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Would you like to inspect the original subtitles? These are the user uploaded subtitles that are being translated: 1 00:00:11,900 --> 00:00:15,800 For millions of years our ape ancestors lived in the trees. 2 00:00:21,500 --> 00:00:24,700 But then they came down to the ground, and in an evolutionary leap 3 00:00:24,700 --> 00:00:29,000 that was to advance them over all other species, 4 00:00:29,000 --> 00:00:30,400 stood up on their hind legs. 5 00:00:31,000 --> 00:00:34,700 It was a critical stage on the way to becoming modern man. 6 00:00:35,800 --> 00:00:38,300 But there was an unavoidable consequence to our becoming upright. 7 00:00:38,300 --> 00:00:42,800 Suddenly the sexual organs were now frontally exposed 8 00:00:42,800 --> 00:00:43,500 in the male 9 00:00:43,500 --> 00:00:46,900 and the female. This was to have a profound effect on our 10 00:00:46,900 --> 00:00:55,400 sexuality then and now. Today, all our lives are affected by 11 00:00:55,400 --> 00:00:58,300 that one simple anatomical fact. 12 00:01:23,400 --> 00:01:27,200 I'm a biologist, and this is a program about human courtship. 13 00:01:27,500 --> 00:01:29,500 But if you think I'm going to be concentrating on 14 00:01:29,800 --> 00:01:33,900 human sexual behaviour, you'll be wrong. With the human animal, love 15 00:01:33,900 --> 00:01:35,900 is much more important than sex. 16 00:01:36,800 --> 00:01:41,100 But what is love anyway? Is it purely a human emotion? 17 00:01:46,500 --> 00:01:49,600 In the animal kingdom, as you move from group to group 18 00:01:49,600 --> 00:01:53,300 you find huge variations in the way sexual behaviour is organized. 19 00:01:58,600 --> 00:02:00,900 Some animals have gaudy sexual signals. 20 00:02:02,300 --> 00:02:06,300 Some do not. Some mate for life. 21 00:02:08,800 --> 00:02:14,300 Most do not. In some species the males mate with as many 22 00:02:14,300 --> 00:02:17,600 females as they can cover. In other species 23 00:02:17,600 --> 00:02:20,500 it's the females that control the time and place of mating. 24 00:02:21,400 --> 00:02:25,300 Some animals indulge in elaborate courtship displays. 25 00:02:25,300 --> 00:02:26,100 Our nearest relatives 26 00:02:26,100 --> 00:02:29,800 however have little or no courtship. Some fathers play a 27 00:02:29,800 --> 00:02:31,300 role in bringing up their young. 28 00:02:33,800 --> 00:02:36,900 But most offspring are brought up with no paternal help. 29 00:02:38,400 --> 00:02:41,000 Since the 1950s when I first began 30 00:02:41,000 --> 00:02:42,900 my studies of chimpanzees at London Zoo, 31 00:02:43,200 --> 00:02:45,200 I've been fascinated by this species, 32 00:02:45,200 --> 00:02:49,400 our closest relative. Chimps are in fact, so close that 33 00:02:49,400 --> 00:02:54,100 we share 98% of our genetic makeup with them. In the wild, 34 00:02:54,100 --> 00:02:57,300 their courtship is perfunctory to say the least. 35 00:02:57,300 --> 00:03:01,600 And females may be mated by one male after another. The act of copulation 36 00:03:01,600 --> 00:03:04,800 lasts only a few seconds, and the females appear remarkably 37 00:03:04,800 --> 00:03:09,800 unmoved by the event. Chimpanzees don't form lasting partnerships 38 00:03:10,100 --> 00:03:13,700 and the males play little part in raising the young. 39 00:03:13,700 --> 00:03:16,800 How is it that we humans are so different in this respect? 40 00:03:19,000 --> 00:03:22,600 I'm on the record as describing human beings as the sexiest primates alive. 41 00:03:22,600 --> 00:03:27,000 Now when I said that, people felt I was being provocative, 42 00:03:27,000 --> 00:03:28,100 but that wasn't the case. 43 00:03:29,000 --> 00:03:32,100 I was making an accurate scientific statement. 44 00:03:33,500 --> 00:03:36,600 There are some very specific ways in which human sexuality 45 00:03:36,600 --> 00:03:38,700 differs from that of our animal relatives. 46 00:03:39,300 --> 00:03:42,000 And the biggest differences are found in the human female. 47 00:03:42,600 --> 00:03:43,200 For instance, 48 00:03:43,300 --> 00:03:46,200 she doesn't advertise when she's fertile. 49 00:03:46,200 --> 00:03:50,100 Indeed, she may not even know herself when she is. So she sexually 50 00:03:50,100 --> 00:03:53,200 active all the time and we'll make love even when there's 51 00:03:53,200 --> 00:03:55,000 no possibility of conception. 52 00:03:56,200 --> 00:03:59,700 Whereas female primates only come on heat for brief periods, 53 00:04:00,000 --> 00:04:03,900 the human female has no sexual season. Throughout most of 54 00:04:03,900 --> 00:04:04,900 her monthly cycle, 55 00:04:05,100 --> 00:04:09,300 she stays attractive to men and is prepared to mate. 56 00:04:09,300 --> 00:04:12,800 Indeed, human females are capable of reproduction and remain sexually 57 00:04:12,800 --> 00:04:15,100 appealing throughout the whole year. 58 00:04:20,100 --> 00:04:23,300 Not only that, females are sexually responsive through most 59 00:04:23,300 --> 00:04:26,400 of their pregnancy and can become sexually active again quite 60 00:04:26,400 --> 00:04:30,500 soon after giving birth. Indeed human females can stay sexually 61 00:04:30,500 --> 00:04:33,900 active for a large part of their adult lives. Frequently for 62 00:04:33,900 --> 00:04:40,600 more than half a century. Human males experience a sexual 63 00:04:40,600 --> 00:04:44,000 climax similar to that of other primates, but unusually, 64 00:04:44,000 --> 00:04:47,600 the human female also experiences an intense orgasm. 65 00:04:48,700 --> 00:04:52,100 The phases of human courtship and the sexual act itself are 66 00:04:52,100 --> 00:04:54,500 all much longer, more elaborate 67 00:04:54,500 --> 00:04:56,500 and more intense than in any other primate. 68 00:04:56,900 --> 00:05:00,900 This extended sexuality isn't some sort of cultural decadence. 69 00:05:01,000 --> 00:05:04,600 It's a basic biological characteristic of our species. 70 00:05:05,100 --> 00:05:08,900 Why have we abandoned the 8-second mating act of the typical baboon. 71 00:05:10,900 --> 00:05:13,100 Finding the answer to this question was the task. 72 00:05:13,100 --> 00:05:16,900 I set myself back in the early 1970s when I began work on 73 00:05:16,900 --> 00:05:18,000 my book 74 00:05:18,100 --> 00:05:18,700 Intimate Behaviour. 75 00:05:19,200 --> 00:05:21,800 I called it Intimate Behaviour because I wasn't just looking 76 00:05:21,800 --> 00:05:23,000 at human sexuality, 77 00:05:23,000 --> 00:05:27,000 I was looking at the whole subject of loving relationships. 