0:00:04 > 0:00:05Decay.
0:00:05 > 0:00:08It happens to everything and everyone.
0:00:09 > 0:00:13We try to keep it out of our everyday lives.
0:00:13 > 0:00:17But decay is one of the most important forces in nature.
0:00:17 > 0:00:21It underpins all life on Earth.
0:00:23 > 0:00:26So what would we see, if we let it loose in our homes?
0:00:33 > 0:00:36To find out, we've built a home of our own
0:00:36 > 0:00:38inside this box.
0:00:42 > 0:00:45We've filled it with everything you might find in a typical kitchen
0:00:45 > 0:00:51and garden. And now we're going to let it all rot.
0:00:53 > 0:00:55Well, here it is.
0:00:55 > 0:01:00A team of engineers and scientists have spent eight months recreating
0:01:00 > 0:01:04a kitchen and garden. On the inside is all the food you'd expect,
0:01:04 > 0:01:07as if a family were just about to have a party.
0:01:07 > 0:01:11Also on the inside are the bacteria and fungal spores that are going
0:01:11 > 0:01:15to start the process of decay. I can't wait to see what happens next.
0:01:16 > 0:01:20Over eight weeks, we're going to track every step
0:01:20 > 0:01:26of the extraordinary process that breaks down and recycles our everyday things.
0:01:26 > 0:01:31The house will be our lab, as we reveal the unexpected order behind
0:01:31 > 0:01:35the chaos of decay, and will help us understand why
0:01:35 > 0:01:38life itself depends on this process.
0:01:41 > 0:01:45At times what we find might be disturbing and repellent...
0:01:46 > 0:01:49This is probably going to be absolutely atrocious.
0:01:50 > 0:01:52HE COUGHS
0:01:52 > 0:01:55But there will also be moments of surprise.
0:01:55 > 0:01:59The mould has just covered that entire box.
0:02:00 > 0:02:02..as we uncover hidden beauty.
0:02:20 > 0:02:24And I'll go beyond the box to see how decay affects our lives...
0:02:24 > 0:02:27Ah! Can't do it!
0:02:27 > 0:02:29..how we detect it...
0:02:29 > 0:02:32Do you remember seeing the film The Blob?
0:02:32 > 0:02:34..how we fight it.
0:02:34 > 0:02:37It's definitely the best two-year-old sandwich I've ever had.
0:02:38 > 0:02:42Something on this scale has never been attempted before,
0:02:42 > 0:02:44so things might not go according to plan.
0:02:45 > 0:02:49Ah! Now that's where all the flies went.
0:02:49 > 0:02:53But whatever happens, it will be a fascinating journey
0:02:53 > 0:02:58into the fate that awaits all living things.
0:02:58 > 0:03:00To be broken down.
0:03:00 > 0:03:03To be recycled. To be reborn.
0:03:23 > 0:03:25It's a surprising thought,
0:03:25 > 0:03:27life relies on death.
0:03:31 > 0:03:34Living things, us included, can only be made
0:03:34 > 0:03:37from the remains of dead things.
0:03:38 > 0:03:41And that's the incredible cycle we hope to capture,
0:03:41 > 0:03:45inside our After Life House.
0:03:45 > 0:03:50As a biologist, I can't wait to see what new life will emerge from these
0:03:50 > 0:03:53dead things by the time we're done.
0:03:53 > 0:03:57This is day one. We have eight weeks to go.
0:04:01 > 0:04:06This is my first chance to see inside the box.
0:04:06 > 0:04:09And a party was obviously just about to happen.
0:04:09 > 0:04:12Over here we've got cooked rice and chilli, there's cups of tea.
0:04:12 > 0:04:14Over in the corner there's a raw fish,
0:04:14 > 0:04:17that's going to get very smelly pretty fast.
0:04:17 > 0:04:21Cheese and a fruit bowl here, masses of fruit flies on that, probably,
0:04:21 > 0:04:25I mean, we don't know, it hasn't been tried before.
0:04:25 > 0:04:28A vegetable box over here, again, it all looks fresh,
0:04:28 > 0:04:31but that will, in a week or two, begin to rot down.
0:04:31 > 0:04:35And look at this, a raw chicken.
0:04:35 > 0:04:36Sausages, hamburgers, all this is
0:04:36 > 0:04:39going to attract flies like nobody's business.
0:04:39 > 0:04:43Out here in the garden you've got a whole pig on a spit.
0:04:43 > 0:04:45That's going to become very smelly.
0:04:45 > 0:04:48But it's not just food items out here in the garden.
0:04:48 > 0:04:50We have a compost heap. We have a woodpile.
0:04:50 > 0:04:52They'll rot down too.
0:04:52 > 0:04:55It'll be interesting to see how, as all the things decay,
0:04:55 > 0:04:58the wood and the plants and the pig, how they will interact.
0:04:58 > 0:05:02Over there in the corner we have a dead rat as well.
0:05:02 > 0:05:06In fact everything in here has been carefully arranged to help us
0:05:06 > 0:05:09unravel the underlying patterns of decay.
0:05:09 > 0:05:14We're going to keep an eye on how humid it is, and how hot it is.
0:05:14 > 0:05:19It's already up to 66% RH which will make things go really quite fast.
0:05:19 > 0:05:25I'm not sure if I'll be overcome by the heat, the stench or the flies.
0:05:27 > 0:05:30Insects are my own speciality.
0:05:30 > 0:05:35Together with moulds and bacteria, they are key agents of decay,
0:05:35 > 0:05:38things that will break all this down.
0:05:38 > 0:05:42To make sure they are all present in our house from the start,
0:05:42 > 0:05:46we're introducing a selection of common species.
0:05:46 > 0:05:48Look at that, straight underneath!
0:05:48 > 0:05:51These guys, blow flies, are going to be the ones
0:05:51 > 0:05:53to watch in the early stages.
0:05:53 > 0:05:55And there they go.
0:05:55 > 0:05:58Well, that's it. We're up and running
0:05:58 > 0:06:02and it's time to leave all this to the agents of decay.
0:06:02 > 0:06:05Now, for nearly two months,
0:06:05 > 0:06:09we're going to track every stage in the process of decay.
0:06:10 > 0:06:13And we're not the only ones following events.
0:06:13 > 0:06:17The box and its contents are on display to the public within
0:06:17 > 0:06:20Edinburgh zoo, to help explore our reactions to this
0:06:20 > 0:06:22little understood process.
0:06:22 > 0:06:25Oh my God, I've never seen anything like it
0:06:25 > 0:06:26That's a real pig.
0:06:26 > 0:06:28Ew, that's gross!
0:06:28 > 0:06:30Oh, there's a mouse.
0:06:30 > 0:06:34That's disgusting, eugh!
0:06:34 > 0:06:36Look at that fish.
0:06:36 > 0:06:40Can we go out now cos it's going to make us feel sick?
0:06:40 > 0:06:42THEY LAUGH
0:06:42 > 0:06:43I agree.
0:06:54 > 0:06:57For the first 24 hours of our project,
0:06:57 > 0:07:01visible signs of decay are subtle.
0:07:01 > 0:07:06But the agents of decay are already battling it out to decompose
0:07:06 > 0:07:09the food and get to the nutrients locked inside.
0:07:09 > 0:07:16I want to investigate who's got the advantage in this opening stage
0:07:20 > 0:07:24Well, it's the second day and it's really warm in here, it's 25 degrees.
0:07:24 > 0:07:27That's like a warm summer day, so some things are drying out
0:07:27 > 0:07:30the chilli con carne is already growing a layer of mould,
0:07:30 > 0:07:34and that shows that there are fungal spores drifting around in the atmosphere
0:07:34 > 0:07:37all the time and settling on food.
0:07:37 > 0:07:42Over here, the sandwiches which originally filled the box,
0:07:42 > 0:07:46up to the top, have sagged down to about half their height.
0:07:46 > 0:07:50But what's really interesting me is what's happening over here.
