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00:00Behind the coral reefs of an ancient sea, dawn breaks softly on a quiet lagoon.
00:12Along the shoreline, tropical groves teeming with life are beginning to stir.
00:25On this day, the forest will awaken to the cries of a newcomer.
00:37Archaeopteryx, the world's oldest bird.
00:51150 million years ago, the descendants of creatures from the land and sea first took to the skies.
01:01Today, more than 9,000 species of birds inhabit the planet.
01:07Their plumage, a masterpiece of design, granting them perhaps the ultimate freedom, flight.
01:17The origin of birds, even today, is somewhat of an evolutionary mystery.
01:23But Archaeopteryx may have offered scientists a key.
01:33The origin of birds, even today, is a very unique.
01:43The origin of birds, even today, is a very unique.
01:49VIOLIN PLAYS
02:19VIOLIN PLAYS
02:49VIOLIN sorta, just 50 years ago.
02:51For eons, only one giant supercontinent stretched across the planet.
02:56Now, as it slowly divided, distinct bodies of land were being shaped into the continents
03:04that would eventually become Eurasia and North America.
03:13At the time, the dinosaur was king.
03:17Animals of epic proportion roamed throughout North America.
03:22Animals feasting on lush forest land that spread from coast to coast.
03:30But to the east, a completely different scenario was unfolding.
03:35Situated much farther south than it is today, Eurasia was largely underwater.
03:49Two islands with palm-like ferns dotted the coastline.
04:02In the Jurassic period, the sky was the domain of the so-called winged lizard, pterosaur.
04:10It was the first vertebrate to fly.
04:19Pterosaurs probably descended from small reptiles or dinosaurs, forming the first successful
04:25line of flying creatures.
04:34How animals like pterodactylists learned to fly is unknown.
04:41Developing a lighter skeletal structure than land-bound vertebrates was the first step,
04:46and an arm with one extremely elongated finger to support a large single wing.
04:55Its wing had no feathers, just a large fibrous membrane.
05:00Folded compactly, these giant wings allowed pterosaur enough mobility to climb trees.
05:09Hollow bones with sturdy but light weight support were another new evolutionary design.
05:20Pterosaurs flew like gliders, soaring on the tropical currents along the shoreline.
05:31Sharp-eyed hunters, they scoured the coral reefs and lagoons teeming with fish, mollusks,
05:37starfish, and other sea life.
05:40Fighting prey, they swooped to the surface and with their long beaks escaped with their catch.
05:50But while the pterosaur reigned sovereign over the skies, another attempt at flight was underway.
06:05The rolling hills in the Bavarian countryside of southern Germany were once covered by tropical lagoons.
06:16Over time, their soft, muddy sediments hardened into beds of limestone.
06:24Today, that limestone is quarried in the town of Solnhofen for use in building construction.
06:34But the slabs that peel away in thin sheets have also yielded remarkable finds for paleontologists.
06:49Hidden in the layers of limestone are perfectly preserved fossils that may help unravel the mysteries of our past.
06:59Dr. Peter Wellnhofer of the Bavarian State Museum has been studying this site.
07:06We're now at the bottom of the ancient sea.
07:13This formation was made by the accumulation of the Jurassic Sea 150 million years ago.
07:21There are about 90 meter thick layers of limestone, and these lie in each formation like plates.
07:33The rocks were made of fine lime sponges, and they covered the ground and formed a lagoon.
07:40At the same time, from open seas and from the land, organisms, animals and plants were washed to this place and accumulated in this lagoon.
07:52They died and dried and accumulated on the ground, buried in the mud.
08:01And the muddy layers that covered the ground preserved the fossils as a result.
08:05This mud on the ground turned to rock from the pressure of the sediment.
08:11More than 600 different kinds of life forms, including the pterosaur, have left perfect imprints in these rocks.
08:28Among them, one unusual fossil of a creature discovered more than a century ago.
08:34An animal that ignited debate in 19th century scientific circles about the new theory of evolution.
08:41It was an imprint of a single feather less than three inches long.
08:59Next to surface, a fossil without a skull.
09:09This animal appeared to have feathers like a bird, but unlike birds, a long tail.
09:17Perhaps most puzzling of all, its legs looked reptilian.
09:26With a combination of features, the bones could not be classified as pterosaur or bird.
09:33The fossil was named Archaeopteryx, or ancient wing, because of its feather imprint.
09:41Whether this animal was a bird or reptile was anyone's guess.
09:51Bird or reptile?