78 00:05:27,500 --> 00:05:30,500 Now, we all talk a lot about love, but very few of us 79 00:05:30,500 --> 00:05:34,100 stop to analyse it scientifically. I suppose we feel if we do that, 80 00:05:34,100 --> 00:05:36,900 we'll somehow destroy the magic. But that's not the case. 81 00:05:36,900 --> 00:05:40,600 In fact, the more we understand love, the more fascinating 82 00:05:40,600 --> 00:05:44,200 the subject becomes. But how does it all begin? 83 00:05:44,500 --> 00:05:46,400 How does boy meet girl? 84 00:05:47,600 --> 00:05:50,800 When children stop being toddlers and go to school, 85 00:05:50,800 --> 00:05:55,000 something strange happens. All over the world a major split now occurs 86 00:05:55,000 --> 00:05:59,500 between the sexes. Boys gather together in gangs. And girls 87 00:05:59,500 --> 00:06:03,100 keep to themselves in all female groups. And the groups are 88 00:06:03,100 --> 00:06:04,300 not really separate, 89 00:06:04,300 --> 00:06:06,600 they're often actively hostile to one another. 90 00:06:14,100 --> 00:06:17,800 This is an important step in sexual development. 91 00:06:17,800 --> 00:06:21,000 In this pre sexual phase, young males and females must become strangers 92 00:06:21,000 --> 00:06:24,400 to one another so that, when puberty arrives, they can forge 93 00:06:24,400 --> 00:06:28,600 an entirely new kind of relationship. One in which undue familiarity 94 00:06:28,600 --> 00:06:31,200 does not dull the excitement of discovery. 95 00:06:41,000 --> 00:06:44,400 The all-male and all-female groups start to lose their mutual 96 00:06:44,400 --> 00:06:47,500 hostility and replace it with mutual curiosity. 97 00:06:58,100 --> 00:06:59,700 The new attachments are powerful, 98 00:06:59,700 --> 00:07:03,000 but so too is the sense of belonging to one's old gang. 99 00:07:03,400 --> 00:07:07,000 But sooner or later, the childhood gangs will lose this unequal 100 00:07:07,000 --> 00:07:08,400 struggle for loyalty. 101 00:07:12,400 --> 00:07:16,100 A new activity now arrives on the scene. Parading. 102 00:07:16,100 --> 00:07:18,600 All over the world, young adults can be observed gathering together 103 00:07:18,600 --> 00:07:22,800 in large informal groups. On sea fronts, parks, High streets 104 00:07:22,800 --> 00:07:23,500 or clubs. 105 00:07:24,000 --> 00:07:27,700 The main preoccupation is simply making visual contact with 106 00:07:27,700 --> 00:07:31,700 as many members of the opposite sex as possible. 107 00:07:31,700 --> 00:07:35,500 Parading leads to a more direct display of interest. This bolder eye 108 00:07:35,500 --> 00:07:38,000 to eye contact is the first step 109 00:07:38,000 --> 00:07:40,400 on the lengthy sequence of human courtship. 110 00:07:42,800 --> 00:07:46,300 During this phase, primeval sexual influences are at work below 111 00:07:46,300 --> 00:07:50,900 the surface. Careful research in certain nightclubs 112 00:07:51,100 --> 00:07:53,900 has revealed that the closer girls are to their moment of ovulation, 113 00:07:53,900 --> 00:07:58,400 the skimpier their costumes will be. Their display 114 00:07:58,400 --> 00:08:02,500 of naked flesh is unconsciously dictated by their physiology. 115 00:08:09,300 --> 00:08:13,100 For some young males, this visual phase of mate selection 116 00:08:13,200 --> 00:08:17,100 becomes an exciting game to be relished and refined. 117 00:08:17,200 --> 00:08:20,300 Here, it's skillfully played out on scooters in the streets of Rome. 118 00:08:20,300 --> 00:08:26,500 In this purely visual stage of courting a mate, 119 00:08:26,500 --> 00:08:29,500 decisions can be made in an instant, within the glance of an eye. 120 00:08:29,700 --> 00:08:33,100 The brain has evaluated hundreds of pieces of visual information 121 00:08:33,200 --> 00:08:34,400 and has made a judgment. 122 00:08:34,500 --> 00:08:39,700 She's attractive or she's not. He likes her or he does not. 123 00:08:40,290 --> 00:08:41,200 Some of her signals 124 00:08:41,290 --> 00:08:43,200 he will understand consciously. 125 00:08:43,500 --> 00:08:45,900 Others, he'll be reacting to without even realising it. 126 00:08:53,800 --> 00:08:55,900 So what are these sexual signals? 127 00:08:56,200 --> 00:08:59,100 What does the human animal see as sexy? 128 00:09:13,100 --> 00:09:16,700 Throughout the animal kingdom, males are attracted to females who 129 00:09:16,900 --> 00:09:20,400 transmit signals of health and fertility. Positive signals 130 00:09:20,400 --> 00:09:24,000 of potential childbearing and child-rearing. 131 00:09:25,000 --> 00:09:28,200 The same is true for human males. 132 00:09:28,600 --> 00:09:31,700 Even if breeding success is farthest from their minds when 133 00:09:31,700 --> 00:09:35,100 they look at a passing female, it still influences their feelings 134 00:09:35,100 --> 00:09:35,900 towards her. 135 00:10:11,400 --> 00:10:14,900 It's the same for human females. When they look at males, 136 00:10:15,200 --> 00:10:19,100 their ancient impulses encourage them to seek out signs of masculine power 137 00:10:19,100 --> 00:10:24,500 and strength, indications of protective prowess. 138 00:10:24,500 --> 00:10:28,400 Although health and vigour are important displays for both sexes, 139 00:10:28,400 --> 00:10:31,800 many human sexual signals are specific to one gender or the other. 140 00:10:33,300 --> 00:10:36,100 Some of these gender signals are obvious enough, such as the 141 00:10:36,100 --> 00:10:39,000 broader shoulders of the male or the narrower waist of the female. 142 00:10:41,000 --> 00:10:45,200 The smooth skin and soft roundedness of the female body, 143 00:10:45,200 --> 00:10:49,200 and of course the high-pitched voice, are juvenile qualities 144 00:10:49,200 --> 00:10:54,700 making males feel protective. The thick neck, facial hair, deep voice 145 00:10:54,700 --> 00:10:58,400 and muscular torso of the male offer a strong visual 146 00:10:58,400 --> 00:11:03,300 contrast saying I'm a protector. Many male costumes exaggerate 147 00:11:03,300 --> 00:11:08,100 these gender signals. Male shoulders are widened by padded jackets, 148 00:11:08,900 --> 00:11:16,600 or even further enlarged by adding epaulets, or huge shoulder pads. 149 00:11:20,600 --> 00:11:23,400 And sometimes by extraordinary ritualistic costumes 150 00:11:23,500 --> 00:11:28,900 like these deliberately imposing uniforms of these Tibetan Monks. 151 00:11:33,900 --> 00:11:37,200 Emancipated females who wish to be more assertive 152 00:11:37,200 --> 00:11:42,200 in modern society mimic the broad torso look when they power dress. 