0:07:53 > 0:07:57The most obvious change so far has been on the surface of our chicken.
0:07:57 > 0:08:01Our time lapse cameras show these blotches appearing on its skin,
0:08:01 > 0:08:03over the course the past day.
0:08:06 > 0:08:08To find out what's producing them,
0:08:08 > 0:08:12I've asked Dr Clare Taylor, a microbiologist, to join me.
0:08:18 > 0:08:22Well, Clare, that chicken is beginning to look a bit discoloured.
0:08:22 > 0:08:26- It smells a bit as well. - There's beginning to be a slight whiff. What have you got on this?
0:08:26 > 0:08:29I tell you what I've got a UV light
0:08:29 > 0:08:32so we can take a look more closely at the surface.
0:08:32 > 0:08:34Now, ultraviolet I use for other things,
0:08:34 > 0:08:37but I'm interested to see what happens here.
0:08:37 > 0:08:40- Now you can't see it. - No, can't see anything.
0:08:40 > 0:08:41Take a look at that!
0:08:41 > 0:08:46It's glowing! So all these areas are glowing sort of blue.
0:08:46 > 0:08:52Exactly, so where you can see those glowing bits, that's bacteria.
0:08:52 > 0:08:56- Any particular kind? - That's likely to be pseudomonas.
0:09:02 > 0:09:06Pseudomonas is a common type of food spoilage bacteria.
0:09:07 > 0:09:11Our microscope shows a whole colony glowing under the UV light.
0:09:15 > 0:09:19There could be as many as a billion individual bacterial cells
0:09:19 > 0:09:21in this sample alone.
0:09:24 > 0:09:26In sheer number terms,
0:09:26 > 0:09:30bacteria are the most common agents of decay on the planet.
0:09:30 > 0:09:34And, on dead animals, they're the first to attack.
0:09:34 > 0:09:37Because they're already on the scene.
0:09:38 > 0:09:42All creatures carry bacteria while they're alive.
0:09:42 > 0:09:46These pseudomonas bacteria were on our chicken before it was killed,
0:09:46 > 0:09:48feeding on its skin secretions.
0:09:48 > 0:09:53Now it's dead, they've quickly switched to decomposing its flesh.
0:09:58 > 0:10:01With ample food, and enough moisture,
0:10:01 > 0:10:03they've multiplied rapidly.
0:10:03 > 0:10:08As colonies of bacteria like this expand, something surprising happens.
0:10:08 > 0:10:13The bacteria start to coordinate their actions.
0:10:13 > 0:10:15Working together to benefit the colony.
0:10:15 > 0:10:20The bacteria send signals to each other to direct what they do.
0:10:20 > 0:10:25So the bacteria are talking to each other, telling each other where they need to go.
0:10:26 > 0:10:30These E-coli bacteria have been genetically modified
0:10:30 > 0:10:32to allow us to see this in action.
0:10:34 > 0:10:40When the colony reaches a critical size all the bacteria start flashing in unison.
0:10:42 > 0:10:46Bacteria are constantly exchanging chemicals that allow them
0:10:46 > 0:10:51to sense their own numbers and those of rival colonies.
0:10:52 > 0:10:55They can even detect when they have the numbers
0:10:55 > 0:10:57to overwhelm a competitor.
0:11:04 > 0:11:10Back on our chicken, these tactics have allowed food spoilage bacteria to gain the upper hand.
0:11:10 > 0:11:14But their actions are setting off a chain of events
0:11:14 > 0:11:19that will attract a whole new set of decomposers.
0:11:19 > 0:11:23As they break down the cells of the chicken to feast on the protein inside,
0:11:23 > 0:11:26the bacteria are releasing strong smelling gases.
0:11:30 > 0:11:36blow flies can pick up the smell of decomposing flesh within minutes of an animal's death.
0:11:36 > 0:11:43So it's likely they've already laid eggs on the chicken and other meat throughout the box.
0:11:44 > 0:11:49We'll find out if we start seeing maggots in the next few days.
0:11:51 > 0:11:54These gases send a signal to us too.
0:11:54 > 0:12:00It's our most important clue that food spoilage bacteria have been at work.
0:12:00 > 0:12:04Right, let's see what folks make of these chicken drumsticks.
0:12:05 > 0:12:10I want to see how sensitive we are to even the smallest signs of decay.
0:12:12 > 0:12:17Hi, guys, would you care to have a smell of this?
0:12:17 > 0:12:19- Erggh! I can smell it from here. - Urgh!
0:12:19 > 0:12:22THEY LAUGH
0:12:22 > 0:12:27- It's horrible.- Stop it. - It's not nice.
0:12:28 > 0:12:31So, if you found that in your house, what would you do?
0:12:31 > 0:12:35I wouldn't eat it. I think I'd put it in the bin.
0:12:35 > 0:12:38- I'd throw it away immediately. - Throw it out.
0:12:38 > 0:12:40It's disgusting.
0:12:42 > 0:12:46We fight a daily battle to keep this kind of decay out of our kitchens.
0:12:48 > 0:12:54Looking round the box already makes me think about what a challenge this really is.
0:12:54 > 0:12:57Decay is a relentless opponent.
0:12:57 > 0:13:02So, I'm interested in exploring what we've learnt about delaying its effects.
0:13:03 > 0:13:06And in America, there's a team that's taking on
0:13:06 > 0:13:10the ultimate food preservation challenge.
0:13:10 > 0:13:12GUNSHOTS
0:13:14 > 0:13:17Keep your head down or it's going to get shot off you!
0:13:17 > 0:13:19GUNSHOTS
0:13:20 > 0:13:24Now, this is not necessarily the first place I'd think of
0:13:24 > 0:13:28when it comes to the latest advances in food science,
0:13:28 > 0:13:32but the US army is right on the frontline in the war against decay.
0:13:34 > 0:13:38Feeding an army in the field has always presented a challenge.
0:13:38 > 0:13:41Soldiers need food that is quick to prepare,
0:13:41 > 0:13:43light to carry and long lasting.
0:13:43 > 0:13:47Traditionally, the US military uses vacuum packed food
0:13:47 > 0:13:52called MREs, meals ready to eat.
0:13:52 > 0:13:56Special packaging stops moisture and oxygen getting in
0:13:56 > 0:14:01so bacteria can't grow. MREs have a shelf life of three years.
0:14:03 > 0:14:05There's a problem though.
0:14:05 > 0:14:09MREs are not exactly popular with the people who have to eat them.
0:14:11 > 0:14:15Hands-down-worst MRE made is the veggie omelette.
0:14:15 > 0:14:18It's like eating a... I don't know.
0:14:18 > 0:14:22Wet, soggy cardboard is the best way I think you can describe it.
0:14:22 > 0:14:27If I had to eat an MRE every day, that would basically suck.
0:14:27 > 0:14:29GUNFIRE
0:14:29 > 0:14:33So, when the army went looking for ways to spruce up the menu,
0:14:33 > 0:14:36it wanted something more appealing.
0:14:36 > 0:14:39Something that was quick and easy to eat.
0:14:39 > 0:14:44And could deliver the huge amounts of energy that soldiers require.
0:14:44 > 0:14:47The solution was a surprise.
0:14:49 > 0:14:53A sandwich. But not just any sandwich.
0:14:53 > 0:14:58A sandwich that remains fresh and tasty in the field for up to three years,
0:14:58 > 0:15:02without refrigeration, freeze drying or the need to add water.
0:15:02 > 0:15:04That is extreme preservation.
0:15:04 > 0:15:07So how did they do it?
0:15:08 > 0:15:14Food scientist Michelle Richardson was part of the team that developed the sandwich.
0:15:14 > 0:15:19Her first challenge was to control the moisture you'd find in a typical sandwich.
0:15:22 > 0:15:23HE LAUGHS
0:15:25 > 0:15:28These sandwiches do not look very happy.
0:15:28 > 0:15:30They really don't.
0:15:30 > 0:15:37That's a ham and cheese wedge that's been in the car for three days.
