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00:00Fies competition details following the program
00:30.
03:44Now it's bleached dry by the sun, too arid to support much life.
03:51250 million years ago, it was lush, rich with plants and teeming with exotic beasts.
03:57In the late Permian, something like 260 million years ago, there was a great range of animals,
04:15very complex food chains, and in any single place you went in the world,
04:20you would have found a range of different plant eaters, several different carnivores feeding on them.
04:27And it was then the most complex ecosystem there had ever been on Earth.
04:36We wouldn't have had a scene of antelope or lots of deer-like creatures.
04:40Instead, we would have seen a very large number of creatures living very low to the ground
04:46with these large teeth extending out from them.
04:50Among them would have been larger herbivores and larger carnivores.
04:53But I think the strongest sense we would have gotten is how different it looks from anything today.
04:58That's what really strikes me. It was an entirely different type of world.
05:05This distant world lay hidden from us until, 20 years ago, a farmer discovered an unusual footprint.
05:12A farmer came across the footprint and saw it was quite unique for the area and picked it up and took it to his farmhouse.
05:34But he didn't really understand the significance of it until, about 10 years ago,
05:41the geological survey geologist who was mapping the area came across it and asked the farmer where he'd found it.
05:48And the farmer then brought him to this site.
05:51And he was amazed by what he saw and alerted me at the museum.
05:56And I came out and was absolutely enthralled by the sheer detail.
06:08The footprint is a frozen moment in the Permian,
06:12laid down on a riverbank alongside other activity in the time between two floods.
06:17The whole sequence must have occurred over a period of about eight weeks.
06:33That is, from the original flood to the drying up to the impression of the footprints
06:38to the burying again by a subsequent flood.
06:41Eight weeks in geological time.
06:43Eight weeks in the Permian, 250 million years ago.
06:46Eight weeks, a mere instant in time, preserved like this.
06:53The footprint was made by a therapsid, ancient Greek for arched beast.
07:03Although this family of creatures lived 50 million years before the dinosaurs,
07:09they were far more advanced than them.
07:16Fossils show they were reptiles that were fast evolving into mammals.
07:20In the late Permian of South Africa and Russia, where we know these animals best,
07:27there are three or four major groups of mammal-like reptiles that made up these complex ecosystems.
07:33There were small ones about the size of a mouse, through dog-sized ones,
07:36right up to some animals about the size of a rhinoceros.
07:39They're halfway between a reptile and a true mammal.
07:42Their behavioural characteristics, I think, probably would have been a mix
07:46between what we associate with reptiles and what we see with mammals today.
07:49It would have just been a sense of great strangeness.
07:55But what's strangest of all is that these creatures are our distant ancestors.
08:01This was the time when the ancestors of the mammals, the hairy animals, including ourselves,
08:11really radiated and became very important.
08:15Well, mammal-like reptiles are our distant ancestors.
08:17They are the precursors of the first true mammals.
08:23With each new fossil find,
08:25paleontologists are discovering more about how mammals evolve from reptiles.
08:31The footprints can give a clear insight.
08:38The footprint clearly shows this inward curl on the first four digits
08:45in towards the midline of the body.
08:48That tells us quite a bit about how the animal was walking
08:52because it's really showing a rotation of the foot,
08:56the planted foot, in the wet sand.
