-sex homicides that are male killing male. And as you can see, the percentage is always close to 100%. On average, 95% of same-sex homicides are committed by males, and ___________, these don't include war killings, which would bring the percentages even closer to 100%. And from what evidence that we have, a dominance among men translates into mating and reproductive opportunities. So we're a species that's experienced an evolutionary history in which our male ancestors won mating opportunities through the use or threat of force. In that regard, our apple has not fallen far from the evolutionary tree. But in other ways, human mating and reproduction are profoundly different from what we see in our close relatives, and they've changed a lot since our early ancestors. For example, males in ___________, orangutans and gorillas, spend time and effort competing for mates, but don't spend much time with individual females and don't provide resources. They don't provide food for their offspring. So that's a big change. Although most human _________ allow polygamous marriage, that is one man married to more than one woman, even within polygamous societies, most marriages are monogamous. And in the average hunter-gatherer society, almost 80% of _______ women are monogamous, so that's different. And, importantly, men _______ resources for their mates and offspring. So how did we get there? Well, in species where males _____ each other for mates, dominant males indicated by the larger, ______ male symbols here, tend to have more mating opportunities, and hence more offspring. And subordinate males tend to have fewer mating _____________ and are more likely to fail to reproduce. So this sets up an interesting situation, because for subordinate males, it would be advantageous to _______ monogamy rather than winning lots of mating opportunities. One mate is better than none. The _______ is that in general, subordinate males cannot defend females from dominant males, and besides, females tend to ______ mating with dominant males for the genetic benefits, _________ stronger, _________ offspring. So what changed all of this was probably several ___________ _________ together around the same time. By about two and a half million years ago, we had started to ___________ more meat into our diet. We know this from various lines of evidence, including - this is cool - _____ tool cut _____ on animal bones dated to 2.5 million years ago. That's cool. I love this stuff! And then by about 2 million years ago, brain size really started to increase, and with that came a ___________ of the juvenile period, so now kids became both really ______ and costly for a long period of time. And this made male provisioning both possible and necessary. Possible because it's much ______ to bring back calories, protein, fats, in the form of meat than trying to do that by transporting plant foods, and necessary because kids became so energetically costly that __________ females would have had trouble providing resources for themselves and their offspring. And when we look at ______ hunter-gatherer societies, that's what we see. These are aggregate data across several hunter-gatherer societies on net daily calories. Are you bringing in more calories than you consume, through foraging, or are you consuming more than you bring in? And the green bars are net daily caloric surplus, in other words, bringing in more than you consume. And the red bars are a deficit, so you're _________ more than you bring in. And you'll notice that men from about 20 years of age to 60 years of age are operating at a daily caloric surplus. They bring in, generally through hunting, more calories than they can consume, and these calories are distributed. If it's _____ game, it's _________ distributed equally to everybody in the village or camp. Smaller _____ can be brought back to individual family, but this contrasts with what's going on with women, in their reproductive years, they're operating at a _____ _______ deficit. _________, lactation, carrying babies, are _________ costly energetically and limit one's ability to forage efficiently. So male ____________, both possible through hunting, and necessary. And this change had profound _______ on human ______ and reproduction. In a sense, it ______ the balance for _______. So now it was sometimes worth mating with a subordinate male, even if he may not possess the best genes, if he provided resources. And this is baboon pornography. (Laughter) I probably should have warned you there'd be monkey porn. This is from PlayBaboon Magazine. _______, I'm going to stop with the jokes. This is a female baboon in estrus, so her genitals are _______, and this happens in a lot of primate species. Females' appearance changes over the cycle, and becomes more attractive and this _______ male competition for females during the fertile part of the cycle, with ________ males tending to monopolize copulations, ______ to ovulation. Well. We don't look like this. And you knew that. But what you might not know is that women's attractiveness does ______ over the cycle. My lab, and others, have _____ that women's faces, voices, even