0:15:37 > 0:15:40If we open it up, we'll just have a look at this thing
0:15:40 > 0:15:46cos if you had that in your backpack for three days...
0:15:46 > 0:15:50That was just a normal shop-bought sandwich.
0:15:50 > 0:15:55Urgh! It's soggy. It's really soggy. Look at that.
0:15:55 > 0:15:59You wouldn't really want to eat that in the field?
0:15:59 > 0:16:02You really wouldn't want to eat it for two reasons. It wouldn't taste good,
0:16:02 > 0:16:06because the texture is not what you typically get. And also
0:16:06 > 0:16:11because of that moisture excess you may have bacteria growing in it.
0:16:11 > 0:16:15If you can control the moisture, you can slow down the process of decay.
0:16:15 > 0:16:19Without water, bacteria cannot grow.
0:16:19 > 0:16:24That's why drying is the classic way to stop food decaying.
0:16:24 > 0:16:28But a sandwich without water would be inedible.
0:16:28 > 0:16:33So Michelle has taken inspiration from another classic preservation technique.
0:16:33 > 0:16:36Well, this right here is strawberry jam
0:16:36 > 0:16:40- and as you can see in here, it's very firm.- Yeah.
0:16:40 > 0:16:43It's made from strawberries. Most fruits and vegetables contain
0:16:43 > 0:16:49a lot of water, probably 95% water, but by adding different ingredients,
0:16:49 > 0:16:53what that does is it holds the water in very tightly.
0:16:53 > 0:16:57- Right, so it's locked away in there? - Yes.
0:16:57 > 0:17:02The sugar added to jam acts as what's called a humectant.
0:17:02 > 0:17:05It traps the water from the fruit inside the jam.
0:17:05 > 0:17:08That's why the jam is moist enough to spread,
0:17:08 > 0:17:11but doesn't make the bread soggy.
0:17:11 > 0:17:14Crucially for the battle against decay,
0:17:14 > 0:17:17the water is also now locked away from bacteria.
0:17:17 > 0:17:21The army's sandwiches deploy a whole range of ingredients
0:17:21 > 0:17:24that have these water-retaining properties.
0:17:24 > 0:17:28Honey, sugar and salt have all been enlisted.
0:17:28 > 0:17:33Bacteria need water to thrive. Most also need oxygen too.
0:17:33 > 0:17:37Michelle has found a way to cut off supplies of that as well.
0:17:37 > 0:17:42Now, when I opened the pack I found this inside
0:17:42 > 0:17:44- and I assume that's not edible. - No, it's not.
0:17:44 > 0:17:46What is this for?
0:17:46 > 0:17:49This is an oxygen scavenger.
0:17:49 > 0:17:53Basically what's contained in here are little iron shavings.
0:17:53 > 0:17:56Oh, right. Iron filings.
0:17:56 > 0:18:00If there is any oxygen or moisture still inside the packaging,
0:18:00 > 0:18:05they'll react with the iron filings, and become trapped in a layer of rust.
0:18:05 > 0:18:10This will prevent yeast and mould from growing as well as bacteria but
0:18:10 > 0:18:14it will also prevent chemical reactions that require oxygen from taking place.
0:18:14 > 0:18:18This is one seriously hi-tech sandwich!
0:18:18 > 0:18:20Yeah, it is.
0:18:20 > 0:18:23These simple but ingenious solutions have combined to make
0:18:23 > 0:18:28a food that is highly resistant to decay.
0:18:28 > 0:18:31But the ultimate test is whether anyone wants to eat it.
0:18:31 > 0:18:35It's definitely the best two-year-old sandwich I've had. Better than a lot of new ones too.
0:18:35 > 0:18:37I'm a big fan. I like the bread.
0:18:37 > 0:18:41The bread just makes it, it's definitely great,
0:18:41 > 0:18:42especially for two-years-old.
0:18:43 > 0:18:47These sandwiches don't stay fresh for ever.
0:18:47 > 0:18:52But they do show that, if you can reduce the moisture and oxygen that
0:18:52 > 0:18:57bacteria thrive on, you can hold off decay for a very long time.
0:19:07 > 0:19:09Back at the house, water and oxygen
0:19:09 > 0:19:14certainly aren't in short supply, so bacteria are thriving.
0:19:18 > 0:19:21And over the last eight days of decay we've started to see
0:19:21 > 0:19:24the first maggots appearing in our pig.
0:19:24 > 0:19:28I'd expect their numbers to rocket in a week or so.
0:19:29 > 0:19:32Other insects have been busy around our dead rat.
0:19:32 > 0:19:35These are sexton beetles.
0:19:35 > 0:19:39In the wild they'll bury the carcasses of small mammals
0:19:39 > 0:19:41to protect them from rival insects.
0:19:41 > 0:19:45Their own larvae then break down the flesh.
0:19:45 > 0:19:49But in our box, things are not quite going to plan.
0:19:49 > 0:19:54Despite all the activity, our rat remains unburied.
0:19:54 > 0:19:59So I'll try laying out a new rat and see if they prefer it.
0:20:00 > 0:20:04But the most dramatic change has been in our kitchen.
0:20:04 > 0:20:08It's been overrun by the next agent of decay, mould.
0:20:22 > 0:20:24Moulds are masters of decay.
0:20:24 > 0:20:28They're a form of fungi, the most versatile
0:20:28 > 0:20:31and important decomposers on the planet.
0:20:31 > 0:20:34Fungi can rot almost anything.
0:20:34 > 0:20:39In our box, moulds are attacking our fruit and vegetables.
0:20:43 > 0:20:49And they're also on our meat, battling with the bacteria for dominance.
0:20:50 > 0:20:53It'll be fascinating to see how that one plays out.
0:20:56 > 0:21:01The typical house will contain about 1,000 different species of mould.
0:21:01 > 0:21:08They can start to grow the moment their spores land on a suitable food source.
0:21:08 > 0:21:12I want to see which ones are at work in our box.
0:21:18 > 0:21:23Well, in the kitchen there is mould absolutely everywhere.
0:21:23 > 0:21:26The vegetables in the tray are covered in fungus.
0:21:26 > 0:21:29There's at least three sorts of fungus I can see.
0:21:29 > 0:21:34The hamburgers, sausages, even the hamburgers that are wrapped up are now covered in mould.
0:21:34 > 0:21:38That's looking quite... woah! That might blow at any time.
0:21:38 > 0:21:42The soft fruit in particular have been attacked.
0:21:42 > 0:21:46The peaches have gone and there's mould everywhere.
0:21:46 > 0:21:49The melon's just incredible, it's really been hammered.
0:21:49 > 0:21:52It's just covered, all over there.
0:21:52 > 0:21:55I'm a little bit nervous about taking this lid off.
0:21:57 > 0:22:02This is going to be... Urgh!
0:22:02 > 0:22:05Urgh! That's an incredible smell.
0:22:05 > 0:22:08It's almost sweet.
0:22:12 > 0:22:16It's an incredible sort of yeasty, smell.
0:22:18 > 0:22:23The mould has just covered the entire box.
0:22:23 > 0:22:28That's actually quite beautiful in a bizarre way.
0:22:33 > 0:22:40It's like just furry growths everywhere.
0:22:40 > 0:22:44That's amazing! That's only a week.
0:22:50 > 0:22:55In close up, the unexpected beauty of mould is even clearer.
0:23:05 > 0:23:08These networks of filaments we see on the surface of our bread
0:23:08 > 0:23:10are the mould's fruiting body.
0:23:25 > 0:23:33At the ends of the filaments are spore heads, each packed with individual spores,
0:23:33 > 0:23:36all waiting to be released to grow into new colonies.
0:23:40 > 0:23:47There are 500 spores in every cubic metre of air in the average home.
0:23:47 > 0:23:51So there's plenty of competition for the chance to attack our bread.
0:24:02 > 0:24:07I've asked Dr Patrick Hickey, our fungi expert to investigate
0:24:07 > 0:24:11which moulds have managed to gain control.