09:54The debate over Archaeopteryx continued at full tilt.
09:58Finally, the fossil landed at the British Museum of Natural History.
10:04Its superintendent was Sir Richard Owen, a leading 19th century anatomist.
10:12Examining the fossil of Archaeopteryx, he made his pronouncement, unequivocally a bird.
10:25Owen noticed the V-shaped bone in the center of the fossil imprint.
10:31He realized it was a furcula, a strangely shaped collar bone found only in birds.
10:44An Archaeopteryx fossil found in 1877 clearly showed the presence of wings.
10:52The first specimens found were so perfectly preserved that they were thought to be forgeries.
11:06Archaeopteryx has lizard-like teeth and another feature not found in modern birds.
11:14Three sharply hooked claws in its wings.
11:24Despite its somewhat reptilian features, this indeed was the world's first bird.
11:31The Orinoco River in Venezuela, a habitat resembling Archaeopteryx's primitive nesting row.
12:00This is a home to another ancient bird with remarkably similar features.
12:13Called Watson, this spiky crested bird is the size of a chicken.
12:21The adult bird has no claws in its wings, but the newborn chick has hooked claws just like Archaeopteryx,
12:28the only modern bird with vestiges of its evolutionary past.
12:37With these claws, the young chicks move deftly from one branch to another.
12:44Evidence like this convinced some scientists that Archaeopteryx evolved from a creature that lived in the trees.
12:58Experts still have many conflicting theories about the origins of birds.
13:05At the University of Kansas, Dr. Larry Martin describes how he thinks birds evolved.
13:11Martin believes that primitive arboreal reptiles developed feathers to help them glide through the treetops.
13:17He's convinced that a relative of Lagosuchus, a reptile that lived more than 200 million years ago, is the ancestor of birds.
13:32The proto-birds would have been small lizard-like reptiles that lived in trees.
13:41I don't think that they would have been very well adapted for bipedal locomotion on the ground.
13:47It seems at least reasonable to suppose that feathers originally were used as flight structures.
13:59If an animal can leap or glide from tree to tree, it could move quickly and efficiently through the forest.
14:08Dr. Martin says that scales covering small arboreal reptiles gradually evolved into feathers,
14:22allowing Lagosuchus to increase the range of its jumps.
14:27Though they look entirely different, both scales and feathers are made of the same substance, a protein called keratin.
14:47Reptiles originally developed tough scales to protect their skin.
14:52But over time, Martin suggests, their transformation into feathers gave them freedom to glide through the forest.
15:04But no intermediary fossil has ever been found linking reptiles to Archaeopteryx.
15:10The question remains, if the membrane-winged pterosaur could fly without feathers, why not birds?
15:20For 20 years, the Archaeopteryx fossil preserved at the Jurassic Museum in Bavaria was mistaken for an entirely different animal.
15:38A dinosaur called Kamsognathus.
15:44Kamsognathus was a carnivorous dinosaur about two feet long that lived in the late Jurassic period.
15:53Dr. John Ostrom of Yale University is one of the world's leading authorities on dinosaurs.
16:08He believes that the origin of birds rests with a small, highly active dinosaur, not a reptile.
16:18Dr. Ostrom has done a comparative analysis of Archaeopteryx and Kamsognathus, and identified 20 significant points of similarity between the two.
16:33The skull, the backbone, the pelvic girdle, and almost every other feature of the skeleton.
16:52As certainly Archaeopteryx suggests, its skeletal anatomy clearly indicates an active creature.
17:00It may then have been warm-blooded or endothermic.
17:05And if that's the case, then feathers, the early feathers, the initial feathers, may have served some endothermic role, perhaps as a form of primitive insulation.
17:22Oostrom speculates why dinosaurs may have evolved into feathered creatures.
17:31With a bird-like metabolism, he argues, Kamsognathus had to maintain a consistently high body temperature to keep up its activity level.
17:50So its scales evolved into feathers for insulation.
18:05Dr. Ostrom believes that these feathered dinosaurs were the forerunners of birds.
18:11Birds can fly using their forearms or wings, and they can use their legs and feet as legs to run about.
18:22No other creature other than certain insects have two completely independent means of locomotion.
18:31I think that's one of the reasons why birds are so successful today.
18:36Where did birds come from?
18:39After more than a century of debate, there is no conclusive evidence to verify either theory.
18:46How and why feathers finally evolved is one of the great unknowns.
18:52But eventually, birds would play a major role in virtually every habitat across the globe.
18:59Archaeopteryx, the planet's first bird, may not have flown gracefully, according to some scientists.
