Eyewitness II; #113; Skeleton

Presentation of this program was made possible by the Corporation for Public Broadcasting and by annual financial support from viewers like you. [musical intro] Hidden inside every one of us is a structure essential to life. Yet

when glimpsed it can fill us with deep fear. [inaudible] As varied in shape and size as all the creatures across the face of the earth. [music] Fish, birds, Amphibians and reptiles, and mammals... all have what we commonly think of as a skeleton. An internal frame of bones on which the soft body hangs.. the endo-skeleton. The skeleton supports the body, anchors the muscles, and forms a hard shield for the vital organs. It permits movement, feeding, procreation.. life itself. An elephant's thigh bone is a hundred times bigger than a vole's, yet

both, like mole and monkey, hedgehog and horse, share the same design of bones. The spine, rigid yet able to bend dramatically, supports the entire body from the limbs, which gets [inaudible] movement, to the cage of ribs protecting the heart and lungs, to the skull, casing for the brain and the vital senses. It's a design which includes what is to us the most interesting skeleton of all- our own. The human skeleton begins life with over three hundred bones, which slowly fuse into the two hundred and six bones of the adult man or woman. A body that can grow to almost nine feet - so tall that an ordinary table is at knee height, or remain so stunted it could ride a spaniel as a horse, and with a skull which guards the only brain capable of studying itself. The skeleton. Foundation of the living body. [music]

An image of its death. It's a cause for mockery. [laughter] As Winston Churchill said of a rather gaunt rival: 'I've seen better looking faces on a pirate flag'. The skull and crossbones: emblem of danger, from pirate flags to poison bottles. [carnival music] But occasionally this set of rattling bones is an invitation to the carnival, to come and laugh at death - a symbol of freedom from earthly cares. Every creature on Earth reveals its style of movement with it's skeleton. [birds squawk] The enormous thrust needed to help a bird take off and fly comes from its chest, a breast bone with a huge keel to anchor the powerful wing muscles.

In land animals movement comes from the rear. The hips and pelvis, connected to the spine, transmit the thrust from the hind legs through the entire body. This is true whether the action is running at great speed, leaping across rivers, [water sounds] or bounding over long distances, or just dealing with an inconvenience. [music] Yet what about fish, which have no legs or wings? Here, a flick of the tail pushes the water back, driving the fish forward; and since in water they carry no weight, fish bones are light. For animals which do have hind legs the tools on the end of them can have a multitude of uses.

They can kick out as weapons. Or kick water like paddles. [water sounds] They can grip like pincers. Hook a fish clean out of water, Or in the case of the Ibex, find footholds on almost vertical rock. They can be flat shoes that carry the animal at great speed. Some animals can stand on their hind limbs, if only for a few moments. For humans, this posture is a way of life. We have a spine originally designed for an animal that travels on all fours. By standing upright, our spine has modified to an S shape, so the body is balanced over the legs and feet, and the weight carried

on the thigh and the shin - the largest and strongest bones in the body. [wind sounds] Powerful and resiliant. [music] Moving on the hind legs alone requires a highly tuned sense of balance, and makes possible a whole new range of movement. Movement begins at the hip, a classic ball and socket joint combining strength and mobility. Further down, the knee acts as a hinge, allowing the lower part of the leg to move forwards and backwards. And at the bottom, the ankle

and the heel tilt the foot downwards for thrust against the ground. Hips, knees, ankles work in perfect harmony, moved by muscles, controlled by the brain. There are times it does help to have someone pulling the strings. [music] The skeleton has taught us almost everything we know of the evolution of life on earth. For the skeleton is the body's most enduring element and its permanent record, sinking at the depth to the bottom of river, lake, sea or swamp, to be transformed over millions of years into rock. Fossils: the only clues we have of

our early ancestors, from [inaudible] to dinosaur, from fish to mammoth, to the primitive humanoids, and so to ourselves. (music) In all air-breathing animals the lungs need strong protection, yet enough freedom to expand. The ribs - a flexible cage with joints on the front at the breast bone and at the back anchored on the body's central pillar: the spine. A column made up of a row of linked bones: the vertebrae, from nine in a frog to 400 in some snakes. The spine runs from the tip of the tail, if an animal has one, right up to the twisting and turning joints at the base of the skull,

though from shoulders to head can be some distance. Each vertebrae can move only a small amount in relation to the next one. But over the whole length, the movements add up to great flexibility. Far more common than a long neck is the extension of the spine in the other direction: the tail. Used by many creatures for balance, an extra limb, or to just flick away flies. And in evolving from a horizontal support to a vertical column on two legs, the human spine has lost none of its flexibility, at least not in the young and very fit. [music] Bone itself can be pliable.