odors, are more attractive to men during the fertile part of the cycle. But these changes are extremely ______. And compared to other primates, the evidence indicates that we've evolved to suppress cues to _________. That in a sense, ovulation is concealed in humans. But think about what impact this would have. This would mean that dominant males would not be able to monopolize ___________ near ovulation. It would protect the pair bond from invasion by a dominant male. So that a male in a pair would have more confidence that he was the father of the offspring. The couple is having sex throughout the cycle. And this is unique to human mating, we don't see it in many other primates. We have sex throughout the cycle. And so this would essentially increase a male's confidence in _________, because a dominant or some other male wouldn't be able to target the female and bully their way in at the fertile point in the _____. And this would have _________ implications for parental investment, in particular, males providing resources for their offspring. Because across _______, when _____ provide resources for offspring, they target those resources toward their own biological offspring, and they avoid investing in the offspring of unrelated males. And so the evolution of male care for offspring and investing in _________ and offspring, pair bonding, and concealed ovulation, went very much hand-in-hand over our _________. We have also evolved a specialized psychology for _______ long-term ________ _____________ with the ___________ of investing in _________ together. We fall in love. All around the world, people prefer mates who are kind and generous and capable and willing to care for mates and offspring. In one of the largest cross-cultural _______ of human mate preferences ever conducted, covering 33 countries shown in red here, the single most important mate choice criterion to both men and _____, was mutual love and attraction. But as you also know, people are not always perfectly faithful to their mates. And in particular, women sometimes face a tradeoff between good genes and investment. Women sometimes find themselves in relationships with men who may be ______ providers, but may not possess the best quality genes for offspring making them strong and healthy. And several features of women's mating psychology seem to have _______, in part, to resolve this trade off. And I mean, __________ genes, if you will, from outside of the long-term relationship. For example, women have more ______ _________ about men other than their long-term partner, during the fertile part of the cycle, and that's particularly true if the long-term partner has physical signs of being lower in genetic quality, like he's less physically __________. I think that's interesting. (Laughter) That's why I'm talking about it, I hope you do too. And women's mate ___________ similarly change over the cycle so that they prefer more dominant, more masculine males during the _______ part of the cycle. These are results of a study that I conducted on women's preferences for men's ______. And I used ________ ________ to manipulate recordings of men's voices to make them sound either more masculine or more dominant, or more subordinate, more feminine. And I had women rate them on how attractive would this man be for a short-term, purely sexual relationship, and for a long-term committed relationship? And I also got information about where women were in their cycles. Were they in the fertile or non-fertile part of the cycle? These were all women not taking hormonal contraception. And what I found was that women preferred a more masculine, dominant-sounding voice, ____________ in the fertile point of the cycle, and only for a sexual relationship versus a long-term _________ relationship. Now, this sounds like science fiction, but it's science, fact. Because this result has been shown lots of times across a variety of domains from women's preferences for men's voices, that this result was replicated by another lab. Women's preferences for men's faces, bodies, odors, and even behavior. Well, I said that we would get to orgasm. (Laughter) And we're there. I just want to _____ by saying I'm for it. (Laughter) I'm pro-orgasm. I think more people should have more orgasms. But from a __________ perspective, women's orgasm is especially fascinating because there's ________ indicating that it increases the probability that conception will result from an act of sex. There's evidence that it brings sperm up through the female reproductive tract and toward the egg. And think about what the ____________ here could be. If women were more likely to have orgasms with some men than others, then this could be a mechanism by which they choose, not ___________, to be fertilized by some males and not others. And wouldn't you _______ that women would be more likely to have orgasms with males of high genetic quality? And in fact, a study by my lab published just a couple of years ago found that women reported more orgasms, earlier _____ orgasms, that is, they were easier to achieve, they ________ them more quickly, when they were having sex when their mate was