0:00:08 > 0:00:12'Imagine you woke one day to find yourself
0:00:12 > 0:00:14living in the body of a creature
0:00:14 > 0:00:18completely different to what you used to be.
0:00:21 > 0:00:24Your shape, your body parts,
0:00:24 > 0:00:26your individual cells.
0:00:28 > 0:00:33Rearranged by some unknown force into something new.
0:00:33 > 0:00:35You have been transformed.
0:00:37 > 0:00:40This is what happens to countless creatures.
0:00:43 > 0:00:45It is called metamorphosis.
0:00:47 > 0:00:50It is how the tadpole is changed into a frog.
0:00:53 > 0:00:55How the caterpillar becomes a butterfly.
0:00:58 > 0:01:01It is one of nature's most powerful phenomena,
0:01:01 > 0:01:05and to me one of nature's most mysterious.'
0:01:06 > 0:01:11Metamorphosis is such a spectacularly odd kind of change.
0:01:11 > 0:01:14A creature stops itself in its tracks,
0:01:14 > 0:01:17seems to tear itself apart
0:01:17 > 0:01:20and then rebuilds itself as a completely different kind of creature.
0:01:21 > 0:01:24I don't think you can help but be intrigued by that.
0:01:29 > 0:01:31'Generations of artists and writers
0:01:31 > 0:01:35have been drawn to the idea of metamorphosis.
0:01:35 > 0:01:38Imagining creatures that shapeshift,
0:01:38 > 0:01:41that turn into something else.
0:01:43 > 0:01:48Visions that feed our dreams and nightmares.'
0:01:50 > 0:01:53I wonder if our fascination with metamorphosis
0:01:53 > 0:01:57is because somewhere written deep in the science of it
0:01:57 > 0:02:01there's a half-perceived truth about us.
0:02:01 > 0:02:05'So how does nature work, this seeming miracle
0:02:05 > 0:02:07of turning one creature into another?
0:02:10 > 0:02:15What is the truth behind this extraordinary, beautiful process
0:02:15 > 0:02:18that has taken such a hold on our imagination?
0:02:19 > 0:02:23And might it even in some way happen to us?
0:02:44 > 0:02:45Two thousand years ago,
0:02:45 > 0:02:49the Roman poet Ovid wrote an epic poem
0:02:49 > 0:02:52retelling tales from Roman and Greek mythology
0:02:52 > 0:02:56of a man being turned into a werewolf,
0:02:56 > 0:02:59a woman changed into a tree.
0:03:00 > 0:03:02The title Ovid chose for his poem
0:03:02 > 0:03:04was Metamorphoses,
0:03:04 > 0:03:09a word from ancient Greek that means to change form.
0:03:12 > 0:03:14And many hundreds of years later,
0:03:14 > 0:03:20when scientists began to study the process of real transformation in nature,
0:03:20 > 0:03:23they chose to use this same word.'
0:03:31 > 0:03:34I've always thought that metamorphosis was weirdly interesting.
0:03:34 > 0:03:38Apart from the phenomenon of a creature turning itself into another creature,
0:03:38 > 0:03:41what intrigues me is the fact that
0:03:41 > 0:03:44metamorphosis as a concept
0:03:44 > 0:03:46has two forms, two meanings.
0:03:46 > 0:03:48There's the scientific meaning
0:03:48 > 0:03:51but there's also a metaphorical meaning
0:03:51 > 0:03:54that we find in books and that we use when we talk about ourselves.
0:03:55 > 0:03:58And I suppose what interests me
0:03:58 > 0:04:00is whether the connection is just metaphorical
0:04:00 > 0:04:05or whether there's something deeper going on, a deeper connection.
0:04:22 > 0:04:28'I want to begin by understanding more about what metamorphosis means in the natural world.
0:04:32 > 0:04:34Most of us think we're familiar with it.
0:04:35 > 0:04:39Every child knows that a caterpillar turns into a butterfly
0:04:42 > 0:04:45but it seems to me that even this transformation
0:04:45 > 0:04:48is rather extraordinary.
0:04:54 > 0:04:57Professor Stuart Reynolds is an entomologist
0:04:57 > 0:04:59who has studied the intricate sequence of events
0:04:59 > 0:05:02that makes up this metamorphosis.'
0:05:06 > 0:05:09This here is a chrysalis
0:05:09 > 0:05:12and the chrysalis
0:05:12 > 0:05:18is a stage intermediate between the caterpillar and the butterfly.
0:05:18 > 0:05:24So one of those attaches itself and turns into that?
0:05:26 > 0:05:29'Virtually every stage of metamorphosis
0:05:29 > 0:05:33seems to have something unexpected about it
0:05:34 > 0:05:39and how the caterpillar turns itself into a chrysalis is no exception.'
0:05:39 > 0:05:43- These guys live in a kind of suit of armour all the time.- Yeah.
0:05:43 > 0:05:47Their skeleton is on the outside and so if they want to grow,
0:05:47 > 0:05:51they have to grow a new skeleton that's a bit bigger
0:05:51 > 0:05:53- and we call this moulting. - Right.
0:05:53 > 0:05:58When you moult you split the old skeleton and crawl out
0:05:58 > 0:06:02- and then you inflate the new one from inside.- OK.
0:06:02 > 0:06:06Sometimes by swallowing air, for example, blowing themselves up.
0:06:06 > 0:06:07Fantastic!
0:06:07 > 0:06:13The formation of this chrysalis is just another example of moulting.
0:06:13 > 0:06:16There's probably several days
0:06:16 > 0:06:18during which it's forming
0:06:18 > 0:06:23this rather different shape of creature inside the old caterpillar.
0:06:23 > 0:06:25- In, still inside itself? - Absolutely inside.
0:06:25 > 0:06:26Oh, that's weird.
0:06:26 > 0:06:30So the demolition job of the caterpillar
0:06:30 > 0:06:34and the beginnings of the construction of the new creature
0:06:34 > 0:06:37is happening while it's still in that skin?
0:06:37 > 0:06:40Yes. While it still looks like a caterpillar,
0:06:40 > 0:06:41but actually it's not really.
0:06:46 > 0:06:48'The formation of the chrysalis
0:06:48 > 0:06:50hidden inside the body of the caterpillar
0:06:50 > 0:06:55marks the beginning of the metamorphosis.
0:06:55 > 0:06:57But what triggers this in the first place?
0:06:59 > 0:07:04What tells the caterpillar that this moult won't be like the others?
0:07:04 > 0:07:07That it is time to begin the change into a butterfly.'
0:07:10 > 0:07:14When it's a last-stage caterpillar like this one,
0:07:14 > 0:07:17it has some clever way of saying,
0:07:17 > 0:07:22"Well, actually, this next moult is going to be different, chaps."
0:07:22 > 0:07:24- Klaxons start going off! - Absolutely.
0:07:24 > 0:07:26Yeah, it's a real emergency moment
0:07:26 > 0:07:31because absolutely every tissue inside the caterpillar
0:07:31 > 0:07:34is going to have to be involved in this.
0:07:35 > 0:07:38What actually triggers that?
0:07:38 > 0:07:42That's a hormone called a juvenile hormone.
0:07:42 > 0:07:44And it's a timing signal.
0:07:44 > 0:07:46As long as you have the juvenile hormone,
0:07:46 > 0:07:48you go on being a caterpillar.
