Category
📺
TVTranscript
00:01The Earth, an epic story, four and a half billion years in the making, with drama and surprise at every turn.
00:13It's the story of a tiny planet, unique in the universe, because here alone, life began.
00:21Right from the get-go, the natural world has displayed a spectacular and thrilling diversity of colour, form and extraordinary behaviour.
00:35It's also the story of our own journey into being.
00:42Once vertebrates took over the land, there was no stopping them, with reptiles taking the lead.
00:51In their race for world domination, they became the biggest animals to walk the Earth.
01:00For 180 million years they ruled.
01:05But they weren't alone.
01:08We mammals had our humble beginnings in their shadows.
01:22The world is full of surprises, and many lie hidden beneath our feet.
01:32Weather eroded out of the ground, or exposed during mining and construction work, chance discoveries of fossils have captivated us for centuries.
01:43And none more so than those of giants.
02:00It took a long time for people to figure out what they meant.
02:04Since the birth of human societies, the giant remains have inspired legends of dragons.
02:18Through the Middle Ages, fossils were either thought to be dragon bones, or the work of the devil.
02:24In some cultures, they were viewed with fear and suspicion.
02:30But enlightenment would come.
02:35As early as the 11th century, a Chinese scientist was interpreting the Earth's history through fossils.
02:46It took longer for Europeans to catch on.
02:55Past attempts to classify different minerals assumed fossils were rocks that had formed in the ground that just bore a resemblance to living things.
03:05It was only in the last few centuries that it was proposed that once living materials had somehow become impregnated with rock.
03:18At the time, it was still believed the world was only a few thousand years old.
03:38And the biblical flood was considered a likely cause of the petrified remains.
03:57Still, in a God-fearing world, most rejected the notion that extinction was possible and dismissed the significance of fossils.
04:06In the late 1700s, things were changing.
04:21Anatomists were recognizing animals that must have walked the land once, but are now gone.
04:27In the early 1800s, a French naturalist, George Cuvier,
04:33started naming extinct reptile groups, the huge marine reptiles and the pterosaurs, the flying reptiles, from quarries in Germany.
04:47Other specimens were found in England, and in 1842, famous anatomist Richard Owen created a new name for these great beasts.
05:01They were the dinosaurs.
05:04The earth had been around for 4 billion years, and in the later part, life appeared and began to colonize.
05:16Crustaceans.
05:17Crustaceans.
05:18Mollusks.
05:19Insects.
05:20Fish.
05:21And amphibians.
05:22All were carving out niches on an evolving planet.
05:23But the next chapter was perhaps the most exciting.
05:30245 to 66 million years ago, known to geologists as the Mesozoic,
05:36the middle age of life, is better known to most of us as the age of the dinosaurs.
06:01It began with disaster.
06:15During the history of life, there have been five major mass extinctions.
06:21But this was the biggest.
06:26Around 250 million years ago, at the end of the Permian period, something happened that obliterated 90% of life on Earth.
06:39Just what is something of a mystery?
06:43A key theory is that violent volcanic activity pumped ash into the air, choking the atmosphere with volcanic gases.
06:56Fossil evidence in Siberia shows that huge volcanoes buried the ground under 6 meters of magma.
07:08The ash clouds blocking the sun would have reduced the temperature.
07:18Glaciers could have formed, locking up water and reducing sea levels.
07:27The volcanic gases would have fallen as acid rain, killing light.
07:42The shallower seas would have released methane.
07:46Bacteria, feeding on the dead, would churn out carbon dioxide, adding to what the volcanoes were already pumping into the air.
07:58Leading next to more greenhouse gases and more climate chaos.
08:03It may have coincided with an asteroid collision.
08:22There's evidence of a 120 kilometer crater under what is now Australia.
08:28An asteroid would have the same effect.
08:33Throwing debris into the atmosphere that would block out the sun and cool the Earth.
08:43Fires raged across the planet.
08:49Another source of the greenhouse gas, carbon dioxide.
09:05It's also suggested that the oceans were in trouble.
09:12Fires raged across the planet.