more masculine and more dominant, and what's interesting is that this was true only for their orgasms from sexual intercourse, but not from other partnered sexual behaviors. I'll let you use your imagination what those might be. So we've seen that thinking like an ____________ can enable us to predict things about ourselves that we did not already know, and would not likely have guessed for a long time. We didn't know that women's mate preferences changed over the cycle. Until evolutionary thinking led us to that discovery. So that's one point that I want to make. But we've also seen how evolutionary thinking can clarify and unite _______ parts of the human experience, and help us understand the best and the worst of ourselves, from violence and aggression and infidelity to men's care for their children, sexual attraction, sexual pleasure, and even the strength and fragility of romantic love. Thank you. (Applause)

Solution

attempt
laughter
consciously
formidable
brain
forms
human
lineage
modern
timed
start
healthier
ovulation
paternity
darker
women
evolution
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large
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lengthening
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scientific
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muscular
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specifically
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percent
words
questions
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tipped
swollen
romantic
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Original Text

Hi there. I could be wrong, but I think this talk may have the distinction of being the one talk in this series that ends with orgasm. (Laughter) But let's not get ahead of ourselves. (Laughter) Have you ever thought about the fact that you're here, alive on this planet because every one of your ancestors reproduced? Every one, in an unbroken chain, all the way back to the first life on this planet, over three and a half billion years ago. That's a lot of reproducing. And for the past billion years, your ancestors reproduced sexually. So sex is a pretty big deal. But you probably knew that. But let's talk about human mating. Why does human mating take the forms that it does? Why are we attracted to certain people? Why do we sometimes form long-term romantic relationships? Why do we sometimes cheat? Now I don't mean why consciously do we do these things. I don't mean what happens in the brain to cause it. I mean, why did we evolve these feelings and these behaviors? In other words, how did the underlying brain structures and brain chemistry contribute to our ancestors' reproductive success so that those traits got passed on into the present generation while others didn't. Answering evolutionary questions like this is like being a crime scene investigator, we're left with the evidence, and we have to try to establish what happened. So let's go back six or seven million years ago to our early ancestors. This is right after the split between our lineage and the lineage that would eventually give rise to chimpanzees. Now these were small brained apes, they walked on two legs, and males probably fought each other for mating opportunities. We know this because males fight for mates in all of our closest living relatives, chimpanzees, orangutans, gorillas. And because males are larger than females when they fight for mates. And the fossil record indicates that our male ancestors were larger than females. So males tend to be larger, more muscular, stronger, more physically aggressive, when they fight for mates. Our species has all the hallmarks of a species that's experienced an evolutionary history of male fighting for mates. For example, men have, on average, 60 percent more muscle mass, and 75 percent more upper body muscle mass, and those differences in musculature translate into large sex differences in strength. The average man is stronger than 99.9% of women. These are data on hand strength, which is a good predictor of overall upper body strength, on over 600 men and women. And as you can see, there's a large sex difference. And in fact, not one of almost 400 women had as strong of a hand strength as the average man. So, men can open jars. (Laughter) And move furniture or at least two things that we're good for. Who cares, right? The answer is that men care. Men, especially young men, seem really concerned about figuring out who's the toughest or strongest, or the most physically formidable, and sometimes they devise elaborate ways for determining this. From early development, boys and men are more physically aggressive than girls and women all over the world, and this aggression sometimes results in violence. Men have a virtual monopoly on same-sex homicides. In other words, men are vastly more likely to kill each other than women are to kill each other. These are data from every society from every time period in history for which data were available when the authors compiled them, on proportion of same-sex homicides that are male killing male. And as you can see, the percentage is always close to 100%. On