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For nine months, the baby's been fully equipped for life in the warm liquid world of the womb, relying on its mother for food and oxygen. It's in for a rude shock. As the baby is squeezed down the birth canal, dramatic changes have to happen. The key to success is the trauma of the birth itself. It's so severe; the baby has adrenalin levels even higher than that of a person suffering a heart attack. This rush of adrenalin wills kick-start the baby's breathing. Well done, that's brilliant. Here he comes. Yet even now during birth, the baby's windpipe and lungs are still full of liquid from the womb. If they aren't quickly emptied, it will drown. The fluid drains away as it's absorbed into the lung walls. Air rushes in. Life-giving oxygen can enter the blood vessels of the lungs. The first breath triggers further upheavals inside the tiny body. That's it, Jane. Well done, sweetheart. Well done. Excellent! Well done! Well done. Remarkably, even at this late stage, the heart of the baby is not yet ready for life outside the womb. In one of the interior walls of the heart there is a hole. This opening was vital when the baby had to pump blood to the placenta. Now it's a liability. Blood flowing through a newly-opened vessel will slam shut a flap of tissue to seal the vulnerable hole? It forms a solid wall, and the four chambers of the heart are finally complete. In an adult, such major changes would require open-heart surgery, but here they are happening instantaneously and unseen inside the baby. This is the miracle of birth. Now we'll cut his cord. Can Richard cut the cord? It's a boy - Bob. The umbilical cord, the last link to his mother, is cut. Bob's first challenge is to keep warm. A heat-sensitive camera reveals the coldest parts as blue. Bob's toes and nose suffer most. The delivery room is 15 degrees colder than his mother's womb. He looks fine. Yes! A special type of fat is concentrated on his back and around his chest. This baby fat can be broken down to release emergency heat. But for the first six months of life, Bob's ability to control his temperature is very limited. For the moment, he relies on blankets and cuddles. He's shivering a bit. You see his little lips going. He's cold. A little bit cold. He looks...dark hair, yeah. Those little marks will be gone by tomorrow. It'll take no time at all. It was all a bit of a push. Bob's tight squeeze through the birth canal has left his head an odd, pointed shape. His skull is so pliable because the 22 different bones that make it up haven't yet fused together, leaving holes between the bone plates. Bob would never have made it out of the womb if his skull hadn't evolved to be this way. From now on Bob will live under the watchful eye of his proud parents, Jane and Richard Jeffers. His hazardous journey into the world is over. Thanks, Richard. That's brilliant. There we are. Just pop him down here. It's just amazing to see that he's perfectly formed in absolutely every way, his arms, and his legs. He's got quite a tidy little nose. He's got a nice mouth. He's got quite a wide mouth. Everything is just perfect. It's just a miracle. You don't see that they're wrinkled up and all those other things. His face looks really quite well established for a small baby. He's got a lot of character. In a strange sort of way, he looks like a little old man. Although Bob is helpless, he has a fantastic survival strategy. Parents find their new baby irresistible. Oh, Bob. Is that nappy bothering you? They do control you to a point. Their demands are paramount. If they cry and want feeding, you've got to do that. You can't ignore their needs, because they're dependant on you. This is the best bit, isn't it? A bit of fresh air to that bottom. It's almost as if Bob has put his parents under a spell. You're just too good to be true Can't take my eyes off of you You'll be like heaven to touch And I want to hold you so much At long last love has arrived... Bob's first picture. You're just too good to be true can't take my eyes off of you Over a period of six months; we followed Bob's rapid development. Just a few weeks after birth he was a bundle of reflexes, a handy set of automatic responses that help him survive. Can he hear you? Yes, he's startled by loud noises, and he can definitely hear me. A young baby will try to grip with his hands anything he touches. Young apes grasp on to their mother's fur. But even in hairless humans this grasping reflex can be useful for holding on. I'm just going to check his reflexes. A reflex is activated by any touch to the palm. Here, the baby's hand has grasped a finger. Inside the hand, you can see the muscles that even just after birth can support the weight of the baby. Ironically, the hardest thing for babies to learn is to let go. Their fingers have to be prized open. And Bob's toes will try to grip as well, a throwback to our ape-like ancestors who held on to things with their feet. These reflexes are completely involuntary. They require no more conscious control than the contraction of the eye's pupil to light. Are you ready? Ready for your milk? Another reflex helps Bob find food. Although he doesn't know where food comes from, whenever something brushes his cheek he automatically turns his head from side to side and parts his lips. This is the rooting reflex. He just finds it himself. He'll find it. You just need to put his head somewhere remotely near, and he's there. And that's not all. The milk that's produced in the mother's breast can be activated merely by the sound of the baby crying. So a team in London is finding out what's going on inside the head of this baby girl to see how she does it. You're a very good baby. Very smiley. They measure the electrical