0:07:48 > 0:07:51You take it away and then you start to metamorphose.
0:07:59 > 0:08:03'As the juvenile hormone leaves the body of the caterpillar,
0:08:03 > 0:08:07so a cascade of processes is set in motion.
0:08:09 > 0:08:12And the metamorphosis begins.
0:08:13 > 0:08:18The caterpillar stops feeding and finds a resting spot.
0:08:19 > 0:08:21It makes itself a little pad of silk
0:08:21 > 0:08:27and from this hangs upside-down by the tip of its tail.
0:08:30 > 0:08:34For the final time, the caterpillar sheds its skeleton
0:08:36 > 0:08:40and the chrysalis that has been growing inside emerges.
0:08:46 > 0:08:48Where is the creature that was?
0:08:49 > 0:08:51And where is the creature that will be?
0:09:04 > 0:09:07This X-ray scan is as close as we can get
0:09:07 > 0:09:10to seeing the scale of the transformation
0:09:10 > 0:09:13that is occurring inside the chrysalis.
0:09:15 > 0:09:17The structures highlighted in yellow
0:09:17 > 0:09:19make up the respiratory system
0:09:19 > 0:09:22that allows the caterpillar to breathe.
0:09:23 > 0:09:25Slowly, through the course of metamorphosis,
0:09:25 > 0:09:28this is entirely remodelled.
0:09:30 > 0:09:34Almost all the other major organs are also changed.
0:09:38 > 0:09:41It is a process that can take for some species a few days,
0:09:41 > 0:09:43others weeks.
0:09:44 > 0:09:48But when it is done, a new creature emerges.
0:09:59 > 0:10:03The caterpillar has been replaced by a very different being.
0:10:04 > 0:10:06A creature with wings,
0:10:06 > 0:10:10with a new brain, eyes and legs.
0:10:11 > 0:10:15And most important, the ability to reproduce.
0:10:21 > 0:10:23But crucially, remarkably,
0:10:23 > 0:10:27it is still the same individual insect.
0:10:27 > 0:10:31Its unique genetic code has not changed.
0:10:33 > 0:10:38No wonder people have seen something almost magical in this transformation.
0:10:46 > 0:10:48According to legend,
0:10:48 > 0:10:50it was when the Hindu god Brahma
0:10:50 > 0:10:54watched the caterpillars in his garden change into chrysalises
0:10:54 > 0:10:55and then into butterflies
0:10:55 > 0:11:00that he conceived the idea of reincarnation.
0:11:00 > 0:11:02Perfection through rebirth.
0:11:03 > 0:11:07The ancient Greeks associated the butterfly with the soul
0:11:07 > 0:11:12and used the same word, psyche, to describe both.
0:11:14 > 0:11:18But what is the biological meaning behind this metamorphosis?
0:11:18 > 0:11:21Why lead two lives in one?'
0:11:23 > 0:11:25If you're doing perfectly well as a caterpillar,
0:11:25 > 0:11:27why not just stay as a caterpillar?
0:11:27 > 0:11:30I mean, what do you think the purpose of the trick is?
0:11:30 > 0:11:33Well, the trouble with being a caterpillar
0:11:33 > 0:11:37is that it's hard to get around.
0:11:37 > 0:11:40And if you see what these caterpillars
0:11:40 > 0:11:43- have done to this plant here, there's...- Yes.
0:11:43 > 0:11:47There's not a lot of food left for another generation of caterpillars.
0:11:47 > 0:11:53So if I were a caterpillar and I had ambitions to reproduce,
0:11:53 > 0:11:55I would like to go somewhere else.
0:11:55 > 0:11:59So what do you do? Well, you have some wings.
0:11:59 > 0:12:04All right, but are you saying then that the purpose is to do two different jobs?
0:12:04 > 0:12:05Yeah.
0:12:05 > 0:12:08The really great thing about metamorphosis
0:12:08 > 0:12:12is it allows specialisation.
0:12:12 > 0:12:15You can have an adult that has wings
0:12:15 > 0:12:18that allows you to find mates,
0:12:19 > 0:12:22fly around, find the right kind of food plant,
0:12:22 > 0:12:27and then you can have a specialised caterpillar form
0:12:27 > 0:12:29that does really nothing but eat.
0:12:29 > 0:12:35It just enables each stage to do its job in the best way possible.
0:12:36 > 0:12:40'And this is the real advantage of metamorphosis.
0:12:40 > 0:12:42By dividing the creature's life into two parts,
0:12:42 > 0:12:47each life form can perform very different roles.'
0:12:50 > 0:12:53I think one of the most interesting things for me talking to Stuart Reynolds
0:12:53 > 0:12:58was you have a creature which has lots of legs and trundles about in plants.
0:12:58 > 0:13:01It's turning into something that has few legs and flies.
0:13:01 > 0:13:06And it's easy, I suppose, to be focused on that
0:13:06 > 0:13:09and his point was that that's almost hiding
0:13:09 > 0:13:12something more important about metamorphosis,
0:13:12 > 0:13:15which is what you're really changing is a creature
0:13:15 > 0:13:18that can't move about much and which eats leaves
0:13:18 > 0:13:21into one which feeds on nectar and flies.
0:13:22 > 0:13:26So the real change isn't a physical transformation, however spectacular it looks,
0:13:26 > 0:13:30the real change is in the way of life of the creature.
0:13:33 > 0:13:36'If it were only butterflies that used this trick
0:13:36 > 0:13:38of living two lives in one,
0:13:38 > 0:13:41then metamorphosis would be an oddity,
0:13:41 > 0:13:43but it is not.
0:13:51 > 0:13:54Of the one million species of insect we know of today,
0:13:57 > 0:13:58from beetles
0:14:01 > 0:14:03to bees
0:14:05 > 0:14:06to flies,
0:14:06 > 0:14:10most undergo some form of metamorphosis.
0:14:11 > 0:14:16It's a trick insects evolved around 300 million years ago.
0:14:19 > 0:14:23Yet metamorphosis is more widespread than just the insects
0:14:23 > 0:14:25and more ancient too.
0:14:28 > 0:14:32It is in the ocean where metamorphosis first evolved
0:14:32 > 0:14:36and where it takes on even more dramatic forms.
0:14:58 > 0:14:59These are adult sea urchins.
0:14:59 > 0:15:02They live in the depths of the ocean floor
0:15:02 > 0:15:06feeding mainly on algae and other plants.
0:15:09 > 0:15:13But the sea urchins begin life as very different creatures,
0:15:13 > 0:15:16tiny microscopic larvae,
0:15:16 > 0:15:20which swim in surface waters and feed off plankton.
0:15:24 > 0:15:27Doctor Paola Oliveri is a biologist
0:15:27 > 0:15:30who studies the process of development in sea urchins.'
0:15:33 > 0:15:37So you can see this is a sea urchin larva.
0:15:37 > 0:15:40- Here you can see there is the mouth, stomach.- Right.
0:15:40 > 0:15:42This big round thing.
0:15:42 > 0:15:46- Now this one's not metamorphosing yet?- Not yet.
0:15:46 > 0:15:47It's getting ready.
0:15:50 > 0:15:55'How this larva is transformed into the juvenile or young adult sea urchin
0:15:55 > 0:15:59shows metamorphosis at its most disturbing.
