0:00:03 > 0:00:07Welcome to a new and very strange world of nature.
0:00:09 > 0:00:13It's been taken over by the weird subatomic particles of
0:00:13 > 0:00:15quantum physics.
0:00:18 > 0:00:22CHURCH BELL RINGS
0:00:25 > 0:00:28As a physicist, I've spent my working life studying
0:00:28 > 0:00:31how these particles behave in the laboratory.
0:00:34 > 0:00:38But now I'm heading out into the natural world.
0:00:38 > 0:00:41I'm on a mission to prove that quantum physics can solve
0:00:41 > 0:00:45the greatest mysteries in biology.
0:00:45 > 0:00:47This is a real adventure for me.
0:00:47 > 0:00:51I'm very much out of my comfort zone trying to apply
0:00:51 > 0:00:55the very careful ideas I'm familiar with in a physics laboratory
0:00:55 > 0:00:58to the messy world of living things.
0:01:00 > 0:01:05I believe that quantum physics could hold many of life's secrets,
0:01:07 > 0:01:09that deep in the cells of animals,
0:01:09 > 0:01:13particles glide through walls like ghosts...
0:01:15 > 0:01:17..that when plants capture sunlight...
0:01:19 > 0:01:22..their cells are invaded by shimmering waves
0:01:22 > 0:01:24that can be everywhere at the same time.
0:01:26 > 0:01:28And that even our human senses
0:01:28 > 0:01:32are tuning in to strange quantum vibrations.
0:01:34 > 0:01:38In the fantastic world of quantum biology,
0:01:38 > 0:01:42life is a game of chance,
0:01:42 > 0:01:44played by quantum rules.
0:01:48 > 0:01:50This is what I hope to convince you of,
0:01:50 > 0:01:54to show you that quantum mechanics is essential in explaining
0:01:54 > 0:01:58many of the important processes in life, and potentially, that
0:01:58 > 0:02:03quantum mechanics may even underpin the very existence of life itself.
0:02:19 > 0:02:23My quest begins with one of the most majestic sights in nature.
0:02:24 > 0:02:26Migration.
0:02:30 > 0:02:33Every winter, barnacle geese arrive right on cue
0:02:33 > 0:02:35at the same Scottish river.
0:02:38 > 0:02:42The end of an epic 2,000-mile voyage from Svalbard,
0:02:42 > 0:02:44high above the Arctic Circle.
0:02:47 > 0:02:50Of course, many birds head south for winter
0:02:50 > 0:02:52then back home for summer.
0:02:55 > 0:02:59But for decades, exactly how birds navigated with such accuracy
0:02:59 > 0:03:02was one of the greatest mysteries in biology.
0:03:04 > 0:03:08So the most recent discovery has caused a sensation.
0:03:10 > 0:03:12In the past few years,
0:03:12 > 0:03:14one species of bird has helped
0:03:14 > 0:03:16create a scientific revolution.
0:03:16 > 0:03:20I was one of many physicists who was shocked to discover that it
0:03:20 > 0:03:25navigates using one of the strangest tricks in the whole of science.
0:03:25 > 0:03:27It utilises a quirk of quantum mechanics,
0:03:27 > 0:03:30one that bamboozled even the greatest of physicists,
0:03:30 > 0:03:34from Richard Feynman to Albert Einstein himself.
0:03:34 > 0:03:37So you might be surprised to discover the identity of this
0:03:37 > 0:03:40mysterious creature.
0:03:40 > 0:03:43Say hello to the Quantum Robin.
0:03:50 > 0:03:52This is the European robin.
0:03:54 > 0:03:58Every year, she migrates from northern Europe
0:03:58 > 0:04:00to the tip of Spain and back.
0:04:06 > 0:04:08In this laboratory in the woods,
0:04:08 > 0:04:12biologist Henrik Mouritsen is trying to solve the mystery
0:04:12 > 0:04:14of how she does it.
0:04:15 > 0:04:18But he's found himself in MY world,
0:04:18 > 0:04:21the strange world of quantum mechanics.
0:04:26 > 0:04:29Quantum mechanics describes the very weird behaviour of
0:04:29 > 0:04:31subatomic particles.
0:04:36 > 0:04:38Down in this realm of the very small,
0:04:38 > 0:04:41we have to abandon common sense and intuition.
0:04:43 > 0:04:48Instead, this is a world where objects can spread out like waves.
0:04:48 > 0:04:51Quantum particles can be in many places at once
0:04:51 > 0:04:55and send each other mysterious communications.
0:04:55 > 0:04:58I set out to understand how the bird finds its way,
0:04:58 > 0:05:01but it just turned out that the data
0:05:01 > 0:05:05more and more pointed towards this as
0:05:05 > 0:05:10the only explanation that could bring all the different results together.
0:05:12 > 0:05:16Henrik's investigating a longstanding theory -
0:05:16 > 0:05:20that robins navigate by the Earth's magnetic field.
0:05:21 > 0:05:25His laboratory is an ingenious magnetic bird cage.
0:05:26 > 0:05:30And these plastic cones lined with scratch-sensitive paper
0:05:30 > 0:05:32provide the key measurements.
0:05:37 > 0:05:42Henrik's artificial magnetic field is like the Earth's, except that
0:05:42 > 0:05:44HE can point it in any direction he likes.
0:05:49 > 0:05:53Inside their cones, the robins always respond to the field,
0:05:53 > 0:05:55leaving scratches in a single direction.
0:05:59 > 0:06:02The big mystery is HOW.
0:06:03 > 0:06:06The Earth's magnetic field is incredibly weak,
0:06:06 > 0:06:10far too weak for any living creature to detect.
0:06:11 > 0:06:14But Henrik has found an intriguing clue
0:06:14 > 0:06:17by giving the Quantum Robin a mask.
0:06:17 > 0:06:20We have a little leather hood similar to what you put on a falcon,
0:06:20 > 0:06:22you know, but just for a robin,
0:06:22 > 0:06:24and you have then a hole in front of one eye
0:06:24 > 0:06:26or a hole in front of the other eye.
0:06:26 > 0:06:30And what we can see is that if you cover up the right eye, you turn off
0:06:30 > 0:06:34their magnetic compass processing in the left part of the brain.
0:06:34 > 0:06:35If you cover up this eye,
0:06:35 > 0:06:38you turn the compass off in this part of the brain.
0:06:40 > 0:06:44The robin's magnetic compass seems to be in her eyes.
0:06:48 > 0:06:51I can show you what's going on using my own eye.
0:06:51 > 0:06:53Now, we use our eyes for vision,
0:06:53 > 0:06:56but we also have a second light-detecting mechanism.
0:06:56 > 0:07:00If I shine this torch into my eye,
0:07:00 > 0:07:03you can see that my pupil closes down.
0:07:03 > 0:07:06It's basically a defence mechanism to protect my eyes.
0:07:08 > 0:07:11My eye is responding to particles of light - or photons.
0:07:13 > 0:07:15The energy provided by the photons
0:07:15 > 0:07:19is clearly enough to activate chemical reactions.
0:07:19 > 0:07:21After all, that's what controls my eye muscles.
0:07:23 > 0:07:27Light must be causing similar chemical reactions
0:07:27 > 0:07:28in the robin's eyes.
0:07:30 > 0:07:35In fact, it's the power supply for a unique form of magnetic compass...
0:07:37 > 0:07:39..inside her cells...
0:07:41 > 0:07:44..in the weird world of subatomic particles...
