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Culture Express
  • 5/17/2025

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00:00From the start of Earth's existence, life evolved with chaos and disaster,
00:14surviving deep underground to return to the oceans once again.
00:30Life endured ice, then prospered when finally oxygen became abundant.
00:45From microbes to the first complex creatures,
00:48life was always searching for new frontiers on a miracle planet.
01:00450 million years ago, the Earth had become a less violent planet.
01:16It was no longer being bombarded by giant meteors from space.
01:20The great ice ages had passed.
01:23Nothing yet lived on the land,
01:26but in the warm and shallow seas which fringed the continents,
01:29there was a rich diversity of life.
01:32Fish had not yet evolved jaws, so these Arendapses,
01:37the distant ancestors of terrestrial life,
01:39remained close to the coast where they could feed.
01:43Segmented creatures, the trilobites had diversified into many species.
01:49Just beneath the surface, the mantle is made up from molten rock,
01:58which moves slowly with the force of gravity.
02:01The movement is both circular as well as vertical.
02:06This convection drives the restless drifting of the continents.
02:20The Ice Age
02:24The Ice Age
02:29The Ice Age
02:34The Ice Age
02:39The Ice Age
02:44The Ice Age
02:49Oceans are drained as the land masses collide,
02:53but the waters move elsewhere, and so new environments are born.
03:05Continents move very slowly,
03:14And over millions of years, the changes are dramatic.
03:20But not only were the continents being forced to change,
03:24life was also modifying its shape.
03:27An arms race had begun.
03:37In the French National Museum of Natural History,
03:40Dr. Daniel Gouger has studied this period of prehistory
03:44and the armored and predatory fish that had evolved.
03:48410 million years ago, giant predators were hunting the oceans.
04:06These creatures had developed a new and mighty weapon.
04:10The jaw.
04:12With the invention of the jaw,
04:14you get to a new possibility for the animal to become a predator.
04:22They have a unique skeletal structure that does not exist in any fish today.
04:27The front part of its body was shielded in hard, armor-like bones.
04:31Instead of teeth, they had bony plates in their mouths
04:35which acted like a pair of razor-sharp scissors.
04:41With strong jaws, the placoderms dominated the seas of the Devonian period.
04:47They were like armored sharks.
04:49Our early ancestors had no chance against predators like these.
04:55The Ostechians were there,
04:58but they were absolutely under the dominance of these placoderms.
05:04We, the Ostechians, were under the dominance of these placoderms.
05:08We, the Ostechians, were under the dominance of these placoderms,
05:11which were adapted to all kinds of environment.
05:14They represent about 75 to 80 percent of the vertebrates you find in the Devonian.
05:24So our Ostechian ancestors were certainly in the shadow of the placoderms
05:32because they couldn't develop.
05:34Over millions of years, the jawless fish, Arandaspis, had become extinct.
05:40But one of the fish that had evolved was this, called Eusthenopteran.
05:45Science knows it as one of the lobed-finned fishes,
05:49and this one was the stepping stone to the creatures
05:52which would eventually come to walk on land.
05:55It was a good swimmer, but could not compete with the placoderms,
06:00so it had to seek alternatives.
06:10Life was now becoming a series of strategies, both for predator and prey.
06:16Strategies that were sometimes dictated by the earth itself.
06:24The clues are in the rocks,
06:28and the history of the continents as they shift.
06:33The fossil record now is widely scattered,
06:37but when we move back into the deep,
06:40we can see that the history of the continents is changing.
06:43The history is widely scattered, but when we move back in time,
06:47the sites move together to where the creatures once lived.
06:56The interior of this continent was empty, a dry desert with no life.
07:06But when the continents clashed, the force threw up a great mountain range.
07:13We know it as the Caledonian Mountains.
07:19The northernmost site of those ancient mountains are in Norway,
07:24here at Sognefjord.
07:29The folds and curves in the rocks can only hint
07:33at the forces which are at work in the earth.
07:37At the point of collision, solid rock can bend and twist
07:41as the massive forces at work blend one vast landmass with the next.
07:47When the ancient continents of Baltica and Orientia met,
07:52they shaped the hard rocks as if they were putty in the hands of a potter.
07:59This sinuous rock formation is known by geologists as a fold.