19:10But it may have been better equipped to fly than previously imagined.
19:17Ornithologist Alan Faduccia of the University of North Carolina has been studying the fossilized imprints of Archaeopteryx feathers,
19:25comparing them with those of modern birds.
19:43An evolutionary line is generally punctuated by a trail of fossils in different stages of development.
19:50No such link exists in birds.
19:55These are photographs of the left wing of the Berlin specimen of Archaeopteryx.
20:02And they're quite important because they show the wing of a modern bird virtually unchanged in any significant detail in 150 million years.
20:19And they show a number of other characteristics.
20:22If we look closely at the microstructure of these feathers, we find that, in fact, even in their microstructure, they're unchanged.
20:37This is the feather imprint of the first Archaeopteryx fossil discovered in 1861.
20:44The shaft of the feather, from base to tip, is a little off-center.
20:49These are the feathers of a modern turtle dove.
20:55Just like the Archaeopteryx specimen, its feathers are asymmetrical, with off-center shafts.
21:03Viewed in cross-section, a single feather undulates in a gentle S-curve.
21:15This anatomical feature is shared by all birds that fly.
21:22The secret to flight was, in fact, this asymmetry.
21:41How is the construction of the feather related to flight?
21:46Dr. Akira Ozuma of the University of Tokyo conducted this experiment.
21:52First, flat plates with a central axis are placed in a row.
21:59They represent the wings of a flightless bird.
22:02These plates are then exposed to wind.
22:07Pummeled by wind, the plates bend in different directions without stabilizing.
22:14Flight with such wings would be impossible.
22:17Next, an experiment with undulating plates bearing an off-centered axis
22:30to simulate the wings of Archaeopteryx and other birds that fly.
22:34When wind is applied, all the plates rise and stabilize,
22:48each plate perfectly aligned to form the shape of a wing.
22:53These undulating plates are stable even when exposed to strong air currents.
23:00The wings of modern aircraft are designed on the basis of this aerodynamic shape.
23:12150 million years ago, Archaeopteryx already had sophisticated wings with perfectly aligned feathers.
23:21150 million years ago, Archaeopteryx was capable of some power flight.
23:28Racing through the forest, scientists believe Archaeopteryx was an agile runner.
23:33Unable yet to reach the heights, Archaeopteryx was capable of some power flight.
23:40But far beyond the treetops, pterosaur dominated the Jurassic skies.
23:59Unlike Archaeopteryx, pterosaurs had lighter bodies and hollow bones, allowing them to soar.
24:09To date, only half a dozen Archaeopteryx fossils have ever been identified, all from Zollhafen, Germany.
24:19In 1992, another bird fossil was discovered in China.
24:26Since then, bird fossils of a later generation have been found in greater numbers.
24:40In the hills of Liaoning Province in northeast China lie sediments from the early Cretaceous period.
24:48This was once a subtropical region like Zollhafen, with forests of ferns and palm trees encircling a large lake.
25:08It is here that clues about the birds that came after Archaeopteryx surfaced next.
25:17Cynorus, or Chinese bird, was about four inches long.
25:27Scientists believe that Cynorus was a forest dweller, feeding on insects and small reptiles.
25:38The skeletal structure reconstructed from the fossils closely resembles that of modern birds.
25:48Compared to Archaeopteryx, Cynorus had smaller teeth, shorter hooked claws on its wings, and an almost non-existent tailbone.
26:01Another significant structural advancement was the appearance of a sternum.
26:07With this newly developed breastbone, it could develop stronger muscles to power its wings.
26:19But like the ancient pterosaurs, the most important anatomical feature observed in Cynorus is hollow bone, allowing for more efficient flight.
26:29Dr. Lao Chen Gang of the Natural History Museum of Beijing.
26:39Dr. Lao Chen Gang of the Natural History Museum of Beijing.
26:44Cynorus's hollow bones were equipped with special air sacs.
26:48Those air sacs in the bones and in other parts of the body were connected to the lungs.
26:54With this kind of a system, it was able to use the oxygen in the air to produce maximum energy.
27:01Air sacs are essential to sophisticated flight.
27:07More than a hundred million years ago, Cynorus had nearly perfected the body structure found in modern-day birds,
27:14a development that would eventually lead to an evolutionary explosion within the species.
27:20When they branch off and achieve flight, they seem to undergo a burst of evolution, something we've never seen before.