0:07:46 > 0:07:49..a place where only quantum physics
0:07:49 > 0:07:51can explain what's going on.
0:07:56 > 0:08:00To see why, imagine the chemical reactions in the robin's eye
0:08:00 > 0:08:03taking place in mountains and valleys of energy.
0:08:05 > 0:08:07To get a reaction to start,
0:08:07 > 0:08:10you have to push molecules to the top of a mountain.
0:08:11 > 0:08:14Thanks to Henrik's experiments,
0:08:14 > 0:08:17we now know that light does most of the hard work.
0:08:19 > 0:08:22But when it reaches the very peak,
0:08:22 > 0:08:26the molecule becomes incredibly sensitive to the slightest touch.
0:08:30 > 0:08:33The key point here is that the robin's chemical compass is now
0:08:33 > 0:08:37balanced on an energy peak between two valleys.
0:08:37 > 0:08:40Going one way produces one set of chemical products -
0:08:40 > 0:08:43the other, a different set.
0:08:43 > 0:08:47Now, even a tiny change in the Earth's magnetic field can tip the
0:08:47 > 0:08:53molecule over the top, but the way this happens defies common sense.
0:08:53 > 0:08:55The final piece of the puzzle
0:08:55 > 0:08:57depends on one of the truly
0:08:57 > 0:08:59mind-boggling ideas in physics.
0:08:59 > 0:09:00But don't worry if you find it
0:09:00 > 0:09:02hard to understand -
0:09:02 > 0:09:03even Albert Einstein
0:09:03 > 0:09:05called it "spooky".
0:09:07 > 0:09:11The idea is called quantum entanglement.
0:09:11 > 0:09:14It involves particles that seem to communicate faster
0:09:14 > 0:09:16than the speed of light.
0:09:17 > 0:09:21In 1935, Einstein published a famous paper
0:09:21 > 0:09:23arguing that it was impossible.
0:09:24 > 0:09:26But Einstein was wrong.
0:09:27 > 0:09:31In recent years, extremely delicate experiments have shown that
0:09:31 > 0:09:35subatomic particles really are entangled.
0:09:35 > 0:09:37It means they can subtly
0:09:37 > 0:09:40and instantaneously influence each other across space.
0:09:42 > 0:09:46And now it seems the same thing is going on inside the robin's eye.
0:09:49 > 0:09:52When a photon enters the robin's eye,
0:09:52 > 0:09:56it creates what's called an entangled pair of electrons.
0:09:57 > 0:10:02Here's how it works. Each electron has two possible states.
0:10:02 > 0:10:06For simplicity, I'm choosing to call them Red and Green.
0:10:06 > 0:10:08Now, here's the weird thing.
0:10:08 > 0:10:11Until I measure it, it's neither one nor the other,
0:10:11 > 0:10:13but both at the same time.
0:10:16 > 0:10:19Think of the electrons like spinning discs.
0:10:20 > 0:10:23They're simultaneously red AND green.
0:10:23 > 0:10:25But by firing a dart...
0:10:27 > 0:10:30..I can force the first electron to be one or the other.
0:10:32 > 0:10:35So far, it's just a game of chance.
0:10:36 > 0:10:39I don't know what I'll get until I try it.
0:10:43 > 0:10:45So I know my first electron is red.
0:10:45 > 0:10:48Suppose I now measure the second electron.
0:10:48 > 0:10:52You'd think I'd have a 50/50 chance of getting red or green.
0:10:52 > 0:10:56After all, that's what you'd expect in the normal, everyday world.
0:10:56 > 0:10:57But you'd be wrong.
0:11:00 > 0:11:04In quantum entanglement, the electrons are mysteriously linked.
0:11:09 > 0:11:11For example, if I get red on the first...
0:11:12 > 0:11:15..I ALWAYS get red on the second.
0:11:18 > 0:11:20It's not a game of chance any more.
0:11:22 > 0:11:26It's as if the first electron is telling the second one what to do.
0:11:29 > 0:11:32That's why Einstein called it spooky.
0:11:33 > 0:11:37The electrons seem to know that they should both have the same colour,
0:11:37 > 0:11:39no matter how far apart they are.
0:11:41 > 0:11:43The really important part is that
0:11:43 > 0:11:47the two electrons needn't be the same colour.
0:11:48 > 0:11:51They can be entangled in a different way,
0:11:51 > 0:11:53so that if the first electron is red...
0:11:55 > 0:11:57..the second one is always green.
0:12:03 > 0:12:06It seems that this mysterious connection is the ultimate secret
0:12:06 > 0:12:09of the Quantum Robin's compass...
0:12:12 > 0:12:15..because the direction of the Earth's magnetic field
0:12:15 > 0:12:17can influence the outcome.
0:12:18 > 0:12:23Near the equator, they may be more likely to be red-red.
0:12:23 > 0:12:27But near the pole, they may be more likely to be red-green.
0:12:27 > 0:12:31And that's the vital factor that finally tips the balance of
0:12:31 > 0:12:33the robin's chemical compass.
0:12:35 > 0:12:39Tiny variations in the Earth's magnetic field change the way
0:12:39 > 0:12:42electrons in the robin's eye are entangled,
0:12:42 > 0:12:45and that's just enough to trigger her compass.
0:12:46 > 0:12:50Now, finally, we can see how something as weak as the Earth's
0:12:50 > 0:12:55magnetic field can tip that balance one way or the other.
0:13:00 > 0:13:02If the message changes,
0:13:02 > 0:13:05the chemical reaction tips a different way...
0:13:07 > 0:13:09..changing the robin's compass reading.
0:13:11 > 0:13:15Suddenly it looks like it's a fundamentally quantum mechanical
0:13:15 > 0:13:17phenomenon in birds.
0:13:17 > 0:13:21It would be one of the first, if not THE first, in biology.
0:13:23 > 0:13:26Biologists better get used to the weirdness of physics.
0:13:27 > 0:13:31The robin is navigating by "spooky" quantum entanglement.
0:13:35 > 0:13:37To see subtle quantum effects,
0:13:37 > 0:13:40even in a controlled, austere environment of a physics lab,
0:13:40 > 0:13:41is really difficult.
0:13:41 > 0:13:44And yet here's the robin doing it with ease.
0:13:45 > 0:13:49These experiments are real and verifiable, and yet even though
0:13:49 > 0:13:53I'm seeing them with my own eyes, I still find it hard to believe.
0:14:02 > 0:14:04Bird navigation has brought physics
0:14:04 > 0:14:08and nature together as the science of quantum biology.
0:14:10 > 0:14:13There's a whole new world to explore.
0:14:14 > 0:14:18But its pioneers have found that it doesn't just affect birds.
0:14:19 > 0:14:21It affects every single one of us.
0:14:23 > 0:14:25Because the latest experiments say
0:14:25 > 0:14:28you're doing quantum physics right now.
0:14:29 > 0:14:32And believe it or not, you're doing it with your nose.
0:14:38 > 0:14:40Hello, Jem!
0:14:40 > 0:14:41Hello.
0:14:41 > 0:14:44Hello, little girl! Hello...
0:14:44 > 0:14:46Our sense of smell is remarkable,
0:14:46 > 0:14:49and quite different from our other senses of sight and hearing.
0:14:49 > 0:14:52Among the thousands of scents that we can recognise,
0:14:52 > 0:14:56many of them may well trigger very powerful memories and emotions.