08:05Here is another part of those vanished mountains,
08:09at Monreith Bay in Scotland.
08:13430 million years ago, these twisted and tortured rocks,
08:18folding over and upon each other,
08:21were also part of the shoreline of the Aeatus Sea.
08:34The southern tip of the collision is in the east of the United States.
08:41This, too, was once a part of the Caledonian Range.
08:45The strata folds its way for thousands of miles from the USA to Norway.
08:52But of greater interest to prehistorians
08:55is what happened when the Caledonian Mountains were forced up,
08:59when the ancient Aeatus Sea was drained
09:01and the rich diversity of life it sheltered
09:04was abruptly forced to seek alternatives.
09:15The Earth may seem a permanent place,
09:18but it is restless and responsive to the forces
09:21that surge beneath its surface.
09:23The formation of continents, seas and mountain ranges
09:27take millions of years,
09:28but the power is awesome.
09:54The mountains were forced up for over 40 million years.
09:57Geologists believe that some of the peaks
09:59were almost as high as Mount Everest.
10:04But what is intriguing is that many fossils of those creatures,
10:07which were our early ancestors,
10:09are found where the foothills of the Caledonian Range once stood.
10:16The moisture-laden winds are halted by the peaks.
10:18They rise and cool, then rain falls in torrents.
10:27Parts of the sea were moved inland.
10:30They became rivers.
10:32And then, where the country flattened,
10:34the water spread out to become freshwater lakes.
10:42New environments were created.
10:44The sea became more fertile,
10:46and the land became more fertile.
10:48The sea became more fertile,
10:50and the land became more fertile.
10:52The sea became more fertile,
10:55New environments were created,
10:57new frontiers to challenge life.
11:08Some plant life had evolved,
11:10but its grip on the land was tenuous.
11:14Often the land was bong dry,
11:17and when it rained,
11:19the force of the rushing water would erode the soil,
11:21taking with it the mosses and ferns,
11:23which struggled to grow.
11:34The lakes, when they were tranquil,
11:36must have been inviting environments,
11:38just out of reach.
11:42But life itself took a part
11:44in the opening up of these new freshwater habitats.
11:48The rock face alongside this river
11:50was once the edge of an ancient freshwater lake.
11:55370 million years ago,
11:57this was at the foothills of the ancient Caledonian Range.
12:02Today, it's called Red Hill,
12:04in the state of Pennsylvania.
12:08This was the site of one of the earliest known forests.
12:18These leaves
12:20are from the earliest known trees on the planet,
12:23which spread their branches and changed the world.
12:41A tree is called a tree,
12:44a tree is called Archaeopterus.
12:49Scientists think that it was not unlike today's conifers,
12:53the pines and larches with thin needle-like leaves.
12:58They had roots which spread wide and deep,
13:00and would help bind the soil when the floods came.
13:06Like today's trees,
13:07the trunk thickened with every year of growth,
13:09and scientists believe
13:11that it may have grown as tall as 20 meters,
13:13just over 60 feet.
13:15What it gave to life
13:17was shelter from the sun.
13:30Dr. Stephen Sheckler
13:31has studied the impact that Archaeopterus had,
13:34both upon the environment
13:36and the life that was in lakes and swamps.
13:40We'll just get under that piece
13:41and use that as a lever to help.
13:43This is a good-sized Archaeopterus stump.
13:47It's the kind that's pretty typical
13:49for the trees of this time.
13:51Yeah, that'd be 25 centimeters.
13:5325 centimeters, okay.
13:56So, that's another big one.
13:58Then we've got some small ones here.
14:02Exactly, yeah.
14:03Should I slide back to here now?
14:05Yeah, that's a good idea.
14:07By marking the fossiled stumps,
14:09he and his students
14:10can then work out how dense
14:12this ancient forest may have been.
14:15This young forest behind us, I think,
14:17is actually a very close analog
14:19to the appearance
14:21of what the first Archaeopterus forest
14:22would have looked like.
14:24Trees with white bark that are bare now
14:26would have been about the size
14:28of the early Archaeopterus.
14:30So, the whole ecosystem was transformed
14:32by the introduction of the Archaeopterus.
14:35What previously had been an open environment
14:37with relatively low primary productivity
14:40became a closed canopy environment
14:42with a much higher rate of productivity.