153 00:11:44,200 --> 00:11:48,000 For the fashion industry, manipulating all these visual signals, 154 00:11:48,000 --> 00:11:51,800 improving our nature, becomes a matter of professional expertise. 155 00:11:51,800 --> 00:11:56,200 What I'd like to do Phillip, I'd like to dilate 156 00:11:56,200 --> 00:12:01,000 her pupils, to open them up more and to make her irises green 157 00:12:01,000 --> 00:12:04,100 to change them from brown to green and clean 158 00:12:04,100 --> 00:12:04,600 the whites of her eyes 159 00:12:04,600 --> 00:12:08,900 so her eyes are going to stand out much more. We could put a mask 160 00:12:08,900 --> 00:12:13,200 over the whole eye, lighting the eye out a little bit and 161 00:12:13,200 --> 00:12:17,000 then put the green in. Yes, that's the green looks great. 162 00:12:18,300 --> 00:12:20,000 By making the irises paler, 163 00:12:20,000 --> 00:12:22,900 they contrast more with the black of the pupil. 164 00:12:23,100 --> 00:12:26,900 So when the pupil itself is artificially enlarged, the impact 165 00:12:26,900 --> 00:12:30,900 is even greater. Enlarged pupils are a normal reaction to sexual arousal. 166 00:12:30,900 --> 00:12:33,700 So they are unconsciously appealing. 167 00:12:39,200 --> 00:12:42,000 The whiteness of the whites of the eyes is associated with 168 00:12:42,000 --> 00:12:43,500 youthful health and vigour. 169 00:12:43,800 --> 00:12:46,000 So this is also exaggerated. 170 00:12:52,000 --> 00:12:55,600 Now she has super eyes, but what about the rest of the face? 171 00:12:58,400 --> 00:13:04,900 Let's, let's clean up first the little crease marks just here 172 00:13:05,100 --> 00:13:06,600 on the edge of her lips. 173 00:13:07,600 --> 00:13:11,900 Again, a flawless complexion indicates health and the inherent 174 00:13:11,900 --> 00:13:13,700 sexuality of youthfulness. 175 00:13:14,400 --> 00:13:18,200 That's why any small crease lines are so carefully removed. 176 00:13:23,900 --> 00:13:25,500 I kind of like this colour here. 177 00:13:25,500 --> 00:13:27,100 That would be good, more red. 178 00:13:27,100 --> 00:13:28,600 Just bring out the muscular. 179 00:13:31,000 --> 00:13:34,600 The lips are made slightly more red, imitating the change 180 00:13:34,600 --> 00:13:37,500 in colour that occurs during sexual arousal. 181 00:13:37,600 --> 00:13:42,500 So if we now just do a colour correction 182 00:13:42,500 --> 00:13:44,000 to bring all of the skin, 183 00:13:44,000 --> 00:13:48,700 I'd like all her skin just to be a little richer 184 00:13:50,100 --> 00:13:52,700 and the skin colour is warmed up a little 185 00:13:52,700 --> 00:13:55,700 to create the impression of a healthy sexual glow. 186 00:13:58,500 --> 00:13:59,700 That's perfect. 187 00:14:00,800 --> 00:14:01,900 That's perfect. 188 00:14:02,200 --> 00:14:03,500 189 00:14:03,600 --> 00:14:04,200 We've got it. 190 00:14:05,500 --> 00:14:10,300 So what I want to do here is to stretch her legs along quite 191 00:14:10,300 --> 00:14:15,000 considerably maybe as much as 20% really we need to go through 192 00:14:15,000 --> 00:14:19,600 the legs stretching the thigh bone and the shinbone more. 193 00:14:19,600 --> 00:14:23,700 Less stretch on the feet and the knees so that we keep 194 00:14:23,700 --> 00:14:27,300 it as realistic as possible while making it as languid and 195 00:14:27,300 --> 00:14:28,700 as long as possible. 196 00:14:29,400 --> 00:14:32,400 Exaggerated leg length is an important 197 00:14:32,400 --> 00:14:34,200 sexual signal, especially in females. 198 00:14:34,600 --> 00:14:37,400 This is because the legs grow longer in relation to the rest 199 00:14:37,400 --> 00:14:39,700 of the body as puberty approaches. 200 00:14:40,000 --> 00:14:44,300 So super long legs means super adultness, and therefore super sexuality. 201 00:14:44,300 --> 00:14:48,300 Tiny bit more. 202 00:14:49,000 --> 00:14:56,000 Yeah, let's see a before and after. Yeah, that's great. 203 00:14:56,900 --> 00:14:57,500 That's great. 204 00:14:57,500 --> 00:15:01,200 That's long. Doesn't look too unrealistic and good proportions. 205 00:15:03,200 --> 00:15:06,800 When people meet there are many ways in which 206 00:15:06,800 --> 00:15:10,000 they can transmit sexual signals. With a smile, of course. 207 00:15:12,000 --> 00:15:15,000 And for long-haired individuals, the unconscious grooming 208 00:15:15,000 --> 00:15:17,100 of the hair, which says in effect, 209 00:15:17,100 --> 00:15:20,300 look I'm making myself more attractive, more appealing for you. 210 00:15:24,300 --> 00:15:27,100 Then there's that human speciality made possible by 211 00:15:27,100 --> 00:15:41,100 our naked skin, the blush. This blushing of the visible skin 212 00:15:41,400 --> 00:15:44,800 as a social signal is superficially similar to the flushing that 213 00:15:44,800 --> 00:15:49,200 occurs in the final stages of lovemaking. The blush starts 214 00:15:49,200 --> 00:15:52,400 at one spot in the centre of each cheek and then spreads 215 00:15:52,400 --> 00:15:55,400 to cover the whole of the face, the neck and even the upper torso. 216 00:15:55,400 --> 00:16:00,900 To the male onlooker, 217 00:16:00,900 --> 00:16:04,000 this skin change is strangely attractive because it 218 00:16:04,000 --> 00:16:07,900 of its implied innocence. It has a virginal quality that appeals 219 00:16:07,900 --> 00:16:08,300 to him. 220 00:16:13,100 --> 00:16:16,700 The use of a so-called blusher in modern makeup, supposedly 221 00:16:16,700 --> 00:16:20,200 to highlight the cheekbones, mimics the start of a blush and 222 00:16:20,200 --> 00:16:22,300 inevitably acquires some of its appeal. 223 00:16:28,500 --> 00:16:32,200 The rounded hemispherical breasts of the human female transmit 224 00:16:32,200 --> 00:16:36,200 a powerful sexual signal unique to our species. Monkeys and apes 225 00:16:36,200 --> 00:16:39,100 are completely flat chested when they're not giving 226 00:16:39,100 --> 00:16:42,600 milk to their young. But the human female retains her swollen breasts 227 00:16:42,600 --> 00:16:46,700 throughout her adult life. Breasts may have a maternal function, 228 00:16:46,700 --> 00:16:50,600 but their shape is purely sexual in significance. 229 00:16:51,500 --> 00:16:53,400 This breast shape appears to have evolved 230 00:16:53,400 --> 00:16:55,400 as a mimic of the rounded buttocks. 231 00:16:56,000 --> 00:16:58,000 Most female primates' sexual signals occur 232 00:16:58,200 --> 00:17:02,000 in the rump region, but in our species with its vertical body posture, 233 00:17:02,200 --> 00:17:05,090 it was necessary to have a frontal display as well. 234 00:17:08,090 --> 00:17:11,500 If you think that's far-fetched, just look at these two cleavages 235 00:17:11,700 --> 00:17:13,700 to see how similar the shapes are. 236 00:17:14,500 --> 00:17:14,900 Great. 