activity in the brain when she looks at different faces. A baby's brain is nowhere near finished. New connections between the hundred billion brain cells are being made all the time. Throughout babyhood, the brain is sculpted. So our experiences in our first few years will determine the brain we have as adults. This developing brain is so demanding that over half of all the food Bob eats goes to driving it. To supply this much energy, it is essential that he moves on from milk. To deal with solid food, things are stirring underneath his gums. His first teeth will grow up from tiny tooth buds that have been hidden in his jaw since long before he was born. But they won't start to burst through his gums until he's around six months old. For the first time, over 40 days, this dramatic event has been filmed. No wonder babies cry when their teeth come through. At birth, Bob was a tiny bundle of reflexes and flailing limbs. Over the following six months, he has grown quicker than he ever will again. He has more than doubled in size. But he hasn't just been putting on weight. What is less obvious is that his mind has matured. For the first time, he can control his hands and reach out to grab objects. He is turning his desires into actions, a sign of his burgeoning personality. A baby at this age is soon ready for the next key advance: mobility. One stage ahead of Bob is Zak Troullous. Zak is already seven months old and lives in London. Over the next few months, he'll take his first steps and speak his first words. But for now that's all in the future. He seems to be developing very normally. And that's great. Has he tried to pull himself to stand or anything like that? When he's sitting down, he goes forward or falls on his face. So he's a bit scared. Right, it's a good time now while he's sitting to think about making sure that the environment is safe for him. Because everything tends to go straight from hand to mouth. He's trying to chew his shoe. Zak's mouth is the most sensitive part of his body. The tongue is teaming with nerve endings. That's why babies are so keen to use their mouths to explore the world. But Zak's scope for exploration is limited. He still relies on his parents to get around. Things will have to change. We normally associate crawling with reptiles. Think of the sprawling waddle of a lizard. But it's actually a powerful way of getting around. All movement of the human body is surprisingly complicated and difficult to analyze. But in order to understand motion, analysis is what you need. That's what these little markers are all about. They can be tracked on a computer to reveal the underlying motion of my skeleton. It's the only way you can follow something even as seemingly simple as the movement of a limb. Dozens of joints and bones moving in harmony. Even a clapping stickman is characteristically human. This baby is doing the diagonal crawl, moving opposite limbs together, and right arm, left leg, then left arm, right leg. The arms absorb the shock of impact, while the power is provided by the legs. The top speed of a crawling baby is about two kilometres an hour, and the average baby crawls perhaps 200 metres a day. If you look carefully, motion capture can identify seven different types of crawling. The elephant crawl is where just one limb is moved at a time. But the diagonal crawl is the most popular. It's extremely efficient, combining stability with speed. This crawl takes a while to perfect, as Zak is finding out. He's crawling slowly. But he's still got that wobble. As each day goes by, he gets better. Bad coordination. Once he gets that... He needs a bit more confidence. Before I put him down, I gather a few toys, and I go into the kitchen for a few minutes. I know he won't move. But now, because he's crawling, he's going to the stairs. You've got to keep an eye on him every second of the day. Until he started crawling, Zak had no fear of heights. Now he is increasingly wary. We're gonna put your weights on. At a university in America, Karen Adolph experiments with crawling babies to discover how they deal with treacherous slopes. As a further challenge, the babies are weighed down with two kilograms of lead. They then meet the apparatus. Mother tempts her daughter from the other end of the ramp. Come on, Natalie! Once she's scoped her target, the baby visually assesses the slope. She confirms the severity of it with careful touches of her hands. Karen has discovered that they can gauge the angle of a safe slope to within just two degrees, a tiny fraction of the slope overall. If they decide it's a bit too steep, they'll adjust their crawl, maybe even coming down backwards. Crawling is not just about how to crawl, but what's sensible to crawl down. If its way too steep, the baby will wisely avoid the drop altogether. However, the real revolution in getting around is still to come. Zak, are you gonna walk over to Daddy? Are you gonna make it? Zak is 11 months old. He's about to express what human beings have felt throughout 3,500,000 years of evolution: an overwhelming desire to rise up on two feet and free the hands. Can you walk to Daddy? Zak already has the strength to stand up with a bit of support. But his ability to walk comes not just from his legs, but also from deep inside his ear of all places. At the end of the ear canal are the bones we use for hearing. Behind these is the balance organ. The balance organ is a miracle of engineering, made up of three circular tubes full of liquid. Anchored to the inside walls of these tubes are tiny hairs. Zak is a new-experience junkie. As eating is food for physical growth, so experience is food for brain development. Oh, where's it gone? It's gone! Zak may be walking, but he faces another barrier to further progress.