Whale bone has been used for centuries, most notably in corsets, tightening women's waists into tiny circles, sometimes no bigger than a saucer. Light, certainly. But it's lack of elasticity caused circulation problems, fainting fits, even fractures. Bone is a remarkable material. Active living tissue with nerves and blood vessels. And a center honeycombed with holes that reduce weight. Some bones have marrow, which produces blood cells, and all bones store minerals for the body. Indeed, without minerals, bones can bend like rubber. And when a bone is broken it has the extraordinary ability to mend itself, although sometimes it does need a little help.

But there is another kind of skeleton, not made of bone and not on the inside of the body. The vast majority of animals have an external suit of armor which surrounds and protects the soft boneless body: the exoskeleton. Some exoskeletons had even changed the very shape of the land. Coral reefs and islands are created by billions of tiny marine polyps, living together in communities. Each animal makes its own chalky exoskeleton and as it dies the skeleton remains, fusing with others to form a growing mass of coral. [waves crashing] (wave sounds) But the most common form of underwater skeleton is also the most effective. The shell. The simplest shield. and a powerful protector. People have always been fascinated by the beauty of the shell, and have used this simple

skeleton for an extraordinary variety of ornament and decoration. The crab, like lobsters, shrimp and other crustaceans, has a softer shell, and joints covered in tough skin. Water reduces shell weight, so that these creatures can grow larger than those on land, but their shells are rigid and cannot expand. In order to grow they have to shed the old skeleton. The crab finds a safe place to hide, sometimes literally under the protection of its mate. Until the news skin hardens it will be highly vulnerable. The old skeleton splits down the abdomen, and the crab falls out backwards, leaving the shell behind.

It is this sense of regeneration and growth which has made the shell into a symbol of birth and renewal. Renaissance art expressed this in Venus rising newborn from the shell of a scallop. For deep within the shell, there is a sense of power and eternity, and always the sound of the sea. (music) Land animals with exoskeletons also need to shed their casing to grow. Here the building material is [inaudible], hard, flexible, and highly adaptable. Some creatures can bend enough to perform surprising feats of self protection, curling and uncurling by stretching their dorsal segments. Other animals have even more external protection.

Turtles have endo skeletons, but with a bony outer shell. They enjoy the best of both worlds, plus enormous strength. All skeletons cover the most vital body parts, and survival depends on the strength of the covering. Yet however strong the shell may be, survival isn't guaranteed. [birdsong] The thrush beats a snail against the stone anvil until the shell breaks. It is not only the shell which needs to be strong. The bird's skull has to withstand these jarring impacts. [woodpecker pecking] The woodpecker has taken this to extremes. With a tremendously strong skull and beak, it hammers through the bark of a tree to find insects, and it can be heard three miles away. Yet there are skulls which take far more powerful blows without flinching. The skull of a musk ox is reinforced by shock absorbent bone,

Which is fortunate, since each of these animals weighs nearly half a ton and could smash straight through the brick wall of a house. The skull reveals more about an animal than any other part. Weight, size, shape, and position of the organs tell us how well the creature sees and hears, what it hunts, and how it survives. The skull is a blueprint of lifestyle. It is perhaps because the skull is essential for survival that people have put it to so many uses: cultural, practical, and superstitious. Ceremonial drums have been made from the skulls of the vanquished warriors of rival tribes, just as the Norsemens' custom of drinking from their enemy's skulls has led to the Scandinavian drinkers greeting: 'Skal'.

