1 00:00:00,120 --> 00:00:01,800 The following content is provided 2 00:00:01,800 --> 00:00:04,030 under a Creative Commons license. 3 00:00:04,030 --> 00:00:06,880 Your support will help MIT OpenCourseWare continue 4 00:00:06,880 --> 00:00:10,740 to offer high quality educational resources for free. 5 00:00:10,740 --> 00:00:13,350 To make a donation or view additional materials 6 00:00:13,350 --> 00:00:17,237 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:17,237 --> 00:00:17,862 at ocw.mit.edu. 8 00:00:21,620 --> 00:00:25,490 PROFESSOR: OK, more about sociobiology. 9 00:00:25,490 --> 00:00:27,920 See what kind of subjects they study. 10 00:00:27,920 --> 00:00:33,040 I can tell you about later this week 11 00:00:33,040 --> 00:00:34,690 we will have a quiz on Wednesday. 12 00:00:34,690 --> 00:00:40,030 It'll be a short quiz just based on the mating behavior 13 00:00:40,030 --> 00:00:49,100 chapter in Scott that I talked about last week on Wednesday. 14 00:00:49,100 --> 00:00:51,960 And then on Friday we started sociobiology, 15 00:00:51,960 --> 00:00:54,940 so it'll be on the first two chapters 16 00:00:54,940 --> 00:00:57,690 of the sociobiology book, things we 17 00:00:57,690 --> 00:01:01,850 said in class including today. 18 00:01:07,570 --> 00:01:10,470 I know you have a homework due, but it's not due till Friday, 19 00:01:10,470 --> 00:01:12,370 and you've had quite a bit of time for it. 20 00:01:18,516 --> 00:01:19,016 All right. 21 00:01:22,750 --> 00:01:26,100 These are just some major issues in sociobiology 22 00:01:26,100 --> 00:01:29,040 and major different definitions. 23 00:01:29,040 --> 00:01:31,930 When sociobiologists use the term fitness, 24 00:01:31,930 --> 00:01:35,470 they're generally when they talk about fitness costs, 25 00:01:35,470 --> 00:01:38,900 fitness benefits, what do they mean? 26 00:01:38,900 --> 00:01:41,830 It's not like survival of the fittest, 27 00:01:41,830 --> 00:01:47,620 but it's related to that. 28 00:01:47,620 --> 00:01:51,990 It always means, it's always talking 29 00:01:51,990 --> 00:01:53,950 about survival of your genes. 30 00:01:53,950 --> 00:02:01,370 So it's defined as the number of surviving offspring or more 31 00:02:01,370 --> 00:02:04,970 precisely, the number of an individual's own genes passed 32 00:02:04,970 --> 00:02:06,185 on the surviving offspring. 33 00:02:16,400 --> 00:02:19,170 So fitness costs are anything that 34 00:02:19,170 --> 00:02:26,700 reduces the probability of gene survival and benefits things 35 00:02:26,700 --> 00:02:31,260 that increase the probability of gene survival. 36 00:02:31,260 --> 00:02:36,140 So a little bit about how sociobiologists think about it. 37 00:02:36,140 --> 00:02:39,310 Think of possible fitness benefits and costs 38 00:02:39,310 --> 00:02:46,490 to a female bird if she engages an extra pair of copulations. 39 00:02:46,490 --> 00:02:49,360 She's got to mate, but she flies off and mates 40 00:02:49,360 --> 00:02:53,690 with another male too, not necessarily deserting 41 00:02:53,690 --> 00:02:54,560 the first male. 42 00:02:59,110 --> 00:03:01,540 So what are the fitness benefits, 43 00:03:01,540 --> 00:03:03,180 and what are the costs to her? 44 00:03:05,980 --> 00:03:07,810 And are they the same for the male? 45 00:03:10,510 --> 00:03:15,080 So I want you to think about how you could get information 46 00:03:15,080 --> 00:03:16,740 to test those kinds of things. 47 00:03:16,740 --> 00:03:19,710 What would you have to look for? 48 00:03:19,710 --> 00:03:25,780 We can make up reasons for why it could help her pass on more 49 00:03:25,780 --> 00:03:32,220 genes, having another nest, laying eggs there, having 50 00:03:32,220 --> 00:03:34,960 more offspring, but that only works 51 00:03:34,960 --> 00:03:36,265 if the first ones survive. 52 00:03:40,600 --> 00:03:42,920 Like if the male is taking care of those eggs 53 00:03:42,920 --> 00:03:46,560 and wouldn't want to desert them because then his fitness would 54 00:03:46,560 --> 00:03:51,920 go down, it would cost him his fitness. 55 00:03:51,920 --> 00:03:55,730 But there are certainly costs too. 56 00:03:55,730 --> 00:03:58,630 The male can change his behavior towards a female 57 00:03:58,630 --> 00:04:05,090 to make it more difficult for her to pass on genes. 58 00:04:05,090 --> 00:04:07,720 So what kind of data would you have to collect? 59 00:04:07,720 --> 00:04:11,620 You'd have to follow these birds over a period of time, 60 00:04:11,620 --> 00:04:14,780 and it's difficult to do it precisely 61 00:04:14,780 --> 00:04:22,210 unless you can collect DNA data on the younger birds 62 00:04:22,210 --> 00:04:28,530 and find out how many offspring does she really have. 63 00:04:28,530 --> 00:04:33,580 And you then would compare birds that engage in this kind 64 00:04:33,580 --> 00:04:37,720 of extra pair copulation and the ones that don't. 65 00:04:37,720 --> 00:04:40,660 That's the kind of thing that sociobiologists do. 66 00:04:44,810 --> 00:04:47,150 So let's deal with some of the misunderstandings, 67 00:04:47,150 --> 00:04:50,040 and there's been a lot of them that have appeared. 68 00:04:50,040 --> 00:04:52,420 Alcock quotes these three people. 69 00:04:52,420 --> 00:04:58,200 These are the quotes that I selected from Alcock. 70 00:04:58,200 --> 00:05:06,100 Derek Bickerton says that when a bird practices what zoologists 71 00:05:06,100 --> 00:05:09,880 call extra-pair copulation, can we really call this adultery? 72 00:05:09,880 --> 00:05:12,705 The intent of the two activities is completely different. 73 00:05:17,890 --> 00:05:21,070 Michael Rose said there's the fundamental problem 74 00:05:21,070 --> 00:05:24,150 that if most people calculate Darwinian plans of action, 75 00:05:24,150 --> 00:05:27,960 they certainly aren't aware of it introspectively. 76 00:05:27,960 --> 00:05:30,865 Net Darwinian fitness doesn't figure in the great lyric 77 00:05:30,865 --> 00:05:31,365 poems. 78 00:05:36,360 --> 00:05:39,480 And then William Kimler, he criticizes 79 00:05:39,480 --> 00:05:44,050 the sociobiological claim that adulterous women have sometimes 80 00:05:44,050 --> 00:05:47,370 raised their genetic fitness by cuckolding a social partner 81 00:05:47,370 --> 00:05:49,930 on the grounds that she might be seeking 82 00:05:49,930 --> 00:05:51,770 more emotional satisfaction rather 83 00:05:51,770 --> 00:05:57,490 than simple genetic benefit 84 00:05:57,490 --> 00:06:04,540 So you can understand their statements, 85 00:06:04,540 --> 00:06:06,000 and there's a lot of truth in them. 86 00:06:06,000 --> 00:06:10,220 But is it really a criticism of sociobiology. 87 00:06:10,220 --> 00:06:15,960 First of all these first two guys 88 00:06:15,960 --> 00:06:21,650 are confusing conscious intent with the outcome. 89 00:06:21,650 --> 00:06:26,290 sociobiologists don't care about the conscious intent 90 00:06:26,290 --> 00:06:31,070 of the animal or the person, He only 91 00:06:31,070 --> 00:06:35,960 cares about the result, the outcome, in passing on genes. 92 00:06:35,960 --> 00:06:40,995 So fitness is not about conscious intent. 93 00:06:44,680 --> 00:06:50,860 And Kimler is a more common kind of mistake in these criticisms 94 00:06:50,860 --> 00:06:52,640 that you see of sociobiology. 