09:17Today, the temperature difference between the polar ice caps and the tropics causes movement.
09:23Ocean currents, which help to distribute oxygen.
09:30When there were no ice caps, there was less movement of water.
09:34And some think that the ocean stagnated, losing oxygen and gradually killing off life.
09:46Bacteria would have increased, feeding on the dead, releasing carbon dioxide that would have bubbled up through the water.
09:57A lethal soup for most marine creatures.
10:08A staggering 95% of life in the oceans.
10:14And more than two thirds of life on land were obliterated.
10:18Barely a tree was left standing.
10:41The fossil record reveals the global collapse of forests.
10:46Sediment from the late Permian was rich in the pollen of conifers.
11:05But after this dramatic event, there is no pollen.
11:10Soils are packed with the roots of fungi.
11:14Probably consuming the decaying trees.
11:17But the catastrophe was an opportunity.
11:34A chance for the survivors to try again.
11:37To rebuild and fight to dominate their competitors.
11:41The start of the Mesozoic, the first of three acts, was built from the rubble as the world entered the Triassic period.
11:58252 million years ago, the world was still one huge land mass, Pangaea.
12:05The climate was much hotter.
12:06There were no polar ice caps.
12:07The land was mostly hot desert.
12:12Amphibians were doing well.
12:13And in the early Triassic, the frogs and the salamanders were starting to evolve.
12:17The frogs and the salamanders were starting to evolve.
12:24But amphibians had to grow up in the serious desert.
12:26The salamanders were starting to grow in the upper flame forest.
12:27The frogs and the salamanders were starting to evolve in the Near Triassic.
12:32Amphibians were doing well and in the early Triassic the frogs and the
12:39salamanders were starting to evolve but amphibians had to stay in the few wet
12:56areas unlike another group there had been an evolutionary breakthrough in
13:17reptiles with the ability to lay eggs on land and with dry tough scaly skin to
13:25retained water with these attributes the hot landscape belonged to them
13:55for 60 million years lizard-like proto mammals called synapsids dominated the
14:15world but they had competition
14:25while the synapsids would give rise to the mammals diapsids were the great
14:32granddaddies of all the other animal groups to walk the earth today
14:37the major reptile groups lizards crocodiles and snakes would emerge from these
14:50Triassic animals but not for a while
15:12though the tortoise family did have its roots here soft shelled turtles are ancient
15:18but still far more advanced than the species of the Triassic which didn't
15:24have shells just broad squat bodies
15:27but there was another little branch of the family tree with greater
15:32amnesty
15:34and there was another little branch of the family tree with greater amnesty it was a
15:36the archosaurs
15:45the archosaurs
15:53and there was another little branch of the family tree with greater ambition
16:01archosaurs while reptile sprawl with their legs spread to the sides like
16:16that amphibian ancestors these newcomers started to position their legs under
16:22their bodies better supporting their weight allowing faster and more
16:27efficient movement this group would give rise to crocodiles and the winged
16:46reptiles the pterosaurs but the first family to branch off was something
16:55different somewhere between 230 and 240 million years ago the earliest
17:07dinosaurs stepped onto the stage they were small but unusual not only were their
17:19legs under their bodies but they walked on their hind legs long tails and strong
17:27thigh muscles made them speedy
17:31though dinosaurs had made some breakthroughs they were slow burners for millions of years they
17:54remained small with only a few species that lived in the shadows of the other large reptiles of their
18:00time particularly phytosaurs and other huge crocodile like animals they were not closely related to
18:12crocodiles but were remarkably similar in appearance and lifestyle
18:17so
18:18so
18:24the world they look at is
18:25so
18:26the world they love is
18:33so
18:34the world they look at is
18:39the world they look at is
18:47lived in was dominated by conifer trees.
18:51It took them a while to recover from the Permian extinction,
18:54but they gradually recolonized.
19:00The pine forests had an understory of scrubs and vines.
19:05There were no grasses or flowering plants.
19:07In drier places, there were prairies.
19:18But instead of grass, they were covered in ferns.