14:48This was the first forest canopy
14:50to provide shade and shelter.
14:53These trees spread their pine-like needles
14:55and provided protection,
14:57helped the soil to retain moisture,
14:59which in turn would help
15:01other plant communities.
15:04They helped change the landscape.
15:12Their influence didn't stop on land.
15:15Archaeopterus grew along the lakeshores
15:17and helped change this environment, too.
15:22Archaeopterus shed their branches,
15:24which then fell into the water,
15:26would eventually become waterlogged
15:28and sink.
15:31They would decay.
15:32Their nutrients would be leeched out
15:34into the lake waters
15:36so that the trees provided
15:38both food and shelter for the fish.
15:43The fossil record shows
15:44that our distant ancestors
15:46moved into lake environments
15:48at around the same time
15:50that the Archaeopterus did.
15:53The Archaeopterus was the first
15:55of its kind in the world.
15:57Our ancestors moved into lake environments
15:59at around the same time as the predators.
16:04There were still challenges,
16:06but one of them would help life
16:08to make the next great step
16:11on the miracle planet.
16:18In the world today,
16:19mountains still play their part
16:21in shaping the land
16:23as well as the life that lives on it.
16:28In South America,
16:29the Amazon rainforest
16:31needs the waters
16:33that run off the mountains after rain.
16:44The deluges of the wet season
16:46spread out through the rainforest,
16:49one of the richest ecosystems on Earth.
16:53When the forest is flooded,
16:54it provides nutrients and shelter
16:56for an amazing diversity of fish life.
16:59The armored pleco looks almost prehistoric,
17:05while the predatory arowana
17:07glides through the sunken forest.
17:15So frequent is the flooding
17:16that the trees have also adapted
17:18to spending much of their lives inundated.
17:22They provide both food and shelter
17:24to help sustain the rich variety of life.
17:31The muddy waters of the Amazon
17:32and other rainforest rivers
17:34perhaps can give us a glimpse
17:36of what life might have been like
17:38when it adapted to fresh water.
17:43The Amazon does not remain flooded
17:45all through the year.
17:47After the wet season,
17:49the sun begins to wield its power.
17:54By June, the waters dry up
17:56and can drop in some places
17:58by as much as 18 meters,
18:00almost 60 feet.
18:04And when it does drop,
18:06there are winners and losers.
18:09As the water becomes hot,
18:11there is little oxygen for the fish,
18:14so they flounder on the surface
18:16desperately trying to take gulps of air.
18:19But there is none to be had,
18:21so they die to become food for the scavengers.
18:26Yet around them, oxygen is everywhere.
18:52Scientists believe that 370 million years ago,
18:55the world would have experienced
18:57similar shifts in the annual climate.
19:04And yet again, the trees played their part.
19:14While their fallen branches gave shelter,
19:17the bacteria contributing to this breakdown
19:20consumed oxygen,
19:21thus depleting the levels in the water.
19:39Today in the Amazon and elsewhere,
19:41there are fish that can handle this.
19:44The lungfish,
19:46relics from the past
19:47that are able to take oxygen.
19:50As normal fish do, from the water.
19:52But they can also breathe air.
19:55And when the Amazon dries up,
19:57this fish will survive.
19:59Often buried in wet mud,
20:01breathing as we do,
20:03with lungs.
20:17Recent research shows that lungfish
20:19are close relatives to our distant ancestors
20:22who lived in the shallows
20:23when the first forests took root on land.
20:28Dr. Per Alberg has studied Eusthenopteran,
20:31and he believes that our distant ancestor
20:34had lungs like the lungfish of today.
20:38The lungfish is moved into
20:40a freshwater swamp environment
20:42at the same time as the earliest tetrapods,
20:45and right alongside them,
20:47we find them together in the same strata.
20:49So when we look at modern-day lungfish
20:51and how their respiration works,
20:53what we're looking at is probably something
20:55that's closely convergent onto early tetrapods.
20:57Lungs evolved in all likelihood
20:59to help the animal to breathe
21:01when living in warm, tropical waters
21:04with a low oxygen content.
21:07This is the way science believes
21:09early fish developed lungs.
21:11First, the upper part of the oesophagus,
21:13the airway,
21:15swelled and formed the precursor of a lung.