95 00:06:52,640 --> 00:07:00,930 They fail to separate proximate cause from ultimate causes. 96 00:07:00,930 --> 00:07:06,020 They don't separate proximate motivational states are 97 00:07:06,020 --> 00:07:10,320 very distinct from the ultimate results, 98 00:07:10,320 --> 00:07:14,940 meaning passing on the genes. 99 00:07:14,940 --> 00:07:18,320 So Alcock summarizes it by saying 100 00:07:18,320 --> 00:07:21,600 understanding the difference between proximate and ultimate 101 00:07:21,600 --> 00:07:25,860 hypotheses which are different but complementary to one 102 00:07:25,860 --> 00:07:29,840 another can help us avoid the kind of confusion 103 00:07:29,840 --> 00:07:31,930 evident in Kimler's complaint about sociobiology. 104 00:07:36,150 --> 00:07:37,860 OK, so make sure you understand that. 105 00:07:37,860 --> 00:07:40,650 You might be asked, I might make up something 106 00:07:40,650 --> 00:07:44,570 and say what's wrong with this criticism. 107 00:07:44,570 --> 00:07:48,340 You should be able to separate these two kinds of hypotheses, 108 00:07:48,340 --> 00:07:52,780 the two kinds of causation I should say. 109 00:07:52,780 --> 00:07:58,440 So let's take one specific behavior and contrast 110 00:07:58,440 --> 00:08:02,820 approximate mechanisms and causes and ultimate outcomes. 111 00:08:02,820 --> 00:08:06,090 We did this before. 112 00:08:06,090 --> 00:08:08,580 Let's do it for the human tendency 113 00:08:08,580 --> 00:08:12,960 to eat high fat, sweet foods. 114 00:08:12,960 --> 00:08:15,680 So for proximate mechanisms, we want 115 00:08:15,680 --> 00:08:18,160 to consider psychological and physiological, 116 00:08:18,160 --> 00:08:20,710 anatomical mechanisms, the proximate 117 00:08:20,710 --> 00:08:26,235 causes, and then separately, the reasons that they evolved. 118 00:08:29,320 --> 00:08:35,610 Those are the ultimate causes in terms of Darwinian theory 119 00:08:35,610 --> 00:08:38,580 and sociobiology, which uses Darwinian theory 120 00:08:38,580 --> 00:08:41,289 as it's main tool. 121 00:08:43,980 --> 00:08:46,220 So for example, this human desire 122 00:08:46,220 --> 00:08:49,930 to eat high fat, sweet foods, ultimate causes 123 00:08:49,930 --> 00:08:52,740 would evolve to increase genetic fitness. 124 00:08:52,740 --> 00:08:54,600 And that sort of goes without saying. 125 00:08:57,310 --> 00:09:01,750 Genetic fitness doesn't involve long term survival. 126 00:09:01,750 --> 00:09:07,374 It involves survival long enough to pass on the genes 127 00:09:07,374 --> 00:09:07,915 successfully. 128 00:09:10,700 --> 00:09:13,500 I should say it doesn't very much involve long term 129 00:09:13,500 --> 00:09:17,480 survival, just we pointed out, I think, 130 00:09:17,480 --> 00:09:23,330 before that even grandma and grandpa can still 131 00:09:23,330 --> 00:09:27,500 benefit their genetic fitness by taking care of offspring, 132 00:09:27,500 --> 00:09:31,250 providing funds to help their offspring, 133 00:09:31,250 --> 00:09:37,170 and help their grandchildren or children go to college. 134 00:09:37,170 --> 00:09:38,920 Things like that. 135 00:09:38,920 --> 00:09:43,610 So that's a role after they're no longer reproducing. 136 00:09:43,610 --> 00:09:47,980 Just how important that is in evolution of humans 137 00:09:47,980 --> 00:09:50,050 and certainly even more in other species 138 00:09:50,050 --> 00:09:55,070 where there may be more debate about that. 139 00:09:55,070 --> 00:09:57,330 Now proximate causes are the kinds 140 00:09:57,330 --> 00:10:01,210 of things studied in this department, taste 141 00:10:01,210 --> 00:10:03,790 effects on hunger and eating, the innate releasing 142 00:10:03,790 --> 00:10:07,000 mechanisms, the same thing ecologists talk about. 143 00:10:07,000 --> 00:10:11,050 Brain mechanisms, hormonal mechanisms, various feeding 144 00:10:11,050 --> 00:10:13,110 reflexes and fixation patterns. 145 00:10:13,110 --> 00:10:17,560 Those are all the proximate mechanisms we could talk about, 146 00:10:17,560 --> 00:10:20,350 and we could map those out for human desire 147 00:10:20,350 --> 00:10:24,950 to eat high fats and sweet foods. 148 00:10:24,950 --> 00:10:29,070 What about my question, what are the advantages 149 00:10:29,070 --> 00:10:30,935 of fat and sweet foods? 150 00:10:34,500 --> 00:10:36,840 Can you tell me? 151 00:10:36,840 --> 00:10:38,420 What's so good about fat? 152 00:10:41,430 --> 00:10:45,630 Why do you choose it if you're going on a long, cross country 153 00:10:45,630 --> 00:10:47,885 hike that's going to last for several days? 154 00:10:50,700 --> 00:10:54,560 You need a lot of energy to do that. 155 00:10:54,560 --> 00:10:57,630 How much energy is there in fat compared 156 00:10:57,630 --> 00:10:59,576 with what there is a carbohydrate? 157 00:11:02,410 --> 00:11:03,850 Or protein for that matter. 158 00:11:06,540 --> 00:11:12,650 Aren't candy bars just as good as sausage? 159 00:11:12,650 --> 00:11:20,230 Well, candy bars with a lot of fat are the most beneficial 160 00:11:20,230 --> 00:11:21,980 for those long hikes. 161 00:11:21,980 --> 00:11:26,950 Think of the way humans evolved as hunter gatherers. 162 00:11:26,950 --> 00:11:30,400 You can get a lot more energy per gram, 163 00:11:30,400 --> 00:11:32,960 more than twice as much from fat. 164 00:11:32,960 --> 00:11:37,420 Nine calories per gram, actually kilocalories. 165 00:11:37,420 --> 00:11:39,220 We call them calories. 166 00:11:39,220 --> 00:11:41,890 Nine calories per gram in fat and only four 167 00:11:41,890 --> 00:11:45,430 for carbohydrate and protein. 168 00:11:45,430 --> 00:11:48,260 Very good reason why we evolved, that 169 00:11:48,260 --> 00:11:52,175 desire to eat high fat and sweet foods. 170 00:11:52,175 --> 00:11:53,820 Why sweet? 171 00:11:53,820 --> 00:11:54,940 Quick energy. 172 00:11:54,940 --> 00:11:57,380 Fat is slow to digest. 173 00:11:57,380 --> 00:12:01,510 You might need the energy much sooner. 174 00:12:01,510 --> 00:12:04,890 For that, the sweet carbohydrates 175 00:12:04,890 --> 00:12:05,960 digest the fastest. 176 00:12:09,650 --> 00:12:11,820 That's why I carry glucose pills here. 177 00:12:14,921 --> 00:12:15,420 OK. 178 00:12:20,410 --> 00:12:25,990 OK, let's talk about this interesting controversy that 179 00:12:25,990 --> 00:12:33,520 occurred in the 1960s, Wynne-Edwards and George C. 180 00:12:33,520 --> 00:12:35,700 Williams. 181 00:12:35,700 --> 00:12:37,335 Williams is great to read. 182 00:12:37,335 --> 00:12:40,210 If you ever get a chance, he's written some really interesting 183 00:12:40,210 --> 00:12:42,420 things. 184 00:12:42,420 --> 00:12:44,910 Wynne-Edwards wrote this book. 185 00:12:44,910 --> 00:12:46,260 He was British. 186 00:12:46,260 --> 00:12:51,770 It was published by a press in Edinborough, 1962, Animal 187 00:12:51,770 --> 00:12:53,985 Dispersion in Relation to Social Behavior. 188 00:12:57,130 --> 00:13:01,590 It became very popular, and the views 189 00:13:01,590 --> 00:13:06,220 expressed there persisted and they persist even today 190 00:13:06,220 --> 00:13:08,710 in public perceptions of evolution. 