19:28Pangaea would have been a bit like a giant version of Australia.
19:37It was so vast, that it experienced different climate zones.
19:45Some regions were seasonal.
19:53There were warm, wet tropics near the coast.
20:03But the interior was a vast, arid desert.
20:07It was so vast.
20:12Reptiles evolved to exploit every niche.
20:15There were even some that took to the waves.
20:22Around 250 million years ago, the first ichthyosaurs were swimming in the sea.
20:29They were the dolphins of the age.
20:31They were reptiles, not mammals.
20:32They were reptiles, not mammals.
20:36They were reptiles.
20:37They were reptiles, not mammals.
20:41They were reptiles.
20:42They were reptiles.
20:43They were reptiles, not mammals.
20:48They were reptiles.
20:49They were reptiles.
20:50They were reptiles, not mammals.
20:55They were reptiles.
20:56They were reptiles.
21:02They were entirely aquatic, and unlike most reptiles,
21:07had to give birth to live young at sea, as dolphins do today.
21:15Which group of reptiles they evolved from is unknown,
21:19but they were hugely successful.
21:32While they took over the oceans, another group of reptiles took to the skies.
21:46Pterosaurs are archosaurs, cousins to the crocodiles and dinosaurs.
21:56They looked like a freakish hybrid between a lizard and a bat,
22:00but were related to neither.
22:08Only insects had mastered the power of flight before the pterosaurs.
22:18And it might have been leaping in pursuit of insect prey
22:21that drove the pterosaurs' unique adaptations.
22:30The pterosaurs were very small.
22:40At around the time pterosaurs and dinosaurs branched out,
22:44their common ancestors were very small.
22:47It's been suggested that an adaptation to small body size was fur-like feathers,
23:01and an increased metabolism.
23:03the pterosaurs were very small.
23:09Despite these breakthroughs,
23:10the larger animals ruling the world were still primitive.
23:14Crocodile-like archosaurs.
23:22But that was to change.
23:25With more disaster.
23:26Towards the end of the Triassic, the world went through more extremes.
23:44Volcanoes and earthquakes began to tear Pangaea apart.
23:48As the land mass split, water began to fill the gap, the beginnings of the Atlantic Ocean.
24:07Again, the impacts on volcanoes and changing sea levels altered the climate and challenged life.
24:24Most of the large animals were wiped out.
24:29The primitive crocodile-like archosaurs vanished.
24:32But the smaller, faster species survived.
24:50Dinosaurs and pterosaurs were ready to exploit a world without competition.
24:55The world without competition.
25:04201 million years ago, a new age began.
25:09The Jurassic.
25:14Pangaea was split in half.
25:19One supercontinent drifted north.
25:22Laurasia.
25:26The other, Gondwana, moved south.
25:31The gaps created and infilled with water led to more evaporation and therefore, more rainfall.
25:38The Jurassic was like a hot, humid greenhouse.
25:54A plant paradise.
25:55A plant paradise.
26:19There were still no flowers or grass.
26:20But the earth was blanketed in ferns, mosses and cycads.
26:21The trees became giants, like ginkgos and huge sequoias, the biggest trees we have today.
26:37The abundance of giant plants fueled the growth of the dinosaurs.
26:47The abundance of giant plants fueled the growth of the dinosaurs.
26:51At the end of the Triassic, one group of dinosaurs were taking things to the next level.
27:08For example, Plateosaurus.
27:09A multi-ton, 10-metre long herbivore, one of the biggest creatures to walk the earth at that time.
27:26It was a basal sauropod, a family that would go on to produce the biggest animals ever to walk the earth, including some beasts weighing over 100 tons.
27:42But while dinosaurs were supersizing, beneath their feet, mammals remained small and inconspicuous.
28:05They were not the stars of the Jurassic, but mammals were going through radical changes as well.
28:14The mammals had already made some major changes, giving them the edge over their reptile ancestors.
28:29The hearing capabilities of reptiles is limited, with small bones attached to the jaws.
28:44But in mammals the bones separated and became more delicate and sensitive.
