[MUSIC] So welcome back. Now, I've brought up a couple of times the question of why evolution has left us with such a variety of gene variance and personalities. I once mentioned before that selection would usually reduce variation, and yet we still have a lot of variation in behavioral genes. But if we look at the dopamine and serotonin systems together, the optimum system is probably one of balance and that could be achieved with a mixture of alleles. So, being extremely happy, while on the other hand being extremely anxious and bothered are probably less optimal than the middle of being happy sometimes and anxious at other times. Anxiety plays a positive role in optimizing your ability to survive, particularly in some environments, but we don't live in a Stone Age environment anymore and its likely that alleles which seem disadvantageous today in our culture, they could have been adaptive under some circumstances. A lot of these gene variants are very old and as I mentioned with the marmots their frequency varies between populations, so perhaps they were favored in the past in some habitats. The low activity MAO allele apparently arose at least 25 million years ago, as it's also present in old world monkeys. It's been suggested that it might suit primates to have populations containing both warriors, that is more cautious, level headed individuals, with a high activity allele, and worriors with low activity allele. Well nowadays, unless your life is devoted to warfare or competitive sport, aggressive traits are probably less beneficial. But in the past, genetic predisposition for aggression, it might have been linked to competition, a fight for limited resources. Aggression may have been a useful trait to aid hunting, to defeat rivals, to impress females. A lot of other behavioral alleles that might be disadvantageous in our strange society, may be adaptive in other environments. It's been noted that during famines children with ADHD survive better, probably they're just more persistent at getting food. More puzzling perhaps is that 1% of people from all nations have psychotic episodes, sharing the responsible alleles of ancient. It's unlikely that psychotic episodes were more advantageous in the Stone Age than they are today, so perhaps these alleles in the right combination are beneficial. Many alleles associated with schizophrenia are also associated with intelligence, so that when you get the wrong combination of these alleles or you just get too many of them that you fall off a genetic cliff. Even with the wrong genetic combination, the environment is still going to have something to say about how they're expressed. What I suggest you do is look at some of the YouTube videos of neuroscientist, James Fallon. I've provided some things. He's a remarkable man of considerable fame and in himself provides a lesson on what it is to be a human. Fallon is an expert on psychopathy, who can identify clues by studying their brain scans, and of recently did he find out that he himself has the neurological and genetic correlates of psychopathy. Scans show that his orbital cortex is inactive, and that should be a problem if that’s the grey matter involved in social adjustment, and ethics and morality and the suppression of impulsivity and aggression, but to hold the difficulty he also has all the main gene variants linked to aggression including of course the low activity MAO allele. He screened his genome, and he underwent the scan after finding out from his mother that he has eight potential killers amongst his ancestors. Patsies mother was particularly concerned as Ezra Cornel, Fallons uncle from the 17th century, was hanged for murdering his mother. That was probably the first documented matricide in the United States. He was related to Lizzy Borden of whom you may have heard. Lizzy Borden took an axe and gave her mother 40 whacks, when she saw what she had done she gave her father 41. Well, so why isn't Fallon an axe murderer? Well as he says of himself, Fallon has quite a few psychological traits, traits often found in psychopaths, but he's not a violent man. So remember what we said about the impact of environment, particularly social factors, on determining how we turn out. Fallon believes he's not violent, because he lacks something common amongst killers, which is early exposure to violence and abuse. Dr. Fallon credits his upbringing in a highly nurturing environment, which was not only not abused, but he was showered with a wonderfully loving family support. He credits that, these positive chartered experiences with negating any potential genetic vulnerabilities to violence. Let's finish having a little chat about our animal friends, connecting that with us. Some social scientists don't like the idea that human behavior can be encoded in our genes, but the notion that animal behavior is in the genes is well accepted. Well when we think of domestication, we always think first of dogs. Different dog breeds have different behaviors. That is the point of dogs, that they come in different behavioral types, hence there breed names. There's Retrievers, there's Shepherds, there's Terriers, there's Bulldogs, there's Wolfhounds. You can't train a Retriever to guard sheep, it's been tried, so just how did we domesticate dogs from what was once a fearsome predator? Well, here's a wolf skull and as you can see, it's quite a long, low skull. It's got this relatively flat top here. The teeth are obviously very large, and the whole thing, you can look at it, the whole thing is quite navo. Now compare that with a domestic dog. This is a French bulldog. As you can see, the process of domestication has gone really quite a long way with this dog. The whole face now is very much shorter than that of the wolf, it's very much shorter. It's been contracted here towards the brain case, and the brain case is domed, it's got a much deeper front than the wolf skull has. Now, do you remember we took apart a very similar process didn't we, when we compared human with chimp skulls. You remember, that chimps are to a very considerable extent, or humans, beg your pardon, are to a very considerable extent, sexually mature baby chimps. You might also remember we call this process paedomorphism, which means that the adult retains infantile or juvenile features. Or likewise adult dogs, retain many of the characteristics of the juvenile wolf, including short broad skulls and that juvenile behavior traits such as whining and barking, and submissiveness. Now interestingly, a similar consolation of juvenile features is also seen in the domestication of other animals such as cows and rabbits. You get dwarf and giant varieties. You get piebald coat colors. You get curly hairs, curly tails, and floppy ears in most domesticated animals. Well that brings us to over 60 years of experiments in Russia, involving domesticating the silver fox. The greeting project was started in the 1950's by the soviet scientist Dimitri Belyaev. He selected for tame foxes by killing all nervous and aggressive ones, turned out he was selecting for paedomorphism. That's because he was selecting for juvinilized foxes, but those adults retain the playful and trusting nature of puppies. Out of 25 generations, the juvenilized foxes not only had playful behavior with people, they also had the