191 00:13:08,710 --> 00:13:12,150 Pollution 192 00:13:12,150 --> 00:13:13,410 I summarize it here. 193 00:13:13,410 --> 00:13:18,130 You interpreted almost every aspect of social behavior 194 00:13:18,130 --> 00:13:21,050 to be altruistic self sacrifice that 195 00:13:21,050 --> 00:13:23,425 advances the welfare of the species. 196 00:13:27,860 --> 00:13:33,590 That is, what evolves? 197 00:13:33,590 --> 00:13:35,635 Well, things that are benefiting to the species. 198 00:13:39,540 --> 00:13:48,160 Konrad Lorenz mentions species benefit in his book 199 00:13:48,160 --> 00:13:52,086 that summarizes many years of work in ethology. 200 00:13:57,000 --> 00:13:59,840 Can someone tell me why that didn't 201 00:13:59,840 --> 00:14:05,030 hurt Konrad Lorenz if he was wrong? 202 00:14:05,030 --> 00:14:06,900 Well, let's first show that he was wrong. 203 00:14:06,900 --> 00:14:09,810 That's what George C. Williams did in 1966. 204 00:14:09,810 --> 00:14:12,990 Just four years later, he published a book 205 00:14:12,990 --> 00:14:15,490 at Princeton University Press, Adaptation 206 00:14:15,490 --> 00:14:18,220 and Natural Selection. 207 00:14:18,220 --> 00:14:21,970 He presented the counter thesis that evolved adaptations 208 00:14:21,970 --> 00:14:26,410 including behavioral ones were extremely unlikely to promote 209 00:14:26,410 --> 00:14:31,340 the long term survival of entire populations or species 210 00:14:31,340 --> 00:14:36,120 at the expense of individual reproduction. 211 00:14:36,120 --> 00:14:39,480 And you can read there on page 30 in Alcock 212 00:14:39,480 --> 00:14:42,160 his thought experiment. 213 00:14:42,160 --> 00:14:48,300 You imagine a group of individuals. 214 00:14:48,300 --> 00:14:55,250 And most of them limited their reproduction. 215 00:14:55,250 --> 00:14:59,220 This sounds a lot like current problems 216 00:14:59,220 --> 00:15:01,580 we have with population control, doesn't it? 217 00:15:01,580 --> 00:15:07,310 They limited their reproduction for the benefit of the group 218 00:15:07,310 --> 00:15:07,860 as a whole. 219 00:15:11,054 --> 00:15:12,720 Let's say they're a small group, there's 220 00:15:12,720 --> 00:15:14,420 difficulty obtaining enough food, 221 00:15:14,420 --> 00:15:16,690 so they limit their reproduction to make 222 00:15:16,690 --> 00:15:19,280 it easier for the whole group. 223 00:15:22,270 --> 00:15:27,010 But say you had a few individuals there, 224 00:15:27,010 --> 00:15:29,770 said heck with that. 225 00:15:29,770 --> 00:15:32,510 I want more kids. 226 00:15:32,510 --> 00:15:37,190 And they don't follow that practice. 227 00:15:37,190 --> 00:15:39,235 They're not feeling so altruistic. 228 00:15:43,090 --> 00:15:46,960 Where did my slide go here? 229 00:15:46,960 --> 00:15:47,460 OK. 230 00:15:50,850 --> 00:15:51,610 What would happen? 231 00:15:54,290 --> 00:15:58,160 Well, the ones having more offspring, 232 00:15:58,160 --> 00:16:01,220 those genes are going to increase. 233 00:16:01,220 --> 00:16:06,290 The ones limiting their reproduction 234 00:16:06,290 --> 00:16:09,640 will not increase at the rate those people 235 00:16:09,640 --> 00:16:10,985 that violate that rule. 236 00:16:14,400 --> 00:16:21,240 And eventually the genes of those people that are 237 00:16:21,240 --> 00:16:23,202 think about their own reproduction, 238 00:16:23,202 --> 00:16:24,660 those are going to become dominant. 239 00:16:30,170 --> 00:16:33,370 And Williams argued that pretty forcefully in this book, 240 00:16:33,370 --> 00:16:38,600 and from that point on, any scientist read it, 241 00:16:38,600 --> 00:16:44,660 it totally changed the way people were looking 242 00:16:44,660 --> 00:16:48,940 at evolution by natural selection as applied to animals 243 00:16:48,940 --> 00:16:50,215 in general, not just humans. 244 00:16:53,910 --> 00:16:55,930 So what about effects like this? 245 00:16:55,930 --> 00:16:59,790 I mentioned overcrowding results in population declines. 246 00:16:59,790 --> 00:17:02,160 We know that it does. 247 00:17:02,160 --> 00:17:05,880 And these declines are caused by physiological and behavioral 248 00:17:05,880 --> 00:17:08,690 effects of stress. 249 00:17:08,690 --> 00:17:14,430 Example, you can find in animals that 250 00:17:14,430 --> 00:17:18,109 live in overcrowded conditions overactive adrenal gland 251 00:17:18,109 --> 00:17:23,829 secretions, decreased immune system function, 252 00:17:23,829 --> 00:17:25,205 increased social conflict. 253 00:17:29,990 --> 00:17:35,230 Those kinds of effects reduce fertility, 254 00:17:35,230 --> 00:17:39,760 and that makes them what we call a Darwinian puzzle 255 00:17:39,760 --> 00:17:42,710 of great interest to sociobiologists. 256 00:17:42,710 --> 00:17:44,660 Darwinian puzzles are things that 257 00:17:44,660 --> 00:17:49,475 don't seem to fit our view of genetic fitness. 258 00:17:54,790 --> 00:17:57,200 But we're neglecting one thing here, 259 00:17:57,200 --> 00:18:03,300 and it seems to have been neglected by Williams. 260 00:18:03,300 --> 00:18:07,200 And that is, Wilson discusses the issue 261 00:18:07,200 --> 00:18:09,950 of group selection quite extensively. 262 00:18:09,950 --> 00:18:12,710 And he cites George C. Williams. 263 00:18:12,710 --> 00:18:16,150 He was very aware of Williams' book. 264 00:18:16,150 --> 00:18:19,580 He admired Williams. 265 00:18:19,580 --> 00:18:25,960 So he was careful to evaluate the conditions that 266 00:18:25,960 --> 00:18:31,070 could favor interdemic selection for genes. 267 00:18:31,070 --> 00:18:32,770 What's a deme. 268 00:18:32,770 --> 00:18:36,240 It's the population, the smallest population of people 269 00:18:36,240 --> 00:18:41,520 interbreed fairly randomly, at least 270 00:18:41,520 --> 00:18:43,520 in the modeling of their behavior. 271 00:18:46,140 --> 00:18:48,740 So in other words, issues that favor some kind of group 272 00:18:48,740 --> 00:18:56,340 selection which involves altruism in most cases, 273 00:18:56,340 --> 00:18:57,780 but it's a very complex issue. 274 00:18:57,780 --> 00:19:01,700 And the arguments about it continue to this day. 275 00:19:01,700 --> 00:19:06,850 In fact, sociobiologists discounted group selection 276 00:19:06,850 --> 00:19:13,760 so completely after about 1975 when sociobiology appeared. 277 00:19:13,760 --> 00:19:15,980 It was actually in the 1980s when it really 278 00:19:15,980 --> 00:19:18,030 took hold and studies of animal behavior 279 00:19:18,030 --> 00:19:22,260 were dominated by sociobiological studies. 280 00:19:22,260 --> 00:19:24,800 And they weren't talking about group selection at all. 281 00:19:24,800 --> 00:19:32,210 It's only more recently where there's 282 00:19:32,210 --> 00:19:36,810 more people that are focusing on factors in group selection. 283 00:19:36,810 --> 00:19:39,930 The exception was, of course, the social insects 284 00:19:39,930 --> 00:19:43,880 which in their colonies they function almost 285 00:19:43,880 --> 00:19:52,410 as a single organism, where of course things 286 00:19:52,410 --> 00:19:57,934 that benefit the group were paramount for reproduction 287 00:19:57,934 --> 00:20:06,500 of the social insect ants, bees, and other social insects. 288 00:20:06,500 --> 00:20:12,755 It's a special topic of Wilson's empirical studies. 