21:18Moving from the sea into the freshwater
21:20made this become larger.
21:22The inner surface was covered with capillary vessels
21:25to absorb more oxygen,
21:27which was essential for survival
21:29in those early lakes.
21:32If lungs had not been present in our ancestry,
21:34there is no way that our ancestors
21:36would have made it to become
21:38truly competent terrestrial animals.
21:41We would still be flopping around
21:43in the shallows today.
22:02Modern fish are the descendants
22:04of those early lungfish.
22:19But the lung of the modern fish
22:21is no longer used for breathing.
22:23Instead, it has evolved into an air bladder,
22:25which helps it keep its equilibrium
22:27when it changes depth in the water.
22:30Most of the ancient fish that stayed in the ocean
22:32did not develop lungs,
22:34so they eventually became extinct.
23:00But to step on land,
23:01you need to be able to walk as well as breathe,
23:04and that was the next challenge to be met
23:07on the Miracle Planet.
23:13Muddy streams are as good as anywhere
23:15to look for the evidence of those first creatures
23:17which began to make the move
23:19from water to land.
23:22Dr. Jennifer Clack
23:23from Cambridge University in England
23:25made a remarkable find
23:27in East Greenland.
23:30The fossil in this rock
23:31has been dated at 360 million years,
23:34and it belongs to an early tetrapod,
23:37creatures which developed limbs.
23:44Even more remarkable,
23:45it clearly has fingers.
23:51It's the first record of any animal
23:53with a hand and fingers.
23:56The creature is called Ancanthostega,
23:59and from the fossil,
24:01Dr. Clack has made detailed sketches
24:03of what she and other experts
24:05think the animal looked like.
24:09The tail appears to be made up from fins,
24:11more characteristic of a fish than a reptile.
24:15Looks like a fish,
24:16but it's actually a tetrapod.
24:20It has a long tail,
24:22more characteristic of a fish than a reptile.
24:25Looks like a fish,
24:26except it has limbs rather than fins.
24:30But its skull was stronger than the skull of a fish,
24:33and she believes it was able to move its neck.
24:40It evolved from fish
24:41that made their way into the fresh water
24:43and could breathe air when they had to for survival.
24:48But where the earlier fish had fins,
24:50now it had limbs.
24:53It was a strange creature,
24:54about a meter or three feet long.
25:00Until now, the fossil evidence
25:02had only ever revealed creatures with five fingers.
25:12It had eight.
25:16That was extraordinary,
25:18because previous to that,
25:19it had always been assumed
25:21that five digits was the primitive number,
25:23and you couldn't have more than five.
25:26So that really got us thinking about the origin of limbs,
25:30and it put a new spin on the whole story
25:34of where limbs came from and how they developed.
25:38Not much longer than here,
25:39but you've got that big sort of fleshy body around,
25:41full of muscles that move.
25:44To start with,
25:45she believed that the limbs had obviously evolved
25:47for it to walk on land.
25:50Detailed analysis of the skeleton
25:52ruled out that possibility.
25:55From the way that the limbs were joined to the body,
25:57they would not have been able to carry weight
25:59out of the water.
26:04You don't find that anywhere else.
26:10Mystery.
26:11But they certainly go back in evolution
26:14to use an optron and things like that,
26:16because it had them.
26:18They go back right to the beginning.
26:21The humerus and the radius and ulna
26:23are fixed at an angle
26:26that wouldn't allow the limb to bend like that.
26:31The articulations here and here
26:34suggest that the arm is carried sideways,
26:38and that there's no weight-bearing function.
26:44They performed detailed skeletal analysis
26:46and then made a computer model of the creature.
26:56But this produced even more questions.
26:59The animal was able to wriggle its way forward
27:01through the water,
27:02almost as if it was swimming.
27:05But it would have been very slow without fins.
27:09It would have been very difficult
27:11to make it very slow without fins.
27:18So why hands with fingers?
27:25A possible answer came once again from Red Hill,
27:28the site of the first known forest.
27:36Here is also evidence of rich and varied life
27:39in a freshwater lake.
27:42Dr. Ted Deschler
27:43from the Academy of Natural Sciences in Philadelphia
27:46has been working here.
27:48This is the fin spine of an acanthodian fish
27:51and made for a rigid pectoral fin.