0:14:56 > 0:14:58It's as though our sense of smell is
0:14:58 > 0:15:01wired directly to our inner consciousness.
0:15:01 > 0:15:03It's also different in another way.
0:15:03 > 0:15:07The other senses of sight and hearing rely on us detecting waves -
0:15:07 > 0:15:08light and sound.
0:15:08 > 0:15:12But our sense of smell involves detecting particles -
0:15:12 > 0:15:13chemical molecules.
0:15:15 > 0:15:18Recently, scientists have begun to realise that when it comes to
0:15:18 > 0:15:23our sense of smell, something very mysterious is going on.
0:15:23 > 0:15:24GUNSHOT
0:15:29 > 0:15:33For decades, biologists thought they knew exactly how our noses
0:15:33 > 0:15:35sniffed out different chemicals.
0:15:38 > 0:15:41But physicists like Jenny Brookes think there could be a new
0:15:41 > 0:15:44ingredient in the mix.
0:15:44 > 0:15:47And it smells like quantum mechanics.
0:15:47 > 0:15:50A lot of people speak of the sense of smell and olfaction,
0:15:50 > 0:15:54and the science of olfaction as being a problem that's been solved
0:15:54 > 0:15:56and we know all about it - and we do know a lot about it.
0:15:56 > 0:15:58We know about the ingredients,
0:15:58 > 0:16:01we know about the equipment that we use to smell.
0:16:01 > 0:16:04But I would argue that there's a little bit more to understand.
0:16:07 > 0:16:11To understand more, I need someone to help me with a smell test.
0:16:14 > 0:16:15And Jem is going to sniff him out.
0:16:21 > 0:16:24Every human being gives off a cocktail of chemicals.
0:16:26 > 0:16:29Jem's nose could detect a single gram of it
0:16:29 > 0:16:32dissolved over an entire city.
0:16:36 > 0:16:39So she has no trouble finding the man I'm looking for.
0:16:46 > 0:16:50Meet Colin the gardener, a man who's used to smelling the flowers.
0:16:52 > 0:16:56Right, then, Colin, I'm going to put your sniffing skills to the test.
0:16:56 > 0:17:00- Cool.- I've got a selection of chemicals here,
0:17:00 > 0:17:02and I want you to tell me what they remind you of.
0:17:02 > 0:17:03OK.
0:17:04 > 0:17:06I'll start you off easily.
0:17:06 > 0:17:07COLIN SNIFFS
0:17:07 > 0:17:09Oh, that's...
0:17:09 > 0:17:12- like a minty, minty vapour rub... - It is, yeah.- ..sort of thing.
0:17:12 > 0:17:14- Yeah, this is... - Something what you'd rub...
0:17:14 > 0:17:18- This is men...menthol.- Menthol. - Yeah.- But it's that essence.
0:17:19 > 0:17:21Right, here's the next one.
0:17:22 > 0:17:25Ah. You should be able to recognise this one.
0:17:26 > 0:17:28That's baking with my daughter.
0:17:28 > 0:17:31- Mm-hm.- Erm, icing sugar sort of thing...
0:17:31 > 0:17:32- Vanilla.- Vanilla, yeah.
0:17:36 > 0:17:39When our noses detect a chemical,
0:17:39 > 0:17:41they fire a nerve signal to our brains.
0:17:44 > 0:17:48But different chemicals create different sensations.
0:17:52 > 0:17:54The standard explanation for this is to do with
0:17:54 > 0:17:56the shape of the molecules.
0:18:00 > 0:18:03The conventional theory that goes back to the 1950s
0:18:03 > 0:18:07says that the scent molecule has a particular shape that allows it
0:18:07 > 0:18:10to fit in to the receptor molecules in our nose.
0:18:15 > 0:18:18If it has the right shape, it's like a hand in a glove,
0:18:18 > 0:18:22or a key in a lock. In fact, it's called the lock and key mechanism.
0:18:22 > 0:18:25With the wrong shape, it won't fit into the receptor.
0:18:25 > 0:18:28But with the right shape, it fits into the receptor,
0:18:28 > 0:18:31triggering that unique smell sensation.
0:18:35 > 0:18:38Different receptors are wired to different parts of our brains.
0:18:41 > 0:18:45So, when a menthol molecule locks into its specific receptor,
0:18:45 > 0:18:47it triggers that minty fresh sensation.
0:18:50 > 0:18:53But the lock and key theory has always had a problem...
0:18:55 > 0:18:58..and Colin's next test will show you why.
0:18:58 > 0:19:00OK, how about...
0:19:00 > 0:19:02this one?
0:19:02 > 0:19:03Quite a strong smell.
0:19:03 > 0:19:05Oh, that's...
0:19:05 > 0:19:08- Yeah.- What does it remind you of? What does it conjure up?
0:19:08 > 0:19:10What memories?
0:19:10 > 0:19:12I think Christmas.
0:19:12 > 0:19:15- Christmas cake.- Yeah. Marzipan.
0:19:15 > 0:19:17Marz...marz...yeah, that's it, yeah.
0:19:17 > 0:19:19- Almonds.- Very, yeah.
0:19:19 > 0:19:24Colin identified the smell of marzipan or almonds.
0:19:24 > 0:19:28In fact, it's due to a scent molecule called benzaldehyde.
0:19:28 > 0:19:33What I didn't give him to smell was this other chemical - cyanide.
0:19:33 > 0:19:36Both benzaldehyde and cyanide have the same smell,
0:19:36 > 0:19:37they both smell of almonds,
0:19:37 > 0:19:40but these molecules are both very different shapes,
0:19:40 > 0:19:42so the lock and key mechanism,
0:19:42 > 0:19:46as an explanation for how we smell, can't be the whole story.
0:19:49 > 0:19:54So why would two molecules with different shapes smell the same?
0:19:55 > 0:19:59Quantum biology has a head-spinning explanation.
0:20:02 > 0:20:06It says our noses aren't smelling chemical molecules...
0:20:09 > 0:20:11..they're LISTENING to them.
0:20:14 > 0:20:18It's not just the shape of a scent molecule that matters.
0:20:18 > 0:20:21Let's take a closer look at this model of a cyanide molecule.
0:20:21 > 0:20:24The white ball here is a hydrogen atom,
0:20:24 > 0:20:27and the grey sticks are the bonds that hold it together
0:20:27 > 0:20:29with the carbon and nitrogen.
0:20:29 > 0:20:31But the reality isn't as simple as that.
0:20:31 > 0:20:34I can give you a better sense of what's going on
0:20:34 > 0:20:36if we look at this larger white ball.
0:20:36 > 0:20:39You see, atoms don't just sit still.
0:20:39 > 0:20:44The bonds that hold them together are like vibrating strings,
0:20:44 > 0:20:48and that gives us a whole new way of thinking about smell.
0:20:51 > 0:20:56The bizarre new quantum theory of smell is all about vibrating bonds.
0:20:58 > 0:21:00HE PLAYS HARMONICS ON GUITAR
0:21:04 > 0:21:08Chemical molecules are playing music for our noses.
0:21:09 > 0:21:14Imagine a receptor molecule in my nose is like my guitar.
0:21:14 > 0:21:18Before it can make a sound, a scent molecule has to enter my nose,
0:21:18 > 0:21:22and when that scent molecule is in place, its chemical bonds
0:21:22 > 0:21:26provide the strings, and it's ready to be played.
0:21:28 > 0:21:31The receptor molecules contain quantum particles -
0:21:31 > 0:21:33electrons.