08:59but the fifth digit here is is not part of that rotation so that the the the
09:06interpretation here is that as the foot was placed down on the ground the thumb
09:11went down first second third fourth and then there was a rotation of the of the
09:16toe and the fifth digit went down now that is is classic for for an animal
09:22which is not an upright gate it's it's it's an elbows out reptilian type of
09:27gate and also the overlap or the near overlap of the hind behind right foot
09:33with the front right foot here shows that the it was able to to bring its back
09:38foot almost into the front foot footprint which meant it must have bent its back in
09:45a sinuous sort of way so not only had it elbows out it also had a swinging gate
09:50of the backbone so that even though these animals were were trying to become
09:55mammals they were still pretty much walking like reptiles
10:10still reptiles at this time but the conditions in the Permian were ideal for
10:16rapid evolution there are conditions under which evolutionary change is quite likely
10:23to happen and there are conditions under which it's really not very likely to
10:26happen at all and the conditions under which is for it to happen you have to
10:31get lots of things right and first of all you have to have a population of of the
10:35right sort of size it really shouldn't be too big otherwise you know or any any
10:40sort of variation that crops up is likely to be swamped on the other hand it
10:43shouldn't be too small because if it's too small then and any changes that is
10:47leads are very very quickly to extinction so you know sort of middle-sized
10:50population but within that middle-sized population we had lots and lots of
10:55genetic variation because if you don't have genetic variation then there's
10:58nothing for natural selection to select among
11:01with great genetic variation amongst the animals of the Permian and with many
11:09millions competing for limited food and water only the fittest survived
11:14the places where fossilized therapsids are found indicates just how much of a
11:24struggle it was to stay alive
11:31it appears that the animals migrated to this point before they died that's why
11:37there are so many in this area and the likely scenario is of a shrinking water hole
11:41where the animals came to to drink but were drought-stricken so this is silt
11:47stone laid down in those periodic floods and here buried within that silt stone is
11:53a complete articulated skeleton
12:05it's a pig sized herbivore it's a good therapsid mammal-like reptile here you can
12:15see the head of the femur and the femur sitting here the tail going through the
12:20vertebrae the backbone here right curled around here towards skull and there's
12:25the skull sitting on its side the snout pointing in this direction there's the
12:31the eye there's the nostril and there's the top of the snout the lower jaw this big
12:37shaped lower jaw coming up towards the back of the head here so it's a pretty
12:42good specimen with strong competition for limited resources mammalian traits would
12:49have aided survival benefiting the therapsids over the reptiles we can
12:55distinguish them from other reptiles because they show a number of features
13:00that mammals now have and they show us that these were acquired step by step and
13:06largely during the permian so for example the permian mammal-like reptiles many of
13:10them had differentiated teeth that means they didn't just have uniform peg-like
13:15teeth as all typical reptiles do so they had incisor teeth as we do at the front of
13:22the mouth they had long canine teeth again as we do and then they had cheek
13:27teeth for chewing at the back and this was associated with a really major change in
13:32their feeding patterns they had jaws just like our ones that they could rotate and
13:37they could chew they could move them back and forward side to side and chew in a
13:41complex way whereas typical reptiles simply have a hinge-like jaw apparatus
13:46which just opens and shuts like that and they can't chew their food they simply
13:50gulp it and swallow it whole
13:53as full skeletons of the therapsids are assembled
13:57paleontologists develop a clear picture of their anatomy and how they moved
14:02but what did these creatures look like
14:08and how did they differ from the reptiles they evolved from
14:16for the first time in a unique collaboration the beasts of the Permian have been brought to
14:31for life
14:3850 million years but a world it's strangely sophisticated for their time
15:03very few representations of these therapsids exist so a paleontologist and a model maker have come
15:13together to try to reconstruct some of these remarkable creatures they had a whole range of
15:20different teeth just like a modern mammal you notice like a line or whatever these huge canine
15:25teeth and then quite sharp piercing incisors at the front and then the teeth in the back Neil Gorton has
15:32worked with Hollywood's biggest names to build accurate therapsid models he needs precise details of
15:38their anatomy and behavior
15:41and what about coloration I mean if they do you know they always say they could be purple they could be green