237 00:17:22,200 --> 00:17:25,500 Milder sexual signals are also transmitted by the rounded 238 00:17:25,500 --> 00:17:30,000 female shoulders, and the smooth rounded knees, again providing 239 00:17:30,000 --> 00:17:33,000 visual echoes of the primeval buttock display. 240 00:17:37,200 --> 00:17:41,200 Another form of self mimicry. The large female lips in both 241 00:17:41,200 --> 00:17:45,400 shape and colour mimic the external genitals. When the labia 242 00:17:45,400 --> 00:17:49,200 redden during sexual arousal, the lips also become swollen 243 00:17:49,200 --> 00:17:53,400 and redder, a change artificially heightened by the application 244 00:17:53,400 --> 00:17:56,800 of lipstick. A cultural exaggeration that's been employed 245 00:17:56,800 --> 00:17:59,400 by women since the days of ancient Egypt. 246 00:18:04,000 --> 00:18:09,400 247 00:18:11,600 --> 00:18:13,800 When it comes to the basics of 248 00:18:13,800 --> 00:18:14,900 sexual attraction, 249 00:18:15,100 --> 00:18:18,500 we may be animals, but we can be very sophisticated animals. 250 00:18:18,900 --> 00:18:21,300 We have a conscious perception of what is beautiful 251 00:18:21,300 --> 00:18:25,600 and what is sexy, as well as a biological one. 252 00:18:25,600 --> 00:18:28,600 And one culture's ideal of beauty can differ greatly from another's. 253 00:18:28,600 --> 00:18:31,700 In the West for example, a slender figure is considered especially 254 00:18:31,700 --> 00:18:33,000 attractive for females. 255 00:18:34,000 --> 00:18:37,200 And a moderately muscular frame is preferred for males. 256 00:18:40,200 --> 00:18:43,900 In contrast, among the Maasai of East Africa, an incredibly 257 00:18:43,900 --> 00:18:47,900 slim figure which, to us, looks almost effeminate, is the epitome 258 00:18:48,000 --> 00:18:56,900 of masculine beauty. This contrasts strikingly with the much 259 00:18:56,900 --> 00:18:59,800 heavier body that spells beauty in many of the islands of 260 00:18:59,800 --> 00:19:04,300 the South Pacific, where it applies to both males and females. 261 00:19:14,200 --> 00:19:17,300 Wherever you look as you go around the globe, there are local 262 00:19:17,300 --> 00:19:20,600 beauty standards that are sometimes strange to foreign eyes. 263 00:19:25,300 --> 00:19:28,600 They're often too subtle to be appreciated by outsiders, 264 00:19:28,900 --> 00:19:32,900 but of enormous importance within the societies concerned. 265 00:19:41,400 --> 00:19:45,500 For instance among the Toga of Southern India, female hairiness 266 00:19:45,500 --> 00:19:49,300 is especially appealing to men. Even to the extent of heavy 267 00:19:49,300 --> 00:19:50,600 female eyebrows. 268 00:19:57,500 --> 00:20:00,000 But although beauty standards do vary around the world, 269 00:20:00,000 --> 00:20:03,400 there are a few universals that apply to the whole human species. 270 00:20:06,400 --> 00:20:09,300 The outline of the adult male body for instance. 271 00:20:09,700 --> 00:20:12,600 To be sexually appealing, the male needs to have a triangle 272 00:20:12,600 --> 00:20:15,200 formed by wide shoulders above a narrow waist. 273 00:20:24,300 --> 00:20:28,400 To females, another important male signal, is a compact muscular behind. 274 00:20:29,100 --> 00:20:32,000 Perhaps because of its sexual thrusting power. 275 00:20:32,000 --> 00:20:36,100 Male muscularity in general is appealing. But the dividing line between the 276 00:20:36,100 --> 00:20:39,500 well-muscled and the muscle-bound is a fine one. 277 00:20:39,500 --> 00:20:43,400 Because an over cultivated physique implies vanity. 278 00:20:47,100 --> 00:20:50,900 By contrast, a flabby body lacks the key signals. 279 00:20:54,400 --> 00:20:58,000 Another quality that has universal sex appeal, is youthfulness. 280 00:20:58,500 --> 00:21:02,100 Sex drive and fecundity are at their highest levels among 281 00:21:02,100 --> 00:21:05,600 the youngest adults. The male sex drive peaks at the age of 18, 282 00:21:05,600 --> 00:21:08,800 and the females fecundity, at 22. 283 00:21:12,300 --> 00:21:16,400 When a survey of sexual appeal was made in 190 different 284 00:21:16,400 --> 00:21:18,100 societies around the world. 285 00:21:18,100 --> 00:21:20,900 It was discovered that the most important feature common 286 00:21:20,900 --> 00:21:24,800 to all cultures was a healthy body and a clear unblemished skin. 287 00:21:33,800 --> 00:21:36,300 Beyond the eyeing up stage, 288 00:21:36,300 --> 00:21:39,200 we come to the next phase of the human courtship sequence. 289 00:21:39,400 --> 00:21:40,300 The pickup. 290 00:21:41,400 --> 00:21:43,300 How do people break the ice? 291 00:21:43,900 --> 00:21:47,600 Well a useful device is the cultivation of the lucky accident. 292 00:21:47,600 --> 00:21:51,500 Some irrelevant completely non-sexual factor, like exercising 293 00:21:51,500 --> 00:21:54,100 the dog is introduced into the equation. 294 00:21:54,800 --> 00:21:58,100 The individuals involved are not actively seeking a partner, 295 00:21:58,100 --> 00:21:59,800 that would be too obvious. 296 00:21:59,800 --> 00:22:03,000 Instead, they're engaged in a common pursuit which just happens to 297 00:22:03,000 --> 00:22:03,900 bring them together. 298 00:22:12,100 --> 00:22:15,400 More formal meetings between young people offer an opportunity 299 00:22:15,400 --> 00:22:19,400 to parade, eye up, display and pick up, all at the same time. 300 00:22:23,400 --> 00:22:26,900 These young Maasai males show off their prowess by leaping up and down 301 00:22:26,900 --> 00:22:28,700 in their vertical dance. 302 00:22:28,900 --> 00:22:31,900 They're watched discerningly by the young girls of the village, 303 00:22:31,900 --> 00:22:35,600 who, even at this tender age are already deeply involved in 304 00:22:35,600 --> 00:22:38,200 the exciting business of mate selection. 305 00:22:46,700 --> 00:22:50,200 The hair flick signals the interest of a male in a particular female. 306 00:22:51,200 --> 00:22:55,700 All around the world new connections are being made. 307 00:22:55,700 --> 00:22:59,700 New links are being forged, as friendly words take over from 308 00:22:59,700 --> 00:23:01,000 shy glances. 309 00:23:01,200 --> 00:23:02,900 We've arrived at the chatter. 