0:21:34 > 0:21:38As they leap from one atom to another, they vibrate the bonds of
0:21:38 > 0:21:40the scent molecule,
0:21:40 > 0:21:43like my fingers plucking a guitar string.
0:21:43 > 0:21:44GUITAR NOTE CHIMES
0:21:46 > 0:21:49What's remarkable about this theory is that it tells us
0:21:49 > 0:21:53our sense of smell is about the vibrations of molecules,
0:21:53 > 0:21:54or wave-like behaviour,
0:21:54 > 0:21:59and not so much about the shape of a particular scent molecule.
0:21:59 > 0:22:02Our sense of smell may be much more like our sense of hearing.
0:22:03 > 0:22:05HE PLUCKS HIGH NOTE
0:22:07 > 0:22:09A particular molecule, say that of grass,
0:22:09 > 0:22:12will vibrate at a particular frequency.
0:22:12 > 0:22:15HE PLUCKS LOW NOTE
0:22:19 > 0:22:21But a different molecule, say, that of mint,
0:22:21 > 0:22:24will vibrate at a different frequency.
0:22:24 > 0:22:26HE PLUCKS MID-RANGE NOTE
0:22:31 > 0:22:33PLUCKED NOTE REVERBERATES
0:22:35 > 0:22:36HIGHER NOTE REVERBERATES
0:22:38 > 0:22:41This would explain why cyanide smells like almonds.
0:22:43 > 0:22:46The two molecules have different shapes,
0:22:46 > 0:22:50but their chemical bonds just happen to vibrate
0:22:50 > 0:22:51at the same frequency.
0:22:53 > 0:22:57The constant vibration in the odorant is almost
0:22:57 > 0:22:59literally like a particle of sound.
0:22:59 > 0:23:02So, yeah, we're saying that the process of smell could be
0:23:02 > 0:23:05exactly like an acoustic resonance event,
0:23:05 > 0:23:11it could be very analogous to, erm, hearing and seeing, actually.
0:23:12 > 0:23:15But can we really be listening with our noses?
0:23:17 > 0:23:20A bizarre theory needs a bizarre experiment to test it.
0:23:22 > 0:23:24Here's how it works.
0:23:24 > 0:23:29Scientists used a molecule that smells fruity, like orange blossom.
0:23:31 > 0:23:32But if the theory is right,
0:23:32 > 0:23:38then I should be able to change its smell by changing its vibrations.
0:23:38 > 0:23:40The molecule contains
0:23:40 > 0:23:43lots of hydrogen atoms like this,
0:23:43 > 0:23:47bonded to carbon atoms, but what if I were to replace all these atoms
0:23:47 > 0:23:51with a different form of hydrogen called deuterium?
0:23:51 > 0:23:54Now, it won't change the shape of the molecule,
0:23:54 > 0:23:57but it will change the way it vibrates.
0:23:57 > 0:24:02And here's why - deuterium is twice as heavy as normal hydrogen,
0:24:02 > 0:24:05and so it vibrates more slowly.
0:24:05 > 0:24:09Now, different vibrations mean different smells,
0:24:09 > 0:24:12so if I were to make a new form of this chemical,
0:24:12 > 0:24:15all packed with deuterium atoms instead of normal hydrogen,
0:24:15 > 0:24:17it should smell different.
0:24:20 > 0:24:25Quantum biologists found a unique way to carry out this experiment.
0:24:28 > 0:24:29A smell comparison,
0:24:29 > 0:24:33using the real experts in fruity aromas.
0:24:33 > 0:24:36INSECTS BUZZ
0:24:36 > 0:24:37Fruit flies.
0:24:38 > 0:24:41First, the flies were trained to avoid the modified version
0:24:41 > 0:24:44of the fruity molecule.
0:24:44 > 0:24:46To be honest,
0:24:46 > 0:24:49I haven't got a clue how you go about training a fruit fly,
0:24:49 > 0:24:51but apparently you can.
0:24:53 > 0:24:58In the laboratory, the flies had to pass through a kind of maze.
0:25:01 > 0:25:03They were then given a choice.
0:25:07 > 0:25:10Go right for the nice, fruity smell,
0:25:10 > 0:25:14or left, for the nasty, modified version.
0:25:14 > 0:25:18HE STRUMS GENTLY
0:25:21 > 0:25:23They could definitely smell the difference.
0:25:27 > 0:25:31They always preferred the original and turned right.
0:25:39 > 0:25:42The fruit fly experiment gives hard evidence
0:25:42 > 0:25:45that quantum smell theory really works.
0:25:47 > 0:25:52But ultimately, it works in harmony with the lock and key theory.
0:25:53 > 0:25:57First, the scent molecule fits into the receptor...
0:25:59 > 0:26:02..then those molecular vibrations take over.
0:26:05 > 0:26:09Incredible as it seems, flies, humans
0:26:09 > 0:26:13and dogs may be smelling the sound of quantum biology.
0:26:17 > 0:26:21Our sense of smell is fascinating and mysterious as it is,
0:26:21 > 0:26:24but to think that when I encounter a particular scent
0:26:24 > 0:26:28and that sets off a whole wave of memories
0:26:28 > 0:26:32and emotions in my mind, that it's underpinned,
0:26:32 > 0:26:34that it's triggered by quantum mechanics,
0:26:34 > 0:26:37I think makes it even more remarkable.
0:26:37 > 0:26:40CROWS CAW
0:26:49 > 0:26:53The mysterious influence of quantum physics
0:26:53 > 0:26:55reaches into every corner of the natural world.
0:26:59 > 0:27:02In fact, it inhabits the walls
0:27:02 > 0:27:04of every living cell on Earth.
0:27:08 > 0:27:11Because the latest experiments suggest a magical solution
0:27:11 > 0:27:14to one of the greatest mysteries of nature.
0:27:18 > 0:27:21The miracle of metamorphosis.
0:27:30 > 0:27:34The transformation of a tadpole into a frog
0:27:34 > 0:27:37has never been fully explained.
0:27:37 > 0:27:41In little more than six weeks, the tadpole breaks down,
0:27:41 > 0:27:44then reassembles in its adult form.
0:27:44 > 0:27:49But the big mystery is how it happens so fast.
0:27:49 > 0:27:52When you think about it, there's nothing more extraordinary
0:27:52 > 0:27:54than a tadpole turning into a frog.
0:27:54 > 0:27:56Take its tail, for example.
0:27:56 > 0:28:00Over a period of several weeks, it gets reabsorbed into the body
0:28:00 > 0:28:04and the proteins and fibres that make up the flesh
0:28:04 > 0:28:08get recycled to form the frog's new limbs.
0:28:08 > 0:28:10But for this to happen,
0:28:10 > 0:28:13trillions and trillions of chemical reactions work together,
0:28:13 > 0:28:18breaking molecules, forming new ones in a carefully orchestrated dance.
0:28:18 > 0:28:22But the fibres that hold flesh together are very, very strong.
0:28:22 > 0:28:26They're a bit like these ropes holding my raft together.
0:28:26 > 0:28:31In order to dismantle the raft, I'd have to undo these very tight knots.
0:28:33 > 0:28:34You could think of it like this...
0:28:36 > 0:28:40..a tadpole is held together by long ropes of proteins
0:28:40 > 0:28:42knotted together by chemical bonds.
0:28:44 > 0:28:48The bonds are so strong that they should last for years,
0:28:48 > 0:28:52much longer than the tadpole's entire life span.