floppy ears and short snouts. So the new foxes wag their tails when they're happy, they vocalize and bark like domesticated dogs. They've developed color patterns like domesticated dogs. They've lost their musky fox smell. Now in the wild foxes, in wild foxes the hormones involved in stress called corticosteroids rise sharply in young adults. Levels are much lower in the tame foxes, they have a lot more serotonin, which probably helps them stay calm. To emphasize, none of these features of hormones, cotevires were selected for a whole suite of physical and behavioral changes that you see when you compare dogs to wolves, were quiet in foxes, by selecting that single behavioral trait, tameness. So an ancestor will not in fact select for each of these traits individually in wolves, you get a whole lot of stuff for free, when you select against aggression. When selecting against aggression you're favoring juvenile traits, because juveniles and infants show much less aggression than adults. So basically, you've frozen development and now have an animal as an adult that looks and behaves much more like a juvenile. Then of course later, people can directly select from attributes they like, by breeding together the ones with curly tails, or snub noses, or the herd animals because they behave like three quarter grown wolves that nip at the ankles of prey but don't attempt to kill. Over the last few hundred years we've taken dogs infantile features and we've emphasized them even further for selective breeding. We've created hundreds of breeds to fulfill different roles, but some of them, are bred purely for their looks. This kind of breeding really tells us a lot of course about what kind of people we are, what it is that we like about dogs. We've inborn to appreciate the young. Our pet dogs have the very symmetrical large eyes, conspicuous face, that bring out the feelings we have of infants. Now an interesting feature is that the domesticated foxes, like most domesticated animals, have smaller brains than their wild progenitors, and prematurely start development of Area 13 which is a late developing part of the limbic brain that establishes adult emotional reactions, such as aggression, where humans also have unusually small Area 13's. Surprisingly, following several million years increasing brain size, in the last 10,000 years, our brain sizes have declined, from an average 1,567 cubic centimeters to 1,248 cubic centimeters. Limited nutrition in agricultural populations may have been a factor in this shrinkage. It's also been suggested that when we started to live in over crowded urban environments, the more aggressive and impulsive, hence more developmentally mature, bigger brained people may have been selected against. Quite a few geneticists, including Jim Watson of Watson and Crick fame, think we may be self taming ourselves. In 2012, Gerald Crabtree of Stanford suggested that our intelligence, as well as our brain size has been declining. He thinks the peak was about 7,000 years ago, but now he doesn't relate this to our domesticating ourselves. His argument is based on the idea that for most, more than 99% of human evolutionary history, we have lived as hunter gatherer communities, surviving on our wits. Well she suggests that's the evolution of big brained humans, however, since the invention of agriculture and cities, natural selecting on our intellect has effectively stopped. This suggests that this has allowed mutations to accumulate in the genes, which has endowed us with our brainpower. A comparison of the genomes of parents and children have felt that on average there are between 25 and 65 new mutations occurring in the DNA of each generation. You may remember from an earlier lecture, it averages at 36 mutations. Well Crabtree's analysis predicts about 5,000 new mutations in the last 120 generations, which covers a span of about 3000 years. He then estimates that over this time we've all sustained genome mutations harmful to our intellectual and emotional stability. This is a quote from his paper, a hunter gatherer who did not correctly conceive a solution to providing food or shelter probably died, along with his or her progeny, whereas a modern Wall Street executive that made a similar conceptual mistake would receive a substantial bonus and be a more attractive mate. Or in other words, the consequences for being stupid were much worse in the Stone Age. Essentially, Crabtree's saying that the fruits of science and technology have enabled up to rise above the constraints of nature, so it didn't matter if we dumbed down. Well from Crabtree's point of view, the good side to this is that judging by society's rapid pace of discovery and advancement, future technologies are bound to reveal solutions to the problem. We're not gonna end up as couch potato man trapped watching soap operas without knowing how to use the remote control. Crabtree's ideas have been critiqued quite heavily as you might expect, because even though our brains have got smaller, that doesn't necessarily mean we're not selecting for intelligence in other ways, as it's quality of wits rather than quantity that counts. That seems to be true for the hobbits that I mentioned last week, the little people who lived in Indonesia up to 12,000 years ago. They had brains small even by a chimpanzee's standards. Here's one of those hobbits and here's the chimpanzee, basically same sized brains, perhaps the hobbit even slightly smaller brain, and yet the hobbits were still capable of making sophisticated tools and they used fire. So another issue, is that Crabtree's focusing on natural selection. Well aside natural selection, Darwin had another big idea, and that was sexual selection. Well what if intelligence didn't just evolve to aid survival, but also to aid sexual success. One of the great surprises for David Bus, who's one of the leading evolutionary psychologists studying mate choice, was that when he did his study of sexual preferences in 37 cultures all around the world, he found that in every single culture, the top two most desired qualities in a mate for both sexes were kindness and intelligence. This psychological trace outweighed physical appearance, money, even status. We don't know how long these traits have been select for, but Geoffrey Miller at the University of New Mexico proposes that perhaps one of the reasons that we are so smart and so relatively trusting and kind to each other is that our ancestors, who were smarter than average and kinder than average, attracted more mates, and higher quality mates. You may have pulled up sharp at the thought of us being kind to each other, but think of the thousands of people who compress into football stadiums. They're strangers to each other, yet they bop along quite well, or thousands of chimps together like this and there will be slaughter. Well, of course trouble can break out between rival supporters of different teams. Here and elsewhere, there's evidence that we have great within-group cohesion, even if we can still be very aggressive to outside groups, and for continuing popularity of war. So, perhaps the solution to our problems is to increase the scope of who we think is within our group. It would really help life enough a lot if we could include other species in the group, as well as our own. Yay!