0:24:11 > 0:24:15Now, Patrick, it's only week one and we've got incredible fungal growth
0:24:15 > 0:24:17all over the kitchen. Particularly on the bread.
0:24:17 > 0:24:21Well, the bread is a perfect food source for the fungi.
0:24:21 > 0:24:25The spores probably landed on the bread when it was being prepared and
0:24:25 > 0:24:30they've grown quickly into the bread and they're taking up the nutrients.
0:24:30 > 0:24:34What we're actually seeing is two moulds meeting.
0:24:34 > 0:24:37In the background, we've got a dark green-grey mould
0:24:37 > 0:24:40that's penicilium. These bright dots in the front
0:24:40 > 0:24:43are the sporilating structures of aspergillus competing.
0:24:43 > 0:24:47So they're kind of trying to out compete each other for the bread,
0:24:47 > 0:24:48for the food resource.
0:24:50 > 0:24:55Each mould is trying to seize territory by out-growing its competitors.
0:24:56 > 0:25:00But they are also using powerful chemical weapons to try to
0:25:00 > 0:25:05kill off other moulds and rival decomposers, like bacteria.
0:25:06 > 0:25:10In the case of penicillium, the toxin it produces to win
0:25:10 > 0:25:15the battle for decay, has turned out to be highly beneficial to us.
0:25:15 > 0:25:19We call it penicillin.
0:25:19 > 0:25:23But not all moulds are good for us.
0:25:23 > 0:25:27Now, I have to admit, I sometimes cut the mould off bits of bread
0:25:27 > 0:25:30and toast it. Is that really harmful?
0:25:30 > 0:25:33Well, what you're scraping off is really the tip of the iceberg.
0:25:33 > 0:25:37The fungus grows deep into the bread and it also depends on what kind of
0:25:37 > 0:25:40mould is growing into the bread. You have various different moulds,
0:25:40 > 0:25:44some of which are harmless. Others like aspergillus produce deadly mycotoxins,
0:25:44 > 0:25:49these are toxic chemicals, which can rot your liver,
0:25:49 > 0:25:50they can give you cancer.
0:25:50 > 0:25:53So, what you're saying is, I shouldn't really do that.
0:25:53 > 0:25:56It's dangerous I should just throw it in the bin.
0:25:56 > 0:25:59Absolutely, the fungus penetrates quite deep into the bread you're
0:25:59 > 0:26:04not going to get rid of the toxins in the mould just by scraping it off.
0:26:05 > 0:26:09Most of us might prefer not to have to cope with mouldy bread
0:26:09 > 0:26:16in the first place. Moulds and other types of fungi are things that ruin our food, and may cause us harm.
0:26:17 > 0:26:21But fungi are vital to life on this planet.
0:26:24 > 0:26:27They're amongst the Earth's oldest life forms.
0:26:27 > 0:26:32On land, they pre-date plants by at least 300 million years.
0:26:34 > 0:26:37And they rise to almost any challenge.
0:26:48 > 0:26:52There is a fungus growing inside the brain of this ant.
0:26:52 > 0:26:55It's producing chemicals that control the ant's behaviour,
0:26:55 > 0:26:59forcing it to climb to the top of a plant.
0:26:59 > 0:27:02Then the killer fungus bursts out of the ant's head,
0:27:02 > 0:27:04allowing its spores to spread.
0:27:11 > 0:27:15Fungi have found ways to work on a microscopic level too.
0:27:15 > 0:27:19This one is lying in wait for tiny roundworms.
0:27:19 > 0:27:24At the right moment, it strangles them in a vice-like grip,
0:27:24 > 0:27:28then feeds on their flesh.
0:27:32 > 0:27:36But it's fungi's unrivalled ability to decay organic matter that
0:27:36 > 0:27:40makes them so important to us.
0:27:40 > 0:27:42A world where fungi couldn't decay things
0:27:42 > 0:27:46would be a very different place.
0:27:49 > 0:27:53To see just how different, we have to go back in Earth's history.
0:27:53 > 0:27:56To a period when a new form of organic matter emerged.
0:27:56 > 0:28:01One that challenged fungi's powers of decay.
0:28:03 > 0:28:07The fate of life on Earth, hung in the balance.
0:28:10 > 0:28:13Rewind 300 million years to the Carboniferous Period.
0:28:13 > 0:28:16A time when plants, struggling to compete for sunlight,
0:28:16 > 0:28:18had evolved into trees.
0:28:23 > 0:28:26That new organic material was wood.
0:28:26 > 0:28:31It gave plants the strength to grow taller.
0:28:31 > 0:28:35But this evolutionary leap left fungi behind.
0:28:35 > 0:28:38They weren't able to decompose wood.
0:28:38 > 0:28:43The delicate mechanism of decay had been upset.
0:28:43 > 0:28:47Without decay the trees grew, died and lay where they fell.
0:28:49 > 0:28:53The effect on the planet's climate was spectacular.
0:28:55 > 0:28:59Professor Lynne Boddy is an expert in the history of fungi.
0:28:59 > 0:29:02Trees absorb carbon dioxide from the air.
0:29:02 > 0:29:04They absorb nutrients from the soil.
0:29:04 > 0:29:07And then the carbon is locked up within the trees,
0:29:07 > 0:29:13so when they fall and die, the carbon is still locked up inside them.
0:29:13 > 0:29:18- So huge changes simply because trees can't decay?- Absolutely.
0:29:21 > 0:29:25With fungi unable to break down wood, over time, more and more
0:29:25 > 0:29:29carbon was removed from the air and locked up in dead trees.
0:29:29 > 0:29:32The Earth's atmosphere began to change.
0:29:36 > 0:29:40Oxygen levels shot up from 20% to 30%,
0:29:40 > 0:29:43as carbon dioxide levels dropped.
0:29:43 > 0:29:48This allowed insects to grow to gigantic proportions.
0:29:50 > 0:29:53Spiders were as wide as a human head.
0:29:56 > 0:30:02Dragonflies were ten times larger than they are today.
0:30:02 > 0:30:07If the atmosphere had stayed like this, life on our planet would have looked very different.
0:30:08 > 0:30:13The stumbling block for fungi was a molecule in trees called lignin.
0:30:13 > 0:30:15It's what makes wood tough.
0:30:15 > 0:30:20It took 50 million years for fungi to evolve a way to overcome it.
0:30:20 > 0:30:23And Lynne is able to show me the modern descendents of
0:30:23 > 0:30:26the fungi that solved the problem.
0:30:26 > 0:30:29If you pick up that log we could have a better look.
0:30:29 > 0:30:31No, the one underneath. That one, there.
0:30:31 > 0:30:33The first thing I see about it, it's not heavy at all.
0:30:33 > 0:30:36- It's light as a feather. - It hardly weighs anything.
0:30:36 > 0:30:39Yes, it's been rotted and you can see that it's really white.
0:30:39 > 0:30:41Why is it white?
0:30:41 > 0:30:45It's white because the fungi have broken down the lignin in the wood.
0:30:45 > 0:30:47- Which was brown.- Yes.
0:30:47 > 0:30:51It's pretty easy to see what effect the fungi have had on the wood,
0:30:51 > 0:30:53but can we actually see the fungi themselves?
0:30:53 > 0:30:55We can't actually see them rotting the wood,
0:30:55 > 0:30:57not with our naked eye because they're microscopic.
0:30:57 > 0:31:03To show me the fungi in action, Lynne has grown this sample in soil.
0:31:03 > 0:31:07- That's pretty.- What we've got here is a little bit of beech wood
0:31:07 > 0:31:10that's got the fungus growing in it, and then you put the wood
0:31:10 > 0:31:13on top of this soil, and the fungus has grown out of the wood,
0:31:13 > 0:31:17looking for other pieces of wood that they can colonise and get food from.
0:31:20 > 0:31:24The fungus sends out a network of tiny threads called hyphae.
0:31:28 > 0:31:33They've aggregated together so we can actually see them with the naked eye.