0:28:52 > 0:28:57So how can it turn into a frog in just a few weeks?
0:28:57 > 0:29:01The explanation involves one of the most important molecules of life.
0:29:03 > 0:29:07Tiny widgets in all our cells called enzymes.
0:29:07 > 0:29:11The enzymes are the actual machinery of the cell.
0:29:11 > 0:29:15They are actually the little machines inside cells
0:29:15 > 0:29:19that do the chemical transformations that are involved in everyday life.
0:29:19 > 0:29:21They are absolutely crucial.
0:29:21 > 0:29:24And the reason they're so crucial is because what they are able to do
0:29:24 > 0:29:30is to accelerate chemical reactions by enormous amounts.
0:29:30 > 0:29:34Let me show you just how quickly enzymes get to work.
0:29:35 > 0:29:39Inside this bottle is a substance called hydrogen peroxide.
0:29:39 > 0:29:41You're probably most familiar with it
0:29:41 > 0:29:43as the chemical used to bleach hair.
0:29:43 > 0:29:45In fact, I obtained this sample
0:29:45 > 0:29:47from my local hairdressers.
0:29:47 > 0:29:50Hydrogen peroxide is also produced in the body,
0:29:50 > 0:29:53and it's the job of the liver to get rid of it.
0:29:53 > 0:29:55The way it does that is using an enzyme
0:29:55 > 0:30:00which breaks down hydrogen peroxide into water and oxygen.
0:30:00 > 0:30:04Now, to show you just how quickly this enzyme works,
0:30:04 > 0:30:06I'm going to do a quick demonstration.
0:30:06 > 0:30:08I've got some liver here which I've chopped up
0:30:08 > 0:30:11in order to release the enzyme.
0:30:13 > 0:30:17Now, watch what happens when I add this liver mixture
0:30:17 > 0:30:20containing the enzyme to the hydrogen peroxide.
0:30:20 > 0:30:23Watch how quickly the oxygen is released.
0:30:35 > 0:30:37CROWS CAW
0:30:38 > 0:30:44Just 100 grams of liver fired my rocket nearly 20 feet.
0:30:47 > 0:30:50Liver enzymes make the breakdown of hydrogen peroxide
0:30:50 > 0:30:52incredibly efficient.
0:30:52 > 0:30:55It happens a trillion times faster.
0:30:55 > 0:30:58That's a million, million times faster than it would otherwise.
0:31:01 > 0:31:03In metamorphosis, it's enzymes
0:31:03 > 0:31:06that dismantle the tadpole's tail.
0:31:07 > 0:31:09And that means breaking down
0:31:09 > 0:31:11an incredibly tough protein
0:31:11 > 0:31:12called collagen.
0:31:14 > 0:31:18Collagen is one of the most important proteins in the biological world.
0:31:18 > 0:31:22It's the protein which actually gives that resilience, that elasticity
0:31:22 > 0:31:25to tendons, to cartilage,
0:31:25 > 0:31:28and of course to our skin, as well.
0:31:28 > 0:31:32And in the tail of the tadpole, it provides the kind of scaffold
0:31:32 > 0:31:35that supports that structure.
0:31:35 > 0:31:38Now, when the tadpole is transformed into the frog,
0:31:38 > 0:31:42what you need to do is to essentially have an enzyme,
0:31:42 > 0:31:45collagenase, which will literally snip the collagen down
0:31:45 > 0:31:49into small pieces and thereby take that scaffold apart.
0:31:53 > 0:31:58But how do enzymes break chemical bonds apart so incredibly fast?
0:32:00 > 0:32:05Let me show you why it's a problem only quantum biology can solve.
0:32:07 > 0:32:11Think of it this way, all these different parts of the knot
0:32:11 > 0:32:15are like subatomic particles - electrons, protons -
0:32:15 > 0:32:18that hold the different parts of the molecule together.
0:32:18 > 0:32:23Now, to untie the knot, enzymes have to move protons about.
0:32:23 > 0:32:27But as you can see, this takes quite a bit of effort
0:32:27 > 0:32:31and a lot of time if there are many knots to unpick.
0:32:32 > 0:32:34Physicists have a fancy way of saying
0:32:34 > 0:32:36"put in effort to get something done".
0:32:36 > 0:32:40They say you have to overcome an energy barrier.
0:32:46 > 0:32:49OK, here's my energy barrier.
0:32:51 > 0:32:53And here's my proton.
0:32:55 > 0:32:56To break a bond apart,
0:32:56 > 0:32:59it needs enough energy to get over the barrier.
0:33:01 > 0:33:05The trouble is, when we work out how long this would take,
0:33:05 > 0:33:08it's much too slow to break down a tadpole's tale.
0:33:10 > 0:33:14But this is where protons turn into ghosts.
0:33:17 > 0:33:20I wouldn't blame you for thinking that this is an idea
0:33:20 > 0:33:23that a clever theoretician has come up with,
0:33:23 > 0:33:27that it's just mere speculation - something that we have no proof of.
0:33:27 > 0:33:31But we do. It takes place all the time.
0:33:33 > 0:33:34In the quantum world,
0:33:34 > 0:33:38protons don't have to go over barriers.
0:33:41 > 0:33:43They can tunnel...
0:33:43 > 0:33:45straight through.
0:33:46 > 0:33:49Tunnelling strikes at the very heart of what is most strange
0:33:49 > 0:33:51about quantum mechanics.
0:33:51 > 0:33:54It's like nothing we see in our everyday world.
0:33:54 > 0:33:58A quantum particle can tunnel from one place to another
0:33:58 > 0:34:02even if it has to pass through an impenetrable barrier.
0:34:02 > 0:34:07They are not solid objects like balls in our everyday world.
0:34:07 > 0:34:10They have spread out, fuzzy,
0:34:10 > 0:34:15wavelike behaviour that allows them to leak through an energy barrier.
0:34:15 > 0:34:18A particle can disappear on one side of the barrier
0:34:18 > 0:34:21and instantaneously reappear on the other.
0:34:23 > 0:34:27In nuclear physics, this effect is a proven fact.
0:34:28 > 0:34:32Without quantum tunnelling, the Sun simply wouldn't shine.
0:34:35 > 0:34:37But I never thought I'd see it...
0:34:39 > 0:34:41..in a tadpole.
0:34:41 > 0:34:45It's hard to stress just how weird this process is.
0:34:45 > 0:34:48It's as though I would approach a solid brick wall and,
0:34:48 > 0:34:53like a phantom, disappear from one side and reappear on the other.
0:34:57 > 0:35:01The most important advantage of tunnelling is its speed.
0:35:03 > 0:35:06It happens incredibly quickly -
0:35:06 > 0:35:09much faster than if protons go OVER the barrier.
0:35:11 > 0:35:15As a nuclear physicist, quantum tunnelling is my bread and butter.
0:35:15 > 0:35:18Subatomic particles like protons do it all the time.
0:35:18 > 0:35:21But what has this got to do with biology?
0:35:27 > 0:35:30The answer is that without quantum ghosts,
0:35:30 > 0:35:33the metamorphosis of a tadpole would be impossible.
0:35:35 > 0:35:38Remember, chemical bonds are basically knots.
0:35:41 > 0:35:45Tunnelling unties them - fast.
0:35:45 > 0:35:47Have a look at these two knots.
0:35:47 > 0:35:50Now, on the face of it they look identical,
0:35:50 > 0:35:52but there's a subtle difference.