28:58Improving their ability to feed.
29:13The teeth of reptiles, even advanced ones like crocodiles, are uniform.
29:19All the same shape.
29:21Whatever they bite, they must swallow whole.
29:26But the teeth of mammals adapted, so they had not only biting teeth, but grinding ones too.
29:34That could break down a mouthful before it was swallowed.
29:38Though not related to their modern day lookalikes, there was a great radiation in mammalian form.
30:00They were adapting to different niches, and the Jurassic had species that looked somewhat like anteaters, beavers, badgers, and flying squirrels.
30:24But how our ancestors were finding new ways to live and exploit different resources.
30:31Researchers argue about at what point these ancestors became the true mammals we know today.
30:41But by the end of the Jurassic, the three modern mammalian groups were established.
30:48The monotremes were first.
31:01Like their reptilian ancestors, these mammals still laid eggs, but now produced milk to feed their young from modified sweat glands on their bellies.
31:11Only two animals remain today from a once diverse family.
31:18The echidna and the platypus.
31:32Towards the end of the Jurassic, the family had branched to include the marsupials.
31:39Which gave birth to live young, but at a very early stage of development.
31:44Keeping them safe in a pouch until they matured.
31:47And the placental mammals with extended pregnancies to produce more highly developed offspring.
32:00The birth of our own mammalian group.
32:07Dinos had the upper hand.
32:12But fossils of a wolverine-like mammal, Reponomamus, had baby dinosaurs in its stomach.
32:24Life was exploding and diversifying all over the planet.
32:37The seas were teeming with life.
32:39A so-called Mesozoic marine revolution was taking place.
32:43With fierce competition between predators and prey, driving rapid evolution.
32:59Bony fish, along with sharks and rays, were starting to look much more like their relatives today.
33:05The Permian extinction had wiped out the trilobites.
33:23But now the first crabs and lobsters had evolved to take their place.
33:29There were a multitude of giant marine animals, the top predators in the sea.
33:50Including new families of marine crocodiles.
33:53The sea was dominated by mollusks, squid relatives, in particular, ammonites, which lived in all the oceans of the world.
34:08But the land remained the kingdom of the dinosaurs.
34:15Many of the smaller dinosaurs were bipedal, dashing about on two legs.
34:25Walking on two legs left the arms free to do other things.
34:31Many were feathered, perhaps for warmth.
34:38These were useful traits already in place that facilitated a huge leap for one small group of dinosaurs.
34:49Flight.
34:50Perhaps the most famous of fossils, Archaeopteryx is often called a missing link between reptiles and birds.
35:04Though in truth, there was no one link.
35:17It was a gradual evolution of one branch of the dinosaur's family tree.
35:22Pterosaurs were not dinosaurs.
35:28They had leathery wing membranes and walked on all fours.
35:33While these new dinosaur descendants walked on two legs.
35:37And used feathers to create a lightweight but flexible wing.
35:42What was one small step for a little dinosaur was a giant leap for bird kind.
36:00Once the basic body form was established, evolution happened quickly.
36:11Birds rapidly diversified, spreading around the world and filling the skies.
36:41The world was busy and diverse, but ready for more upheaval.
36:48Though less devastating, another extinction event marks the transition from the Jurassic to the final act of the age of dinosaurs.
37:00The Cretaceous.
37:03145 million years ago.
37:10Sea levels were rising because of mountains being formed beneath the ocean.
37:15The fluctuating flooding deposited silt, rich in the calcium bodies of tiny creatures like plankton.
37:26These gradually built up to become chalk.
37:33Latin for chalk is Creta.
37:36And so much came from this era that it was named the Cretaceous.
37:41The supercontinents broke further, becoming more like the ones we know today.
37:54Laurasia gave rise to Eurasia and North America.
38:00And Gondwana breaking to form South America, Africa, India, Australia and Antarctica.
38:13The Cretaceous was warmer than today.
38:16But as the land masses separated, the range of temperature extremes grew.
38:25The dinosaurs thrived on every continent, reaching the crowning glory of their diversification.