289 00:20:17,290 --> 00:20:20,930 I mentioned what a Darwinian puzzle is. 290 00:20:20,930 --> 00:20:22,710 And this is the way it's defined. 291 00:20:22,710 --> 00:20:25,140 Anything that appears to reduce an individual's 292 00:20:25,140 --> 00:20:27,670 chance of reproducing successfully 293 00:20:27,670 --> 00:20:30,560 even by a small degree becomes by definition 294 00:20:30,560 --> 00:20:31,520 a Darwinian puzzle. 295 00:20:34,820 --> 00:20:37,830 Because it seems to go against the very thing we're saying 296 00:20:37,830 --> 00:20:40,190 is the driver in evolution. 297 00:20:43,680 --> 00:20:48,130 I just took a couple of examples here. 298 00:20:48,130 --> 00:20:50,850 The first one, very simple, we talked about it before. 299 00:20:50,850 --> 00:20:54,140 Why do whirligig beetles congregate 300 00:20:54,140 --> 00:20:57,180 so much when large groups of them 301 00:20:57,180 --> 00:20:59,130 are attacked more often than smaller groups? 302 00:20:59,130 --> 00:21:00,640 They congregate in order to forage. 303 00:21:04,640 --> 00:21:07,960 And when they're in these large groups, 304 00:21:07,960 --> 00:21:12,690 it does have a cost in reproduction of any individual 305 00:21:12,690 --> 00:21:17,900 if we look at it statistically, OK? 306 00:21:17,900 --> 00:21:25,150 But if you measure the attacks per individual 307 00:21:25,150 --> 00:21:30,420 as group size increases, you find out that it goes down. 308 00:21:30,420 --> 00:21:34,120 In other words, you benefit by being 309 00:21:34,120 --> 00:21:38,510 in the group because yes, the group might get attacked more 310 00:21:38,510 --> 00:21:40,770 if you're in a larger group than a smaller group, 311 00:21:40,770 --> 00:21:44,770 but the chance of an individual being attacked actually 312 00:21:44,770 --> 00:21:45,370 goes down. 313 00:21:48,730 --> 00:21:50,070 And this outweighs the costs. 314 00:21:53,880 --> 00:21:59,270 Second one is why do humans love pet dogs so much? 315 00:21:59,270 --> 00:22:02,965 Even though dogs can spread disease and cause lethal bites. 316 00:22:08,610 --> 00:22:14,395 And yet it's a long history of humans' attachment to dogs. 317 00:22:18,210 --> 00:22:22,930 It could be a maladaptive side effect of proximate mechanisms 318 00:22:22,930 --> 00:22:28,570 that evolved for other reasons, like for example, caregiving 319 00:22:28,570 --> 00:22:32,000 responses, need for companionship. 320 00:22:32,000 --> 00:22:34,720 We're also very social animals. 321 00:22:34,720 --> 00:22:38,620 Desire for protection, human responses 322 00:22:38,620 --> 00:22:41,740 to loyal friendliness. 323 00:22:41,740 --> 00:22:47,250 Just interpreted in terms of modern conditions, 324 00:22:47,250 --> 00:22:52,300 for most people it's difficult to imagine 325 00:22:52,300 --> 00:22:59,940 that the costs are really less than the benefits. 326 00:22:59,940 --> 00:23:03,640 But in earlier times, my belief is 327 00:23:03,640 --> 00:23:06,280 that dogs which have been associated-- 328 00:23:06,280 --> 00:23:10,760 and if you look at paleontological records 329 00:23:10,760 --> 00:23:17,600 you find bones of dogs in the remains of human settlements 330 00:23:17,600 --> 00:23:23,030 a very long time ago, at least 30,000 years, probably more. 331 00:23:23,030 --> 00:23:25,240 Some claims it goes back much further 332 00:23:25,240 --> 00:23:28,070 into ancestors of humans. 333 00:23:28,070 --> 00:23:30,710 But at least humans have kept dogs for a very long time. 334 00:23:30,710 --> 00:23:33,910 What would be the big advantage to those early groups of humans 335 00:23:33,910 --> 00:23:36,800 of having a dog? 336 00:23:36,800 --> 00:23:43,035 Think of the dog senses, what the dog can sense that we 337 00:23:43,035 --> 00:23:43,535 can't. 338 00:23:48,800 --> 00:23:50,340 You have pet dogs at home. 339 00:23:50,340 --> 00:23:52,547 You must know some of this. 340 00:23:52,547 --> 00:23:53,630 Think about their hearing. 341 00:23:57,340 --> 00:24:02,670 They know if there's an intruder on your property 342 00:24:02,670 --> 00:24:06,030 or just a stranger or even grandma come to visit. 343 00:24:06,030 --> 00:24:09,560 They know long before you do. 344 00:24:09,560 --> 00:24:11,530 And they make a noise, and they let 345 00:24:11,530 --> 00:24:15,310 you know something's out there. 346 00:24:15,310 --> 00:24:21,640 And we know their incredibly good olfactory sense. 347 00:24:21,640 --> 00:24:24,410 So they make incredibly good companions 348 00:24:24,410 --> 00:24:30,300 for hunting and for protection of the whole group. 349 00:24:30,300 --> 00:24:38,400 And I think those effects would explain, 350 00:24:38,400 --> 00:24:42,360 even though people were getting occasionally bit by dogs 351 00:24:42,360 --> 00:24:46,470 and suffering lethal bites, it probably 352 00:24:46,470 --> 00:24:51,350 didn't happen very often when the dog was socialized properly 353 00:24:51,350 --> 00:24:53,821 from infancy. 354 00:24:53,821 --> 00:24:54,320 Why? 355 00:24:54,320 --> 00:24:59,690 Because remember, this phenomenon of imprinting 356 00:24:59,690 --> 00:25:02,150 we talked about, there's something like that in dogs, 357 00:25:02,150 --> 00:25:09,310 and they socialize to humans, and they're not dominated. 358 00:25:09,310 --> 00:25:13,020 Their allegiance is not dominated by other dogs, 359 00:25:13,020 --> 00:25:15,920 by humans. 360 00:25:15,920 --> 00:25:18,450 And that makes the chances of getting 361 00:25:18,450 --> 00:25:21,680 one of those bites a lot less. 362 00:25:21,680 --> 00:25:25,650 You'd get problems when the dog, especially some species of dog, 363 00:25:25,650 --> 00:25:30,070 gets very attached to guarding humans. 364 00:25:30,070 --> 00:25:33,850 And it's usually a stranger or a child 365 00:25:33,850 --> 00:25:37,810 that does something with the neighbor's dog or something, 366 00:25:37,810 --> 00:25:39,760 sometimes even their own. 367 00:25:39,760 --> 00:25:42,950 Dogs make mistakes, and sometimes the dog 368 00:25:42,950 --> 00:25:44,780 is so attached just to the master 369 00:25:44,780 --> 00:25:49,640 that the children aren't fully incorporated in the master's 370 00:25:49,640 --> 00:25:51,360 group. 371 00:25:51,360 --> 00:25:53,010 This can happen. 372 00:25:53,010 --> 00:25:55,610 So anyway, yes, they do cause legal bites, 373 00:25:55,610 --> 00:25:58,690 but I don't think it would have been, 374 00:25:58,690 --> 00:26:02,950 we wouldn't have kept dogs for so very long if there weren't 375 00:26:02,950 --> 00:26:06,090 benefits, fitness benefits, that outweigh the cost. 376 00:26:09,170 --> 00:26:11,730 So that's the way I would solve that Darwinian puzzle. 377 00:26:14,970 --> 00:26:20,290 OK, now in the appendix of Alcock's chapter, 378 00:26:20,290 --> 00:26:31,060 he raises specific questions in his question two. 379 00:26:31,060 --> 00:26:37,810 I just selected two of them that seemed to me 380 00:26:37,810 --> 00:26:41,430 to be a little less obvious than B and D. Number 381 00:26:41,430 --> 00:26:46,420 B is, I can read it to you. 382 00:26:46,420 --> 00:26:50,000 225. 383 00:26:50,000 --> 00:26:53,330 This questions in the appendix are quite interesting, 384 00:26:53,330 --> 00:26:58,690 and we'll look at them every once in a while. 