0:35:52 > 0:35:55This knot has the two short ends
0:35:55 > 0:35:57of the rope on the same side.
0:35:57 > 0:35:59Whereas this one
0:35:59 > 0:36:01has the two short ends on opposite sides.
0:36:02 > 0:36:06Now, you'd think that wouldn't make a difference, but it does.
0:36:06 > 0:36:08You see, THIS knot...
0:36:09 > 0:36:11..is very hard to break,
0:36:11 > 0:36:13whereas THIS one...
0:36:14 > 0:36:16..is easy.
0:36:17 > 0:36:19Quantum tunnelling...
0:36:21 > 0:36:24..turns strong knots into weak ones.
0:36:27 > 0:36:28So in a tadpole,
0:36:28 > 0:36:33the entire collagen scaffold breaks apart easily.
0:36:33 > 0:36:38And finally, other enzymes rebuild it in the shape of a frog.
0:36:42 > 0:36:46The quantum tunnelling of particles is one of those weird features
0:36:46 > 0:36:47of the subatomic world
0:36:47 > 0:36:50that a physicist like me is very familiar with.
0:36:50 > 0:36:53After all, it's responsible for radioactive decay
0:36:53 > 0:36:55and it goes on inside the Sun.
0:36:55 > 0:36:59It's the reason why the Sun and all stars shine.
0:36:59 > 0:37:02But to discover this going on inside every cell of every
0:37:02 > 0:37:07living organism on the planet, because every cell contains enzymes,
0:37:07 > 0:37:09now, THAT I find truly amazing.
0:37:13 > 0:37:17Quantum biology casts its spell over every living creature.
0:37:19 > 0:37:23We've seen that birds, mammals, insects
0:37:23 > 0:37:28and amphibians are governed by the strangest laws in science.
0:37:30 > 0:37:32But the most dramatic recent breakthrough concerns
0:37:32 > 0:37:37the single vital process on which all these forms of life depend.
0:37:39 > 0:37:42The conversion of air and sunlight
0:37:42 > 0:37:43into plants.
0:37:49 > 0:37:54This fine specimen is a Larix decidua, or European larch.
0:37:54 > 0:37:57It's about 100 feet high and right at this moment,
0:37:57 > 0:38:00passing just this side of the planet Venus,
0:38:00 > 0:38:02is a bullet with this tree's name on it.
0:38:05 > 0:38:06The bullet is a photon
0:38:06 > 0:38:10nearing the end of its long journey from the Sun.
0:38:14 > 0:38:17Its ultimate destiny is to kick-start
0:38:17 > 0:38:21a series of chemical reactions that underpins all life on Earth...
0:38:23 > 0:38:25..photosynthesis.
0:38:25 > 0:38:27Every second of every day,
0:38:27 > 0:38:3216,000 tonnes of new plant life are created on Earth.
0:38:32 > 0:38:35And for me, it's incredible to think that our existence
0:38:35 > 0:38:38on this planet depends on what happens
0:38:38 > 0:38:40in the next trillionth of a second.
0:38:51 > 0:38:54The crucial first stage of photosynthesis
0:38:54 > 0:38:56is the capture of energy from the Sun.
0:38:58 > 0:39:00It's nearly 100% efficient,
0:39:00 > 0:39:04vastly superior to any human technology.
0:39:06 > 0:39:10But the way that every plant on Earth achieves this
0:39:10 > 0:39:12is one of the great puzzles in biology.
0:39:13 > 0:39:16When it turned out that quantum weirdness might hold the answer,
0:39:16 > 0:39:19physicists could hardly believe it.
0:39:21 > 0:39:23It was like a revelation.
0:39:23 > 0:39:25It was very exciting, because I was
0:39:25 > 0:39:26used to working on problems
0:39:26 > 0:39:29that were quite abstract experiments.
0:39:29 > 0:39:33I am a theoretician, but I always related my theory
0:39:33 > 0:39:35to experiments that were very clean in the lab,
0:39:35 > 0:39:36things that you can control.
0:39:36 > 0:39:39But now, finding out that the things that I knew can help me
0:39:39 > 0:39:42to understand better how nature works,
0:39:42 > 0:39:46really, scientifically, it was like a...
0:39:46 > 0:39:48a new inspiration to my life,
0:39:48 > 0:39:53so I would say I fell in love with this field.
0:39:55 > 0:39:59Textbook biology says the colour of green plants
0:39:59 > 0:40:01comes from chlorophyll molecules.
0:40:02 > 0:40:06Inside the living cells, they absorb light from the Sun.
0:40:09 > 0:40:12This energy is then transferred incredibly quickly
0:40:12 > 0:40:15to the food-making factory at the heart of the cell.
0:40:19 > 0:40:21The entire event takes
0:40:21 > 0:40:24just a millionth of a millionth of a second.
0:40:24 > 0:40:26When the photon hits the cell,
0:40:26 > 0:40:30it knocks an electron out of the middle of a chlorophyll molecule.
0:40:30 > 0:40:35This creates a tiny packet of energy called an exciton.
0:40:35 > 0:40:36The exciton then bounces its way
0:40:36 > 0:40:39through a forest of chlorophyll molecules
0:40:39 > 0:40:43until it reaches what is called the reaction centre.
0:40:43 > 0:40:46Now, that is where its energy is used to drive chemical processes
0:40:46 > 0:40:51that create the all-important biomolecules of life.
0:40:51 > 0:40:54The problem is, the exciton needs to find its way to the reaction centre
0:40:54 > 0:40:56in the first place.
0:41:02 > 0:41:06Textbook biology can't explain how the exciton does this.
0:41:09 > 0:41:12Because, of course, it doesn't know where it's going.
0:41:15 > 0:41:17It just bounces around like a pinball
0:41:17 > 0:41:20in a process called a random walk.
0:41:24 > 0:41:26Sooner or later,
0:41:26 > 0:41:28it will pass through every single part of the cell.
0:41:31 > 0:41:35But this isn't the most efficient way to get around.
0:41:38 > 0:41:42Because when the exciton eventually does reach the reaction centre...
0:41:43 > 0:41:45..it's by pure chance.
0:41:50 > 0:41:53If the exciton just blindly and randomly
0:41:53 > 0:41:55hops between the chlorophyll molecules,
0:41:55 > 0:41:58it would take too long to reach the reaction centre
0:41:58 > 0:42:01and would have lost its energy as waste heat.
0:42:01 > 0:42:05But it doesn't. Something very different must be going on.
0:42:07 > 0:42:10The vital clue comes from recent experiments
0:42:10 > 0:42:12that stunned the world of science.
0:42:15 > 0:42:18Chemists fired lasers at plant cells
0:42:18 > 0:42:21to simulate the capture of light from the Sun.
0:42:23 > 0:42:27They confirmed the exciton wasn't bouncing along a haphazard route
0:42:27 > 0:42:28through the cell.
0:42:30 > 0:42:32This original understanding didn't explain what
0:42:32 > 0:42:34we were observing in the lab.
0:42:34 > 0:42:36So the mystery lies in, OK,
0:42:36 > 0:42:40so then, what is the explanation for what we are observing in the lab?
0:42:42 > 0:42:46The solution is that plants obey the most famous law
0:42:46 > 0:42:48in all of quantum mechanics...
0:42:50 > 0:42:52..the uncertainty principle.
0:42:56 > 0:42:58It says it you can never be certain
0:42:58 > 0:43:01that the exciton is in one specific place.