15:46they could be anything because color never survives but I mean you're right what would be a good guess
15:49you're right I mean we would imagine that they would have some kind of camouflage they might have
15:54had a sort of brownish greenish upper surface and paler under surface that's just based on looking at
16:00modern animals that like a crocodile will be yeah they sort of blend into the background somehow so
16:05that any predator wouldn't spot them from a distance and we're all fed that kind of Jurassic Park and when
16:13dinosaurs ruled the world you know all those kind of movies so suddenly to find out there's this whole
16:17different kind of animal something that was part mammal part reptile just a completely different world
16:24after 250 million years the beasts of the Permian can now be seen again
16:33there are known to be about 15 different species of therapsids
16:55most were herbivores but at least three species were carnivores these were not very fast-moving
17:11animals you know so they were fearsome enough against each other against us but they couldn't
17:16keep up with a modern antelope you know but then the thing they're preying on is even slow yeah and
17:21heavier but they can still do I mean it's like a modern-day crocodile can do quiet turn of speed
17:25that's right no it's a huge beast you know they probably relied on a sort of lunge predation you
17:30know they would wait for the the prey and then leap at it and run at it but if you could outpace it
17:34for a hundred yards you'd be free of all the therapsids moss chops was the largest growing to a full 16 feet in length
17:47moss chops were massive creatures very strange to our eyes they had rather heavy bodies and short legs
17:58but huge skulls and moss chops is unusual in that it's got a very thickened skull roof obviously not a
18:04very intelligent animal why did it have a thickened skull roof it's believed that perhaps moss chops would
18:11have engaged in head-to-head butting of some sort crashing the head to heads together maybe males
18:16fighting for females of course the old story mass chops was a plant-eater with a voracious appetite
18:25it stayed well clear of antiosaurus a vicious carnivore
18:33many of these were somewhat dog-like in shape they had very large canine teeth which shows they
18:46were for piercing flesh and for for eating meat antiosaurus I think may have been really one of the
18:55more hideous predators in the history on earth we are so surrounded by images of dinosaurs as gigantic
19:03and monstrous carnivores but were we to see an antiosaurus I think would be far more of a shock
19:08this is a cross between a reptile and a mammal so imagine a large lion that has reptilian characteristics
19:16and you have I think a pretty good view of this creature but very large teeth not much intelligence
19:22but nevertheless a very powerful and ferocious beast lumbering around the Permian water holes was the
19:34list resaurus slow and placid they eat out a pig like existence eating anything they could find
19:40mr. Saurus was quite often the size of a pig but you get the sense of rather a shuffling low animal
19:56it's feeding off vegetation low to the ground it lives in large herds so a fascinating beast but
20:03certainly it would have never won a beauty contest paleontologists are keen to discover just how
20:12mammalian these therapsids really were two crucial questions are whether they were warm-blooded and
20:18whether they produced live young one of the the mysteries that we haven't yet solved is is is whether
20:27the therapsids added as a group actually laid eggs or or live young if someone gave birth to live young
20:39it would open some other options for them it allows them to have different ways of looking after the
20:44young and protecting them because if you lay eggs in a hole in the ground or in a nest or something like
20:50that then they're at the mercy of of predators and so on if you retain them inside your body then you can
20:56protect them that way in all the world's fossil sites not a single therapsid egg has ever been
21:04found suggesting they do produce live young but the only proof would be the discovery of a pregnant
21:11therapsid and again none has been found so can we be sure that therapsids were partly mammal here at
21:21Washington University a research project reveals that like all mammals therapsids were probably warm-blooded
21:27paleontologist Pete Ward had long wanted to know what the bone structure was inside this baby therapsid's head
21:38all mammals have a series of very thin bones called turbinate bones these turbinate bones are found in
21:48the nasal passages what they do is they warm air when it comes into us if you're in a cold climate or
21:54any place where it's cold at all you don't want cold air cooling your blood so you build these turbinate
21:59bones so one of the things we can do is examine the fossils of these creatures and look for these
22:05turbinate bones and that would be a very strong clue that indeed these if not mammals are certainly on
22:10the grade to becoming good mammals after months of waiting Pete Ward has an important appointment at
22:20the local hospital he has been given an hour on the cat scan to investigate his fossil well the reason