385 00:26:58,690 --> 00:27:01,070 The first one is actually, the first question 386 00:27:01,070 --> 00:27:02,320 is also very interesting. 387 00:27:02,320 --> 00:27:03,415 This is question two. 388 00:27:07,230 --> 00:27:11,790 Part B is, the readiness of some adult birds with offspring 389 00:27:11,790 --> 00:27:16,010 nearby to scream loudly when in the grasp of a predator. 390 00:27:20,070 --> 00:27:22,346 Why would that challenge a Darwinian adaptations? 391 00:27:25,620 --> 00:27:31,400 It probably wouldn't challenge him as much as C would. 392 00:27:31,400 --> 00:27:35,540 But some people could argue with that, 393 00:27:35,540 --> 00:27:40,280 because how often is that scream of the bird going 394 00:27:40,280 --> 00:27:42,780 to either startle a predator-- of course 395 00:27:42,780 --> 00:27:44,720 it's designed to startle the predator, 396 00:27:44,720 --> 00:27:46,280 so the bird can get away. 397 00:27:46,280 --> 00:27:49,350 And then if the predator pursues the adult 398 00:27:49,350 --> 00:27:54,790 instead of going after her nest, the nest might be spared. 399 00:27:54,790 --> 00:28:00,110 And in fact, the young birds, and some of them anyway, 400 00:28:00,110 --> 00:28:03,460 will have a response to that scream from the adult. 401 00:28:03,460 --> 00:28:05,210 And they will huddle and be quiet, 402 00:28:05,210 --> 00:28:07,730 and they're pretty well camouflaged, 403 00:28:07,730 --> 00:28:10,640 they might not even be detected. 404 00:28:10,640 --> 00:28:13,810 But what about A? 405 00:28:13,810 --> 00:28:17,470 The arduous journey of an ocean-dwelling salmon 406 00:28:17,470 --> 00:28:22,630 to locate and swim up a stream it locates by olfactory sense, 407 00:28:22,630 --> 00:28:26,860 swims up the stream-- actually the stream 408 00:28:26,860 --> 00:28:30,650 where it came from-- in order to breed. 409 00:28:30,650 --> 00:28:34,400 It entails very high costs, as most of you know. 410 00:28:34,400 --> 00:28:40,260 Salmon will swim very long distances up such streams, 411 00:28:40,260 --> 00:28:44,240 often having to leap because the streams of course 412 00:28:44,240 --> 00:28:47,600 are flowing down, and they have to go back up 413 00:28:47,600 --> 00:28:50,580 to get closer to the source where they want to breed. 414 00:28:53,730 --> 00:28:56,810 So the costs are very high, and they don't all make it. 415 00:28:56,810 --> 00:28:58,710 So what are the benefits? 416 00:28:58,710 --> 00:29:01,756 What are the fitness benefits? 417 00:29:01,756 --> 00:29:03,005 Did we talk about that before? 418 00:29:07,540 --> 00:29:11,300 What's the obvious benefit it must have? 419 00:29:11,300 --> 00:29:15,900 Why do any animals that migrate in order to breed, 420 00:29:15,900 --> 00:29:17,986 why did they go such long distances? 421 00:29:17,986 --> 00:29:18,985 What are the advantages? 422 00:29:24,880 --> 00:29:28,520 It would be the same if we talked about some 423 00:29:28,520 --> 00:29:32,590 of these birds that go very long distances to get to breeding 424 00:29:32,590 --> 00:29:36,200 grounds, even over mountains. 425 00:29:36,200 --> 00:29:38,910 They'll go thousands of miles in some cases. 426 00:29:38,910 --> 00:29:40,585 Some turtles do this too. 427 00:29:43,150 --> 00:29:46,290 What are the benefits? 428 00:29:46,290 --> 00:29:48,110 Because the young are particularly 429 00:29:48,110 --> 00:29:50,680 susceptible to predation, you need 430 00:29:50,680 --> 00:29:54,460 to go to an area which is usually not the area where 431 00:29:54,460 --> 00:29:56,890 your food is most plentiful. 432 00:29:56,890 --> 00:30:00,480 You need to go to an area where the chances of predation 433 00:30:00,480 --> 00:30:02,310 are the least. 434 00:30:02,310 --> 00:30:04,770 In fact, for many species they go to an area 435 00:30:04,770 --> 00:30:07,740 where various members of the species 436 00:30:07,740 --> 00:30:09,850 congregate so even if there is a presenter, 437 00:30:09,850 --> 00:30:15,790 the chance that any one baby animal will be attacked 438 00:30:15,790 --> 00:30:18,079 are reduced. 439 00:30:18,079 --> 00:30:19,495 So those are the fitness benefits. 440 00:30:22,070 --> 00:30:24,310 And then we talked about this before. 441 00:30:24,310 --> 00:30:29,960 We talked about parasitic nesting. 442 00:30:29,960 --> 00:30:32,040 Birds accept eggs from non mates, 443 00:30:32,040 --> 00:30:35,060 even from another species and take care of them. 444 00:30:35,060 --> 00:30:38,160 They feed the hatchlings. 445 00:30:38,160 --> 00:30:41,540 There seem to be no fitness benefits, at least not 446 00:30:41,540 --> 00:30:44,280 immediate ones. 447 00:30:44,280 --> 00:30:48,060 At least in Alcock's reading of it. 448 00:30:48,060 --> 00:30:51,060 The behavior may be a maladaptive side effect 449 00:30:51,060 --> 00:30:53,760 of caregiving fixed action patterns. 450 00:30:53,760 --> 00:30:57,530 So first of all, what does that phrase mean? 451 00:30:57,530 --> 00:31:01,320 What's the caregiving fixed action pattern 452 00:31:01,320 --> 00:31:04,390 that the parasitic bird who lays eggs in another bird's nest 453 00:31:04,390 --> 00:31:06,240 is taking advantage of? 454 00:31:06,240 --> 00:31:08,290 Do you remember? 455 00:31:08,290 --> 00:31:10,110 It should be obvious. 456 00:31:10,110 --> 00:31:13,830 Response to the gape, and often these parasitic birds 457 00:31:13,830 --> 00:31:16,920 like the cuckoo, his gape is even bigger 458 00:31:16,920 --> 00:31:19,460 than most songbirds, so the parent 459 00:31:19,460 --> 00:31:23,720 is a super normal stimulus for eliciting the feeding response. 460 00:31:23,720 --> 00:31:27,270 So it gets fed even more than the bird's own offspring. 461 00:31:30,450 --> 00:31:31,993 Is it completely maladaptive? 462 00:31:40,570 --> 00:31:45,820 What did I say about-- and this changes a little bit 463 00:31:45,820 --> 00:31:50,410 what Alcock said here. 464 00:31:50,410 --> 00:31:53,760 He says there appeared to be no fitness benefits, 465 00:31:53,760 --> 00:31:56,150 but in fact there is a fitness benefit 466 00:31:56,150 --> 00:32:00,550 because in the case of the cuckoo anyway, 467 00:32:00,550 --> 00:32:06,720 the spotted cuckoo in Spain where it's been studied, 468 00:32:06,720 --> 00:32:09,860 the adult birds that lay their eggs in other nests 469 00:32:09,860 --> 00:32:15,450 hang around, and they enforce that caregiving. 470 00:32:15,450 --> 00:32:18,640 The birds that throw their eggs out, 471 00:32:18,640 --> 00:32:20,700 that would be the adaptive response, 472 00:32:20,700 --> 00:32:22,680 the way Alcock's thinking. 473 00:32:22,680 --> 00:32:27,580 But in fact the birds that do that get their nests totally 474 00:32:27,580 --> 00:32:31,750 disrupted, their offspring killed. 475 00:32:31,750 --> 00:32:36,730 So basically, yeah, fewer of their offspring will survive, 476 00:32:36,730 --> 00:32:41,080 but at least some of them will survive. 477 00:32:41,080 --> 00:32:43,190 But this is how you go about dealing 478 00:32:43,190 --> 00:32:44,650 with these Darwinian puzzles. 479 00:32:50,450 --> 00:32:53,330 So this is another. 480 00:32:53,330 --> 00:32:57,000 I want to know how an evolutionary biologist would 481 00:32:57,000 --> 00:32:59,750 respond to this argument of Marvin 482 00:32:59,750 --> 00:33:02,870 Harris about the origins of human welfare. 