0:16:01 > 0:16:04For even before the process is underway,
0:16:04 > 0:16:09what this creature will become can be seen growing inside it.'
0:16:09 > 0:16:11So what is that?
0:16:11 > 0:16:15That is the little juvenile that is growing...
0:16:15 > 0:16:18- That...- Inside the larva.
0:16:18 > 0:16:22- This is turning into that? - Yes. One inside the other.
0:16:22 > 0:16:24And in another couple of hours,
0:16:24 > 0:16:27- the little juvenile here... - Yeah.
0:16:27 > 0:16:31- ..will pop out, literally. - Pop? Pop out?
0:16:31 > 0:16:33Yes, so that first tube feet,
0:16:33 > 0:16:39which are this little tiny kind of like flexible structure
0:16:39 > 0:16:41that we see in the adults,
0:16:41 > 0:16:44the first five tubes will go out.
0:16:44 > 0:16:46- Punctures its way through? - Punctures it.
0:16:46 > 0:16:49- It will finish the metamorphosis. - What about the larval stage?
0:16:49 > 0:16:55Well, then it's completely basically reabsorbed and dies.
0:16:55 > 0:16:57- Reabsorbed? - Yeah, reabsorbed.
0:16:57 > 0:16:58Is that a polite word for being eaten?
0:16:58 > 0:17:00Yes, in a way.
0:17:01 > 0:17:06Part of it and part of it really dies by natural death.
0:17:08 > 0:17:10'In the metamorphosis of the sea urchin,
0:17:10 > 0:17:14the juvenile takes over the body of its larval host
0:17:14 > 0:17:16and then eats it.
0:17:22 > 0:17:27The last act of the larva is to swim down to the deep ocean
0:17:27 > 0:17:29where the juvenile will live.
0:17:35 > 0:17:40And once it reaches the seabed, the metamorphosis begins.
0:17:41 > 0:17:46This time-lapse footage shows the process unfolding.
0:17:49 > 0:17:53The tube feet of the juvenile puncture through the body of the larva
0:17:56 > 0:18:00and slowly, one by one, its spines emerge.
0:18:04 > 0:18:09The juvenile has literally turned the larva inside out
0:18:09 > 0:18:10as if it were a sock
0:18:10 > 0:18:14and in the process extinguished its life.
0:18:16 > 0:18:20For at the end, what is left is just the one life form
0:18:20 > 0:18:22of the juvenile sea urchin.
0:18:32 > 0:18:34The creature's body and its way of life
0:18:34 > 0:18:37have been completely transformed.'
0:18:49 > 0:18:53It does have that slight feeling of the alien popping out from inside.
0:18:53 > 0:18:56It's not really anything like the kind of
0:18:56 > 0:19:00garden variety metamorphosis that we're used to.
0:19:01 > 0:19:03No, it's very different, it's very dramatic.
0:19:03 > 0:19:08With the caterpillar butterfly, most of the animal,
0:19:08 > 0:19:11the cells and the body plan of the caterpillar
0:19:11 > 0:19:15actually is retained after metamorphosis into butterflies.
0:19:15 > 0:19:18This case is very different.
0:19:18 > 0:19:21The larva will not exist any more.
0:19:21 > 0:19:24- Right.- Will be reabsorbed and die
0:19:24 > 0:19:26and will be completely different form.
0:19:27 > 0:19:29The completely different form I can cope with
0:19:29 > 0:19:33but what's slightly worrying here is the second one has got started
0:19:33 > 0:19:35before the first one's stopped.
0:19:35 > 0:19:37- Yes.- Does that not bother you?
0:19:38 > 0:19:40- No. - No, OK, it's just me then!
0:19:40 > 0:19:43It's very dramatic change
0:19:43 > 0:19:46but if you think about the sea urchins
0:19:46 > 0:19:49are actually more related to us
0:19:49 > 0:19:52than a caterpillar and a butterfly.
0:19:52 > 0:19:53- Really?- Yes.
0:19:53 > 0:19:56They're actually our direct cousin.
0:19:57 > 0:20:01Wow, all I can say is I'm glad we changed our way of reproducing and developing
0:20:01 > 0:20:04cos I don't really fancy that!
0:20:07 > 0:20:11'The metamorphosis of the sea urchin appears alien to us,
0:20:11 > 0:20:14but others in the ocean are even more bizarre.
0:20:16 > 0:20:20This is the larva of a species of starfish called Luidia sarsi.
0:20:21 > 0:20:23Just as with the sea urchin,
0:20:23 > 0:20:27the two life forms exist together
0:20:27 > 0:20:29for at the end of the larval form
0:20:29 > 0:20:32can be seen the juvenile form,
0:20:32 > 0:20:34a miniature orange starfish.
0:20:35 > 0:20:40This grows attached to the larva until the moment of metamorphosis
0:20:40 > 0:20:41when it breaks free.
0:20:42 > 0:20:47For a short time, the two forms of the same creature live parallel lives
0:20:47 > 0:20:50until the larva dies.
0:20:54 > 0:20:56With both the starfish and the sea urchin,
0:20:56 > 0:21:01we see the different forms of the creatures overlap in a disturbing way.
0:21:03 > 0:21:07Unlike the caterpillar, this is not simply a remodelling job.
0:21:07 > 0:21:11Here the juvenile is essentially built from scratch.
0:21:13 > 0:21:15But what is common to all these cases
0:21:15 > 0:21:18is that the same genetic code, the same genome,
0:21:18 > 0:21:23controls both versions of the creature before and after metamorphosis.'
0:21:26 > 0:21:29- From the genetic point of view it's the same genome.- Right.
0:21:29 > 0:21:31It's the same creature.
0:21:31 > 0:21:34How does the genome work then? They're different sets of genes?
0:21:34 > 0:21:37No, actually most of the genes
0:21:37 > 0:21:43are going to be used in both life parts.
0:21:43 > 0:21:46In the larva and in the juvenile.
0:21:46 > 0:21:50Certainly there are genes that they are specific for the larval stages
0:21:50 > 0:21:55and genes that they are specific for adult stages.
0:21:55 > 0:21:58That's clever as a piece of engineering though.
0:21:58 > 0:22:02It's like having a factory that follows a programme
0:22:02 > 0:22:04and turns out bicycles
0:22:04 > 0:22:08and then the exact same programme turns out hot air balloons.
0:22:08 > 0:22:09That's beautiful.
0:22:09 > 0:22:12- HE LAUGHS - That's economic! It's magical.
0:22:17 > 0:22:20'In the ocean, many creatures shapeshift,
0:22:20 > 0:22:23transforming themselves into something else.
0:22:27 > 0:22:29The spiny lobster moults and crawls out of its skeleton
0:22:29 > 0:22:32to leave its larval life behind.
0:22:35 > 0:22:38The sea squirt larva absorbs its own tail
0:22:38 > 0:22:40and consumes its own brain
0:22:40 > 0:22:43to allow its juvenile form to take over.
0:22:48 > 0:22:52Metamorphosis is even witnessed in certain species of fish.
0:22:57 > 0:23:00The flat fish moves its eyes to the same side of its head
0:23:00 > 0:23:04so it can better spot predators in its adult life
0:23:04 > 0:23:06swimming on the ocean floor.