27:58Amongst other fossils,
28:01he has found one which gives a hint
28:03to the development of these fingers.
28:06It's a large tooth.
28:10This is a single tooth of Hyneria.
28:13The other tetrapods, such as Acanthostega and Ichthyostega
28:17and a few others from around the world,
28:19also lived in these freshwater environments
28:22in the late Devonian,
28:24along with predators like Hyneria.
28:26And that may have been part of the pressure
28:29which made the early tetrapods specialize in shallow water,
28:33using their early rudimentary limbs
28:37to get into shallow water and swamps to escape predation.
28:44Hyneria would have been a ferocious hunter.
28:54Fossils indicate that it was covered with hard scales like armor
28:57and was a fast-swimming predator,
29:00something to hide from.
29:08Hyneria
29:19Hyneria would have been the most ferocious fish
29:22in the ecosystems at Red Hill.
29:24The body form in Hyneria is clearly an animal
29:28that was able to swim very quickly,
29:30start fast, chase its prey,
29:33grab its prey with huge teeth.
29:35On the contrary, the earliest limbed animals
29:38do not seem like they had the same kind of body plan to escape.
29:43So, our ancestors and Hyneria was not a fair match.
29:56When the early fish moved into freshwater,
29:58it was probably to escape its predators.
30:02But they also had primitive lungs and followed.
30:25It's interesting to see the limbs moving in three dimensions.
30:29Dr. Clack was intrigued by the limbs of our early ancestor.
30:34I would expect these bones to be moving backwards and forwards
30:37relative to the humerus, which they don't seem to be doing.
30:42There are clues in a fish still swimming in Australian waters,
30:46the spotted handfish.
30:59It uses its slightly modified fins to clasp rocks on the seafloor
31:03or to wait in ambush for its prey.
31:15So, Acanthostega might have been doing something similar
31:18in its swampy river.
31:22It could have been pushing aside reeds and undergrowth
31:26that you can't really do with fins.
31:30We see the environment as being monsoonal,
31:32similar in some ways to the Amazon rainforest.
31:35And you have to imagine a swamp-filled environment
31:38with lots of weedy undergrowth
31:41as well as leaves falling in from the trees that lived on the riverbank.
31:47The early trees, by chance, not only dropped their leaves,
31:51more often they dropped entire branches.
32:00These would pile up in the shallows
32:02and provide an ideal hiding place.
32:17To move through such a tangled pile of branches,
32:20hands with fingers would be very useful.
32:24Possibly this was the reason our ancestors developed limbs.
32:47Because these things were air-breathing
32:50and they were living in perhaps stagnant water,
32:54they were using their hands as props
32:57to raise the head out of the water
33:00so that they could breathe the air.
33:03Chance has always seemed to play a part in evolution.
33:34Ultimately, once you've got these
33:38slightly intermediate types of adaptations
33:42that are adapted to neither land nor water, but a bit of both,
33:46then you can build on that
33:49and gradually, over time,
33:52become adapted more and more to land living properly.
34:04There was one more step to take.
34:08The creature that was first to walk on land would not be Ancantastega.
34:34The earliest known footsteps on land
34:37are here on the west coast of Ireland.
34:40This was once a swamp, the foot of the Caledonian Mountains.
34:50These footprints were found in 1992.
34:53There were 260 steps made by an animal
34:56which put weight on the ground
34:58and moved its right and left feet forward alternately,
35:01as the reptiles walk today.
35:21Those first footsteps may have been at night
35:24when it was cooler and safer.
35:32The earliest known animal to walk on land
35:35is called Pedipes
35:37and came ashore perhaps 348 million years ago.
36:02Those first tentative steps across land
36:05were to change the earth forever.
36:14Once life had conquered the land,
36:16nothing seemed to be able to stop it.
36:18For almost another 100 million years,
36:21life spread across the world.
36:25But one dramatic moment in time
36:27would see the virtual extinction of all species.
36:54These rocks are in an area of dry and arid country in South Africa,
36:59known as the Great Karoo.
37:02This was once a stream bed,
37:04about 250 million years ago.
37:09In the rocks are the tracks of the strange,
37:12unusually-shaped,
37:14and unusually-shaped,
37:16Pedipes.