27:32But due to the enormously physically restrictive demands of flight, coupled with the extraordinarily high metabolic rate evolved by birds,
27:43and feathers, which are almost magical structures.
27:48This produced an animal which had never been seen before.
27:58By the end of the late Cretaceous, birds of all shapes and sizes had made their way across the globe,
28:04and were gradually carving their niche in Earth's diverse ecosystems.
28:16Millions of years would elapse between the bursts of evolution that launched life in the seas.
28:22The planet's first life forms were single-cell organisms.
28:34The threat of extinction in the primordial ocean led individual cells to join forces with their neighbors,
28:41sharing scarce nutrients essential for life.
28:44To survive, they would merge, forming a new unicellular organism with two separate strands of DNA.
28:55This was the beginning of sexual reproduction.
29:00These integrated cells reproduced differently from the earliest life forms,
29:05which multiplied asexually by replicating their own bodies.
29:09First, they copied both sets of DNA, producing two identical pairs.
29:19The strands of DNA approach each other, randomly mixing their genes.
29:26Next, the four sets of DNA, each with a different genetic makeup, split into individual cells.
29:39Each cell, in turn, encounters another,
29:45shuffling genes and fusing again into a distinct new body.
29:54This cycle of communion and division is the essence of sex.
29:57Half a billion years ago, the Cambrian seas surged with life.
30:17Though the environment helped to shape this explosion,
30:21biological forces played an even greater role.
30:24To adapt to the changing seas, life forms had developed a sexual reproductive system.
30:34A system that created the conditions for progressive evolutionary change through genetic recombination.
30:40Birds developed feathers, an adaptation unique to their species.
30:55Transforming both skeletal structure and anatomy over the years,
31:00they were able to streamline flight.
31:03The process of evolutionary experimentation would ultimately allow birds to thrive in almost every habitat across the globe.
31:18A system that created the conditions for the nature of the nature of the nature of the nature of the nature of the nature of the nature of the nature of the nature of the nature of the nature.
31:29Today, in the sea, on land, and in the sky, a tapestry of life unfolds.
31:40The creatures on Earth number well over 30 million different species.
31:48The animal kingdom owes its existence to our unlikely ancestors in the primordial seas.
31:59Passing on their heartiest genes to generations that followed,
32:04these simple multicellular organisms would transform the face of the planet.
32:08Birds are not the only winged creatures to take to the skies in a stunning array of shapes, sizes, and colors.
32:25Butterflies are models of diversity, even within a single species.
32:30Here, in the tropical rainforests of the Amazon, lives an elusive butterfly known as the jewel of the forest.
32:41Catching it requires special bait.
32:45In this case, fermenting bananas.
32:48Because these butterflies like to feed on the juice of overripe fruits.
32:52Aglius is the name of this butterfly.
33:05Its red and blue winged patterns stand out against the dark of the forest.
33:10This red butterfly is also an aglius.
33:28Each individual aglius has a unique winged pattern and color.
33:31They all belong to the same species.
33:43Aglius butterflies are constant innovators in the realm of genetic design.
33:51Every winged pattern comes in the three primary colors.
33:55Red, blue, and yellow.
33:57But no two butterflies look alike.
34:14These graceful creatures are indeed forest jewels.
34:18Across the globe, in Okinawa, Japan, ecologist Kenji Uesugi believes that there are many important reasons for diversification.
34:35Mr. Uesugi has been studying a type of butterfly called Menelites polytees.
34:40It's a kind of swallowtail butterfly with a white striped pattern on its wings.
34:47Some of the females of this swallowtail species have slightly different wing patterns.
34:53Red spots accentuate the white band.
34:59This distinctive design is the result of generations of change in the gene pool.
35:05The red spotted butterflies here are in the minority.
35:11Because the males prefer the white striped females, the reds have fewer opportunities to breed.
35:20These butterflies have predators, birds like the Bulbul.
35:24In perpetual threat of attack, some of the eye-catching white butterflies show battle scars.
35:34Chunks missing from their wings.
35:36But for some reason, the birds never select the red ones.
35:46Will the same thing happen under laboratory conditions?
35:50Red and white butterflies are placed in front of a bird simultaneously.
35:58Avoiding the red, the bird again selects the white.
36:01The results are repeated again and again.
36:13In each case, the red butterfly is left unharmed.
36:17In Okinawa lives another kind of swallowtail.
36:32A poisonous butterfly called Menemonaga.
36:40The butterfly on the left closely resembles the red-spotted Menelides polities.
36:44It is likely that birds shun the red butterfly, mistaking it for the poisonous Benemonaga.