The skull traditionally harbors the soul. So the holy Tibetan lamas drink from ceremonial skull cups, a symbol of consuming another's mind. [chanting] Many 19th century doctors believed in phrenology, the so-called science which taught that a person's character could be read from the shape of their skull, each area governing a part of the personality. Queen Victoria had the skull shapes of all the royal children analzyed. Even today, people may respond to odd behavior by exclaiming, "You need your head examined!" No part of the skull reveals as much about lifestyle as the jaws and teeth. From vegetation-eating animals with jaws that move up and down and

sideways, to the rodents' large sharp front teeth for gnawing, and the strong thick jaws of the lion with a huge muscle that runs from the front to the back of the skull, giving it the most powerful bite of all the animals. Yet the strength of some birds beaks is just as awesome. The Scarlet Macaw can crack open rocks to get at vital mineral salts. But the most unusual jaws belong to the snake, with joints that unhinge and spread to an opening up to eight times the size of the snake's head. That's equivalent to a man swallowing a German Shepherd Dog whole. The snake's muscles are powerful enough to crush the skull of its prey. The skull is the body's strongest bone

structure, protecting the organs of sight, smell, taste, and hearing, guarding the vital entry of food and oxygen, and encasing the most complex control center ever known. The eyeballs and the air channel are both well shielded by the bones of the face, While the highly adaptable jaw bone helps the 32 teeth chew their way through half a ton of meat and plants each year. But to the human mind, the sight of a skull does represent a threat. No part of the body is so full of mystery. Our instant repulsion when coming upon such a clear vision of death is linked to the instinctive urge for survival. Only the elephant is likewise fascinated by and afraid of its own bones, perhaps not surprising since these creatures have been systematically slaughtered and their skulls desecrated for one special part: the tusks. Made of ivory, these highly modified teeth serve both as tools and weapons,

and not only in elephants. The male Barbarossa pig has four tusks, two of which actually grow up through the roof of its mouth. Ivory is the most widely used skeleton material, adapted to every imaginable ornament and artifact. Skeletons in their many forms are all around us, yet they still terrify us. Like the skeleton in the closet, placed there by an evil husband who forced his unfaithful wife to kiss the skull of her former lover every night. In many cultures the human skeleton has become a powerful symbol, an omen. The mere sight of a skeleton is a vivid reminder of our own mortality. In the fortune telling tarot deck, the most feared card is Death.

The skeleton is the monster conjured up to frighten enemies. (music) The leader of the Dance of Death. The Grim Reaper. The dreaded hunter of souls. Yet these images in art have themselves been created by a skeletal part- the hand, or [inaudible], is more elaborate and refined in humans than in any other animal. From the front fin of the earliest fish, it has evolved into the widest possible range of implements, from flippers, rippers,

and paddles, To paws, [inaudible] And hooks. And even to the 13-foot wingspan of the albatross that carries it all around the world in three months. The closely related moles and bats have forelimbs, which have taken opposite paths, one digging into the earth as the other lifts it skyward. That first fin has developed into the human arm and hand, [piano plays] The most versatile and sophisticated instrument on earth. A series of multi-purpose connected joints, ending in a set of fingers, enabling us to perform a greater range of tasks than any mechanical tool. [piano continues] The hand that has passed down to us knowledge. a record and understanding of

ourselves, that has [inaudible] celebrated life and death. Every year the Mexican people shrug off the traditional fear of death and its image. They rejoice and mock and embrace it as a part of life itself. The Day of the dead. Tribute to the departed. To the past. And to life. And this joyous celebration transmits to the world the skeletons ultimate message: That death comes all too soon so drink deeply of the cup of life while it is still full. [musical outro] Presentation of this program was made possible by the Corporation for Public Broadcasting and by annual

financial support from viewers like you. To order a video cassette of this Eyewitness episode call PBS video at 1-800-828-4PBS. Or write to the address on the screen. This is PBS. The modern photographic techniques used in the Eyewitness series bring the animal world to life on the pages of Eyewitness Natural World. Companion book to the Eyewitness series, Eyewitness Natural World is published by Dorling Kindersley. The price is $29.95 plus $5.95 shipping and handling. To order this colorful and informative visual guide Call 1-800-440- 2651. Credit cards are accepted.