37:24These are the strange creatures
37:25which ruled the earth before the dinosaurs.
37:29Dr. Roger Smith of the South African Museum
37:31has studied these creatures for years.
37:34Here's a fantastic trackway of a Deinocephalian,
37:37and it tells us quite a lot about how this animal walked.
37:41I'll just pose myself into its tracks
37:43and we'll see if we can move like a Deinocephalian.
37:47The animal that made these tracks was around 9 feet,
37:51perhaps the length of a Komodo dragon today.
37:57These extinct creatures were reptiles,
38:00but they had some of the same characteristics
38:03that mammals have today.
38:12Dr. Smith is fascinated
38:14as to why they all became extinct at the same time.
38:18We know very little about them.
38:21It is thought they laid eggs,
38:23as do reptiles today.
38:31Yet for millions of years,
38:33they seemed to be the dominant animals on the earth.
38:48Some were herbivores,
38:51and some predators,
38:54with large and sharp fangs.
39:18The mammal-like reptiles
39:20are not as well known as the dinosaurs.
39:23Perhaps it would become quite a surprise
39:25to know that there was such a diversity
39:28of very large, very successful,
39:30very well-adapted animals,
39:32and in fact,
39:34animals from which
39:36formed our human ancestors way back,
39:39that they were around at least 50 million years
39:43before the dinosaurs,
39:45so that the dinosaurs
39:47weren't the first ruling reptiles,
39:49in fact, of the planet.
39:51But their legacy was perhaps crucial
39:54for the miracle planet.
40:01This is the world about 250 million years ago.
40:05Plants were abundant.
40:07So too was oxygen.
40:09Amongst the strange mammal-like reptiles,
40:12one is thought to be the distant ancestor of mammals.
40:17Now, the syrapses are now completely extinct,
40:20but around 250 million years ago,
40:22they were the most common,
40:24the most widespread animal on the land surfaces
40:27of both Gondwana and of Laresia,
40:31that whole supercontinent of Pangaea.
40:34These were the ruling animals at that time.
40:37Now, the other interesting thing about these animals
40:40is they were a transitional form
40:43between reptiles and mammals.
40:45So they were neither true reptiles,
40:47nor were they proper mammals yet.
40:50This was almost a crossroad in evolution.
40:58It's this creature called a cynodont
41:01which is believed to be the ancestor of mammals.
41:10While this little lizard-like creature
41:13is thought to be the ancestor of dinosaurs.
41:28The moment when 95% of species went extinct
41:31is marked clearly by a boundary line,
41:34where the rocks seem to change.
41:37Below that line, there was rich and varied life.
41:39Above, virtually nothing.
41:42They are this bluish-gray color,
41:45typical of soils which are almost permanently saturated,
41:50high water tables and cool conditions.
41:53As we pass through the boundary,
41:55through the extinction event,
41:57we go into these dark reddish-brown mud rocks.
42:01Here, at the same time,
42:03it is also possible to see color changes in the rocks.
42:06The geological evidence seems to point
42:08towards a massive rise in global temperature,
42:12also a sudden decrease in oxygen levels.
42:19These are the fossilized remains of animals
42:22clustered around what Dr. Smith calls
42:25the last pool.
42:28He thinks that this may have been a drying-up waterhole
42:32which attracted many that were desperate to drink.
42:35But as the water dried,
42:38they could not move away,
42:40and died of thirst.
42:51We would look at layer by layer,
42:54through up to that boundary,
42:56and of all the Permian fauna,
42:59only about 5% actually got through.
43:02So this was 95% extinction of the animals
43:06and of the plants that were around
43:09on the land surface at that time.
43:11And this is being backed up
43:13by similar work being done in the oceans,
43:15but it's a very, very catastrophic,
43:17in fact, the most catastrophic mass extinction
43:21that we've ever recorded.
43:23In this fossilized picture of death,
43:26it seems almost as if life had gone full circle.
43:28It had survived fire and ice,
43:31and had grown after the rise of oxygen,
43:34seeming to end when once again the climate changed.
43:48The changes brought about by the mass extinction
43:51came from the earth itself,
43:53the most massive outpourings of lava and gas ever known.
43:57But out of death came life,
44:01on the Miracle Planet.
44:26NASA Jet Propulsion Laboratory, California Institute of Technology