average, 95% of same-sex homicides are committed by males, and importantly, these don't include war killings, which would bring the percentages even closer to 100%. And from what evidence that we have, a dominance among men translates into mating and reproductive opportunities. So we're a species that's experienced an evolutionary history in which our male ancestors won mating opportunities through the use or threat of force. In that regard, our apple has not fallen far from the evolutionary tree. But in other ways, human mating and reproduction are profoundly different from what we see in our close relatives, and they've changed a lot since our early ancestors. For example, males in chimpanzees, orangutans and gorillas, spend time and effort competing for mates, but don't spend much time with individual females and don't provide resources. They don't provide food for their offspring. So that's a big change. Although most human societies allow polygamous marriage, that is one man married to more than one woman, even within polygamous societies, most marriages are monogamous. And in the average hunter-gatherer society, almost 80% of married women are monogamous, so that's different. And, importantly, men provide resources for their mates and offspring. So how did we get there? Well, in species where males fight each other for mates, dominant males indicated by the larger, darker male symbols here, tend to have more mating opportunities, and hence more offspring. And subordinate males tend to have fewer mating opportunities and are more likely to fail to reproduce. So this sets up an interesting situation, because for subordinate males, it would be advantageous to attempt monogamy rather than winning lots of mating opportunities. One mate is better than none. The problem is that in general, subordinate males cannot defend females from dominant males, and besides, females tend to prefer mating with dominant males for the genetic benefits, producing stronger, healthier offspring. So what changed all of this was probably several transitions happening together around the same time. By about two and a half million years ago, we had started to incorporate more meat into our diet. We know this from various lines of evidence, including - this is cool - stone tool cut marks on animal bones dated to 2.5 million years ago. That's cool. I love this stuff! And then by about 2 million years ago, brain size really started to increase, and with that came a lengthening of the juvenile period, so now kids became both really costly and costly for a long period of time. And this made male provisioning both possible and necessary. Possible because it's much easier to bring back calories, protein, fats, in the form of meat than trying to do that by transporting plant foods, and necessary because kids became so energetically costly that individual females would have had trouble providing resources for themselves and their offspring. And when we look at modern hunter-gatherer societies, that's what we see. These are aggregate data across several hunter-gatherer societies on net daily calories. Are you bringing in more calories than you consume, through foraging, or are you consuming more than you bring in? And the green bars are net daily caloric surplus, in other words, bringing in more than you consume. And the red bars are a deficit, so you're consuming more than you bring in. And you'll notice that men from about 20 years of age to 60 years of age are operating at a daily caloric surplus. They bring in, generally through hunting, more calories than they can consume, and these calories are distributed. If it's large game, it's generally distributed equally to everybody in the village or camp. Smaller items can be brought back to individual family, but this contrasts with what's going on with women, in their reproductive years, they're operating at a daily caloric deficit. Gestation, lactation, carrying babies, are extremely costly energetically and limit one's ability to forage efficiently. So male provisioning, both possible through hunting, and necessary. And this change had profound impacts on human mating and reproduction. In a sense, it tipped the balance for females. So now it was sometimes worth mating with a subordinate male, even if he may not possess the best genes, if he provided resources. And this is baboon pornography. (Laughter) I probably should have warned you there'd be monkey porn. This is from PlayBaboon Magazine. Alright, I'm going to stop with the jokes. This is a female baboon in estrus, so her genitals are swollen, and this happens in a lot of primate species. Females' appearance changes over the cycle, and becomes more attractive and this incites male competition for females during the fertile part of the cycle, with dominant males tending to monopolize copulations, closer to ovulation. Well. We don't look like this. And you knew that. But what you might not know is that women's attractiveness does change over the cycle. My lab, and others, have shown that women's faces, voices, even odors, are more attractive to men during the fertile part of the cycle. But these changes are extremely subtle. And