38:41The ancestors of modern greaves, pelicans, cormorants, ducks, pheasants and ostriches all lived alongside their giant dinosaur cousins.
39:09Modern crocodiles evolved in the Cretaceous from their archosaur ancestors.
39:16Reptiles welcomed the first snakes into being.
39:22Some of their close relatives, like the monitor lizards of today, took to the seas, becoming mosasaurs.
39:34More ocean giants to add to the growing variety of marine reptiles.
39:39The Cretaceous brought other dramatic changes.
39:55The arrival of flowering plants, the first step towards the beautiful flora we know today.
40:04Bees and other insects adapted their behaviours and feeding strategies to exploit the new plants.
40:14And in doing so became pollinators.
40:23It may have been competition to attract the insect pollinators that drove the incredible diversity of flowers we know now.
40:29There were other insect breakthroughs too.
40:44The first ants, the first ants, termites, aphids and grasshoppers.
40:59All the major modern groups of animals had evolved.
41:05And the dinosaur kingdom was never bigger or better.
41:11But the perfect storm was brewing.
41:14Volcanoes were changing the atmosphere, releasing greenhouse gases and polluting the air.
41:34Geologists also found a layer in rocks all over the earth, dating to 66 million years ago.
41:40A layer of extraterrestrial iridium, the first clue that a massive asteroid hit the earth.
41:59Ground Zero, the impact zone, was just off the coast of Mexico.
42:04The asteroid was more than 10 kilometers across, but left an incredible crater 150 kilometers wide.
42:23Shock waves sent out tsunamis.
42:25Wildfires ripped across the earth.
42:37All large animals were killed.
42:40Their bodies cooked.
42:43On impact, the asteroid vaporised, filling the atmosphere with dust that blocked out the light.
42:50Killing off plants and destroying whole ecosystems from the ground up.
43:02As the plants withered away, the animals that fed on them starved.
43:07Carnivores would have been able to scavenge the remains of first.
43:13But eventually, they too were to starve.
43:18Raised carbon dioxide levels would have been absorbed by the ocean.
43:39Leading to acidification, destroying the shells of plankton, the base of the food chain.
43:52Killing off marine life.
43:5875% of life was gone.
44:00No animals larger than 25 kilos survived the extinction.
44:10This marked the end of flying pterosaurs, the great marine reptiles, the ammonites that had dominated the seas.
44:19And after a rain of 180 million years, the dinosaurs were gone.
44:31It was the ultimate example of being in the wrong place at the wrong time.
44:36If the asteroid had hit a few minutes later, the rotation of the earth would have moved its impact point.
44:48It would have gone into deeper water, lessening its impact.
44:53And the dinosaurs might still be with us today.
44:55Plants perished, but their seeds and pollen could lie dormant in the soil.
45:17As they recovered from a levelled playing field, flowering plants took the lead and went on to dominate,
45:24creating the colourful, fragrant world we enjoy today.
45:35Another plant was just emerging towards the end of the Cretaceous.
45:41Unlike others that grew from their tips, this grew from its roots.
45:46So it could recover quickly from the grazing of large herbivores, but also from the global disaster.
45:57Grass was to race to become one of the most successful plants on earth.
46:01The dinosaurs were gone, but not entirely.
46:19There was one group of small dinosaurs that somehow managed to hide and wait out the storm.
46:25Like a phoenix rising from the ashes, birds were ready to fly to success.
46:38We are thrilled by the stunning diversity of size,
46:50colour,
46:54and behaviour of the 10,000 species of small feathered dinosaurs we enjoy today.
47:00The mass extinction also cleared the stage, getting rid of the giants.
47:18A disaster.
47:22But also a window of opportunity for another collection of small animals.
47:26Mammals were poised for action.
47:35Our family tree was ready to blossom.
47:40The
47:51Mammals were ready to blossom.
47:54The
47:57Mammals
47:59Mammals
48:02Mammals
48:04Mammals
48:05Mammals
48:06Mammals
48:07Mammals
48:08Mammals
48:17Mammals
48:19Mammals