0:23:09 > 0:23:13In each case, the creatures are changing not just how they look,
0:23:13 > 0:23:15but how they live.
0:23:15 > 0:23:20Is it any wonder that metamorphosis holds such intrigue for us?'
0:23:23 > 0:23:27I suppose I did think that metamorphosis was just something
0:23:27 > 0:23:29strange that tadpoles and butterflies did
0:23:30 > 0:23:32but there are so many branches of life
0:23:32 > 0:23:34that benefit from metamorphosis.
0:23:34 > 0:23:38Insects, amphibians, marine invertebrates, crustaceans.
0:23:38 > 0:23:41It begins to make me wonder
0:23:41 > 0:23:44if evolution couldn't have found some way
0:23:44 > 0:23:47for us to benefit from the same trick.
0:24:05 > 0:24:10'The time when human beings change the most, physically, is in the womb.
0:24:11 > 0:24:15So perhaps we should consider the transformations that take place here
0:24:15 > 0:24:17and what happens when we are born.'
0:24:22 > 0:24:24- Do you see the baby's face just? - Yes.
0:24:24 > 0:24:27- Have you seen this before, Michelle? - No.
0:24:27 > 0:24:29Wow! I'll take a picture. I'll take a picture or two.
0:24:29 > 0:24:31That's amazing.
0:24:31 > 0:24:33It is, it's beautiful actually.
0:24:33 > 0:24:36'Michelle's baby is 27 weeks old
0:24:36 > 0:24:41and is being scanned by consultant obstetrician Christoph Lees.'
0:24:43 > 0:24:47How many weeks ago would the baby have just been a little tiny ball of cells?
0:24:47 > 0:24:49Well, we're 27 weeks now
0:24:49 > 0:24:53so about 20 weeks ago at about six, seven weeks,
0:24:53 > 0:24:57the baby would be about half a centimetre,
0:24:57 > 0:24:58a centimetre long, this long.
0:25:00 > 0:25:03'The most obvious type of change that occurs in the womb
0:25:03 > 0:25:05is the change in shape.
0:25:07 > 0:25:10How from a ball of cells a human form develops,
0:25:10 > 0:25:15with a head, eyes and limbs.
0:25:16 > 0:25:19It is a slow, gradual process
0:25:19 > 0:25:23that occurs in the first 12 weeks of pregnancy,
0:25:25 > 0:25:29but it is not the only type of change that the baby goes through.
0:25:31 > 0:25:36A transformation far more abrupt and dramatic is yet to happen.'
0:25:36 > 0:25:41So you can see the lungs. There's the heart and these are the lungs.
0:25:41 > 0:25:43The lungs are full of fluid at the moment.
0:25:43 > 0:25:47Within about 30 seconds of the baby being born,
0:25:47 > 0:25:51all that fluid is expelled and the lungs suddenly expand.
0:25:51 > 0:25:53SOUND OF HEART BEATING
0:25:54 > 0:25:57'The physiological change that will occur to this baby at birth
0:25:57 > 0:26:01goes well beyond the baby inhaling its first breath of air.
0:26:04 > 0:26:06This is when many of its organs
0:26:06 > 0:26:08will begin to work properly for the first time,
0:26:11 > 0:26:15and even something as fundamental as how blood flows around its heart and lungs
0:26:15 > 0:26:17will be transformed.'
0:26:20 > 0:26:23Do you see that blue flash there?
0:26:23 > 0:26:27- And there's a lot of blood there, isn't there?- Yes. Seems like it.
0:26:27 > 0:26:31And that is going from the right side of the heart into the baby's aorta.
0:26:31 > 0:26:35So the blood that goes into the right side of the heart
0:26:35 > 0:26:38- that in you and me goes round the lungs...- Yes, yes.
0:26:38 > 0:26:41- Then goes back into the left side of the heart and is pumped round the body.- Yes.
0:26:41 > 0:26:45Instead it bypasses the lungs
0:26:45 > 0:26:47and goes straight into the aorta
0:26:47 > 0:26:50through that blue tube there.
0:26:50 > 0:26:53It's not of course a blue tube, but it's called the ductus arteriosus.
0:26:53 > 0:26:54What happens when the baby is born?
0:26:54 > 0:26:58When the baby's born, that collapses very very quickly.
0:26:58 > 0:27:00- What, like that? - Within minutes.
0:27:00 > 0:27:03Those moments, a few moments before and a few moments after,
0:27:03 > 0:27:07the child is changing in how it works in its internal structure,
0:27:07 > 0:27:09probably more radically than in any other time in its life.
0:27:09 > 0:27:11The first 24 hours of a baby's life,
0:27:11 > 0:27:13the most amazing changes are happening.
0:27:13 > 0:27:15In the lungs, in the blood vessels,
0:27:15 > 0:27:18some shrinking, others opening up,
0:27:18 > 0:27:21- so although to you, you look at a baby and...- It's finished.
0:27:21 > 0:27:24Baby looks the same on the day baby's born
0:27:24 > 0:27:26perhaps to the day after to the day after.
0:27:26 > 0:27:30In that time some truly remarkable things have happened in the baby's circulation
0:27:30 > 0:27:32and in the baby's internal organs.
0:27:32 > 0:27:35And of course the kidneys start functioning even better.
0:27:35 > 0:27:36No wonder babies are slightly preoccupied.
0:27:36 > 0:27:40They've got to learn everything in those first few minutes.
0:27:40 > 0:27:42I'm amazed they don't cry more than they do!
0:27:42 > 0:27:45Because they've got an awful lot to be going on with.
0:27:49 > 0:27:53'So in fundamental ways the body of the newborn baby
0:27:53 > 0:27:56works quite differently to how it worked in the womb.
0:28:00 > 0:28:04Only at birth does the baby's blood begin to circulate as it does in us.
0:28:07 > 0:28:12Only then does the baby begin to get oxygen from its lungs
0:28:12 > 0:28:15rather than from the placenta.'
0:28:20 > 0:28:25The changes that you've described are really, they're profound.
0:28:25 > 0:28:27Especially the ones you say happen at birth.
0:28:28 > 0:28:31Is it like metamorphosis?
0:28:31 > 0:28:35Does it share enough similarities with what we would call metamorphosis, do you think?
0:28:35 > 0:28:40I suppose you would be thinking metamorphosis as a change in form
0:28:40 > 0:28:45and where you have moths developing from caterpillars.
0:28:45 > 0:28:47That of course is clear change in form.
0:28:47 > 0:28:52What we're getting with a baby is something much more subtle but no less dramatic.
0:28:52 > 0:28:57Certainly an internal change in form, an internal metamorphosis, if you like,
0:28:57 > 0:29:00but I don't think we could call it metamorphosis,
0:29:00 > 0:29:03metamorphosis as we see in insects.
0:29:05 > 0:29:09'The physical changes that occur at birth are remarkable,
0:29:10 > 0:29:14but in the view of science are better described as development.
0:29:19 > 0:29:24But does this mean that metamorphosis plays no role in our lives?'
0:29:26 > 0:29:30You can't get away from the fact that we are the most extraordinarily changeable creatures
0:29:30 > 0:29:32so it would still seem strange to me
0:29:32 > 0:29:36if metamorphosis didn't happen in our lives,
0:29:36 > 0:29:39just not in a simple straightforward way.