compared to other primates, the evidence indicates that we've evolved to suppress cues to ovulation. That in a sense, ovulation is concealed in humans. But think about what impact this would have. This would mean that dominant males would not be able to monopolize copulations near ovulation. It would protect the pair bond from invasion by a dominant male. So that a male in a pair would have more confidence that he was the father of the offspring. The couple is having sex throughout the cycle. And this is unique to human mating, we don't see it in many other primates. We have sex throughout the cycle. And so this would essentially increase a male's confidence in paternity, because a dominant or some other male wouldn't be able to target the female and bully their way in at the fertile point in the cycle. And this would have important implications for parental investment, in particular, males providing resources for their offspring. Because across species, when males provide resources for offspring, they target those resources toward their own biological offspring, and they avoid investing in the offspring of unrelated males. And so the evolution of male care for offspring and investing in resources and offspring, pair bonding, and concealed ovulation, went very much hand-in-hand over our evolution. We have also evolved a specialized psychology for forming long-term romantic relationships with the possibility of investing in offspring together. We fall in love. All around the world, people prefer mates who are kind and generous and capable and willing to care for mates and offspring. In one of the largest cross-cultural studies of human mate preferences ever conducted, covering 33 countries shown in red here, the single most important mate choice criterion to both men and women, was mutual love and attraction. But as you also know, people are not always perfectly faithful to their mates. And in particular, women sometimes face a tradeoff between good genes and investment. Women sometimes find themselves in relationships with men who may be caring providers, but may not possess the best quality genes for offspring making them strong and healthy. And several features of women's mating psychology seem to have evolved, in part, to resolve this trade off. And I mean, recruiting genes, if you will, from outside of the long-term relationship. For example, women have more sexual fantasies about men other than their long-term partner, during the fertile part of the cycle, and that's particularly true if the long-term partner has physical signs of being lower in genetic quality, like he's less physically attractive. I think that's interesting. (Laughter) That's why I'm talking about it, I hope you do too. And women's mate preferences similarly change over the cycle so that they prefer more dominant, more masculine males during the fertile part of the cycle. These are results of a study that I conducted on women's preferences for men's voices. And I used computer software to manipulate recordings of men's voices to make them sound either more masculine or more dominant, or more subordinate, more feminine. And I had women rate them on how attractive would this man be for a short-term, purely sexual relationship, and for a long-term committed relationship? And I also got information about where women were in their cycles. Were they in the fertile or non-fertile part of the cycle? These were all women not taking hormonal contraception. And what I found was that women preferred a more masculine, dominant-sounding voice, specifically in the fertile point of the cycle, and only for a sexual relationship versus a long-term committed relationship. Now, this sounds like science fiction, but it's science, fact. Because this result has been shown lots of times across a variety of domains from women's preferences for men's voices, that this result was replicated by another lab. Women's preferences for men's faces, bodies, odors, and even behavior. Well, I said that we would get to orgasm. (Laughter) And we're there. I just want to start by saying I'm for it. (Laughter) I'm pro-orgasm. I think more people should have more orgasms. But from a scientific perspective, women's orgasm is especially fascinating because there's evidence indicating that it increases the probability that conception will result from an act of sex. There's evidence that it brings sperm up through the female reproductive tract and toward the egg. And think about what the implications here could be. If women were more likely to have orgasms with some men than others, then this could be a mechanism by which they choose, not consciously, to be fertilized by some males and not others. And wouldn't you predict that women would be more likely to have orgasms with males of high genetic quality? And in fact, a study by my lab published just a couple of years ago found that women reported more orgasms, earlier timed orgasms, that is, they were easier to achieve, they achieved them more quickly, when they were having sex when their mate was more masculine and more dominant, and what's interesting is that this was true only for their orgasms from sexual