Human Instinct

Every one of us possesses an armoury of instincts which keep us alive. We are often barely aware of them, but they act every day to protect us from danger and keep us fit and healthy. Babies alter the pitch and volume of their screams depending on how urgently they need help. In the first programme of the Human Instinct series we explore how this most basic of instincts means we're all born to survive. A Baby's Cry Within a few hours of birth, many animals are not only feeding but standing up and walking around. By comparison human babies are virtually useless. So the most important weapon in a baby's survival armoury is an astounding scream. It can reach 97 decibels - equivalent to a pneumatic drill. Babies alter both the pitch and volume depending on how urgent their need of help. The louder and more piercing the scream the quicker the response. With this simple tactic a human baby ensures it gets all it needs - attention, loving care and of course food. A Question of Taste Without food we die. But can our instinct to eat explain why we all crave fatty, often unhealthy, food? Like all our instincts, our appetites were formed millions of years ago. In this uncertain world, laying down fat was the perfect way to ensure against times when food was scarce. Robert Winston inspects a human parasitic roundworm. Our ancestors who craved food which was high in calories and rich in fat lived and passed on their genes to their children - those who didn't, died and left no descendents. Gradually, over millions of years, that craving for calories became instinctive behaviour. But there's an even more sophisticated side to our craving for food. We also instinctively know what is safe to eat and what is not. Our tongue has evolved to have 5,000 taste buds - letting us know what to swallow, and what to spit out. And we also have an instinctive reaction to things which could give us a disease or make us sick. At the London School of Hygiene an

The instinct to have sex is one of the most potent we possess. It’s vital if we are to produce the next generation. In this programme we find out what it is about the way we look, the way we smell and what we possess, that can attract the ideal mate. Salsa dancing is one way to express our deepest desires. The Perfect Date Our instincts drive all of us to have sex - and so potentially to have children. But the way men and women go about this is very different. Two actors were sent on to a London University campus with hidden cameras to ask a simple question: "Will you sleep with me?" One is a woman asking men and the other a man asking women. The results could not be more different. Just as in the original experiment (by Elaine Hatfield of the University of Hawaii and Russ Clark of the University of North Texas) no women said yes but three-quarters of the men thought it sounded a good idea. The difference in men and women’s approach to sex has an evolutionary basis. Each month a woman releases just one egg. Should this egg be fertilised she then has to carry the baby through nine months of pregnancy. It’s a big investment. In contrast a man has virtually limitless sperm available and could father hundreds of children in the same nine months. So it’s not surprising that women tend to be more choosy when deciding just who to have sex with. Men and women both want children, but they have evolved very different approaches to the mating game. A Match Made in Heaven When looking for a partner people instinctively respond to a whole range of signals. The simplest of these is body shape. For women, a narrow waist and wide hips are a sign of fertility and therefore prove highly attractive to men. Women are instinctively drawn to body shapes that signal good genes. So she is more likely to go for a man with wide shoulders and a narrow waist- a sure signal of both physical strength and a good immune system. But we also detec

We’re always competing, even when we least expect it. The will to win is an instinct that’s kept our species alive. In this programme we discover why coming out on top feels so great and why losing feels so bad. Humans are biologically programmed to get a kick out of winning. The Joy of Victory For our ancient ancestors, beating the opposition was important. It meant they were more likely to survive and have children. Those who got a kick out of winning were more successful and passed the desire for victory on to their children. So over generations our bodies have evolved to give us a feeling of euphoria when we win. A Constant Battle As young children we compete for the most useful resource available - our parents’ attention. At the University of Michigan, Brenda Volling asks parents to concentrate their attention on the older of two siblings. Immediately, the younger children try to force their way into the game. If they fail to get noticed they release a powerful and effective weapon: the temper tantrum. This invariably gets them their parent's attention. But when the parent plays only with the younger child things are quite different. The older sibling is far more likely to try to impress by following the rules, patiently waiting their turn, offering to help with the game, or even simply saying "I love you." One study suggests this difference in strategies continues into later life. Frank Sulloway studied historical figures in science. Larger, wider jaws and chins are one sign of a dominant face. He found that first borns were far less likely to be radical thinkers then their younger brothers and sisters. Scientific revolutions such as Darwinism are far more likely to have been started, and supported, by people with at least one elder brother or sister. Sizing up the Opposition We don’t have the energy or resources to compete all the time, so we have evolved hierarchies to avoid this. We are much more likely

A 200,000 year old jawbone tells the story of an elderly woman who was kept alive thanks to the kindness of her companions. Is this jawbone the oldest evidence of human kindness? From this first known example of human compassion to modern day heroes, the final programme in the Human Instinct series explores the most complex of instincts. The instinct to put others first. Blood Ties The mother’s drive to protect her children is the most powerful heroic instinct we know. Cindy Parolin showed no hesitation when she leapt to the defence of her 6 year old son. Attacked by a cougar, Steven was saved by his mother’s incredible bravery as she wrestled with the animal for hours while he was dragged to safety by his brother and sister. But what is it that drives this incredible behaviour? Having children is a way of ensuring our genes are passed on to the next generation. Humans usually have just one child at a time, so they are prepared to do virtually anything to ensure their children are safe. But this protective instinct also expands to the rest of our family. And the more genes we share, the more likely we are to put ourselves out for someone. In a unique experiment, scientist Dr George Fieldman proves this point. People will hold their breath longer for their parents, children or siblings - who share half their genes - than they will for their grandparents, uncles or aunts- who share only a quarter. People will hold their breath longer underwater for more closely-related family. Fast Friends But unlike many animals, humans are also willing to risk everything for people who aren’t related to them. Al Rascon received the medal of honour for his actions in the Vietnam war. He ran into a hail of bullets, risking death, to rescue his injured friend. How has this self-sacrificing instinct evolved? It appears humans have quite a lot in common with vampire bats. These tiny creatures must feed often to survive, and it is not that easy