0:29:53 > 0:29:57'We certainly seem to be afraid that it might happen to us.
0:30:00 > 0:30:02Writers and storytellers have long recognised
0:30:02 > 0:30:04that something about this type of change
0:30:04 > 0:30:07that we see in caterpillars and tadpoles
0:30:07 > 0:30:11nevertheless taps into some deep-set fear.'
0:30:17 > 0:30:19We have a strong sense of identity.
0:30:19 > 0:30:23Our sense of identity is bound up
0:30:23 > 0:30:25with our outer appearance with our shape.
0:30:25 > 0:30:27We look in the mirror and think, Oh yeah, that's me.
0:30:27 > 0:30:33So we don't expect any radical change in that outer appearance.
0:30:38 > 0:30:43We would like to be able to determine what shape we are
0:30:43 > 0:30:47and what changes are undertaken that affect us.
0:30:47 > 0:30:53When we find we can't then of course we lose control.
0:31:00 > 0:31:05'Most famously, this anxiety and fear of transformation
0:31:05 > 0:31:11was explored by Franz Kafka in his short story The Metamorphosis.
0:31:14 > 0:31:17Kafka imagines a man, Gregor Samsa,
0:31:17 > 0:31:23who awakes one day to find himself transformed into a beetle.
0:31:26 > 0:31:31In his new form the character slowly loses everything he once was.
0:31:31 > 0:31:38His place in society, his family and ultimately his life.'
0:31:39 > 0:31:44Kafka is using an image of the man
0:31:44 > 0:31:47who wakes up as a beetle
0:31:47 > 0:31:49in order to explore
0:31:49 > 0:31:56somebody's fall out of the social order he was used to
0:31:56 > 0:31:57and he was familiar with.
0:31:57 > 0:32:02He was used to being in this deadpan terrible job
0:32:02 > 0:32:05that had him work him all the hours that God sent
0:32:05 > 0:32:08and he hates the job, but it's what he's used to.
0:32:09 > 0:32:10He does it all the time
0:32:10 > 0:32:13and all of a sudden that is taken away from him.
0:32:15 > 0:32:17'Kafka's story isn't the only one
0:32:17 > 0:32:22and metamorphosis isn't always something we imagine forced upon us.
0:32:23 > 0:32:27When the respectable Dr Jekyll takes a potion to change himself
0:32:27 > 0:32:29into the vile Mr Hyde,
0:32:29 > 0:32:34the transformation is still frightening but it is self-inflicted.'
0:32:36 > 0:32:39So if you think of Jekyll and Hyde,
0:32:39 > 0:32:43we have one man who feels
0:32:43 > 0:32:49he cannot, in the shape of Dr Jekyll,
0:32:49 > 0:32:54live out everything that he would like to live and be,
0:32:54 > 0:32:58therefore invents Mr Hyde as his dark alter ego.
0:32:58 > 0:33:04Dr Jekyll realised that man is not truly one, but two.
0:33:04 > 0:33:08And he felt very much this dual identity.
0:33:08 > 0:33:11The person he wanted to be, the good person,
0:33:11 > 0:33:15but then he also had instincts and desires
0:33:15 > 0:33:19that were not acceptable to society.
0:33:24 > 0:33:26I think what the writers who use metamorphosis
0:33:26 > 0:33:29as a metaphor for change and transformation are telling us,
0:33:31 > 0:33:35is that our attitude towards change is deeply ambivalent.
0:33:35 > 0:33:38On the one hand we can all like change,
0:33:38 > 0:33:39but on the other hand,
0:33:39 > 0:33:44I think we're all aware that change can be something we are swept up in.
0:33:59 > 0:34:03'Our relationship with change is very different to how metamorphosis
0:34:03 > 0:34:05would appear to work in nature.
0:34:08 > 0:34:12Where it seems to be a process that runs like clockwork,
0:34:12 > 0:34:15rigid and pre-programmed.
0:34:16 > 0:34:19But there is a creature that shows this isn't always the case.
0:34:23 > 0:34:25The humble tadpole.
0:34:37 > 0:34:40The beauty of the tadpoles' metamorphosis
0:34:40 > 0:34:42is that it occurs right in front of our eyes
0:34:42 > 0:34:45in our garden and woodland ponds.'
0:34:48 > 0:34:51- This looks lovely. - Yes, it's nice.
0:34:58 > 0:35:04'Dr Patrick Walsh is a behavioural ecologist who studies this metamorphosis.'
0:35:04 > 0:35:07Did you just decide sometime in your teen years
0:35:07 > 0:35:09you weren't going to grow up?
0:35:09 > 0:35:13Basically! Yeah, I know, I often phone family and friends
0:35:13 > 0:35:16and say I'm getting paid to do the stuff I used to do as a child.
0:35:16 > 0:35:19Let's get these guys here.
0:35:20 > 0:35:23'As any child who has collected tadpoles will have noticed,
0:35:24 > 0:35:29it's often possible to see all the stages of metamorphosis in the same pond.
0:35:31 > 0:35:37This simple observation says something profound about the tadpoles' metamorphosis.
0:35:39 > 0:35:44The difference between the tadpoles isn't because they were born at different times.'
0:35:44 > 0:35:47These would have all been laid nearly at the same time?
0:35:47 > 0:35:50Yeah, pretty much at the same time. Within a week of each other.
0:35:50 > 0:35:55So then why is one tadpole just a tadpole
0:35:55 > 0:35:59and then there are others that have got legs and are well on the way to being frogs?
0:36:00 > 0:36:01Why the difference?
0:36:01 > 0:36:04Well, so that the amount of time that they spend as a tadpole
0:36:04 > 0:36:07and go through metamorphosis will be quicker in one than another.
0:36:07 > 0:36:10And so they'll be kind of, in quotations, making decisions
0:36:10 > 0:36:12about the environment that they're in
0:36:12 > 0:36:15and how favourable it is for them to be in this aquatic environment
0:36:15 > 0:36:17and then trying to hedge their bets
0:36:17 > 0:36:20about what it's going to be like in the terrestrial environment.
0:36:20 > 0:36:23- They don't all make the same decision?- They don't.
0:36:23 > 0:36:25How much variation are we talking about?
0:36:25 > 0:36:29It can be huge. The first ones may come out in late June,
0:36:29 > 0:36:34but we've actually done some observations of them spending their winters as tadpoles.
0:36:34 > 0:36:37So you can have some in the same pond that will develop into frogs,
0:36:37 > 0:36:41and they spend the entire winter as a tadpole and come out the following spring.
0:36:45 > 0:36:46'Scientists have captured images
0:36:46 > 0:36:49which show the complexity of the changes
0:36:49 > 0:36:53that must occur inside the tadpole to turn it into a frog.
0:36:59 > 0:37:01The tadpole's intestines must transform
0:37:01 > 0:37:04to accommodate a new diet,
0:37:04 > 0:37:07from a tadpole that eats mainly algae and plants,
0:37:07 > 0:37:09to a frog that can eat meat.
0:37:12 > 0:37:15The gills that allow the tadpole to breathe underwater
0:37:15 > 0:37:19are of no use to the frog and so must be destroyed.
0:37:24 > 0:37:27And the tadpole's skull, made of cartilage,
0:37:27 > 0:37:32must be replaced by one made of bone and a backbone created.