0:43:04 > 0:43:07Instead, it behaves like a quantum wave,
0:43:07 > 0:43:10smearing itself out across the cell.
0:43:15 > 0:43:18The exciton doesn't simply move from A to B.
0:43:20 > 0:43:23In a bizarre but very real sense,
0:43:23 > 0:43:28it's heading in every direction at the same time.
0:43:28 > 0:43:30It's spreading itself out as a wave
0:43:30 > 0:43:34so that it can explore all possible routes simultaneously.
0:43:34 > 0:43:36This strikes at the very heart
0:43:36 > 0:43:38of what's so strange about quantum mechanics.
0:43:38 > 0:43:42The exciton wave isn't just going this way or that way,
0:43:42 > 0:43:45it's following all paths at the same time.
0:43:45 > 0:43:48That's what gives it such incredible efficiency.
0:44:02 > 0:44:03The beauty of it is...
0:44:05 > 0:44:07..if the exciton is trying every route
0:44:07 > 0:44:09to the reaction centre at once...
0:44:11 > 0:44:15..it's bound to find the fastest possible way to deliver its energy.
0:44:19 > 0:44:22It's hard to express how incredible this discovery seems
0:44:22 > 0:44:24to physicists like me.
0:44:25 > 0:44:28Biological cells are full of the random jiggling
0:44:28 > 0:44:31of billions of atoms and molecules.
0:44:32 > 0:44:36But somehow, excitons maintain their form
0:44:36 > 0:44:40as beautiful, perfect quantum waves,
0:44:40 > 0:44:45transporting the energy that guarantees life on Earth.
0:44:49 > 0:44:53It opened a whole new scientific path for me.
0:44:53 > 0:44:55And I really enjoy the fact that
0:44:55 > 0:44:59to be able to understand fully what is happening there or in the plants,
0:44:59 > 0:45:00you have to interact with scientists
0:45:00 > 0:45:03that have completely different approaches,
0:45:03 > 0:45:06like biologists and chemists.
0:45:06 > 0:45:08But we all have to come together
0:45:08 > 0:45:11to actually understand what is the relevant of this,
0:45:11 > 0:45:12the relevance of this.
0:45:12 > 0:45:15So, for me, this is one of the most exciting parts of this field.
0:45:18 > 0:45:22Real scientific experiments leave no doubt.
0:45:24 > 0:45:27The strange hand of quantum mechanics has shaped
0:45:27 > 0:45:29the entire living world.
0:45:31 > 0:45:36It's not a surprise that you should find quantum tricks being used
0:45:36 > 0:45:37in biological systems.
0:45:37 > 0:45:40The reason is, because they're better.
0:45:44 > 0:45:46Quantum entanglement is normally seen
0:45:46 > 0:45:50in the tightly-controlled conditions of the physics lab.
0:45:51 > 0:45:53But now, we know that robins use it
0:45:53 > 0:45:56to navigate with extraordinary precision.
0:46:00 > 0:46:04Quantum vibrations mean our noses LISTEN to chemicals...
0:46:05 > 0:46:08..enhancing our perception of the world around us.
0:46:12 > 0:46:16The living cells of all animals depend on protons
0:46:16 > 0:46:19that vanish and reappear like ghosts...
0:46:21 > 0:46:24..speeding up the vital processes of life.
0:46:30 > 0:46:32And photosynthesis reveals the big picture.
0:46:34 > 0:46:36A shimmering world
0:46:36 > 0:46:40where quantum waves capture the Sun's energy in an instant.
0:46:42 > 0:46:44Sometimes, people say, "Ah, but physicists have been
0:46:44 > 0:46:47"looking for this for decades."
0:46:47 > 0:46:49Well, biology has had millions of years.
0:46:51 > 0:46:54The ultramodern science of quantum mechanics
0:46:54 > 0:46:56is an ancient fact of life.
0:46:58 > 0:47:00For the end of my journey,
0:47:00 > 0:47:03I want to take these ideas to their logical conclusion.
0:47:03 > 0:47:04Of course, as a scientist,
0:47:04 > 0:47:09any speculations I have have to be backed up by careful experiments.
0:47:09 > 0:47:12So I want to concoct a thought experiment that helps me
0:47:12 > 0:47:16to answer the biggest biological question I can think of.
0:47:16 > 0:47:19Does quantum physics play any role
0:47:19 > 0:47:22in the mechanism of evolution itself?
0:47:28 > 0:47:32In 1859, Charles Darwin stunned the world
0:47:32 > 0:47:35with his Theory Of Evolution By Natural Selection.
0:47:36 > 0:47:39He went on to explain the differences
0:47:39 > 0:47:41between humans and other apes.
0:47:43 > 0:47:46150 years later, there's no doubt that Darwin's theory
0:47:46 > 0:47:48accounts for every living organism
0:47:48 > 0:47:50on land and sea.
0:47:53 > 0:47:55But I'd like to explore the latest,
0:47:55 > 0:47:58extraordinary interpretation of his ideas.
0:47:58 > 0:48:00STIRRING STRINGS
0:48:03 > 0:48:08Could there be a quantum theory of evolution?
0:48:08 > 0:48:13MUSIC: Adagio of Spartacus and Phrygia from Spartacus Suite No.2 by Aram Khachaturian
0:48:35 > 0:48:39Can quantum evolution explain how the snail got its shell?
0:48:43 > 0:48:45The snails I'm used to seeing in my back garden
0:48:45 > 0:48:48tend to have rather bland, boring shells.
0:48:48 > 0:48:50So have a look at this beauty.
0:48:52 > 0:48:55The patterns on its shell very perfectly match
0:48:55 > 0:48:57the lines on the stem.
0:48:59 > 0:49:03It's called a banded snail. Cepaea nemoralis.
0:49:04 > 0:49:07And the pattern isn't there by accident.
0:49:11 > 0:49:13Come and have a look at this.
0:49:17 > 0:49:19Less well adapted snails
0:49:19 > 0:49:21are more likely to be found here.
0:49:21 > 0:49:25This stone is called a thrush's anvil.
0:49:25 > 0:49:27The song thrush is the snail's main predator.
0:49:27 > 0:49:29It catches the snail
0:49:29 > 0:49:32and smashes its shell against the stone to get to the snail.
0:49:32 > 0:49:33Now, what I can see here
0:49:33 > 0:49:36is that there aren't many banded snail shells,
0:49:36 > 0:49:40suggesting that its colours camouflage it very well,
0:49:40 > 0:49:41hiding it from the bird.
0:49:45 > 0:49:47Darwin's theory says
0:49:47 > 0:49:51that evolution depends on variation within a species.
0:49:53 > 0:49:57Snails with camouflage are more likely to survive and reproduce...
0:50:00 > 0:50:02..passing on their shells to the next generation
0:50:02 > 0:50:06so that the species as a whole becomes better adapted.
0:50:09 > 0:50:13So, variation - the random differences between snails -
0:50:13 > 0:50:16is the driving force behind their evolution.
0:50:18 > 0:50:22Now, all species evolve and adapt to their environment.
0:50:22 > 0:50:24But the question I'd like to explore is
0:50:24 > 0:50:27whether quantum mechanics plays a role in this.
0:50:31 > 0:50:33The only way to find out
0:50:33 > 0:50:35is by scientific experiments.
0:50:37 > 0:50:41So, my adventures in quantum biology finally bring me home...
0:50:43 > 0:50:45..to the University of Surrey.