483 00:33:02,870 --> 00:33:05,510 He's a cultural anthropologist. 484 00:33:05,510 --> 00:33:08,440 And this is what he argued. 485 00:33:08,440 --> 00:33:11,080 He argued that human warfare stems 486 00:33:11,080 --> 00:33:13,540 from the inability of pre-industrial peoples 487 00:33:13,540 --> 00:33:16,140 to develop a less costly or more benign 488 00:33:16,140 --> 00:33:18,570 means of achieving low population densities 489 00:33:18,570 --> 00:33:20,830 and low rates of population growth 490 00:33:20,830 --> 00:33:22,980 needed to prevent over exploitation 491 00:33:22,980 --> 00:33:24,830 of essential central resources. 492 00:33:28,070 --> 00:33:31,670 So what's wrong with the argument? 493 00:33:31,670 --> 00:33:36,810 Very simply, he's talking about species benefits. 494 00:33:36,810 --> 00:33:38,870 He's making them more important than benefits 495 00:33:38,870 --> 00:33:46,460 to the individual, benefits meeting fitness benefits, OK? 496 00:33:46,460 --> 00:33:48,340 Remember, they're always using these terms 497 00:33:48,340 --> 00:33:52,080 about benefits and costs very specifically 498 00:33:52,080 --> 00:33:55,838 to refer to probability of gene survival. 499 00:33:59,670 --> 00:34:02,620 OK, more about sociobiology. 500 00:34:02,620 --> 00:34:04,720 And let's just review. 501 00:34:04,720 --> 00:34:07,300 These are from last class. 502 00:34:07,300 --> 00:34:09,840 This is where some of these beautiful 503 00:34:09,840 --> 00:34:12,284 statements of E.O. Wilson. 504 00:34:15,210 --> 00:34:23,190 Remember that the organism in a sense doesn't live for itself. 505 00:34:23,190 --> 00:34:27,389 Its primary function is to reproduce other organisms. 506 00:34:27,389 --> 00:34:33,190 It reproduces genes, and serves as their temporary carrier. 507 00:34:33,190 --> 00:34:35,040 You say, but wait a minute. 508 00:34:35,040 --> 00:34:37,530 You're totally opposed to religion here? 509 00:34:37,530 --> 00:34:38,520 No I'm not. 510 00:34:38,520 --> 00:34:40,110 I'm telling you what the mechanism 511 00:34:40,110 --> 00:34:42,389 is, how humans evolved. 512 00:34:42,389 --> 00:34:44,090 And we will talk specifically about that 513 00:34:44,090 --> 00:34:48,840 later, because I don't agree with Alcock in this point. 514 00:34:48,840 --> 00:34:49,719 OK. 515 00:34:49,719 --> 00:34:53,580 So he talks about the centers of this brain that is more 516 00:34:53,580 --> 00:34:56,730 a reproductive organ than anything else. 517 00:34:56,730 --> 00:35:00,930 The centers of the brain complex tax the conscious mind 518 00:35:00,930 --> 00:35:04,870 with ambivalences whenever the organisms encounter 519 00:35:04,870 --> 00:35:07,890 stressful situations. 520 00:35:07,890 --> 00:35:11,890 Love joint hate, aggression joins fear, 521 00:35:11,890 --> 00:35:15,330 expansiveness joins withdrawal, and so on. 522 00:35:15,330 --> 00:35:19,130 And blends designed not to promote the happiness 523 00:35:19,130 --> 00:35:24,330 and survival of the individual, but to favor 524 00:35:24,330 --> 00:35:28,390 the maximum transmission of the controlling genes. 525 00:35:28,390 --> 00:35:31,040 And that is the view of sociobiology. 526 00:35:31,040 --> 00:35:33,120 That's the theme of his entire book. 527 00:35:35,660 --> 00:35:36,700 OK. 528 00:35:36,700 --> 00:35:38,740 The most important thing in this slide 529 00:35:38,740 --> 00:35:40,620 was what I've underlined here. 530 00:35:40,620 --> 00:35:44,330 You should know what, we will use the term deme occasionally. 531 00:35:44,330 --> 00:35:47,720 It's a special population, defines the smallest local set 532 00:35:47,720 --> 00:35:49,640 of organisms within which interbreeding 533 00:35:49,640 --> 00:35:54,480 occurs reasonably freely. 534 00:35:54,480 --> 00:35:58,310 But you should be able to separate population and society 535 00:35:58,310 --> 00:36:00,740 because they seem to be the same. 536 00:36:00,740 --> 00:36:05,330 But populations bounded by a zone of sharply reduced gene 537 00:36:05,330 --> 00:36:08,540 flow, whereas the society's founded 538 00:36:08,540 --> 00:36:11,640 by zone of sharply reduced communication. 539 00:36:11,640 --> 00:36:16,260 Now in many cases, those two things might coincide. 540 00:36:16,260 --> 00:36:19,020 But they certainly don't always coincide. 541 00:36:19,020 --> 00:36:22,090 They're defining a different aspect 542 00:36:22,090 --> 00:36:25,305 of the large group of a certain species. 543 00:36:30,510 --> 00:36:34,410 The evolutionary pacemaker-- you're 544 00:36:34,410 --> 00:36:36,990 talking about that when both behavior and body 545 00:36:36,990 --> 00:36:39,740 structure change in evolution. 546 00:36:39,740 --> 00:36:41,900 And when that happens, when they are 547 00:36:41,900 --> 00:36:44,420 able to collect adequate data on it, 548 00:36:44,420 --> 00:36:47,340 it seems that the behavior of changes 549 00:36:47,340 --> 00:36:51,220 occur before changes in body structure. 550 00:36:51,220 --> 00:36:58,920 That means-- actually, it's a little overstated here, 551 00:36:58,920 --> 00:37:02,200 because you would have to say the part of the body 552 00:37:02,200 --> 00:37:06,120 that changes first is the brain. 553 00:37:06,120 --> 00:37:08,910 And then structure adapts to what's 554 00:37:08,910 --> 00:37:11,680 needed for the particular behavior that's evolving. 555 00:37:14,565 --> 00:37:15,065 OK. 556 00:37:17,740 --> 00:37:20,520 You should know the term demography, 557 00:37:20,520 --> 00:37:25,610 because we will use it sometimes in the rest the class, 558 00:37:25,610 --> 00:37:27,290 and adaptive demography. 559 00:37:27,290 --> 00:37:32,484 Demography always means the way different ages of a species 560 00:37:32,484 --> 00:37:33,150 are distributed. 561 00:37:35,780 --> 00:37:40,460 How many really young, how many young adult, 562 00:37:40,460 --> 00:37:43,470 how many reproducing age, how many 563 00:37:43,470 --> 00:37:45,560 older ones, how many very old ones. 564 00:37:45,560 --> 00:37:49,130 This is demography, to talk about the demographics 565 00:37:49,130 --> 00:37:50,160 of the society. 566 00:37:50,160 --> 00:37:52,076 They're very different in different countries. 567 00:37:54,510 --> 00:37:57,090 And that will come up again. 568 00:37:57,090 --> 00:38:00,240 So we always talking about different ages or sizes. 569 00:38:00,240 --> 00:38:02,520 Sometimes size is the more important factor 570 00:38:02,520 --> 00:38:03,460 for some things. 571 00:38:07,480 --> 00:38:12,760 We've already seen examples of behavioral scaling, 572 00:38:12,760 --> 00:38:13,890 and we'll see more. 573 00:38:16,670 --> 00:38:19,980 But you want to keep in mind this statement that evolution 574 00:38:19,980 --> 00:38:24,390 leads to compromises in social evolution. 575 00:38:24,390 --> 00:38:26,590 Because adaptations at one level may not 576 00:38:26,590 --> 00:38:28,750 be adaptations at another level. 577 00:38:28,750 --> 00:38:30,580 What's adapted for the individual 578 00:38:30,580 --> 00:38:33,280 may not be adaptive for the family. 579 00:38:33,280 --> 00:38:36,120 Family groups are small enough, though, 580 00:38:36,120 --> 00:38:43,720 that there might be conflicts, but they usually 581 00:38:43,720 --> 00:38:45,560 are resolved in such small groups, 582 00:38:45,560 --> 00:38:48,070 but certainly not at the higher levels. 