310 00:23:03,600 --> 00:23:06,900 This is the information exchange phase in which people find 311 00:23:06,900 --> 00:23:09,700 out as much as possible about one another's backgrounds, 312 00:23:09,700 --> 00:23:12,900 their likes and dislikes. This reciprocal 313 00:23:12,900 --> 00:23:16,300 detective work may take some time, but it's a vitally important 314 00:23:16,500 --> 00:23:20,200 process when embarking on a long-term breeding partnership. 315 00:23:24,400 --> 00:23:27,700 In this particular region of modern China, the young men and 316 00:23:27,700 --> 00:23:30,900 women have a traditional way for overcoming the greatest 317 00:23:30,900 --> 00:23:34,700 problem of the chat up, shyness. Instead of simply mingling 318 00:23:34,700 --> 00:23:35,500 and chatting. 319 00:23:35,700 --> 00:23:39,000 They keep apart and sing their conversation from one group to another. 320 00:23:54,000 --> 00:23:57,000 They might sing about their personal skills 321 00:23:57,000 --> 00:23:59,500 or bravery which can cause a lot of amusement. 322 00:24:09,900 --> 00:24:14,100 The reply might be about property. 323 00:24:14,100 --> 00:24:16,100 The number of tractors in their village for instance. 324 00:24:23,100 --> 00:24:33,000 325 00:24:43,000 --> 00:24:46,500 In the bars of Los Angeles, the chat up technique, like the 326 00:24:46,500 --> 00:24:50,000 clothing, is much more casual. But it works well enough. 327 00:24:57,900 --> 00:24:58,900 328 00:25:06,100 --> 00:25:09,500 Here, contact has been made, and personal involvement 329 00:25:09,500 --> 00:25:17,800 has begun. Now talking becomes the key activity. 330 00:25:22,800 --> 00:25:25,400 Any inconsequential chatter keeps the conversation 331 00:25:25,400 --> 00:25:29,100 going, while the opportunity is taken to slip in important questions. 332 00:25:29,100 --> 00:25:32,300 What's the other's marital status? 333 00:25:32,400 --> 00:25:36,500 What is his or her job? In other words, apart from looks, 334 00:25:36,500 --> 00:25:39,900 what extra benefits could each bring with them to a relationship. 335 00:25:41,700 --> 00:25:43,500 Having received sufficient encouragement, 336 00:25:43,600 --> 00:25:48,600 he can now move in closer, and is rewarded with the first bodily contact. 337 00:26:02,600 --> 00:26:04,700 The problem now is to get rid of one of his new 338 00:26:04,700 --> 00:26:07,200 companions, so that he can end up in a twosome. 339 00:26:07,200 --> 00:26:10,600 But this time, he fails, and they both say goodbye. 340 00:26:11,500 --> 00:26:18,700 Perhaps next time? It's not easy finding the ideal partner 341 00:26:19,100 --> 00:26:22,600 and there'll be many false starts before the blend is right, but 342 00:26:22,600 --> 00:26:26,700 once it is, we see a whole new phase developing, characterised 343 00:26:26,700 --> 00:26:32,000 surprisingly, by what appears to be a return to infancy. 344 00:26:32,000 --> 00:26:33,600 Couples cuddle and caress one another, 345 00:26:34,600 --> 00:26:39,600 call each other silly names, talk in high-pitched voices and 346 00:26:39,600 --> 00:26:41,900 even rock together in one another's arms. 347 00:26:46,700 --> 00:26:47,600 This is the stage 348 00:26:47,600 --> 00:26:50,500 we usually refer to as falling in love. 349 00:26:55,900 --> 00:27:02,200 Dave loves Sue. Joe loves Kim. Love. What is love? 350 00:27:02,200 --> 00:27:05,800 Perhaps it's just a polite word for sex. A romantic way of describing 351 00:27:05,800 --> 00:27:10,000 sexual attraction. Well it isn't. It's much more than that. 352 00:27:10,500 --> 00:27:15,500 Love is a basic biological mechanism and it has a very specific function. 353 00:27:17,500 --> 00:27:21,700 The first time we encounter love is as tiny babies. 354 00:27:21,800 --> 00:27:25,800 This is the age of total security, protection and trust. 355 00:27:29,000 --> 00:27:31,800 But even at this early stage, another urge is beginning to 356 00:27:31,800 --> 00:27:34,600 express itself. The urge to strike out on one's own. 357 00:27:42,600 --> 00:27:46,300 And the process of growing up is the process of this new 358 00:27:46,300 --> 00:27:49,800 urge gradually asserting itself, as the need for maternal 359 00:27:49,800 --> 00:27:51,200 protection grows weaker. 360 00:27:57,500 --> 00:28:01,600 When the infant becomes a teenager, the urge for independence 361 00:28:01,600 --> 00:28:05,300 gains the upper hand, and the bond between parent and child starts 362 00:28:05,300 --> 00:28:09,700 to collapse. Eventually, in what turns out to be a more traumatic event 363 00:28:09,700 --> 00:28:13,600 than either parent or teenager had expected, comes the 364 00:28:13,600 --> 00:28:18,500 moment of first true separation. Here, the first day at College 365 00:28:18,500 --> 00:28:21,300 churns up the emotions as one long-term 366 00:28:21,300 --> 00:28:21,900 love bond slips 367 00:28:22,200 --> 00:28:25,900 into the past tense, and the prospects of a brand new one are 368 00:28:25,900 --> 00:28:27,700 about to appear on the horizon. 369 00:28:31,600 --> 00:28:35,200 It's an intriguing fact, that for a new couple, the first evening 370 00:28:35,200 --> 00:28:40,200 out together usually involves food and drink. We tend to take this for granted, 371 00:28:40,200 --> 00:28:43,000 but there may be a special, deeper reason. 372 00:28:43,000 --> 00:28:47,000 It's almost as if, as with many bird species, humans indulge in courtship feeding. 373 00:28:49,000 --> 00:28:51,400 A hidden camera catches this couple at 374 00:28:51,400 --> 00:28:55,200 the very start of just such a dinner date. As the meal progresses, 375 00:28:55,200 --> 00:28:58,000 their growing intimacy happens as we watch. 376 00:29:05,000 --> 00:29:08,800 They start smiling and leaning forward, not taking their eyes off one another. 377 00:29:24,700 --> 00:29:28,100 Now the first touch, leading to a gentle hand kiss. 378 00:29:50,300 --> 00:29:54,300 And now, like two parents with small infants they each 379 00:29:54,300 --> 00:29:55,200 spoon feed the other. 380 00:30:41,600 --> 00:30:45,100 Finally, again like courting birds, a gift is offered. 381 00:30:51,200 --> 00:30:54,500 The encounter comes to an end. In this familiar event, 382 00:30:54,500 --> 00:30:58,500 we are in reality seeing not only pseudo parental feeding, 383 00:30:58,700 --> 00:31:02,700 but also the reenactment of a primeval exchange deeply embedded 384 00:31:02,700 --> 00:31:06,200 in our species after a million years as hunter-gatherers. 385 00:31:06,800 --> 00:31:10,900 Food sharing, which in primeval times was the very basis of 386 00:31:10,900 --> 00:31:12,100 human society. 