Imagine what it's like for an infant to understand so very little of what's going on around it to feel lost and excluded from the social world. The closest we get to it is a holiday abroad. These are too old. I want something new. Trouble is you can only get so far with mime and pointing. Can you take me to the pyramids, where the kings are buried? As a child, one thing you lack is an accurate way of explaining your desires, exactly what you feel, what you really want, or any way, really, of telling your parents what to get for you. What you need, of course, are words. Every human culture has depended on them, be they spoken or written, like these hieroglyphics. Words and language is the most important thing a child will ever learn. Not just words to describe things you can point at, like sand or rock, but words to describe abstract things: your past, your future, your fears, your hopes; words to describe discoveries and ideas, to communicate them to other people down the generations, ever expanding the wealth of human knowledge and experience. The whole world we have built is built upon language, and yet it all begins so simply. Mama. It seems a miracle, but 15-month-old Zak can begin to master the complex power of language, an infinitely flexible symbolic system, and yet still needs nappies. Bravo! Even more impressively, Zak is teaching English and his parents' other language, Greek. When babies first learn to speak, they use a completely different part of the brain from adults trying to learn a foreign language. That's why it's so natural for babies and such an effort for adults. But it's not just Zak's brain that gives him his power. But with the larynx so high it can't perform its major function in life - speech. By the time Zak is a year old, the larynx needs to have dropped a whole three centimetres lower. Where's Mummy? The lowered larynx now lives up to its other name, the voice box. With more space at the back of the throat, the voice box can make an extraordinary variety of sounds. As air passes through the gap between the vocal chords, it causes them to vibrate. The tighter the chords are, the higher the pitch. And the final sounds are shaped by subtle movements of the tongue. To create just one recognizable word, Zak has to coordinate over 30 different muscles. Mummy, Mummy! Daddy! Yeah, you're in the water. Cold. Unfortunately, this lowered voice box makes humans especially vulnerable to choking on food.
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As a species, however, this occasional problem is outweighed by the power of language. The human larynx has evolved so that the way it changes suits each stage in life. Zak can finally communicate. The quicker they learnt language, and the better they understood the warnings, the more likely they were to survive. In just the same way that a clam has evolved a tough shell to protect it, we have evolved language as our defense. Guys, you need to be careful of the water! Come back up here! But language is not just a simple one-off trick like the clam shell. Its power and flexibility are unique.
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Its given rise to our rich social world, delivering us a decisive advantage over other animals. Alongside language, children learn another skill, a skill adults rarely give much thought to. You and I know that this is me, but we also know that this is me, too. It's so simple it sounds silly. But, in fact, though we take our ability to understand mirrors completely for granted, we're one of very few animal species that has the slightest idea what's going on with them.
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A monkey can't recognize itself in a mirror. But a chimp can. Interestingly, it's a skill humans are not born with. 14-month-old Julia ignores the red dye painted on her nose. She fails to recognize the reflection is her, because she doesn't yet have a proper sense of herself. Julia lacks self-awareness. Unlike Moira, who's over a year older? Yeah! Look at those pretty things!
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