22:27we just don't smash it open and look for these is that in general these are very subtle differences in
22:32the bone and breaking it open may not reveal them however the cat scan should pick up these
22:38differences and in this way we don't have to break an extremely valuable fossil and still get the
22:42information to see the bone structure the cat scan is increased to maximum intensity
22:54the first results are a breakthrough they suggest that therapsids did have turbinate bones
23:00what we're seeing here is some evidence that the terminals did exist it's almost impossible to see
23:07the actual bones themselves they're made of cartilage and that never preserves in the fossil record but
23:12you can see here a contact where these terminals were actually embedded into the bone and that's what
23:18preserves and that's an indication that it's a warm-blooded animal
23:21the transition from cold-blooded reptiles to warm-blooded mammals was rapid
23:23the transition from cold-blooded reptiles to warm-blooded mammals was rapid
23:24partly because of constant changes in climate
23:31the transition from cold-blooded reptiles to warm-blooded mammals was rapid partly because of constant changes in climate
23:39you have conditions that were changing rapidly on earth and animals and plants really had to increase the pace of their race to keep adapted to those conditions
23:46but just as the pace of evolution was reaching its peak disaster struck
23:49disaster struck vast numbers of animals and animals and plants had to increase the pace of their race to keep adapted to those conditions
23:53but just as the pace of evolution was reaching its peak disaster struck
24:01vast numbers of animals were wiped out
24:08it was an extraordinary time
24:11this mass extinction was the greatest of all mass extensions in the history of the earth
24:16and it was not just conditions increasing more of the same
24:20something horrible happened to the earth for me
24:23it was an extraordinary time
24:25this mass extinction was the greatest of all mass extensions in the history of the earth
24:28the earth
24:33the effect was really dramatic
24:35all of these
24:37complex and advanced mammal-like reptiles pretty well disappeared
24:40so that what had been a complex ecosystem with small, medium and large herbivores
24:45small, medium and large carnivores
24:47was cut right down
24:53as the beasts lay dying
24:55at the transition of the Permian and Triassic periods
24:58evolution of life on earth was put in jeopardy
25:02I think really the most dangerous moment in the history of humanity
25:07strange as it may seem happened 250 million years ago
25:10the greatest mass extinction in the history of earth happens
25:13the number of mammal-like reptiles our ancestors dwindles almost to nothingness
25:18if the last of them goes extinct
25:21no mammals exist
25:22if no mammals exist
25:23humans never evolve
25:25so they are an absolutely important and perhaps the most dangerous of links
25:30in our long history
25:31dangerous in the sense that
25:33were this link broken at that time
25:35no humanity
25:37the fossils from the time of this mass extinction show the earth was rapidly heating up
25:52the fact that we're finding these things rolled into tight balls in sedimentary structures suggestive of burrows
25:58indicates to me that this animal is burrowing into the ground probably because of stress
26:02I suspect heat stress
26:07vast swathes of land were bleached dry
26:13the earth was becoming a desert
26:17the climate did become more and more arid
26:20we start to see much more drought effects on the on the animals the skeletons themselves
26:26forming these drought accumulations
26:29and eventually towards the end of the 200 million years ago
26:33we have clear evidence of desert like conditions
26:36where everything was getting very hot and dry
26:39rather than sort of warm and dry
26:44it wasn't just life on land that perished
26:49something catastrophic also happened in the seas
26:52we have record that about 90% of all species in the oceans go extinct as well as on land
27:01and at the same time as on land
27:03that's what makes this mass extinction so mysterious
27:07so what calls this extreme heating effect on land
27:11and the mysterious holocaust in the seas
27:13one theory is an asteroid hit earth
27:28the reason for the end permanent extinction are quite hard to pin down at the moment
27:32people had looked for evidence of an impact
27:34some evidence that a great asteroid hit the earth
27:38but that has not really been demonstrated very successfully
27:51the other view is that there was huge volcanism
27:53that there were enormous eruptions in Siberia
27:56great areas of Siberia
27:59something of the size of Western Europe
28:02covered by basalt lava
28:10but carbon dating of therapsid fossils
28:13shows the extinction happened over a long period
28:17we found that the carbon isotope occurs over 10 or 15 meters of section
28:21and that suggests that the duration of the event
28:24was on the order of a hundred thousand years
28:27too long to be explained by volcanic eruption
28:31or an asteroid impact
28:33so what did cause the massive heating effect?