387 00:31:19,400 --> 00:31:22,400 As the sexual attachment of the couple increases, we see 388 00:31:22,400 --> 00:31:25,700 them displaying a variety of what a called tie signs. 389 00:31:26,400 --> 00:31:29,600 These are forms of body contact that tell other people that 390 00:31:29,600 --> 00:31:31,600 an exclusive pair is forming. 391 00:31:32,200 --> 00:31:35,200 So while they reinforce the closeness of the couple, 392 00:31:35,200 --> 00:31:38,800 they also serve to exclude us from that relationship. 393 00:31:40,500 --> 00:31:42,500 There's the arm around the shoulder. 394 00:31:42,800 --> 00:31:45,800 This is not yet particularly intimate, but there are other 395 00:31:45,800 --> 00:31:49,500 tie signs that will show a gradually increasing mutual trust 396 00:31:49,500 --> 00:31:54,000 between the couple. The arm around the waist. 397 00:32:00,200 --> 00:32:05,300 The double embrace, and next in increasing intimacy, rather unexpectedly, 398 00:32:05,500 --> 00:32:09,000 the contacts move up towards the head region. Because of the 399 00:32:09,000 --> 00:32:09,900 sense organs there, 400 00:32:09,900 --> 00:32:13,300 this is a highly protected area, available only to our most 401 00:32:13,300 --> 00:32:14,700 trusted companions. 402 00:32:22,100 --> 00:32:25,300 With the knee touch, the contacts begin to approach the most 403 00:32:25,300 --> 00:32:26,800 intimate region of the body. 404 00:32:33,500 --> 00:32:35,400 There are two particular aspects of human anatomy 405 00:32:35,400 --> 00:32:38,900 that make us sexually very different from most other animals. 406 00:32:39,600 --> 00:32:40,700 First, 407 00:32:40,800 --> 00:32:44,700 we have near-naked skins, and we've used that nakedness to 408 00:32:44,700 --> 00:32:47,800 gain an additional source of intimate stimulation. 409 00:32:47,800 --> 00:32:50,000 Something denied to our hairier cousins. 410 00:32:52,900 --> 00:32:55,600 There's another sexual difference between us and our animal relatives. 411 00:32:55,600 --> 00:32:59,900 All male monkeys and apes, and indeed 412 00:32:59,900 --> 00:33:03,000 most male mammals have what is called an "os" penis. 413 00:33:03,000 --> 00:33:04,400 This is a penis bone, 414 00:33:04,400 --> 00:33:08,700 and this is one from inside the penis of a walrus. 415 00:33:09,400 --> 00:33:14,400 And this tiny one here is from the penis of a hedgehog. 416 00:33:15,600 --> 00:33:18,700 The function of this bone is to produce an instant erection 417 00:33:18,700 --> 00:33:21,100 the moment that a male approaches a female sexually. 418 00:33:21,100 --> 00:33:23,300 The loss of this bone 419 00:33:23,400 --> 00:33:25,900 in the human male means that his female has to arouse 420 00:33:25,900 --> 00:33:28,600 him strongly before he can penetrate her. 421 00:33:28,700 --> 00:33:32,900 This means that human pre copulatory behaviour becomes much 422 00:33:32,900 --> 00:33:35,000 longer and much more sensuous. 423 00:33:40,600 --> 00:33:45,300 So sex in humans has evolved to be more than merely procreative. 424 00:33:46,300 --> 00:33:49,900 By becoming increasingly pleasurable, less automatic, 425 00:33:49,900 --> 00:33:52,100 it's more subtle and more complex. 426 00:33:55,600 --> 00:33:59,800 And in its final stages, courtship becomes even more prolonged 427 00:33:59,800 --> 00:34:01,300 and intensely erotic. 428 00:34:08,690 --> 00:34:13,100 This is not some modern sophistication. Evolution has programmed us 429 00:34:13,100 --> 00:34:17,400 for this extended body intimacy. For this skin to skin contact. 430 00:34:17,400 --> 00:34:21,500 Using it as a means of strengthening the attachment 431 00:34:21,500 --> 00:34:25,500 of the male and the female for one another. 432 00:34:25,690 --> 00:34:28,800 An attachment that will become biologically very important for them 433 00:34:28,800 --> 00:34:32,800 in the new role they're about to play. 434 00:34:38,900 --> 00:34:41,500 In animal behaviour terms, they've pair-bonded. 435 00:34:41,500 --> 00:34:45,000 That's what love is. The formation of a lasting pair bond. 436 00:34:45,400 --> 00:34:49,690 But what's its function? For true understanding of human sexuality, 437 00:34:50,100 --> 00:34:53,100 we have to look at our children. At the progeny that result 438 00:34:53,100 --> 00:34:54,400 from the sexual act. 439 00:34:56,400 --> 00:34:59,300 As with other monkeys and apes, our offspring, as we all know, 440 00:34:59,600 --> 00:35:03,700 are nurtured inside the female body, but unlike other monkeys 441 00:35:03,700 --> 00:35:07,800 and apes, human babies are totally helpless at birth. 442 00:35:07,800 --> 00:35:11,800 The human baby now goes through 10, perhaps 15 or more years of being 443 00:35:11,800 --> 00:35:13,300 dependent on its parents. 444 00:35:14,000 --> 00:35:17,700 It's a task beyond the resources of a single parent. 445 00:35:17,700 --> 00:35:21,200 Perhaps not in today's welfare state, but certainly in any primeval society. 446 00:35:21,200 --> 00:35:26,000 So they have to be two and there has to be a biological 447 00:35:26,200 --> 00:35:28,800 function to keep the couple together in the interests of the child, 448 00:35:28,800 --> 00:35:34,300 and that mechanism is the pair bond. Nearly all societies 449 00:35:34,300 --> 00:35:37,500 encourage some sort of official reinforcement of the pair bond. 450 00:35:37,500 --> 00:35:47,100 Typically a wedding ceremony. Whether the wedding is highly 451 00:35:47,100 --> 00:35:54,100 traditional, or more flamboyantly modern. Whether it's a protracted 452 00:35:54,100 --> 00:35:55,900 event full of ancient rites. 453 00:35:57,700 --> 00:36:00,000 Or merely, a drive-in quickie. 454 00:36:00,300 --> 00:36:02,800 It always carries the same public message. 455 00:36:02,800 --> 00:36:06,500 Namely we're an exclusive couple now. Hands off. 456 00:36:18,400 --> 00:36:21,800 Even in an arranged marriage, where love has played no part so far. 457 00:36:21,800 --> 00:36:26,700 This muslim man, who's never seen his bride before 458 00:36:26,700 --> 00:36:30,100 his wedding day is saying to the world when he touches her hand, 459 00:36:30,400 --> 00:36:32,900 from now on, we two are unavailable 460 00:36:32,900 --> 00:36:34,800 for pair bonding with anyone else. 461 00:36:42,700 --> 00:36:46,100 And so at last the final stage of the pair bonding process. 462 00:36:46,300 --> 00:36:49,800 The sexual act itself. For those who have enjoyed the natural 463 00:36:49,800 --> 00:36:51,300 process of falling in love, 464 00:36:51,400 --> 00:36:55,100 it's the end of the long courtship sequence. And the mating act too, 465 00:36:55,100 --> 00:36:58,800 is long and intense. Because in our species it's not 466 00:36:58,800 --> 00:37:02,800 concerned merely with procreation, but with mutual sexual rewards. 