0:31:33 > 0:31:38- And they're heading off to find other bits to eat?- That's right.
0:31:38 > 0:31:42The hyphae release powerful enzymes into the wood.
0:31:42 > 0:31:45They are able to break down the lignin into nutrients
0:31:45 > 0:31:47the fungi can then absorb.
0:31:48 > 0:31:52This releases carbon from the wood, back into the air.
0:31:53 > 0:32:00It was the evolution of these enzymes that allowed fungi to rebalance the Earth's atmosphere.
0:32:01 > 0:32:05If those fungi weren't here today then decay would come to a grinding
0:32:05 > 0:32:08halt and we would be in a similar position to what we were
0:32:08 > 0:32:10in the Carboniferous period.
0:32:14 > 0:32:19By evolving the ability to unlock the carbon in dead wood,
0:32:19 > 0:32:22fungi saved the world.
0:32:22 > 0:32:26We still rely on this delicate balance between all living things,
0:32:26 > 0:32:29and the agents that can decompose them.
0:32:47 > 0:32:50At the After Life house another eight days have gone by.
0:32:52 > 0:32:57Just after my last visit we captured something extraordinary.
0:32:57 > 0:33:00The new rat that I left out in the garden has been
0:33:00 > 0:33:04buried by the sexton beetles, as I hoped it would be.
0:33:05 > 0:33:09Despite their size, it took the two of them less than 12 hours to
0:33:09 > 0:33:15get the whole carcass underground, and away from rival decomposers.
0:33:17 > 0:33:19The female will lay her eggs in the rat
0:33:19 > 0:33:23so her young will have food to eat when they hatch.
0:33:24 > 0:33:27In about a month's time, we'll dig up the rat
0:33:27 > 0:33:30and see what the beetle larvae have done.
0:33:37 > 0:33:39Elsewhere in the box,
0:33:39 > 0:33:43bacteria and mould are still battling it out on the meat.
0:33:45 > 0:33:49The bacteria inside this sealed pack of burgers are hard at work,
0:33:49 > 0:33:52producing this build up of gas.
0:33:52 > 0:33:55I'm not looking forward to smelling that.
0:34:01 > 0:34:04Where meat was left exposed to the air, like these sausages,
0:34:04 > 0:34:07mould has been able to move in,
0:34:07 > 0:34:12suggesting that the bacteria have been overwhelmed.
0:34:12 > 0:34:15But just over two weeks in to our project,
0:34:15 > 0:34:20and an army of even more voracious decomposers is taking control.
0:34:20 > 0:34:24The maggot population has exploded.
0:34:25 > 0:34:29Our pig is literally seething with them.
0:34:29 > 0:34:33Maggots are some of decay's most effective operators.
0:34:37 > 0:34:40The question is, how long will it take them
0:34:40 > 0:34:43to munch their way through the contents of our house?
0:34:45 > 0:34:50I haven't even got into the box and already I can see escaping maggots.
0:34:50 > 0:34:54So, even though we try really carefully to keep
0:34:54 > 0:34:57all the insects on the inside, some have escaped.
0:34:57 > 0:35:01They can squeeze through the tiniest gap
0:35:06 > 0:35:09The time-lapse cameras have shown a real fever pitch,
0:35:09 > 0:35:12especially on the chicken and the fish.
0:35:12 > 0:35:17I just want to show you the fish though. It's completely eaten out.
0:35:17 > 0:35:20If I just... look at that, look at the inside of that.
0:35:23 > 0:35:25Pwahh.
0:35:25 > 0:35:28It's just a writhing mass of maggots
0:35:28 > 0:35:32and the smell of ammonia is overpowering.
0:35:32 > 0:35:34They've eaten everything.
0:35:34 > 0:35:39All that remains is the dry skin on the outside and the bones.
0:35:39 > 0:35:42These are the most efficient recyclers on the planet.
0:35:42 > 0:35:45I think they are just amazing insects.
0:35:52 > 0:35:57It's 15 days since I released about 100 blow flies into the box.
0:35:58 > 0:36:03As soon as they mate, female flies look for a place to lay eggs.
0:36:03 > 0:36:05Up to 300 at a time.
0:36:07 > 0:36:12The gases given off in the very early stages of decomposition,
0:36:12 > 0:36:15will have attracted them to the dead meat and fish.
0:36:17 > 0:36:19They're the ideal food source for the maggots,
0:36:19 > 0:36:22when they start to emerge, around 24 hours later.
0:36:24 > 0:36:28Now they've hatched, these maggots have only one aim.
0:36:28 > 0:36:31To eat. Non-stop.
0:36:34 > 0:36:37Now, I've got the thermal image camera here
0:36:37 > 0:36:39and this is actually quite a useful item.
0:36:39 > 0:36:44It can show heat that's produced by organisms.
0:36:44 > 0:36:50The fly larvae, when they feed en masse, do generate quite a bit of heat.
0:36:50 > 0:36:52Now, I'm just shining it on the chicken drumsticks,
0:36:52 > 0:36:56which are cold, they're not hot at all.
0:36:56 > 0:37:00The chicken's not very hot. But wooo! Look at that!
0:37:00 > 0:37:03The burgers are glowing like a beacon.
0:37:03 > 0:37:06Now, that means that there are lots of fly larvae in there and they
0:37:06 > 0:37:11are generating masses of heat, which actually makes them grow faster.
0:37:18 > 0:37:22Our time lapse camera shows how maggots feed as a pack,
0:37:22 > 0:37:28so they can share not just heat, but digestive enzymes too.
0:37:28 > 0:37:31They carefully coordinate their movements.
0:37:31 > 0:37:36As the meat in one burger runs out, the maggots move together, almost
0:37:36 > 0:37:41as a single unit, over to the fresh supplies of the second burger.
0:37:45 > 0:37:48Maggots are a perfectly adapted mechanism for turning
0:37:48 > 0:37:51dead meat into flies.
0:37:52 > 0:37:58At the head end, you've got these amazing hooks,
0:37:58 > 0:38:02which are basically a pair of sharp, curved hooks
0:38:02 > 0:38:08with which the maggot rasps its way through food.
0:38:15 > 0:38:18As you move further down, you see it doesn't have legs.
0:38:18 > 0:38:21There isn't any obvious head, thorax and abdomen.
0:38:21 > 0:38:26It has got these bands of raised bumps,
0:38:26 > 0:38:30they're like spikes for a grub.
0:38:30 > 0:38:33They're bands of raised welts,
0:38:33 > 0:38:38which help the maggot move through its food so it's essentially
0:38:38 > 0:38:40in a pile of slop.
0:38:40 > 0:38:46These welts enable it to undulate through the food.
0:38:46 > 0:38:50Otherwise, it's very hard to move.
0:38:50 > 0:38:55At the other end, let's go down to the back end.
0:38:57 > 0:39:02These structures here are the breathing holes of the fly.
0:39:02 > 0:39:08These are the spiracles through which it gets its air.
0:39:11 > 0:39:16They're on the rear end. It has a pair of them, quite big.
0:39:19 > 0:39:24So it's able to insert its head into wet food and still feed
0:39:24 > 0:39:27while its rear end is in the air.
0:39:28 > 0:39:34All in all, it is just about the perfect eating machine.
0:39:37 > 0:39:40To me, maggots are the clearest example we've seen
0:39:40 > 0:39:44so far of the fundamental principle behind decay.
0:39:44 > 0:39:47Recycling the nutrients from dead animals,
0:39:47 > 0:39:50and turning it into new life.
0:39:50 > 0:39:54But, of course, for many of us they represent everything
0:39:54 > 0:39:57that's disgusting about decay.
0:39:57 > 0:40:02I'm intrigued as to what these strong feelings of revulsion are, so I've devised a little test.
0:40:02 > 0:40:06I'm going to put a £5 note inside a plastic bag
0:40:06 > 0:40:12and I'm going to hide it inside a tub, inside which I'm going to put
0:40:12 > 0:40:19loads of maggots. We're going to end up with a pretty simple test,
0:40:19 > 0:40:21which is essentially this,
0:40:21 > 0:40:25a large box full of writhing maggots and a £5 note.