28:38scientists now think the answer lies in the gradual movement of the earth's continents
28:42and the natural greenhouse gases this produced
28:46it used to be thought that obviously the continents are static
28:49I mean what could be more static than a great chunk of land
28:52in fact it's now clear that the continental rock
28:55sort of sits on top of the rock underneath
28:58almost like scum on the surface of a pond
29:01and one can imagine that the pond is actually quite hot
29:04and is moving therefore with convection currents
29:07and the scum floats on the top
29:09and the continents are the scum
29:11and they keep floating around and hitting each other and breaking apart
29:14about 450 million years ago
29:18the continents began moving towards each other
29:21by 350 million years ago
29:25they began forming a single landmass
29:28Pangea
29:29vast areas lost the coastline that had kept them cool
29:33and began to heat up
29:35when you form a single super continent
29:39you create a vast inland desert area
29:42which perhaps is not friendly to life at all
29:44as the land heated up
29:47so too did the atmosphere and the seas
29:50Tony Hallam has studied the heating effect on the oceans
29:54he believes that a rise in temperature caused enormous deposits of limestone on the seabed
30:00to dissolve producing carbonic acid
30:05this poisoned the waters
30:07depriving them of oxygen throughout the end of the Permian
30:10and into the Triassic
30:12we have clear evidence from the rocks
30:16and from the fossils
30:18that we had pretty stagnant conditions in the earliest Triassic
30:22right across the world
30:23and lack of oxygen is pretty devastating for the vast majority of organisms
30:28and it's a very good wipeout
30:31very good kill mechanism
30:35in the seas creatures which have skeletons begin to die off in large numbers
30:39the reefs die, sponges die, it's a mass extinction
30:45the carbonic acid evaporated from the seas
30:48filling the atmosphere with carbon dioxide
30:51the earth was hit by the greenhouse effect
30:56more carbon dioxide goes into the atmosphere
30:59that produces more heat
31:01and the net effect of that is mass extinction through heating
31:04there had never been anything like it
31:09tide of death from the sea
31:12a drying up of life on land
31:16almost all animals perished
31:19but the Lystrosaurus, the prehistoric pig, survived
31:24and with no animals to challenge them
31:26pigs would rule the world
31:28the Lystrosaurus survived the mass extinction
31:34along with a handful of tiny reptiles
31:49the survivors were few and far between
31:54and as far as we can tell looking at them
31:56there's no way you could have told which animals would survive
31:59and which would not
32:01the only animal you find in abundance is the Lystrosaurus
32:06for the first time in this species lifetime
32:09it was free of predators
32:11it's really quite extraordinary
32:12in the history of the earth
32:14animals always have predators
32:16even predators have predators
32:18only in several instances
32:19have there been large masses of animals with no predators
32:22Lystrosaurus is one of these
32:24no predators
32:25all these predators were killed off in the mass extinction
32:28and where you find them
32:31you don't find one or two
32:32you find hundreds of them
32:33so that they dominated the faunas
32:36and it's a very unusual situation in nature
32:40to have one species representing 90% or more
32:45of the organisms you find
32:47but why did the Lystrosaurus flourish
32:52when other animals perished
32:56Lystrosaurus survives
32:58for one of several possibilities
33:00first of all
33:01it just happened to be
33:02one of the luckiest creatures on earth
33:04there's always that
33:05just dumb luck
33:07secondly it had adaptations
33:09allowing it to survive
33:11the possibilities of this
33:12are that perhaps it could burrow
33:14perhaps it had a food source
33:16that allowed it to survive
33:17under conditions
33:18where there's very little food around
33:20in terms of plants
33:21because plants go extinct
33:22in this mass extinction as well
33:24and Lystrosaurus may have been adapted
33:26to one or two plant sources
33:27which themselves do not disappear
33:30Roger Smith is convinced there is one overriding reason
33:37why the Lystrosaurus survived the extinction
33:40its pig-like snout
33:46it's distinctive in its shovel shape
33:48downward projecting snout
33:50it's got this extremely long snout
33:53and the so-called broken nose syndrome
33:56that in the fossil evidence
33:58always the nose is broken
34:00the snout is broken
34:01but far from being a physical defect
34:05the apparently broken nose
34:07was the key to the Lystrosaurus's success
34:10close examination shows the nose
34:13was part of a flexible fleshy snout
34:16enabling the Lystrosaurus to munch plant matter
34:19in crevices that other animals couldn't reach
34:22the Lystrosaurus was able to survive
34:28because it was dry adapted
34:30basically it had been living on the more drought-stricken areas
34:35around the flood basin
34:36that's where it evolved
34:37and its particularly unique biting mechanism
34:41allowed it to be able to chomp off