467 00:37:03,500 --> 00:37:07,100 The first tender caresses are made more exquisite 468 00:37:07,200 --> 00:37:11,500 by the suddenly super sensitive skin. The first of many physiological 469 00:37:11,500 --> 00:37:16,400 changes that now take place. Lips becoming swollen and sensitive. 470 00:37:17,900 --> 00:37:22,500 Eyes glistening as a film forms across their surface. 471 00:37:22,500 --> 00:37:25,200 Pupils dilating to become huge dark pools. 472 00:37:29,400 --> 00:37:32,300 Respiration increases dramatically as the body starts to 473 00:37:32,300 --> 00:37:36,000 need quantities of oxygen for the vigourous physical actions involved. 474 00:37:37,000 --> 00:37:41,200 The nostrils flare as the respiration rate increases 475 00:37:41,200 --> 00:37:47,100 to nearly four times the normal speed. More and more air is 476 00:37:47,100 --> 00:37:49,800 drawn into the body where the lungs begin to pump harder 477 00:37:49,800 --> 00:37:51,200 and harder. 478 00:37:55,500 --> 00:38:00,900 The heart beats faster as the body embarks on a wholesale redistribution of 479 00:38:00,900 --> 00:38:01,900 the blood supply. 480 00:38:05,100 --> 00:38:09,000 Inside the arteries, natural body chemicals have been released 481 00:38:09,000 --> 00:38:14,100 that produce feelings of euphoria and elation. Blood is pumped from the internal organs 482 00:38:14,100 --> 00:38:16,200 through the arteries to the veins 483 00:38:16,200 --> 00:38:18,900 and capillaries near the surface of the skin. 484 00:38:29,600 --> 00:38:33,300 Sweat glands open, supplying copious perspiration as a cooling agent, 485 00:38:33,300 --> 00:38:37,600 and also as a source of personal scent which unconsciously 486 00:38:37,600 --> 00:38:41,100 stimulates the partner. The whole body becomes much hotter 487 00:38:41,100 --> 00:38:44,500 to the touch and waves of heat can be seen escaping from 488 00:38:44,500 --> 00:38:46,400 the skin and the open mouth. 489 00:38:54,200 --> 00:38:57,800 A heat-sensitive camera reveals the developing pattern of 490 00:38:57,800 --> 00:39:00,800 body heat. The red areas being the hotter ones. 491 00:39:01,500 --> 00:39:05,500 They spread around the face. The soft erectile tissue on the 492 00:39:05,500 --> 00:39:07,800 side of the nose, an erogenous zone. 493 00:39:09,700 --> 00:39:13,600 The lips swollen with blood becoming increasingly hot to 494 00:39:13,600 --> 00:39:14,400 the touch. 495 00:39:16,300 --> 00:39:21,000 The earlobes, another erogenous zone, and eventually, 496 00:39:21,000 --> 00:39:21,700 the whole of the head. 497 00:39:28,500 --> 00:39:29,800 Lower down on the body, 498 00:39:29,900 --> 00:39:32,900 it's possible to see the genital region of the female becoming 499 00:39:32,900 --> 00:39:37,400 intensely heated as sexual arousal progresses and the labia 500 00:39:37,400 --> 00:39:38,600 engorge with blood. 501 00:39:46,800 --> 00:39:49,600 The female breast enlarges dramatically during sexual intercourse, 502 00:39:49,600 --> 00:39:55,200 increasing its size by up to 25%. Blood is pumped 503 00:39:55,200 --> 00:39:58,400 into erectile tissues faster than it can be pumped away. 504 00:40:02,900 --> 00:40:06,400 The nipples swell and become extra sensitive, increasing in 505 00:40:06,400 --> 00:40:08,800 height by as much as one centimetre. 506 00:40:13,200 --> 00:40:16,900 The penis also become swollen and stiffly erect. 507 00:40:16,900 --> 00:40:18,700 Doubling its normal length in the process. 508 00:40:19,800 --> 00:40:22,400 The erect penis is a marvel of fluid mechanics. 509 00:40:22,400 --> 00:40:26,500 The erection is caused by a rush of blood in, up to 60 times 510 00:40:26,500 --> 00:40:29,700 the normal level, and a simultaneous reduction in blood flow out 511 00:40:29,700 --> 00:40:31,800 that helps to maintain it. 512 00:40:35,300 --> 00:40:38,700 At high intensities of arousal, a sex flush appears on the 513 00:40:38,700 --> 00:40:43,100 female body and the shared experience of lovemaking is ultimately 514 00:40:43,100 --> 00:40:48,000 to be reinforced by the orgasm. As the man's muscles spasm, 515 00:40:48,200 --> 00:40:49,800 on his face is portrayed not pleasure, 516 00:40:49,800 --> 00:40:53,700 but surprisingly pain, caused by the extreme physical intensity 517 00:40:53,700 --> 00:40:58,400 of the moment. The male orgasm fulfills its biological function 518 00:40:58,600 --> 00:41:02,300 to deliver a pool of ejaculate inside the vagina, as close 519 00:41:02,300 --> 00:41:03,700 as possible to the cervical aperture. 520 00:41:03,900 --> 00:41:04,200 521 00:41:12,000 --> 00:41:15,000 With a mating act as intense as that, one might imagine that 522 00:41:15,000 --> 00:41:17,700 the human pair bond would be safe for life. 523 00:41:17,700 --> 00:41:20,100 But as we all know, this is not the case. 524 00:41:29,800 --> 00:41:30,900 So what goes wrong? 525 00:41:40,100 --> 00:41:43,200 One of the problems of modern life, is that it puts undue demands 526 00:41:43,200 --> 00:41:46,400 on a breeding system that evolved to operate in small 527 00:41:46,400 --> 00:41:49,600 tribal communities where males are only away from their females 528 00:41:49,600 --> 00:41:53,900 for short periods of time. Today, separations may be much longer. 529 00:42:03,300 --> 00:42:06,700 The pair bond evolved to protect the husband and wife and 530 00:42:06,700 --> 00:42:10,300 the offspring at just such times of conflicting emotion and vulnerability. 531 00:42:12,300 --> 00:42:15,100 But the pair bond is not a perfect system. 532 00:42:19,300 --> 00:42:23,100 Appealing members of the opposite sex may attract a roving eye, 533 00:42:23,100 --> 00:42:27,500 causing repeated conflict of loyalty, even if only in 534 00:42:27,500 --> 00:42:29,200 thought rather than deed. 535 00:42:30,300 --> 00:42:31,900 In complex societies, 536 00:42:32,200 --> 00:42:35,500 there's a temptation to experiment with new sexual experiences 537 00:42:35,700 --> 00:42:39,200 and to stray from the narrow confines of a single pair bond. 538 00:42:42,500 --> 00:42:46,100 Adultery and adulterers have been common throughout history. 539 00:42:46,800 --> 00:42:49,100 The advantage to the male is clear enough. 540 00:42:49,400 --> 00:42:52,900 He may be a caring husband and a good father, but he also 541 00:42:52,900 --> 00:42:57,100 gains from scattering his genetic material over a wider range. 