0:40:25 > 0:40:29Now, I reckon only one person in ten will be able to
0:40:29 > 0:40:33overcome their deep seated revulsion for maggots
0:40:33 > 0:40:37and put their hand in to retrieve the fiver. Well, we'll find out.
0:40:43 > 0:40:49Who would like to put their hand in a bucket of maggots for a fiver?
0:40:49 > 0:40:51Oh, you would, would you?
0:40:53 > 0:40:57It looks like my bin at home. THEY LAUGH
0:40:57 > 0:41:00- I can't do it!- Five pound note.
0:41:00 > 0:41:02No, I can't do it.
0:41:02 > 0:41:05- Maggots.- Ew! SHE LAUGHS NERVOUSLY
0:41:05 > 0:41:08- Oh.- It's a little gross, they're writhing on my fingers.
0:41:08 > 0:41:12Oh, no! Oh! Oh! No, no.
0:41:12 > 0:41:16- No, I can't do it.- Five pound note.
0:41:16 > 0:41:18SHE SCREAMS
0:41:18 > 0:41:21- You're nearly there.- I've got it! Ah!
0:41:21 > 0:41:24You nearly got it. Yes!
0:41:24 > 0:41:26THEY APPLAUD
0:41:28 > 0:41:33This feeling of disgust is an emotion that evolved over thousands of years.
0:41:33 > 0:41:38It's not just maggots. All signs of decay revolt us.
0:41:41 > 0:41:44It's a great mechanism for stopping us
0:41:44 > 0:41:47from eating food that might make us sick.
0:41:47 > 0:41:51But it's also why we so rarely look at decay,
0:41:51 > 0:41:54we're hardwired to be repulsed by it.
0:41:56 > 0:41:59In the next few weeks, I hope our After Life house will start
0:41:59 > 0:42:04to show why this disgusting process is so important.
0:42:04 > 0:42:07Why decomposition is vital to life.
0:42:10 > 0:42:15And there's one part of our box where we're attempting to demonstrate that, in a unique way.
0:42:18 > 0:42:22These dead mustard plants are the starting point of an experiment
0:42:22 > 0:42:27that will help me trace how new life emerges from old.
0:42:28 > 0:42:31I've made liquid compost from the mustard
0:42:31 > 0:42:33and fed it to these seedlings.
0:42:35 > 0:42:40We plan to track individual nitrogen atoms from the dead mustard leaves,
0:42:40 > 0:42:45to see if they are re-used in the new plants.
0:42:45 > 0:42:50No-one has ever followed the cycle of life in this way before.
0:42:52 > 0:42:55In a couple of weeks time we can come back and, with any luck,
0:42:55 > 0:43:01we'll be able to track this vital part of the cycle from death and decay to new life.
0:43:14 > 0:43:19It's the 23rd day in the After Life house.
0:43:19 > 0:43:23The first waves of decay have now passed.
0:43:23 > 0:43:27Vegetables and soft fruit have been consumed by mould.
0:43:27 > 0:43:32In some places there's not much left for them to feed on.
0:43:32 > 0:43:34They'll need to find new supplies.
0:43:39 > 0:43:42Anything with a hard skin, like this orange,
0:43:42 > 0:43:44remains apparently unaffected.
0:43:47 > 0:43:50Maggot activity too has begun to die down,
0:43:50 > 0:43:54leaving behind a sort of meat slurry in our burger packet,
0:43:54 > 0:43:58where a few late developers eke out a meal from the remains.
0:44:03 > 0:44:06Most of the maggots have started to pupate,
0:44:06 > 0:44:09the next stage before they turn into adults.
0:44:09 > 0:44:14So we should soon see an explosion in our fly numbers.
0:44:15 > 0:44:19And our chicken has gone through an alarming metamorphosis.
0:44:19 > 0:44:24Bacteria continue to rot away at it, releasing gases as they feed.
0:44:25 > 0:44:28This week the carcass bloated to even more grotesque proportions
0:44:28 > 0:44:32before deflating as the gases escaped.
0:44:33 > 0:44:37One month into the project and our house really isn't somewhere
0:44:37 > 0:44:40you'd want to visit, unless you had to.
0:44:40 > 0:44:46Every time I go into the box there's one thing that hits me.
0:44:46 > 0:44:52That is, the all-pervading, hideous stink of decay.
0:44:54 > 0:44:57Imagine sticking your nose deep into a rubbish bin.
0:44:57 > 0:45:00That's the smell I'm talking about.
0:45:00 > 0:45:03But if you can get beyond your revulsion,
0:45:03 > 0:45:08the smell of decay gives real clues to its underlying mechanisms.
0:45:08 > 0:45:12And the different ways plants and animals are broken down.
0:45:15 > 0:45:18I want to share some of these smells with our audience.
0:45:18 > 0:45:19I've got two tubs.
0:45:19 > 0:45:24One's got far gone vegetables and this one meat that's far gone.
0:45:24 > 0:45:29I want to find out which our visitors find most disgusting.
0:45:34 > 0:45:39This is decaying vegetables. Have a smell of that. See what you think.
0:45:41 > 0:45:45- It smells like vegetables, still. - Have a good sniff.
0:45:45 > 0:45:48- THEY LAUGH - It's not that bad, is it?
0:45:48 > 0:45:50That's not terrible.
0:45:50 > 0:45:55I think it's only fair to warn you, this is not nice.
0:45:55 > 0:45:57Have a smell of that.
0:45:59 > 0:46:01That smells like a pig barn!
0:46:03 > 0:46:05THEY LAUGH
0:46:07 > 0:46:11As expected, the meat gets the same response every time.
0:46:11 > 0:46:14That's pretty grim, isn't it?
0:46:14 > 0:46:17His eyes are watering!
0:46:17 > 0:46:19Ew!
0:46:19 > 0:46:23Rotting meat is far more dangerous to us than rotting vegetables.
0:46:23 > 0:46:26So we're programmed to find it more offensive.
0:46:26 > 0:46:30But what are we actually smelling?
0:46:30 > 0:46:33Plant cells are largely made up of starches and sugars.
0:46:33 > 0:46:36So when fruit and veg decay, they ferment,
0:46:36 > 0:46:39turning the sugars into alcohol, and releasing
0:46:39 > 0:46:42volatile compounds which have a sweet odour.
0:46:42 > 0:46:46But fish and meat are going to produce really smelly gases
0:46:46 > 0:46:50like hydrogen sulphide, sulphur dioxide and ammonia
0:46:50 > 0:46:51so I'm just going to extract
0:46:51 > 0:46:56some of the gases from the inside of this decaying chicken,
0:46:56 > 0:46:59suck it up into this syringe
0:46:59 > 0:47:04and blow it over a gas analyser and see what happens.
0:47:04 > 0:47:06LOUD BEEPING
0:47:06 > 0:47:12Look at that! The hydrogen sulphide shot up to 10%.
0:47:12 > 0:47:14That really is smelly.
0:47:15 > 0:47:17Oh, God.
0:47:17 > 0:47:20HE COUGHS
0:47:22 > 0:47:27Unlike plant cells, animal cells are made up largely of proteins.
0:47:27 > 0:47:29The foul smelling gases are produced
0:47:29 > 0:47:33when these proteins are broken down into amino acids.
0:47:33 > 0:47:37To understand more about that process, and why the smell
0:47:37 > 0:47:41it generates is such an important part of decay, I am going to
0:47:41 > 0:47:46experience rotting flesh on a scale that even the box can't provide.
0:47:56 > 0:48:00At a secret location in north-west England
0:48:00 > 0:48:06a grotesque but important experiment is taking place.
0:48:06 > 0:48:1165 pig carcasses are being left to rot.
0:48:15 > 0:48:19They're part of an investigation into exactly how
0:48:19 > 0:48:23flesh decomposes, under different conditions.