34:44the more drought-resistant flora
34:47that then invaded the basin
34:49Lystrosaurus had been hanging in the wings
34:53for most of the latest part of the Permian
34:57and when it saw an opportunity
35:00it took the gap so to speak
35:04over the next 10 million years
35:06they roamed the earth
35:07gradually becoming more rodent-like
35:12the tiny reptiles that also survived the mass extinction
35:15grew larger
35:16eventually developing into the dinosaurs
35:20by the time of the dinosaurs
35:22the Lystrosaurus had evolved into a rodent
35:25later beginning the long transition into squirrels, lemurs, monkeys, apes
35:30then humans
35:35mammal-like reptiles are our distant ancestors
35:38they are the precursors of the first true mammals
35:41and had every one of these mammal-like reptiles gone extinct
35:44at the end of the Permian
35:46you and I and no human in this room
35:48or seeing this program would exist
35:50the mass extinction that destroyed almost all the life on earth
35:57is only one of five similar events
36:01the last one wiped out the dinosaurs
36:07scientists like Robert May are now taking a fresh look at these catastrophes
36:11because they fear the world is in the grip of another similar mass extinction
36:15well there are all manner of extinction events in the fossil record
36:20some big some little
36:22but there are five what we call the big extinctions
36:25the things that took away from us anywhere between 80 or 90 percent or more
36:30of all the species that were alive on earth at that time
36:33question is are we standing on the breaking tip of a wave of the great sixth extinction
36:39of a similar size and scale
36:46it does appear that the rate of extinction at the moment is greater than the rate of origination
36:51and it's possibly in the order of magnitude of that of the end Permian extinction
36:57that is the rate of extinction
36:59so we could learn from our end Permian extinction
37:03that this could well be on the way to becoming a mass extinction
37:09and of that sort of proportion
37:11modern day extinction estimates are that many thousands of species go extinct every year
37:17indicating that the extinction rate is highly elevated now
37:20as compared to the rest of geological time
37:22so I think we are in the middle of a tragedy
37:27to assess the extent of this tragedy
37:30scientists have looked for a laboratory of life
37:33a self-contained environment to count the loss of biodiversity
37:42most widely researched is the island of Madagascar
37:46something like a hundred million years ago
38:00during the age of the dinosaurs
38:02Madagascar was still attached to the side of Africa
38:04and it shared all the same dinosaurs and the other creatures of the time
38:08then at that point a hundred million years ago
38:10Madagascar seemingly broke away
38:12became an island
38:14and it's remained an island ever since
38:15which is why today
38:16it has a very unique assemblage of plants and animals
38:24now an extensive project is underway
38:26to quantify the number of plants and animals that are disappearing
38:30or have already gone extinct
38:32already the findings are shocking
38:36three species of bear and two species of hippopotamus have been wiped out
38:41and another 125 birds and mammals are on the brink of extinction
38:50a hundred years ago tens of thousands of these plowshare tortoises lived on the island
38:55now there are only about 200 of them
38:58poor vegetation means these remaining tortoises are no longer growing as large as previous generations
39:05the conclusion of the survey is dramatic
39:15the rate of extinction in Madagascar is even greater than that at the end of the Permian
39:20the cause this time is of course man
39:27as he moved from the coastal areas to the interior vast areas of forest were destroyed
39:34we've had a dramatic loss of forest
39:38and all the lemurs and most of the nearly all of the faunal bite of all the all the biodiversity of Madagascar is concentrated in forest
39:47and now forest cover only about 25% of the country
39:54because of the wide deforestation Madagascar's lemurs have been particularly hard hit
40:08we know that there are at least 15 species of lemurs that have become extinct within the last 2,000 years
40:15so it's really quite recent
40:19this is a brown lemur
40:22hello
40:24and not a very exciting name
40:27he's tame because he was found as a young animal
40:32maybe his parents had been hunted
40:34and he was looked after as a very young animal
40:37and he's now not frightened of humans as you can see
40:40but he doesn't get on with other
40:42he can't live in a group with other lemurs
40:44I mean there are other lemurs of the same species in the area
40:47and he gets attacked by them
40:48but he has his own territory
40:50which is this forestry station
40:51but there's no way he can be
40:53he can really live in the wild anymore
40:55if you look back through history
41:12you can see that humans we have wiped out many many species
41:17something like 2 or 3 species of bird and mammal disappearing every year or so
41:22we all know examples like dodos and the passenger pigeon
41:25and the great flightless birds of New Zealand