36:53Showing off its individual design, the red-spotted butterfly has greatly reduced its risk of predatory attack.
37:00Sexual reproduction certainly creates diversity, but oftentimes that diversity seems meaningless.
37:14However, the creation of that seemingly meaningless diversity, or mutation, and its staying power is of extreme importance in that it expands the possibility for survival when the environment changes.
37:26Genetic diversity provides assurance that life will continue, surmounting the unpredictable and sometimes threatening forces of nature.
37:41One hundred and fifty million years ago, Archaeopteryx was probably the only bird.
38:00But by the end of the Cretaceous period, birds had gained an evolutionary foothold.
38:05Meanwhile, as the ancient pterosaurs dwindled, their cousins, the pterodactyloids, were increasing in size.
38:16Some had wingspans ranging up to thirty-six feet.
38:19In 1985, American scientists, using models, conducted an experiment in the desert to find out how these giant pterodactyloids flew.
38:36The model weighed thirty pounds and had a wingspan of twenty feet.
38:55Graceful fliers, pterosaurs of the late Cretaceous, would catch the slightest draft with their huge wings and glide for hours at a time.
39:04But by the end of that era, sixty-five million years ago, only three species of pterosaur remained.
39:21At about that time, an asteroid, six miles wide, crashed to Earth with the force of an arsenal of nuclear bombs.
39:29The collision triggered dramatic change in the Earth's ecology.
39:46Clouds of debris hovered in the atmosphere, blocking out sunlight.
39:49And for at least a year, the planet endured a winter of destruction.
39:59Entire species of plants and animals perished.
40:02Among those lost to history were the kings of land and sky, the dinosaurs and the once thriving pterosaur.
40:13Left in their wake were flowering plants, insects, mammals and birds.
40:28Dr. George Whitfield of Reading University in England is an expert in biomechanics.
40:41He says the pterosaur's size may have contributed to their downfall.
40:45We analyzed Pteranodon as if he were a modern glider and calculated his strength and how he would perform.
40:58He can circle in very small circles because he flies slowly, sinking very slowly because he's very efficient.
41:04And this makes him a superb thermal soaring aircraft to go up in quite small light thermals.
41:13The disadvantage of developing like this is that he is very large, very weak and cannot fly very fast.
41:23So if the winds increase, he's very badly placed.
41:27While birds developed their ability to fly by flapping their wings, pterosaurs took a different route.
41:37Uniquely specialized creatures, pterosaurs were able to glide on the most gentle currents by growing larger membraned wings.
41:48But in strong winds, they were like kites without strings.
41:51You generally find that a series of species evolve to fit better and better and better the conditions in which they live.
42:02And then if the conditions change, they can't evolve back.
42:07And you find that they've lost the variability needed to fit the new climate in Pteranodon's case.
42:15Whereas the birds were much nearer of the beginning of their evolution.
42:22They had lots of variability available.
42:25And they were both smaller and stronger.
42:29And they could fold their wings completely.
42:32So the birds had a much better chance of living through the changing conditions.
42:37To glide on the currents of evolution, pterosaurs had become highly specialized animals.
42:47Faced with changes in their environment, they no longer had means to adapt.
42:54The age of the first flying creature had come to a close.
42:59Though the pterosaur had vanished, for birds, the age of flight had just begun.
43:12So perfectly adapted for life in the skies, it is hard to imagine that birds had once descended from reptilian creatures.
43:20In Germany, where Archaeopteryx was discovered, Earth's strata dating back 50 million years reveal numerous bird fossils.
43:40This long-legged bird resembling a modern flamingo.
43:43And fossils of 13 others, including the eagle, the falcon, and the crested ibis, have been unearthed.
44:01Today, birds flourish in every corner of the globe, from the polar regions to the equator.
44:24Millions of years since their arrival on the planet, birds still remain unchallenged.
44:43Some migrate thousands of miles across oceans and continents each year.
44:48Others can soar as high as Earth's most magnificent mountain ranges.
44:55Graceful and strong, they have pioneered territory untouched by other living creatures.
45:01Driven by instincts unknown to man, they made the evolutionary leap that has eluded others.
45:19Overcoming the inescapable tug of gravity.
45:24With the pterosaur long vanished, birds alone are sovereign in the skies.
45:31In the skies.
45:32In the skies.
45:33In the skies.
45:34In the skies.
45:35In the skies.
45:36In the skies.
45:36돌� mí.
45:37In the skies.
45:38In the skies.
45:39In the skies.