0:48:27 > 0:48:30And the smell of death is everywhere.
0:48:34 > 0:48:40Well, I haven't been here very long and there's a real whiff of dead animal.
0:48:40 > 0:48:45Sometimes the wind changes direction and it catches your nose.
0:48:45 > 0:48:50I'm used to dealing with smells and excrement and stuff but I'm
0:48:50 > 0:48:55wondering if I'm up to this. There's a lot of dead animals around here.
0:48:59 > 0:49:02The pigs are stand-ins for human remains.
0:49:02 > 0:49:05The aim of the experiment is to help police forensic teams
0:49:05 > 0:49:11establish an accurate time of death, based on the state of decomposition.
0:49:11 > 0:49:15Dr Tal Simmons is the research director for the project.
0:49:15 > 0:49:18And she's going to help me understand how
0:49:18 > 0:49:22the different stages of decay account for what we smell.
0:49:22 > 0:49:24- Good morning, Tal. - Good morning, George.
0:49:24 > 0:49:28- I won't shake hands.- Possibly not. - What's happening here?
0:49:28 > 0:49:31Let's move the cage and we'll be able to see a bit better.
0:49:31 > 0:49:36Well, we've got a pig we put out four days ago.
0:49:36 > 0:49:39He's just begun to really show some of the early stages of decomposition.
0:49:39 > 0:49:44The first thing that's obvious to me, it's swollen up there.
0:49:44 > 0:49:47He's beginning to bloat
0:49:47 > 0:49:53and he'll bloat more in the next couple of days and that's due to the cellular breakdown, inside the body.
0:49:53 > 0:49:57All those cells are starting to collapse, the cell membrane is going.
0:49:57 > 0:50:00It's exuding all the fluids inside the cell.
0:50:00 > 0:50:02A lot of those contain digestive enzymes.
0:50:02 > 0:50:05He's starting to eat himself from the inside.
0:50:05 > 0:50:08The moment blood stops flowing in an animal,
0:50:08 > 0:50:12this process of cell death begins.
0:50:12 > 0:50:16As each cell membrane splits, enzymes inside are released
0:50:16 > 0:50:19and begin to break down other cells.
0:50:19 > 0:50:23Bacteria then start to feed on these protein rich contents,
0:50:23 > 0:50:27releasing the gases that are bloating the pig.
0:50:27 > 0:50:31All of these gases produced inside are coming up the digestive tract.
0:50:31 > 0:50:36So that smell is actually coming out and that's what attracts the flies?
0:50:36 > 0:50:42- We can't smell it but flies can. - It's not obvious at all.- No.
0:50:42 > 0:50:46But, as I know from the rotting meat and fish in the box,
0:50:46 > 0:50:50it doesn't take long for the smell to become something we can detect.
0:50:52 > 0:50:53HE COUGHS
0:50:53 > 0:50:56Oh, that's a lot worse.
0:50:56 > 0:50:58Let's pull this off.
0:50:58 > 0:51:01Oh, dear!
0:51:01 > 0:51:04He's much more advanced, as you can see.
0:51:04 > 0:51:05HE COUGHS
0:51:05 > 0:51:09We're now smelling a cocktail of highly volatile gases and
0:51:09 > 0:51:13liquids produced, not just by the break down of the animal proteins,
0:51:13 > 0:51:17but by the agents of decay themselves.
0:51:18 > 0:51:22The body is largely composed of water, so as the cells break down
0:51:22 > 0:51:26and the cell walls go, you get the liquid coming from that,
0:51:26 > 0:51:29you get the liquid that was part of the organs, and you get the liquid
0:51:29 > 0:51:33that the maggots are excreting as part of their digestive process too.
0:51:33 > 0:51:36If you look at it really closely, it's actually rather interesting.
0:51:36 > 0:51:38It's a fascinating process.
0:51:38 > 0:51:42- I wouldn't say it's attractive. - I wouldn't go that far either!
0:51:43 > 0:51:47Many of the molecules in this cocktail of decomposition fluids
0:51:47 > 0:51:52have a particular property, they are highly electrically charged.
0:51:54 > 0:51:57It's a bit like when you rub a balloon on a woollen jumper.
0:51:57 > 0:52:01The molecules of the balloon pick up a charge, which means they stick to
0:52:01 > 0:52:04other materials they come into contact with.
0:52:04 > 0:52:08Which is why the smell of decay can literally stick to our clothes.
0:52:08 > 0:52:12And it also explains why decay can leave a trace
0:52:12 > 0:52:15that lingers far longer than you might think.
0:52:15 > 0:52:16Top off.
0:52:16 > 0:52:20Tal's colleague Peter Cross is measuring what effect
0:52:20 > 0:52:23the decomposing pigs are having on the surrounding earth.
0:52:27 > 0:52:30Just draw the water up. It's even frothing.
0:52:30 > 0:52:32- It's foaming.- Yeah.
0:52:32 > 0:52:37Well, it's clearly not fresh.
0:52:37 > 0:52:40Argh!
0:52:40 > 0:52:43That's pretty bad!
0:52:43 > 0:52:49This is soil water taken from the site of a buried pig carcass.
0:52:49 > 0:52:53This machine is passing an electrical current through the soil water
0:52:53 > 0:52:57and then measuring how well that soil water conducts electricity.
0:52:57 > 0:53:02The contaminated water is 30 times more conductive than
0:53:02 > 0:53:05soil water taken from ten metres away.
0:53:05 > 0:53:09This is the trace that decay leaves behind.
0:53:09 > 0:53:11We think that because of all the electrolytes
0:53:11 > 0:53:15that are leaching into the soil water from the decomposing pig,
0:53:15 > 0:53:18that they are changing the electrical properties of the soil water.
0:53:18 > 0:53:20How long will that remain?
0:53:20 > 0:53:23I'd expect conductivity to continue increasing for up to two years.
0:53:23 > 0:53:26So that really is a fingerprint of death, isn't it?
0:53:26 > 0:53:28Absolutely, yes.
0:53:36 > 0:53:40And it's a fingerprint that allows scientists to detect
0:53:40 > 0:53:44signs of decay, not just over years, but over centuries.
0:53:44 > 0:53:47OK, Chris, do you want to grab the remote probes?
0:53:47 > 0:53:51Dr Jamie Pringle is a forensic geophysicist.
0:53:51 > 0:53:56Today he's using the conductive qualities of decomposition fluids
0:53:56 > 0:54:00to identify unmarked graves in this churchyard.
0:54:00 > 0:54:05Some are estimated to be 200-years-old.
0:54:06 > 0:54:11Jamie's kit sends an electrical current into the ground to measure conductivity.
0:54:11 > 0:54:15It can detect electrically charged molecules
0:54:15 > 0:54:19left behind by the bodies buried centuries ago.
0:54:20 > 0:54:21BEEPING
0:54:21 > 0:54:25Oh, that's interesting, lads. Looks like it's going down there.
0:54:30 > 0:54:32I've just downloaded the data from the machine
0:54:32 > 0:54:37and the results show there's one, two, three, four, five areas
0:54:37 > 0:54:40of blue, which means it's high conductivity results,
0:54:40 > 0:54:44which suggests to me that's where the graves are going to be located
0:54:44 > 0:54:48and where the decompositional fluids have been retained in the soil.
0:54:48 > 0:54:52This technology opens up new possibilities in forensic science.
0:54:52 > 0:54:56Not only can it be used for unmarked graves, it can be used for
0:54:56 > 0:55:01other things as well, such as looking for buried murder victims.
0:55:01 > 0:55:05For crime fighters, the powerful lingering effect of decay,
0:55:05 > 0:55:08turns out to be one of its most useful qualities.
0:55:27 > 0:55:31We're more than halfway through our investigation of what happens
0:55:31 > 0:55:35when decay is allowed to run its course in a typical home.
0:55:37 > 0:55:41We set out to see how quickly its contents would be broken down
0:55:41 > 0:55:43and transformed into new life.
0:55:45 > 0:55:49One month in, we have our most striking result yet.