0:37:44 > 0:37:48It is an epic reconstruction project, of amazing complexity.
0:37:51 > 0:37:57And yet remarkably it appears that the tadpole can influence
0:37:57 > 0:37:59the timing and the speed of this metamorphosis.
0:38:07 > 0:38:09One way the tadpole is able to do this
0:38:09 > 0:38:13is as simple as where it spends its time in the pond.
0:38:13 > 0:38:16In the warm sunlit water near the surface,
0:38:16 > 0:38:21the biochemical processes that power metamorphosis will be speeded up.
0:38:21 > 0:38:25Whereas in the cooler water at the bottom of the pond,
0:38:25 > 0:38:28these processes will go slower.'
0:38:29 > 0:38:32Different areas of the pond will have different sunlight exposure,
0:38:32 > 0:38:34different amount of food, different predation risks,
0:38:34 > 0:38:37so where they choose to be in that pond
0:38:37 > 0:38:40will have a huge impact on how long it takes them
0:38:40 > 0:38:42to go through the larval period.
0:38:42 > 0:38:45You say the tadpoles choose.
0:38:45 > 0:38:48Yeah, I don't think that they're thinking about things and saying,
0:38:48 > 0:38:51"Oh, it's a really nice day, I think I'll go spend some time up here
0:38:51 > 0:38:53and go through metamorphosis quicker."
0:38:53 > 0:38:56I don't think it's that kind of sense that we would think of making a decision
0:38:56 > 0:38:58about, you know, which restaurant to go to or what not.
0:38:58 > 0:39:01But they are making choices.
0:39:02 > 0:39:05'And they are choices with different consequences.
0:39:07 > 0:39:10By metamorphosing earlier in life and more quickly,
0:39:10 > 0:39:14the tadpole will become a smaller frog, more vulnerable to attack,
0:39:14 > 0:39:18but if it stays in the pond, it may be eaten.
0:39:19 > 0:39:21It's a choice made by the tadpole
0:39:21 > 0:39:25based on an awareness of what is happening around it.'
0:39:28 > 0:39:31There's actually chemical signals released by tadpoles
0:39:31 > 0:39:34- when they're injured or eaten. - Right.
0:39:34 > 0:39:36And so the other tadpoles react to those chemical signals
0:39:36 > 0:39:39so they're able to pick up those chemicals and interpret them.
0:39:39 > 0:39:42So if, once you start, once they start getting killed
0:39:42 > 0:39:46then the amount of that warning chemical builds up in there and that will tell them...
0:39:46 > 0:39:50It's a dangerous place. Yeah, and so then they go through an acceleration of development
0:39:50 > 0:39:53and they think, Well, this is really risky being here.
0:39:53 > 0:39:56I have a better chance on land.
0:39:57 > 0:40:01'And the tadpoles are able to read other signals too.'
0:40:02 > 0:40:05Having ponds that dry out is a really, really big driver
0:40:05 > 0:40:07on how long they spend as tadpoles.
0:40:07 > 0:40:12- So they can actually judge the change in depth of water.- Can they?
0:40:12 > 0:40:17So if it seems to be drying out or decreasing in its depth rapidly
0:40:17 > 0:40:19- they'll accelerate. - It triggers something?
0:40:19 > 0:40:23It'll accelerate so they'll go through metamorphosis because the trade-off is
0:40:23 > 0:40:27I'm an aquatic stage and if I have no water then I'm in a lot of trouble.
0:40:27 > 0:40:29And does the opposite happen? If they're in a pond and it's...
0:40:29 > 0:40:32There's an abundance of the food that they eat,
0:40:32 > 0:40:35they'll just stay at that stage for longer?
0:40:35 > 0:40:37Yeah, so they can stay at that stage and the idea would be then
0:40:37 > 0:40:39that they'd feed and get larger and larger,
0:40:39 > 0:40:42and when they come out onto land they'd be larger frogs.
0:40:42 > 0:40:45And they'd have a competitive advantage.
0:40:45 > 0:40:47- So we know what happens to tadpoles. - Yeah.
0:40:47 > 0:40:51- But the tadpole decisions... - Are much less understood.
0:40:51 > 0:40:53- It's still a mystery how they decide?- Mm-hm.
0:40:53 > 0:40:55So that's future work.
0:40:56 > 0:40:58The mystery of tadpoles.
0:41:03 > 0:41:05'The transformation of the tadpole into the frog
0:41:05 > 0:41:08shows metamorphosis in a new light.'
0:41:12 > 0:41:15I thought one of the most thoughtful things that Patrick said
0:41:15 > 0:41:19was the way he was suggesting that the tadpoles were involved
0:41:19 > 0:41:22in making the metamorphosis happen to themselves.
0:41:22 > 0:41:27It wasn't any longer something which overcame them almost against their will.
0:41:27 > 0:41:31They were evolved in how the metamorphosis happened, how quickly.
0:41:31 > 0:41:32I thought that was interesting.
0:41:32 > 0:41:36It just moves it away from being something entirely pre-programmed.
0:41:36 > 0:41:40It makes it part of the life decisions of the creature itself.
0:41:44 > 0:41:46'So it seems that metamorphosis in nature
0:41:46 > 0:41:48might sometimes be closer
0:41:48 > 0:41:52to the sort of change we are familiar with in our lives.
0:41:54 > 0:41:58Change that we have a degree of control over.
0:41:58 > 0:42:01There are other creatures that change themselves in ways
0:42:01 > 0:42:04that suggest even closer parallels.
0:42:21 > 0:42:25These two locusts are the Jekyll and Hyde of the insect world.
0:42:29 > 0:42:33Through a special transformation, one can turn into the other.
0:42:36 > 0:42:39The physical change involved in this transformation
0:42:39 > 0:42:43is insignificant compared to the other metamorphoses we have seen.
0:42:44 > 0:42:47Yet the change in their way of life is dramatic.
0:42:49 > 0:42:53The green locust live a solitary and inconspicuous existence
0:42:54 > 0:42:57but transformed into the other locust
0:42:57 > 0:42:59it becomes a destructive pest.
0:43:01 > 0:43:06Flying in vast swarms that reek devastation on crops.
0:43:07 > 0:43:11The change is not one of shape, but in behaviour.
0:43:16 > 0:43:21Professor Malcolm Burrows is a neurobiologist who's studying how this happens.'
0:43:25 > 0:43:28I would call that a grasshopper. Is that incorrect?
0:43:28 > 0:43:29No, that's absolutely correct.
0:43:29 > 0:43:33There's something like 4000 species of grasshopper in the world
0:43:33 > 0:43:35and only about 13 of them
0:43:35 > 0:43:40can show this remarkable change from one state, this state,
0:43:40 > 0:43:44to this state, the gregarious phase that forms swarms.
0:43:44 > 0:43:47- That turns into that? - That turns into that.
0:43:47 > 0:43:49Blimey.
0:43:50 > 0:43:54'The difference between the two is shown by an elegant experiment.
0:43:57 > 0:44:00First introduce a green locust into an arena,
0:44:02 > 0:44:04which has empty space on one side
0:44:07 > 0:44:09and a crowd of locusts on the other.
0:44:13 > 0:44:17For a green locust, seeing a crowd of other locusts repels it.
0:44:19 > 0:44:20It wants to be alone.