intercourse, but not from other partnered sexual behaviors. I'll let you use your imagination what those might be. So we've seen that thinking like an evolutionist can enable us to predict things about ourselves that we did not already know, and would not likely have guessed for a long time. We didn't know that women's mate preferences changed over the cycle. Until evolutionary thinking led us to that discovery. So that's one point that I want to make. But we've also seen how evolutionary thinking can clarify and unite diverse parts of the human experience, and help us understand the best and the worst of ourselves, from violence and aggression and infidelity to men's care for their children, sexual attraction, sexual pleasure, and even the strength and fragility of romantic love. Thank you. (Applause)

Frequently Occurring Word Combinations

ngrams of length 2

collocation	frequency
human mating	4
million years	4
mating opportunities	4
dominant males	4
fertile part	4
provide resources	3
daily caloric	3
mate preferences	3
early ancestors	2
males fight	2
male ancestors	2
males tend	2
evolutionary history	2
upper body	2
large sex	2
average man	2
individual females	2
subordinate males	2
providing resources	2
net daily	2
fertile point	2
evolutionary thinking	2

Important Words

ability
achieve
achieved
act
advantageous
age
aggregate
aggression
aggressive
alive
alright
ancestors
animal
answer
answering
apes
appearance
applause
apple
attempt
attracted
attraction
attractive
attractiveness
authors
average
avoid
babies
baboon
balance
bars
behavior
behaviors
benefits
big
billion
biological
bodies
body
bond
bonding
bones
boys
brain
brained
bring
bringing
brings
brought
bully
caloric
calories
camp
capable
care
cares
caring
carrying
chain
change
changed
cheat
chemistry
children
chimpanzees
choice
choose
clarify
close
closer
closest
committed
compared
competing
competition
compiled
computer
concealed
conception
concerned
conducted
confidence
consciously
consume
consuming
contraception
contrasts
contribute
cool
copulations
costly
countries
couple
covering
crime
criterion
cues
cut
cycle
cycles
daily
darker
data
dated
deal
defend
deficit
determining
development
devise
diet
difference
differences
discovery
distinction
distributed
diverse
domains
dominance
dominant
earlier
early
easier
efficiently
effort
egg
elaborate
enable
ends
energetically
equally
essentially
establish
estrus
eventually
evidence
evolution
evolutionary
evolutionist
evolve
evolved
experience
experienced
extremely
face
faces
fact
fail
faithful
fall
fallen
family
fantasies
fascinating
father
fats
features
feelings
female
females
feminine
fertile
fertilized
fiction
fight
fighting
figuring
find
food
foods
forage
foraging
force
form
formidable
forming
forms
fossil
fought
fragility
furniture
game
general
generally
generation
generous
genes
genetic
genitals
gestation
girls
give
good
gorillas
green
guessed
hallmarks
hand
happened
happening
healthier
healthy
high
history
homicides
hope
hormonal
human
humans
hunting
imagination
impact
impacts
implications
important
importantly
incites
include
including
incorporate
increase
increases
indicating
individual
infidelity
information
intercourse
interesting
invasion
investigator
investing
investment
items
jars
jokes
juvenile
kids
kill
killing
killings
kind
knew
lab
lactation
large
larger
largest
laughter
led
left
legs
lengthening
life
limit
lineage
lines
living
long
lot
lots
love
magazine
making
male
males
man
manipulate
marks
marriage
marriages
married
masculine
mass
mate
mates
mating
meat
mechanism
men
million
modern
monkey
monogamous
monogamy
monopolize
monopoly
move
muscle
muscular
musculature
mutual
net
notice
odors
offspring
open
operating
opportunities
orangutans
orgasm
orgasms
ovulation
pair
parental
part
partner
partnered
parts
passed
paternity
people
percent
percentage
percentages
perfectly
period
perspective
physical
physically
planet
plant
playbaboon
pleasure
point
polygamous
porn
pornography
possess
possibility
predict
predictor
prefer
preferences
preferred
present
pretty
primate
primates
probability
problem
producing
profound
profoundly
proportion
protect
protein
provide
providers
providing
provisioning
psychology
published
purely
quality
questions
quickly
rate
record
recordings
recruiting
red
regard
relationship
relationships
relatives
replicated
reported
reproduce
reproduced
reproducing
reproduction
reproductive
resolve
resources
result
results
rise
romantic
scene
science
scientific
sense
series
sets
sex
sexual
sexually
shown
signs
similarly
single
situation
size
small
smaller
societies
society
software
sound
sounds
specialized
species
specifically
spend
sperm
split
start
started
stone
stop
strength
strong
stronger
strongest
structures
studies
study
subordinate
subtle
success
suppress
surplus
swollen
symbols
talk
talking
target
tend
tending
thinking
thought
threat
time
timed
times
tipped
tool
toughest
tract
trade
tradeoff
traits
transitions
translate
translates
transporting
tree
trouble
true
unbroken
underlying
understand
unique
unite
unrelated
upper
variety
vastly
village
violence
virtual
voice
voices
walked
war
warned
ways
winning
woman
women
won
words
world
worst
worth
wrong
years
young