41:28if you calculate from this rate of loss
41:31you might work out that all birds and all mammals on earth
41:34will have disappeared within a few thousand years
41:36as a result of human activity
41:38and many people then would interpret that to mean
41:41we are definitely in an extinction event
41:43as big as any of the big five in the past
41:46and that this one is unique because it's being caused by human activity
41:50it's not only the destruction of forests that causes concern
41:59many scientists also fear a drastic rise in temperature
42:03the extreme heat that eventually led to the Permian mass extinction
42:08began with the movement of continents
42:10and was boosted by the Earth's natural release of greenhouse gases
42:14today man is producing greenhouse gases on a major scale
42:21and like the Permian mass extinction
42:24the heating effect could be catastrophic for life on Earth
42:29I believe that what we are doing to the atmosphere
42:32creating greenhouse gas emissions
42:34is in every way comparable to what happened at the end of the Permian
42:38the end Permian event is to me and my mind a greenhouse event
42:42it is caused by excess CO2
42:44we industrialized humans are doing the exact same thing to the atmosphere
42:49by 2300 or 2400
42:53so we're looking three or four hundred years from now
42:55we may have as much as 60% of all species on Earth today extinct
43:00this sounds like the end of life as we know it
43:05but for the future of evolution of life on Earth
43:09it might not be such a tragedy
43:11for some scientists like Colin Tudge
43:15mass extinctions are not only unavoidable
43:18but essential
43:20mass extinction is absolutely fundamental I think to the history of life on Earth
43:27because Darwin had the idea in the mid 19th century
43:31that so long as you had competition between creatures
43:34then you would get change occurring little by little effectively forever
43:38you know the predators would gradually get sharper teeth
43:41and the prey animals would learn to run faster
43:44and then the predators would get even sharper teeth
43:46and so on and so on
43:47so they would go on changing
43:48and now it seems to be fairly clear
43:51that actually if conditions don't change
43:53then sooner or later
43:55the different creatures that are competing in any one ecosystem
43:59just sort of settle down with each other
44:01and they stay much the same
44:02more or less indefinitely
44:04and it's become sort of fairly clear
44:06that things do settle down in that way
44:08and unless you every now and again
44:10you had these huge extinctions
44:12then evolution would have stopped
44:14and you know we would still be
44:15we would still be amphibians
44:16or we would still be invertebrates
44:17or whatever
44:18and creatures like us would never have appeared
44:20because every now and again
44:21you just have to kick the system
44:22you just have to clear the stage
44:24and just start again
44:25with a few of the creatures that were there before
44:27re-evolving to fill all the niches
44:29so could humans be victims of the current mass extinction
44:37this evolutionary clean-out
44:39humans probably would survive
44:43because one of the factors that helps species to survive
44:47is to be abundant
44:49but especially to be widespread
44:50and humans amongst the various species on earth
44:53are immensely widespread
44:54from poles to equators
44:56so yes indeed
44:57whatever crisis happens
44:58humans are very likely to survive
45:00well if you love humans as I do
45:02the worst case is that we could go extinct
45:04but I don't think that will happen
45:05I believe humans are the least endangered species on the planet
45:08and that's I think maybe the great curse
45:11is that we may end up a thousand years from now
45:14like lystrosaurs in a very empty world
45:19but it's not clear that humans could withstand all global disasters
45:25if the earth was hit by an asteroid like the one that wiped out the dinosaurs
45:30it's far from certain that we would survive
45:33well humans may be pretty good survivors
45:39and of course humans like cockroaches would survive all kinds of climatic changes and other sorts of crises
45:46but some of the big crises that have caused mass extinctions in the past
45:50could very well wipe out humans as well
45:52so that if you think of the massive volcanism
45:54or some of these huge asteroid impacts on the earth
45:58humans there would really suffer badly
46:00you couldn't just devise a bit of technology to avoid it
46:03it's not just like the greenhouse effect that we're seeing at the moment
46:06which we can survive
46:10Humankind often regards themselves as some sort of pinnacle of evolution
46:14some sort of end product as if there was some sort of guiding force putting them there
46:19it of course cannot be true
46:22because we can see the steps that it took to get to humankind
46:27and humankind of course is as imperfect as all those steps that it took
46:31to regard humankind as some sort of great survivor
46:38as opposed to any other anything else on the earth at the moment is irrational
46:43if humans were wiped out in a mass extinction would anything else replace us?