0:44:21 > 0:44:23It heads for a quiet corner.
0:44:27 > 0:44:31But when a darker coloured locust is introduced, it's a very different story.
0:44:33 > 0:44:38This is a gregarious insect. It heads straight for the crowd.
0:44:38 > 0:44:41And it is this behaviour that creates swarms.
0:44:45 > 0:44:50But what triggers the individual locust to switch from one behaviour to the other?'
0:44:50 > 0:44:55In the lab, we can convert this solitary animal into a gregarious animal.
0:44:55 > 0:44:57We can change its behaviour.
0:44:57 > 0:45:01And the bizarre thing we can do is to tickle their hind legs.
0:45:01 > 0:45:02HE LAUGHS
0:45:02 > 0:45:05And we can tickle their hind legs for a couple of hours.
0:45:05 > 0:45:07How did you discover that?
0:45:07 > 0:45:10- Well...- Were you just idly tickling a grasshopper?
0:45:10 > 0:45:14Oh yes, that's the way we pass our time in Cambridge, didn't you know?
0:45:14 > 0:45:16Just tickling animals.
0:45:16 > 0:45:20And what's that mimicking then? I mean, why are you tickling its rear legs?
0:45:21 > 0:45:24When they actually come into contact with other locusts,
0:45:24 > 0:45:27the things that they jostle up against each other are the things that stick out.
0:45:27 > 0:45:30And the main things that stick out are the tips of the hind legs.
0:45:30 > 0:45:34- And that...- And so...- That's the stimulus?- That's the stimulus.
0:45:34 > 0:45:38So tickling them for a couple of hours will change their behaviour
0:45:38 > 0:45:41from being this solitary animal
0:45:41 > 0:45:46that avoids others to ones that actively seeks out other animals.
0:45:46 > 0:45:48But when they do, do they look like him?
0:45:48 > 0:45:50After several generations
0:45:50 > 0:45:53the behaviour leads to changes
0:45:53 > 0:45:56in the form and size of the body as well.
0:45:56 > 0:45:57But the behaviour first?
0:45:57 > 0:45:59But the behaviour is the all-important thing.
0:45:59 > 0:46:01Can they, can they go back?
0:46:01 > 0:46:02They can go backwards as well.
0:46:02 > 0:46:05And then if you keep them isolated for a long time
0:46:05 > 0:46:08they will revert back to this sort of colouration.
0:46:08 > 0:46:12The family photo album of these creatures must be bizarre!
0:46:20 > 0:46:22'This transformation explains
0:46:22 > 0:46:26how it is possible for biblical plagues of swarming locusts
0:46:26 > 0:46:28to emerge apparently from nowhere.
0:46:29 > 0:46:32For much of the time these same creatures that form swarms
0:46:32 > 0:46:37live a solitary life unseen and unnoticed by humans.
0:46:37 > 0:46:42But living in the desert, the locust is always ready to change its way of life.
0:46:51 > 0:46:54Rain brings plentiful food.
0:46:54 > 0:46:57But when the rain stops, food becomes scarce
0:46:58 > 0:47:01and the solitary locust are forced together
0:47:01 > 0:47:05jostling one another as they compete for whatever remains.
0:47:08 > 0:47:12And so the transformation occurs and the locust begin to swarm.
0:47:12 > 0:47:15Swarms which can number in the millions
0:47:15 > 0:47:19as they fly together to find new sources of food.
0:47:26 > 0:47:29But how does the locust jostling and tickling one another
0:47:29 > 0:47:32lead to this astonishing transformation?
0:47:33 > 0:47:37Malcolm's team have found that what produces this change in the locusts' behaviour
0:47:37 > 0:47:40appears to be a single chemical hormone
0:47:41 > 0:47:43also found in the human brain.
0:47:43 > 0:47:45It is called serotonin.'
0:47:46 > 0:47:52This is the part of the nervous system that controls the movements of the hind legs.
0:47:52 > 0:47:54So this is where it gets all the tickling input
0:47:54 > 0:47:58that starts off the whole process.
0:47:58 > 0:48:02And the light is showing us the presence of serotonin?
0:48:02 > 0:48:04That's showing us the presence of serotonin.
0:48:04 > 0:48:07We can follow the changes in these cells
0:48:07 > 0:48:11during the process of changing from solitary to gregarious.
0:48:11 > 0:48:14- Right at that cellular level? - Down at that cellular level.
0:48:14 > 0:48:18So we can look at animals that are fully solitarious animals.
0:48:18 > 0:48:20- Right. - Then we can look at them
0:48:20 > 0:48:24after an hour or after two hours or four hours
0:48:24 > 0:48:30of being exposed to stimuli that will make them change into the gregarious phase.
0:48:30 > 0:48:32- And do they light up differently? - They light up differently.
0:48:32 > 0:48:35And there's a group of cells here.
0:48:35 > 0:48:38Look, there's one here that's shining up very bright at the moment
0:48:38 > 0:48:42and that is a cell that we're very interested in at the moment.
0:48:42 > 0:48:44- A single cell? - A single cell.
0:48:44 > 0:48:47- When it starts having its hind legs tickled...- Yes.
0:48:47 > 0:48:53That cell reacts by starting to crank out a lot more serotonin...
0:48:53 > 0:48:54Than any of the other cells.
0:48:54 > 0:48:58And serotonin being a neurotransmitter starts to change how the animal behaves?
0:48:58 > 0:49:00That's right.
0:49:06 > 0:49:10'So can we consider this transformation a metamorphosis?
0:49:12 > 0:49:16Unlike the metamorphosis that turns the caterpillar into a butterfly,
0:49:16 > 0:49:18the transformation of the locust
0:49:18 > 0:49:22is not an irreversible change from larva to adult.
0:49:25 > 0:49:28It is triggered by a change in the locusts' environment
0:49:28 > 0:49:30and can be undone.
0:49:32 > 0:49:34And in contrast with other metamorphoses,
0:49:34 > 0:49:36the physical changes are minor.'
0:49:38 > 0:49:42For you, then, what counts as metamorphosis?
0:49:42 > 0:49:45Cos when we've looked at caterpillars and butterflies,
0:49:45 > 0:49:46and tadpoles and frogs,
0:49:46 > 0:49:50metamorphosis is just the change of shape, it's what the word says.
0:49:50 > 0:49:52Well, for me it has a much broader definition than that.
0:49:52 > 0:49:57It means that the behaviour of an individual animal
0:49:57 > 0:50:01that has the same set of genetic instructions inside it,
0:50:01 > 0:50:05is to behave in a very different way.
0:50:06 > 0:50:08And that allows it to live a different life?
0:50:08 > 0:50:11And that allows it to live a completely different lifestyle
0:50:11 > 0:50:14from being solitary to now living
0:50:14 > 0:50:17in swarms of millions and millions of animals.
0:50:18 > 0:50:21So is that behavioural change then kind of...
0:50:21 > 0:50:23Is that metamorphosis for you for these fellows?
0:50:23 > 0:50:27That's what I would call metamorphosis in these animals, yes.
0:50:33 > 0:50:36'If we do consider metamorphosis
0:50:36 > 0:50:39to include this remarkable transformation of the locust,
0:50:39 > 0:50:45then suddenly its reach extends well beyond the realm of caterpillars and butterflies.