0:50:48 > 0:50:49Here, in the laboratories,
0:50:49 > 0:50:54I'm planning a new analysis of the most celebrated molecule in science.
0:50:57 > 0:51:01Deoxyribonucleic acid, or DNA.
0:51:04 > 0:51:09Its double helix holds the genetic code for every living organism.
0:51:12 > 0:51:15It's a remarkable fact that Darwin himself had no idea
0:51:15 > 0:51:18what created variation in the species.
0:51:18 > 0:51:22The structure of DNA wasn't discovered until 1953
0:51:22 > 0:51:25by Francis Crick and James Watson.
0:51:25 > 0:51:28The most famous feature of DNA is of course
0:51:28 > 0:51:30its beautiful double helix structure.
0:51:30 > 0:51:32But that's just scaffolding.
0:51:32 > 0:51:35The real genetic secret lies in between.
0:51:38 > 0:51:42The four different-coloured molecules are called bases.
0:51:44 > 0:51:48The colour code on one side - say blue, red, blue -
0:51:48 > 0:51:52forms a gene that parents pass on to their offspring.
0:51:52 > 0:51:55A gene is a bit like a jigsaw puzzle.
0:51:55 > 0:51:57It fits together like this.
0:51:59 > 0:52:04A full strand of the double helix forms a coloured pattern.
0:52:06 > 0:52:09But the other strand always pairs up the same way.
0:52:12 > 0:52:15A blue base always goes with yellow
0:52:15 > 0:52:18and green always goes with red...
0:52:19 > 0:52:24..because only those colours have the right shape to fit together.
0:52:24 > 0:52:27What Crick and Watson realised was that this provides
0:52:27 > 0:52:30a mechanism for passing on the genetic code.
0:52:32 > 0:52:36When cells reproduce, the two strands of DNA separate,
0:52:36 > 0:52:38ready to be copied.
0:52:40 > 0:52:42But red still goes with green...
0:52:44 > 0:52:47..and yellow still goes with blue.
0:52:48 > 0:52:50So bit by bit,
0:52:50 > 0:52:52the cell creates two new strands.
0:52:54 > 0:52:57Two perfect copies of the entire genetic code.
0:52:59 > 0:53:01So far, there's no genetic variation.
0:53:01 > 0:53:05This new copy is identical to the original.
0:53:05 > 0:53:07But here's the interesting bit.
0:53:07 > 0:53:11During the copying process, something very important can happen.
0:53:11 > 0:53:13Sometimes, mistakes creep in.
0:53:16 > 0:53:18They're called mutations.
0:53:19 > 0:53:23Let's have a look at these two bases here.
0:53:24 > 0:53:29The two prongs that hold them together are subatomic particles.
0:53:29 > 0:53:31They're protons.
0:53:31 > 0:53:34They're basically the bonds between the strands of DNA.
0:53:34 > 0:53:38These protons can jump across to the other side.
0:53:40 > 0:53:44If the strands split when the protons have jumped across,
0:53:44 > 0:53:47they find themselves in the wrong position.
0:53:49 > 0:53:54Now, this red base will no longer bind to a green base.
0:53:54 > 0:53:59Instead, it has to bond to a yellow base.
0:54:00 > 0:54:02Slotting this back in,
0:54:03 > 0:54:07we see that now this copy is no longer identical to the original
0:54:07 > 0:54:11because I have a yellow base here instead of a green one.
0:54:11 > 0:54:13We've brought in a genetic mutation.
0:54:15 > 0:54:20Jumping protons would change the snail's DNA.
0:54:20 > 0:54:23It could make a new gene for camouflaged shells.
0:54:24 > 0:54:27The question is, how do protons jump?
0:54:30 > 0:54:34It's my belief that quantum's spookiness can take over.
0:54:35 > 0:54:38Now, for these mutations to take place,
0:54:38 > 0:54:41the protons have to overcome an energy barrier.
0:54:41 > 0:54:44And if you remember what happened with enzymes,
0:54:44 > 0:54:47well, you can probably guess what's coming next.
0:54:50 > 0:54:54Protons can behave as if barriers don't exist.
0:54:56 > 0:54:59They tunnel straight through.
0:55:00 > 0:55:03But does this ghostly effect really happen?
0:55:07 > 0:55:10My colleagues in biology are already looking
0:55:10 > 0:55:13for the very first evidence of quantum mutations.
0:55:16 > 0:55:19Biologists didn't really even know about quantum mechanics,
0:55:19 > 0:55:23so when you tell them that particles can be in two places at once,
0:55:23 > 0:55:25they kind of say, "Well, not in my cells, they can't!"
0:55:26 > 0:55:30Our experiment involves samples of bacteria.
0:55:31 > 0:55:34The first sample is prepared in normal water,
0:55:34 > 0:55:37containing hydrogen nuclei, or protons.
0:55:39 > 0:55:43When the bacteria reproduce, we simply count the mutations.
0:55:44 > 0:55:46But if our theory is correct,
0:55:46 > 0:55:50then we should be able to change the rate at which mutations occur.
0:55:51 > 0:55:55Remember how we tested the quantum theory of smell?
0:55:55 > 0:56:00What if I replaced the proton with its big brother, the deuteron?
0:56:00 > 0:56:03This is the nucleus of an atom of deuterium.
0:56:03 > 0:56:06Now, crucially, a deuteron is twice as heavy as a proton
0:56:06 > 0:56:09and this should influence how easy it is for
0:56:09 > 0:56:12the deuteron to quantum tunnel.
0:56:12 > 0:56:15Quantum mechanics is full of surprises.
0:56:16 > 0:56:18Protons tunnel easily.
0:56:20 > 0:56:22Deuterons...don't.
0:56:28 > 0:56:32These heavier particles are much more likely to bounce straight back.
0:56:35 > 0:56:39So the second sample of bacteria is prepared in heavy water,
0:56:39 > 0:56:41which is full of deuterons.
0:56:43 > 0:56:47Our theory says you should get far fewer mutations.
0:56:48 > 0:56:52And, so far, the results are extremely encouraging.
0:56:52 > 0:56:56The preliminary experiments that we've done gives us a hint
0:56:56 > 0:57:00that the mutation rate is indeed depressed in deuterated water.
0:57:00 > 0:57:04We find that it is lower. So my hunch is that we're right,
0:57:04 > 0:57:08but we'll have to wait a little while before we're sure.
0:57:11 > 0:57:12Final proof lies in the future.
0:57:14 > 0:57:15Even if we're right,
0:57:15 > 0:57:18quantum tunnelling is a rare form of mutation.
0:57:20 > 0:57:23But our results promise hard evidence
0:57:23 > 0:57:27for a new explanation of one of the most fundamental processes of life.
0:57:29 > 0:57:33Even the merest possibility of a new quantum mechanism
0:57:33 > 0:57:37for evolution itself is tremendously exciting.
0:57:37 > 0:57:41In fact, the story of quantum biology is only just beginning.
0:57:41 > 0:57:45What the frog, the robin, the fruit fly and the tree have shown us
0:57:45 > 0:57:50is that real quantum effects are going on in nature all the time.
0:57:50 > 0:57:52And if there's anything we've learnt
0:57:52 > 0:57:54from the history of quantum mechanics, it's this -
0:57:54 > 0:57:59we can never be certain where new discoveries will take us next.
0:58:08 > 0:58:11Quantum biology is a revolution in science.
0:58:12 > 0:58:15But it's time I got back to the physics department.