[MUSIC] Welcome back. So last time we looked at studies suggesting that nurturing parenting compensated for a child's genetic predispostion towards unhappiness. But you may remember from last week's lectures that based on the context of a lot of studies that have followed twins throughout life as they were raised by separate families. And these studies showed twins continued to have many similarities even if they'd never met. While a study of 80 pairs of identical twins showed that 50 of all twins had over three times the epigenetic differences of three year old twins. Twins that spend their lives apart, such as those raised by different families, were most different in their methylation patterns. Showing that methylation markers change as we get older, and experience different environments. Well, the idea is that the environment plays a key role in shaping our epigenome, which in turn, influences the activity of our genes, which in turn, may shape our behavior, lifestyle choices, and health. Which in turn, changes our epigenetic profile, and so it goes on. Our epigenetic profiles mimic our individual life stories, and may be as unique as we are. However, IQ and personality become more alike as twins age, so what do we make of this? Science may be showing us that many personality traits are somewhat set, for good or bad, from birth. But a nurturing environment can rewrite some genetics in some people, because we have lots of genes that react to the environment. Well, that may sound a bit depressing if you did not get a nurturing environment. However, [UNKNOWN] of outlook on life is determined by epigenetics. Things may not be set in stone. If high stress rats were put in a low stress environment as adults, their epigenetic markers still manage to change a bit. Resulting in a more low stress animal. But unlike that, you can have some self awareness. Perhaps you can change your behavior, if you really, really try. You can choose to be attentive, even if your parents never were. And in reality, how important is it to be calm and controlled in response to stress? What would happen if one of those calm, happy rats were to stumble upon a cat? It'd be less concerned about danger, be more likely to die. Whereas, an anxious rat would be on its guard, and could better survive the hostile environment. So through her licking or lack of it, a rat is writing information on their pup's DNA that tells her pup something about their world, and makes them more likely to succeed. Likewise, it might be beneficial to human children, too, to know whether the world says yes to them, it's a friendly place. Or it says no to them, and it's wise to be anxious. They were born into war-ridden society of an inactive cortis or receptor chain and thus a guarded and anxious personality. Don't you think that could be advantageous for survival? So it seems our resilience to stress may be determined by our genetics, the environment, and upbringing, in a way that has been selected to be adaptive. Now, the relative contributions of genetics, the environment, and upbringing are going to be very hard to predict, through a few shared family effects. And these go in every direction. The studies I mentioned last week were showed that the effects of parenting have been exaggerated. Also confirmed a correlation between parental handling of adolescents, being harsh, lax, loving or indifferent, and, and later adolescent behavior. However, they found this was mostly due to the genes shared by the mother and child. These, as yet, unidentified genes are counted both for most of the mother's behavior to the children, and any subsequent antisocial behavior by those children. In [UNKNOWN] studies suggested that it is not so much the parent who influences the child, but the child's genes that influence the parents' response. Parents react to the child more often than the child reacts to the parents. It's also likely that when the parent child bond goes wrong, then this itself will lead to bad alterations in the epigenetics of genes are controlling the behavior, and emotional state of both the mother and the child. Well, that brings us to intervention programs, like The Nurse Family Partnership, the NFP, designed to provide parental advice to high risk folding family in America. Well-trained nurses visit mothers at least twice a month, and they offered advice and assistance. The results have been excellent. NFP trained mothers were four times less likely to neglect or abuse their children, and the nurse visited children had 50% fewer arrests and significantly lower use of drugs and alcohol. And it's extremely cost effective. So similar programs are being set up all over the world. But don't these successes all seem to contradict the genetic studies showing little influence of parenting? Well, twin studies that show antisocial behavior in young people linked to early environment, also showed them losing that behavior as they get older and finding a new environment. People pick an environment that suits them, given half a chance. And the environment that suits you may be, in large part, determined by your genes. Well, experts say that some of the NFP success comes from improving the social and the economic situation of the family, and the mother's ability to cope with problems. The experts also believe that changing the destructive relationship between the mother and child is key. So, basically, we're talking about teaching the parents to understand the child's needs, and presumably therefore, the child's genes. Well, as we've seen, kids with a certain forms of neurotransmitter gene alleles are more likely to be resistant to change, whatever the environment, no matter how bad. Whereas some kids react in an extreme way of good or bad, and these results could involve epigenetic changes. But the implication in this way of looking at things, that they might have