46:52just as the Lystrosaurus was the unlikely survivor of the Permian mass extinction
47:03so too the survivor species of a future extinction is hard to predict
47:09if you remove humans from the planet we're like a big brake on a big car
47:18and we are the brake on those wheels
47:20as soon as we are removed the car takes off and that car is evolution
47:24the rate of evolution has been slowed on this planet because humans are holding it down
47:30you remove us that brake is removed and there's opportunity
47:34so if homo sapiens became extinct anything could happen
47:40we might even be succeeded by animals less developed than us
47:46the dinosaurs which followed the therapsids were grander in scale
47:51but almost certainly less advanced
47:55the lesson is that evolution is not logical
47:58and its outcome is hard to predict
48:01I think one thing people don't understand is that evolution does not go in a direct line
48:07you know from the beginning of life on through to the present day
48:12but in fact there have been many stops and starts
48:16life is diversified then there are mass extinction events which wipe out a lot of life
48:20and then it starts up again often in a somewhat different direction
48:24if humans left I suspect we would see a world that is absolutely inundated and covered by rodents
48:31with the disappearance of humans you would find rodents and rodent-like creatures
48:36in terms of the mammals taking over the world
48:39and that's not a vision that I particularly want to see
48:42and if in amongst the rodents there's a small group of human survivors
48:54what would their future hold?
48:59but supposing there was some kind of catastrophe
49:01let's say another asteroid or some ecological collapse
49:04and human beings became isolated into smaller populations on different sort of islands
49:09like Madagascar for example which is just about the right sort of size
49:12then we have the conditions in which evolution might start to happen all over again
49:17but would there in fact be a premium on brains?
49:20in other words would natural selection favour further braininess?
49:24well there's reasons for thinking it might not
49:26I mean one of the things is that brains are tremendously expensive organs
49:30they take about 20% of all our metabolic energy
49:32so unless the brain was giving you a good payoff in terms of extra food
49:39it wouldn't be favoured by natural selection
49:41and one could see that instead qualities such as muscularity or agility might be favoured instead
49:46in other words human beings in future evolutionary time
49:49could under those circumstances become more ape-like again rather than becoming brainier
49:53following the Permian mass extinction
50:00the Lystrosaurus survived for 10 million years before it began to vanish from the fossil records
50:07if the pattern of human existence is anything like that of the Lystrosaurus
50:13at least we can expect to be around for 10 million years
50:18if you can answer the question what was the name of the biggest therapsid
50:32you could win one of the animatronics models featured in the programme
50:36the number is 0891 888 1290
50:40calls will cost no more than 75 pence and lines are open until the end of the month
50:45next week Equinox looks at why the condition of autism may throw new light on male and female relationships
51:02that's next Monday here on 4 at 9
51:05what's your home worth? 40? 50 grand or more?
51:10if you live in a new house you could be in for a shock
51:13because you may find your house guarantee is useless
51:17and that your home is worth a lot less than you think
51:20how safe is a new house?
51:23Dispatches Thursday at 9 on 4
51:26Fitz continues
51:28one week
51:44all the time
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