583 00:38:48,070 --> 00:38:50,680 And then of course ultimate versus proximate causation, 584 00:38:50,680 --> 00:38:52,830 he discusses. 585 00:38:52,830 --> 00:38:55,060 He made that a major point, and it's 586 00:38:55,060 --> 00:38:58,870 been ever since in the field of sociobiology. 587 00:38:58,870 --> 00:38:59,370 OK. 588 00:38:59,370 --> 00:39:03,670 So then he talks about the prime movers 589 00:39:03,670 --> 00:39:07,890 of social evolution, phylogenetic inertia. 590 00:39:07,890 --> 00:39:11,700 These are the factors that slow evolutionary changes 591 00:39:11,700 --> 00:39:16,720 in social behavior, reduce genetic variation, 592 00:39:16,720 --> 00:39:20,000 will slow evolutionary change. 593 00:39:20,000 --> 00:39:23,400 And that can happen in periods of very reduced population 594 00:39:23,400 --> 00:39:25,700 size, for example. 595 00:39:25,700 --> 00:39:30,510 With less genetic variation in a very small population, 596 00:39:30,510 --> 00:39:33,670 it will slow evolutionary change. 597 00:39:38,110 --> 00:39:49,350 And the term genetic swamping means that if populations 598 00:39:49,350 --> 00:39:53,380 are usually divided into smaller groups, of course, 599 00:39:53,380 --> 00:39:56,940 and often one subgroup begins to change because of altered 600 00:39:56,940 --> 00:39:58,210 environmental conditions. 601 00:39:58,210 --> 00:40:01,620 But if they all aren't subject to the same environmental 602 00:40:01,620 --> 00:40:07,720 conditions, some live further north, some live further south, 603 00:40:07,720 --> 00:40:11,105 some live where there's a new predator, some do not. 604 00:40:14,040 --> 00:40:17,140 It only takes occasional interbreeding 605 00:40:17,140 --> 00:40:20,336 with another subgroup to prevent the less adaptive genes 606 00:40:20,336 --> 00:40:21,085 from disappearing. 607 00:40:23,950 --> 00:40:25,770 OK. 608 00:40:25,770 --> 00:40:26,975 That's genetic swamping. 609 00:40:36,080 --> 00:40:43,110 When food sources change, a group 610 00:40:43,110 --> 00:40:47,010 may not change its habits because of genetic swamping 611 00:40:47,010 --> 00:40:48,380 for the same kind of reason. 612 00:40:48,380 --> 00:40:50,535 Food in some regions can change. 613 00:40:54,370 --> 00:40:57,250 So that's another one, that's all factors that 614 00:40:57,250 --> 00:41:01,010 can slow evolutionary changes. 615 00:41:01,010 --> 00:41:04,500 We talk a lot about the various ecological pressures, 616 00:41:04,500 --> 00:41:08,120 conditions that result in evolution-specific patterns 617 00:41:08,120 --> 00:41:09,950 of social behavior. 618 00:41:09,950 --> 00:41:12,010 He gives examples from anti predator 619 00:41:12,010 --> 00:41:14,435 behavior and other examples from foraging. 620 00:41:20,520 --> 00:41:23,470 I like his quote, when spider webs unite, 621 00:41:23,470 --> 00:41:26,360 they can halt a lion. 622 00:41:26,360 --> 00:41:28,890 Colonies are a lot harder for predators 623 00:41:28,890 --> 00:41:30,015 to approach undetected. 624 00:41:32,520 --> 00:41:35,605 And attacks reduce the probability 625 00:41:35,605 --> 00:41:38,940 of harming any individual when they're in a large group. 626 00:41:38,940 --> 00:41:40,020 We've talked about that. 627 00:41:43,650 --> 00:41:47,940 He points out that even though organized colonies are the most 628 00:41:47,940 --> 00:41:51,330 effective, even an unorganized colony, 629 00:41:51,330 --> 00:41:56,230 an unorganized herd instinct will evolve in animal groups 630 00:41:56,230 --> 00:41:59,580 and still be effective. 631 00:41:59,580 --> 00:42:04,070 And some cattle groups, groups of fish or squid 632 00:42:04,070 --> 00:42:07,930 or flocks of birds are not that well organized, 633 00:42:07,930 --> 00:42:12,550 and yet they still have benefits of forming those groups. 634 00:42:12,550 --> 00:42:16,770 Locust swarms is another one. 635 00:42:16,770 --> 00:42:24,970 Another example of this evolution of social behavior 636 00:42:24,970 --> 00:42:27,650 or because of ecological pressures 637 00:42:27,650 --> 00:42:31,280 related to predation, to synchronize breeding. 638 00:42:31,280 --> 00:42:33,500 We just mentioned that. 639 00:42:33,500 --> 00:42:35,930 Birds that reproduce in colonies, 640 00:42:35,930 --> 00:42:38,430 they may not live that way all the time, 641 00:42:38,430 --> 00:42:40,670 but for reproduction they might live that way. 642 00:42:43,330 --> 00:42:47,860 The social ungulates synchronize their breeding. 643 00:42:55,250 --> 00:42:58,690 What's the name of the ungulate in Africa, the one that 644 00:42:58,690 --> 00:43:01,960 migrates long distances in the Serengeti? 645 00:43:01,960 --> 00:43:04,680 They all breed at the same time. 646 00:43:04,680 --> 00:43:08,680 So the big cats that chase them, are 647 00:43:08,680 --> 00:43:12,700 less likely to get-- they won't get all of them. 648 00:43:12,700 --> 00:43:14,815 The chances of an individual being caught 649 00:43:14,815 --> 00:43:18,010 are a lot less if they all are breeding at the same time. 650 00:43:24,130 --> 00:43:26,790 And then we've already talked about group defense strategies. 651 00:43:29,580 --> 00:43:32,340 We didn't talk about the owl fly larvae. 652 00:43:32,340 --> 00:43:34,430 When confronted by insect predators, 653 00:43:34,430 --> 00:43:38,390 they gang together because individuals 654 00:43:38,390 --> 00:43:41,910 are less likely to be attacked. 655 00:43:41,910 --> 00:43:43,780 You have that in bee colonies. 656 00:43:43,780 --> 00:43:48,110 You have the meerkats that have their lookout 657 00:43:48,110 --> 00:43:50,680 or sort of a guard meerkat. 658 00:43:50,680 --> 00:43:53,140 You have it in muskoxen that form 659 00:43:53,140 --> 00:43:58,240 this circle around their young. 660 00:43:58,240 --> 00:44:02,320 And muskoxen are pretty big, and they're 661 00:44:02,320 --> 00:44:03,890 a pretty good defense against wolves. 662 00:44:03,890 --> 00:44:06,610 So if they're organized, they do it as a group. 663 00:44:06,610 --> 00:44:08,980 They're much more effective at keeping the wolves 664 00:44:08,980 --> 00:44:11,010 from getting at their young. 665 00:44:11,010 --> 00:44:13,130 And the wolves are a lot less likely to be 666 00:44:13,130 --> 00:44:16,320 able to bring down an adult muskox. 667 00:44:19,030 --> 00:44:22,200 And then we've already talked about mobbing by birds. 668 00:44:22,200 --> 00:44:24,540 It occurs in primates as well. 669 00:44:30,940 --> 00:44:35,450 And here's examples related to foraging 670 00:44:35,450 --> 00:44:38,310 where social behavior has adapted 671 00:44:38,310 --> 00:44:39,675 to conditions of foraging. 672 00:44:49,820 --> 00:44:53,090 Groups and cliques can increase competitive ability 673 00:44:53,090 --> 00:44:55,390 and feeding. 674 00:44:55,390 --> 00:44:57,220 They help each other in the smaller group 675 00:44:57,220 --> 00:45:00,080 to compete against other groups. 676 00:45:00,080 --> 00:45:02,045 That's certainly a social adaptation. 677 00:45:05,640 --> 00:45:08,620 Groups, coalitions, and cliques then 678 00:45:08,620 --> 00:45:11,620 increase feeding efficiency by social behavior. 