been better to be one of the kids who is less susceptible to the environment Note in 2011, Jay Nopsky and Kevin Peavert proposed a change in perspective. Based on studies in the medical teams, they proposed that these neurotransmitter alleles, be thought of as plasticity chains. [INAUDIBLE] bond to the vulnerability genes. This means that if the worst behaving kids in a bad environment, those we predict to have the low activity [INAUDIBLE], short servatonin transporter in the like. If they were put in an ideal environment, they might actually rise above the less plastic kids in terms of social skills and IQ. Well, this hasn't yet been proven, but it must be the best hope of the NFP and other intervention programs. Let's get back now to something I told you about last week. In respect of a parents, there's a lot of evidence that the environment's chief influence on the personality of most children is through their peer group. Harris wrote a very famous article researcher back in 1997. She suggested that ancestral human beings reared their children in groups. So the natural habitat of the child was a mixed nursery. A nursery of children of various ages who probably segregated themselves by sex, and they still do. Children, therefore, don't see themselves as apprentice adults. They're not copying adults. They're trying hard to be effective and well liked children, which means finding a niche within groups of peers. Conforming, but also differentiating themselves. A lot of workers suggest that children from the age of eight specialize, and that this is genetically determined instinct. They want to be special. To this end, a child will try out roles, and find what he or she is good at. They'll become the wit, the scholar, the tough. The evolutionary psychologist Frank Sulloway sees each child within the family as selecting a vacant niche. If the oldest child is responsible, the second child will become a rebel. Even amongst twins, small differences in innate character are exaggerated by factors. There is the, the famous, famous and sad case of Laden and Laleh. They're Siamese twins. They are conjoined at the head, and of course, the two girls did everything together, eating, playing, sleeping, because they could never leave each other's side. Well, despite their identical genes and environment, Laden liked animals, while Laleh liked computer games. Laden was a talkative extrovent, while Laleh was shy. They died during surgery to separate them. They got into that surgery knowing that death was very likely, but they wanted lives of separate people. Tim Specter quoted the built-in individuality process of it works all our lives to make us more different than our companions. It's a tendency for human beings to distinguish themselves from their closest companions by building on innate propensities. So, if I was a practical, it pays to be cerebral. And perhaps epigenetic mechanisms are part of making us more unpredictable, and help us develop the individuality that's such a priority to us all. That would be very hard to test. Ideally, you'd like to take a batch of human clones and rear them all identically and see how their behavior and epigenomes turn out. We can't do that with people, but you can with mice. Now, mice aren't a perfect model, because as far as we know, they don't have an have an individuality process on. Mice aren't trying to be different from each other. But it turns out that they do end up different. In one experiment, published in Science in 2013, 40 genetically identical mice spent three months together living in a five story cage with lots of toys. Well, at first these genetically identical mice behaved the same. But over time, they began to have different behavior patterns. Tiny initial differences in the activity of a mouse, which could be due to chance, unequal [INAUDIBLE] with a toy, or meetings with other mice, which might in turn fuel a desire for more adventures. Some mice ended up a lot more adventurous than others, and these grew additional neurons in their hippocampus, which remember is a brain region linked to learning and memory. Epigenetics is the prime candidate for explaining these results. Tiny epigenetic differences change gene activity, which in turn sculpts interactions with the environment. Which then fades back to the epigenome, amplifying the message, which further influences gene expression, shaping behavior, and how we experience the world. So, I just used the word chance. Just chance as well as genes and environment contribute to of individuality. Unpredictably, unpredictability may be built into epigenetics. I mentioned that the epigenome of identical twins diverge over the years. And this is attributed to the environment. Something weird recently discovered, is that identical twins who share the same genes and womb can have epigenetic differences, even before they're born. Well how can that be due to the environment? They share the same womb at the same time. Well epigenetic variations could initially advise randomly, are from small physical differences in the womb. Perhaps one twin has a bigger umbilical cord for example. But Andrew Feinberg at Johns Hopkins University believes that random methylation events are built into our systems as an evolved feature, and that there are hundreds of regions of our genomes where methylation patterns are neither genetically determined nor set by the environment. They happened by chance, and these random epigenetic changes produced more variation in genetically similar offspring, increasing the chance of that some of them at least will survive. What this suggests is that many aspects of our bodies and behaviors are the result of complex interactions between genes and environment, mediated by epigenetics, and with a large dash of chance thrown in. Which goes to show how pointless it is to talk about nature versus nurture. [SOUND]