0:50:47 > 0:50:51Biological metamorphosis, metamorphosis as it happens in nature,
0:50:51 > 0:50:53moves much closer to us.
0:50:56 > 0:50:58We change our behaviour
0:50:58 > 0:51:00and we change in response to our surroundings.'
0:51:05 > 0:51:07When we started this film
0:51:07 > 0:51:11and metamorphosis was just something that tadpoles and butterflies did,
0:51:11 > 0:51:13something physical,
0:51:13 > 0:51:15metamorphosis did seem quite simple.
0:51:16 > 0:51:20But now with the locusts it seems to me it's not nearly so clear cut.
0:51:20 > 0:51:24And that distance between biological metamorphosis
0:51:24 > 0:51:28and the more metaphorical idea that the writers use,
0:51:28 > 0:51:30seems to me that gap is shrinking.
0:51:35 > 0:51:40'Maybe evolution has found a way for complicated creatures like us
0:51:40 > 0:51:45to be able to pull off this trick of changing radically.
0:51:45 > 0:51:48Perhaps we just don't do it physically.
0:51:51 > 0:51:53If a caterpillar wishes to fly,
0:51:53 > 0:51:57it must grow wings and become a butterfly.
0:52:04 > 0:52:06- If- we- wish to fly,
0:52:06 > 0:52:11we do not need to change our bodies, we invent an aircraft.
0:52:14 > 0:52:18I believe it is through our minds that we metamorphose.
0:52:19 > 0:52:22This is how we change our way of life.'
0:52:29 > 0:52:30You see, to my mind,
0:52:30 > 0:52:35how we transform ourselves is a radical version of what the locust does.
0:52:35 > 0:52:37We both transform our behaviour.
0:52:37 > 0:52:42Of course, the key difference is we are the authors of our transformation.
0:52:44 > 0:52:49'We invent technologies that force us to live in new ways.
0:52:51 > 0:52:55We have ideas that radically alter society.
0:52:56 > 0:53:00We dream a better version of ourselves.
0:53:01 > 0:53:06Change conceived in our mind that drives our history.'
0:53:08 > 0:53:10And once those changes are set in motion,
0:53:10 > 0:53:13they become bigger than any of us individually.
0:53:13 > 0:53:15They get a hold of us, they can overwhelm us,
0:53:15 > 0:53:18and surely that is metamorphosis.
0:53:22 > 0:53:25'And this is what Kafka was pointing to in his story.
0:53:26 > 0:53:31How collectively we shape the society in which we live,
0:53:31 > 0:53:33but then that same society
0:53:33 > 0:53:36forces change back upon us as individuals.'
0:53:53 > 0:53:57I believe that we metamorphose not just metaphorically,
0:53:57 > 0:54:01but in the truest, broadest sense of the word.
0:54:04 > 0:54:07Yet I think there will always be that part of us
0:54:07 > 0:54:09that fights against it.
0:54:13 > 0:54:15For in one fundamental way,
0:54:15 > 0:54:18our metamorphosis remains very different
0:54:18 > 0:54:20to that of the caterpillar or the tadpole.'
0:54:25 > 0:54:29Think of a soldier, someone's who's been living in a world of killing and mayhem,
0:54:29 > 0:54:33who then comes back home to a civilian life where nothing's the same.
0:54:34 > 0:54:37Now that to me is as profound a metamorphosis
0:54:37 > 0:54:41as the caterpillar into a butterfly.
0:54:41 > 0:54:43But of course the critical difference
0:54:43 > 0:54:45is that there's no butterfly
0:54:45 > 0:54:48that looks back with remorse to the caterpillar it used to be.
0:54:48 > 0:54:50But we do.
0:54:51 > 0:54:53We remember.
0:54:53 > 0:54:59We can't help but look back and remember the creature we used to be.
0:54:59 > 0:55:03And regret what we might have lost.
0:55:09 > 0:55:13'And this for us is the great irony at the heart of metamorphosis.
0:55:15 > 0:55:19That the same part of us in which metamorphosis is realised,
0:55:19 > 0:55:24our mind, is the same part of us that fears it most.'
0:55:30 > 0:55:33We have this deep conflict about wanting to change,
0:55:33 > 0:55:39wanting newness, wanting to advance ourselves, develop ourselves, and so on and so forth.
0:55:39 > 0:55:43But at the same time we don't want to lose what we were.
0:55:44 > 0:55:48And that's what makes me fear, as it were, profound change.
0:55:48 > 0:55:51Losing that person that I am.
0:55:57 > 0:56:00So we're really the only creatures who were gifted metamorphosis.
0:56:00 > 0:56:05But we're the only ones who can see its darker side really.
0:56:05 > 0:56:08It seems to me that much of our change is self driven.
0:56:08 > 0:56:11And we seek out change actively.
0:56:11 > 0:56:14We don't really suffer it, it doesn't just happen.
0:56:14 > 0:56:17It isn't enacted organically through our bodies.
0:56:17 > 0:56:22We are the one creature that can redefine the nature of life.
0:56:22 > 0:56:25We're not constrained by a biological prescription.
0:56:25 > 0:56:28We're not like caterpillars that are, as it were,
0:56:28 > 0:56:33committed, condemned, fated to become butterflies.
0:56:33 > 0:56:34We could become anything.
0:56:42 > 0:56:44'At the end of Kafka's story,
0:56:44 > 0:56:48the man who has turned into a beetle dies.
0:56:48 > 0:56:51He has lost everything because of the change forced upon him.
0:56:52 > 0:56:56But there is also a scene shortly before he dies
0:56:56 > 0:56:59when he hears his sister playing the violin.
0:57:00 > 0:57:03He notices it precisely because the metamorphosis
0:57:03 > 0:57:06has forced him out of his old routine,
0:57:06 > 0:57:10where he was too busy to notice the over familiar.
0:57:10 > 0:57:13And when he hears, really hears the music,
0:57:14 > 0:57:16he feels completely alive,
0:57:16 > 0:57:18completely human,
0:57:18 > 0:57:22perhaps for the first and last time in his life.'
0:57:33 > 0:57:37I think one of the things that has come out of this film for me
0:57:37 > 0:57:41is that when we started off with caterpillars and butterflies
0:57:41 > 0:57:42and tadpoles and frogs,
0:57:42 > 0:57:45metamorphosis seemed so clear cut.
0:57:46 > 0:57:49You know, nature had invented this very clear thing
0:57:49 > 0:57:52where you were one thing and then you were another.
0:57:52 > 0:57:54It was very clear and very simple.
0:57:54 > 0:57:57And yet when you then apply it to us,
0:57:57 > 0:57:59it's as if all that clarity disappears
0:57:59 > 0:58:02and we're so ambivalent about it.
0:58:02 > 0:58:07It's the thing which we've argued is so important
0:58:07 > 0:58:11to who we are both individually and as a species,
0:58:11 > 0:58:14and yet we're not happy with it.
0:58:14 > 0:58:18It's as if a butterfly was afraid of flying.
0:58:19 > 0:58:22Here we are the most changeable, the most metamorphic of creatures,
0:58:22 > 0:58:24and we're so troubled by it.
0:58:27 > 0:58:28But maybe that's...
0:58:28 > 0:58:31Maybe that's what being human is about.
0:58:36 > 0:58:38Subtitles by Red Bee Media Ltd