679 00:45:11,620 --> 00:45:14,130 He uses the term imitative foraging. 680 00:45:19,610 --> 00:45:21,700 We know the birds form territories 681 00:45:21,700 --> 00:45:25,360 when food is evenly distributed, but you'll still 682 00:45:25,360 --> 00:45:27,430 see imitative foraging in these birds. 683 00:45:27,430 --> 00:45:30,740 When one bird starts eating in a particular place, 684 00:45:30,740 --> 00:45:33,130 other birds just follow. 685 00:45:33,130 --> 00:45:42,050 And cooperative foraging, this is 686 00:45:42,050 --> 00:45:51,430 when you get birds flocking in order to more easily find food. 687 00:45:51,430 --> 00:45:54,460 And when it is find, you're more likely to see it 688 00:45:54,460 --> 00:45:56,900 because there's so many eyes looking for it. 689 00:45:56,900 --> 00:46:01,510 And then they;ll all get some, at least most of them well. 690 00:46:01,510 --> 00:46:04,310 So it's a great benefit in foraging. 691 00:46:04,310 --> 00:46:07,350 The similar things for pack hunting animals 692 00:46:07,350 --> 00:46:11,820 and the cooperation of ants, honeybee communication 693 00:46:11,820 --> 00:46:12,800 which we talked about. 694 00:46:15,540 --> 00:46:17,375 And large prey, of course, is a factor 695 00:46:17,375 --> 00:46:24,870 that encourages group hunting in the large carnivores. 696 00:46:24,870 --> 00:46:28,480 But I point out there at the end that chronic foods shortages 697 00:46:28,480 --> 00:46:33,810 like faced by the moose here in the northern part of New 698 00:46:33,810 --> 00:46:37,820 England and the adjacent parts of Canada 699 00:46:37,820 --> 00:46:41,340 where there's a lot of moose, it makes 700 00:46:41,340 --> 00:46:45,570 solitary, anti-social behavior lot more likely. 701 00:46:45,570 --> 00:46:52,000 OK, so I want to talk a little bit-- well, 702 00:46:52,000 --> 00:46:53,940 this'll be the last thing. 703 00:46:53,940 --> 00:46:55,800 I think there's a little bit more 704 00:46:55,800 --> 00:46:58,210 we'll talk about next time. 705 00:46:58,210 --> 00:47:02,020 Calculation of the inbreeding coefficient 706 00:47:02,020 --> 00:47:05,710 is also called the coefficient of kinship. 707 00:47:05,710 --> 00:47:07,340 We've talked about the importance 708 00:47:07,340 --> 00:47:15,120 of genetic relatedness in breeding and in behavior. 709 00:47:15,120 --> 00:47:19,650 Our own fitness can benefit by helping. 710 00:47:19,650 --> 00:47:21,710 I'm not talking about humans necessarily, 711 00:47:21,710 --> 00:47:24,366 but any animal will benefit if he 712 00:47:24,366 --> 00:47:26,920 helps animals that are closely related. 713 00:47:26,920 --> 00:47:33,750 So let's just look at Wilson's discussion. 714 00:47:33,750 --> 00:47:37,550 He calculates here the genetic relatedness 715 00:47:37,550 --> 00:47:41,427 of the offspring of the mating of two half siblings. 716 00:47:44,170 --> 00:47:47,710 Here's the two siblings, male and the female. 717 00:47:47,710 --> 00:47:50,877 They have the same mother, OK? 718 00:47:50,877 --> 00:47:51,585 Different father. 719 00:47:55,900 --> 00:47:58,500 This is the way you calculate that. 720 00:47:58,500 --> 00:48:00,310 Here's the individual. 721 00:48:00,310 --> 00:48:03,470 We know that here the probability 722 00:48:03,470 --> 00:48:10,830 that A and B are the same for anyone allele is one half. 723 00:48:10,830 --> 00:48:17,670 We know that the probability of A and A prime being the same 724 00:48:17,670 --> 00:48:18,510 is one half. 725 00:48:21,170 --> 00:48:24,840 We know that the probability of A prime and B 726 00:48:24,840 --> 00:48:27,340 prime being the same as one half. 727 00:48:27,340 --> 00:48:30,010 OK, so now we want to calculate the probability 728 00:48:30,010 --> 00:48:33,000 that B and B prime are identical. 729 00:48:33,000 --> 00:48:36,870 That's the coefficient of kinship. 730 00:48:36,870 --> 00:48:39,260 How related are you? 731 00:48:39,260 --> 00:48:42,540 Basically, how many genes-- what's the proportion of genes 732 00:48:42,540 --> 00:48:45,370 you are likely to share with the individual? 733 00:48:45,370 --> 00:48:51,590 And see how that's important in calculating inbreeding. 734 00:48:51,590 --> 00:48:52,090 OK. 735 00:48:52,090 --> 00:48:56,260 So to get that, you simply multiply the one half by one 736 00:48:56,260 --> 00:48:58,450 half, and half, you get one eighth. 737 00:48:58,450 --> 00:49:03,120 So basically one eighth of the genes, the probability 738 00:49:03,120 --> 00:49:06,830 that any one of them one allele is identical 739 00:49:06,830 --> 00:49:08,920 is going to be one eighth. 740 00:49:08,920 --> 00:49:10,150 OK. 741 00:49:10,150 --> 00:49:13,620 So now, here's what I want you to pay attention to. 742 00:49:13,620 --> 00:49:17,440 If we count steps backward from one parent to a common ancestor 743 00:49:17,440 --> 00:49:22,160 and back to the second parent, we get three here. 744 00:49:22,160 --> 00:49:22,660 OK? 745 00:49:26,430 --> 00:49:29,460 One, two, three. 746 00:49:29,460 --> 00:49:30,960 OK. 747 00:49:30,960 --> 00:49:35,870 So if we compute one half to the third power, 748 00:49:35,870 --> 00:49:42,000 we get that number, the inbreeding coefficient. 749 00:49:42,000 --> 00:49:45,400 This makes the assumption that A here is not inbred. 750 00:49:48,540 --> 00:49:50,710 That's called path analysis. 751 00:49:50,710 --> 00:49:54,380 Every possible path leading to every common answer history 752 00:49:54,380 --> 00:49:57,130 is traced separately. 753 00:49:57,130 --> 00:49:59,530 It's the same as the probabilities obtained 754 00:49:59,530 --> 00:50:01,380 from every separate path. 755 00:50:01,380 --> 00:50:04,600 Let's just take one more example. 756 00:50:04,600 --> 00:50:06,120 The full sib mating. 757 00:50:09,250 --> 00:50:11,200 Here are the parents. 758 00:50:11,200 --> 00:50:13,640 Here's two of their offspring. 759 00:50:13,640 --> 00:50:18,200 They both have the same two parents, OK? 760 00:50:18,200 --> 00:50:21,960 They then mate and have this individual offspring. 761 00:50:21,960 --> 00:50:24,890 So you followed the paths. 762 00:50:24,890 --> 00:50:32,520 This path C, A, D. Three steps gives you 1/8. 763 00:50:32,520 --> 00:50:38,070 And then C, B, D, the other path to the other common ancestor. 764 00:50:38,070 --> 00:50:39,610 You get an eighth. 765 00:50:39,610 --> 00:50:41,120 OK? 766 00:50:41,120 --> 00:50:42,830 You have to add those. 767 00:50:42,830 --> 00:50:47,250 So the probability in a full sib mating of getting the shared, 768 00:50:47,250 --> 00:50:52,460 the allele being the same at any one point is one fourth, 769 00:50:52,460 --> 00:50:57,320 which also means approximately 25% of their genes 770 00:50:57,320 --> 00:51:01,780 will have identical alleles. 771 00:51:01,780 --> 00:51:02,960 OK. 772 00:51:02,960 --> 00:51:06,490 And then you can calculate for a first cousin or a more complex 773 00:51:06,490 --> 00:51:07,450 pedigree. 774 00:51:07,450 --> 00:51:08,420 It always works. 775 00:51:08,420 --> 00:51:11,610 And I will post this file online, OK? 776 00:51:11,610 --> 00:51:13,370 That's path analysis. 777 00:51:13,370 --> 00:51:15,430 Very important in the kind of gene 778 00:51:15,430 --> 00:51:18,480 calculations done by sociobiologists.