542 00:42:57,600 --> 00:43:00,500 Through his additional offspring his genes will go marching on. 543 00:43:00,500 --> 00:43:05,100 The risk he runs, is that if he's found out, he may damage 544 00:43:05,100 --> 00:43:07,900 his pair bond and disrupt the rearing of his children. 545 00:43:13,600 --> 00:43:15,900 When it's discovered, an adulterer is nearly always attacked 546 00:43:15,900 --> 00:43:19,600 by society and feelings of guilt can become intense. 547 00:43:20,300 --> 00:43:23,300 You are also accused I use the word accused because no one likes it. 548 00:43:23,300 --> 00:43:24,300 of being a womanizer. 549 00:43:24,300 --> 00:43:25,900 What do they mean by a womanizer? 550 00:43:27,600 --> 00:43:29,700 They mean that I wasn't faithful, to my wife. 551 00:43:29,900 --> 00:43:30,500 Was that true? 552 00:43:30,600 --> 00:43:31,000 Yes. 553 00:43:32,300 --> 00:43:33,500 Did you stop that? 554 00:43:35,100 --> 00:43:39,200 Yes, I don't think it's something I want to talk a great 555 00:43:39,200 --> 00:43:39,900 deal about. 556 00:43:41,400 --> 00:43:45,200 Of course females may stray from the pair bond as well as males. 557 00:43:48,200 --> 00:43:50,100 Among the Wodaabe Nomads in Niger, 558 00:43:50,300 --> 00:43:55,000 this married man is meeting this married woman. In this tribe. 559 00:43:55,000 --> 00:43:58,400 it's accepted as a woman's right that if she's not satisfied 560 00:43:58,400 --> 00:43:59,400 with her own husband, 561 00:43:59,500 --> 00:44:04,100 she can go off with someone else's. In most societies, this pattern of behaviour 562 00:44:04,100 --> 00:44:06,800 is strongly attacked. But its existence 563 00:44:06,800 --> 00:44:10,100 suggests that their must be some genetic advantage for 564 00:44:10,100 --> 00:44:13,000 an adulterous female, as well as for an adulterous male. 565 00:44:13,200 --> 00:44:14,300 What could that be? 566 00:44:14,700 --> 00:44:15,900 She can't scatter her genes 567 00:44:16,200 --> 00:44:17,800 like an unfaithful male. 568 00:44:18,100 --> 00:44:19,900 So what can she gain from it? 569 00:44:26,800 --> 00:44:30,500 To understand this we must return to the moment of the orgasm. 570 00:44:35,200 --> 00:44:39,500 When the male ejaculates, a sperm pool is deposited near to 571 00:44:39,500 --> 00:44:43,700 the cervix, the entrance to the womb. The female usually takes 572 00:44:43,700 --> 00:44:45,800 a little longer to reach her orgasm. 573 00:44:46,200 --> 00:44:49,000 But when she does, it's just as intense. 574 00:44:51,200 --> 00:44:54,900 Her muscular contractions spread through the genital region 575 00:44:55,300 --> 00:45:00,400 to the cervix itself. And seen here on film for the first time 576 00:45:00,400 --> 00:45:04,500 these contractions help to dip the mouth of the uterus 577 00:45:04,500 --> 00:45:07,100 repeatedly into the sperm pool. 578 00:45:07,700 --> 00:45:11,800 And in this way, increase the chances of fertilisation. 579 00:45:13,400 --> 00:45:17,200 It's now thought that by varying the timing of her orgasms, 580 00:45:17,400 --> 00:45:20,700 the human female can increase or decrease her chances of 581 00:45:20,700 --> 00:45:24,000 fertilisation by the sperm of any particular male. 582 00:45:25,500 --> 00:45:28,900 If unfaithful, she could for instance favour the sperm of a 583 00:45:28,900 --> 00:45:32,600 young healthy lover, while continuing to gain protection from 584 00:45:32,600 --> 00:45:35,400 a powerful older husband. 585 00:45:35,600 --> 00:45:38,800 Intriguingly her husband's sperm have their own secret answer to this. 586 00:45:38,900 --> 00:45:44,100 It's what we might call sperm wars. It's usually imagined that 587 00:45:44,100 --> 00:45:47,400 all the millions of sperm deposited by the male are struggling 588 00:45:47,400 --> 00:45:50,700 to fertilise the egg, but new research has proved that this 589 00:45:50,700 --> 00:45:54,900 is not the case. Only a small proportion of them are actual 590 00:45:54,900 --> 00:45:59,300 egg seekers. The rest have another task. They ignore the egg, 591 00:45:59,300 --> 00:46:02,900 because it's their job to fight a rearguard action, to destroy 592 00:46:02,900 --> 00:46:05,500 any foreign sperm that may arrive on the scene. 593 00:46:07,100 --> 00:46:09,900 There are two kinds of these protective sperm. 594 00:46:10,200 --> 00:46:13,800 The first are active ones that search for and kill alien sperm, 595 00:46:13,800 --> 00:46:19,900 but they have no interest in finding the egg. 596 00:46:19,900 --> 00:46:23,500 New research suggests that a man can unconsciously control the numbers 597 00:46:23,500 --> 00:46:24,300 of these killer sperm 598 00:46:24,400 --> 00:46:27,700 in his ejaculate and that would depend on whether or 599 00:46:27,700 --> 00:46:28,600 not he believed 600 00:46:28,600 --> 00:46:32,200 he was the first or second male to mate with a particular woman. 601 00:46:32,200 --> 00:46:34,900 Here's one in action. 602 00:46:40,300 --> 00:46:44,000 This is chemical warfare, again filmed for the first time, 603 00:46:44,600 --> 00:46:47,900 and when the two sperm separate one is left dead. 604 00:46:57,600 --> 00:47:00,100 Other protective sperm are more passive. 605 00:47:00,100 --> 00:47:04,500 These are the blockers. They swim little, but curl their tails are 606 00:47:04,500 --> 00:47:08,500 interlock them. Massing together to form a barrier against invaders. 607 00:47:09,500 --> 00:47:13,000 They will let later sperm from the same male pass but block 608 00:47:13,000 --> 00:47:15,300 the way of sperm from other males. 609 00:47:15,700 --> 00:47:19,500 It's a kind of internal chastity belt which presumably will 610 00:47:19,500 --> 00:47:22,900 not have evolved without some promiscuity to counter 611 00:47:22,900 --> 00:47:24,200 in the first place. 612 00:47:27,300 --> 00:47:31,900 Drenched in a film of sweat, the lovers rest. Now mutually 613 00:47:31,900 --> 00:47:35,800 rewarded through their shared orgasms. Inside the woman's body, 614 00:47:35,800 --> 00:47:37,700 the sperm are active. 615 00:47:38,100 --> 00:47:40,900 Some will be starting their marathon journey in search of an egg. 616 00:47:40,900 --> 00:47:44,600 Others will be standing guard, needed or not. 617 00:47:45,700 --> 00:47:48,500 Promiscuity is a high-risk strategy for the human-animal. 618 00:47:49,000 --> 00:47:52,600 On balance, we're better off less stressed with our pair bonds. 619 00:47:52,600 --> 00:47:57,900 Even today, 99% of humans live in a pair bond. 620 00:47:59,100 --> 00:48:02,400 It's the fundamental condition of the human species. 55575

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