0:55:52 > 0:55:57The clue is in our rapidly increasing fly numbers.
0:56:03 > 0:56:09These flies are the first generation to be born and bred in the box.
0:56:09 > 0:56:14Two weeks ago, they were the maggots that were so active in all the meat.
0:56:16 > 0:56:19Once a maggot has fed enough, it pupates.
0:56:19 > 0:56:23Within about seven days, the adult blow fly emerges.
0:56:25 > 0:56:30It inflates a soft spongy sack on the top of its head to help push itself out.
0:56:41 > 0:56:45Then blood pumps into the wings, spreading them out
0:56:45 > 0:56:47ready for take off.
0:57:03 > 0:57:07There isn't anything better than flies to illustrate
0:57:07 > 0:57:09the transformative power of decay.
0:57:09 > 0:57:12The fly larvae have eaten this pig. I want to show you
0:57:12 > 0:57:16just how little is left behind.
0:57:16 > 0:57:23If I get this torn back without cutting my finger, it's quite tough.
0:57:23 > 0:57:29The outer surface of the skin is now quite dry. Look at that.
0:57:29 > 0:57:35Oh! The smell of ammonia is quite overpowering.
0:57:35 > 0:57:38If I peel it back...
0:57:39 > 0:57:42What we've got here is basically dried skin
0:57:42 > 0:57:46and a few bits of fat All the meat has gone.
0:57:46 > 0:57:50The fly larvae have eaten this pig out completely
0:57:50 > 0:57:54All that's left are some ribs and fat.
0:57:54 > 0:57:58All that meat that was once pig is now flying around this room.
0:57:58 > 0:58:00Who says pigs can't fly?
0:58:10 > 0:58:16Seven days later and the number of blow flies is becoming a problem inside the house.
0:58:23 > 0:58:26Well, it's a week since I was here before
0:58:26 > 0:58:30and, as I predicted, the numbers of flies have absolutely sky rocketed,
0:58:30 > 0:58:32they've gone through the roof.
0:58:32 > 0:58:37I'm going to wear an all-in-one suit for a bit of protection this week.
0:58:39 > 0:58:44I reckon there could be as many as 10,000 flies inside.
0:58:44 > 0:58:47Because our box is sealed, they can't escape to find
0:58:47 > 0:58:51new sources of food and places to lay their eggs.
0:58:51 > 0:58:58I'm worried that their sheer numbers may disrupt the natural course of decay elsewhere in the box.
0:58:59 > 0:59:06There are now simply too many flies here, it's becoming quite unpleasant.
0:59:06 > 0:59:10It's causing a problem because of the fly speck, that's the excrement,
0:59:10 > 0:59:13which they leave on the surfaces, inside the glass.
0:59:13 > 0:59:18So, it's time I tried to reduce them a bit...
0:59:18 > 0:59:20manually.
0:59:20 > 0:59:27The trouble is, they're flying quite low and sitting on surfaces.
0:59:27 > 0:59:29It's hard to get them.
0:59:30 > 0:59:36Half the flies are drunk because
0:59:36 > 0:59:39the fruit bowl has become alcoholic
0:59:39 > 0:59:43and the flies are flying under the influence at the moment.
0:59:43 > 0:59:46It's probably why there are so many on the floor.
0:59:47 > 0:59:51You can hear them.
0:59:51 > 0:59:53A constant buzz.
0:59:53 > 0:59:55This is pretty unpleasant.
0:59:55 > 0:59:59Oh! Look at this!
1:00:02 > 1:00:05It's no wonder that flies are so hard to capture.
1:00:05 > 1:00:09Their compound eyes give them 360 degree vision.
1:00:09 > 1:00:14So they can respond to movement in less than 30 milliseconds.
1:00:14 > 1:00:18Me and my net can only do so much.
1:00:18 > 1:00:22It will be hunger that kills off these flies in the remaining weeks,
1:00:22 > 1:00:25as food supplies in the box run out.
1:00:26 > 1:00:29Their role in our project is coming to an end.
1:00:29 > 1:00:33We should start to see other insects moving in to carry on
1:00:33 > 1:00:37the process of breaking down what's left of the meat.
1:00:41 > 1:00:47In the meantime, the flies need for food is affecting one of our other agents of decay.
1:00:52 > 1:00:57Six weeks in, mould is still ravaging the sandwich box.
1:00:57 > 1:00:59It's even grown out from under the lid.
1:00:59 > 1:01:02And it's attracted the attention of our starving flies.
1:01:07 > 1:01:12Now, this to me, is one of the most amazing things I've ever seen.
1:01:12 > 1:01:19Patrick Hickey has returned to investigate what's been happening to the moulds in our house.
1:01:19 > 1:01:21How many actual species of fungus are here?
1:01:21 > 1:01:25At least 20 or 30, maybe more.
1:01:25 > 1:01:2820 or 30 species of fungus! I can't wait to have a sort of...
1:01:28 > 1:01:32It's the perfect environment. Some of them are fairly dangerous.
1:01:32 > 1:01:39One of the moulds here, aspergillus flavus, a greeny-yellow one,
1:01:39 > 1:01:44can produce a nasty toxin. So, you want to be careful.
1:01:44 > 1:01:48Look at this, it's a solid mat.
1:01:48 > 1:01:52There are the layers of sandwich.
1:01:52 > 1:01:57It's completely through. There aren't any flies, of course.
1:01:57 > 1:02:01It was sealed in the box so the flies couldn't get in.
1:02:01 > 1:02:06Big contrast to the fruit bowl, which was left open.
1:02:06 > 1:02:12A couple of weeks ago it was covered in thick layers of fungus and
1:02:12 > 1:02:15the flies have stripped it bare.
1:02:15 > 1:02:20They've eaten the fungus and spores and recycled the fungi.
1:02:20 > 1:02:24Fruit has become mould. Mould has become flies. Flies fly off.
1:02:24 > 1:02:27And, if they were outside, they'd be eaten by something.
1:02:30 > 1:02:32Outside in the garden,
1:02:32 > 1:02:36other forms of fungi rely on insects to help them do their job.
1:02:36 > 1:02:40This is the fruiting body of a stinkhorn fungus.
1:02:40 > 1:02:44The rest of the fungus is below the soil,
1:02:44 > 1:02:47feeding on wood and plant matter in the soil.
1:02:47 > 1:02:51These stalks emerge when the fungus is ready to fruit,
1:02:51 > 1:02:55growing up to 15cms in less than 24 hours.
1:03:00 > 1:03:04When they break through the top layer of soil,
1:03:04 > 1:03:09they release an intense smell that flies find irresistible,
1:03:09 > 1:03:12the smell of dead and decaying meat.
1:03:12 > 1:03:16The flies strip the jelly-like flesh from the mushroom,
1:03:16 > 1:03:20and help spread its spores.
1:03:20 > 1:03:23Even after 30 years of studying biology,
1:03:23 > 1:03:28I'm still amazed by the complex behaviour of these simple organisms.
1:03:32 > 1:03:39But stinkhorns aren't the strangest things feeding on the decaying wood in our garden.
1:03:39 > 1:03:43Hidden away in our woodpile is something even more intriguing.
1:03:46 > 1:03:49This is a slime mould.
1:03:51 > 1:03:55It's the largest single-celled organism on Earth.
1:03:55 > 1:03:58It can grow to more than three square metres.
1:04:06 > 1:04:09Scientists have recently discovered that these primitive life forms
1:04:09 > 1:04:13have some rather sophisticated talents.
1:04:25 > 1:04:28At Oxford University, Dr Mark Fricker is one of a team of
1:04:28 > 1:04:33botanists and computer scientists studying a species of slime mould
1:04:33 > 1:04:36called Physarum Polycephalum.
1:04:36 > 1:04:39For years slime moulds have fascinated scientists
1:04:39 > 1:04:44with their remarkable ability to solve simple mazes.
1:04:44 > 1:04:46Put food at the end of a maze
1:04:46 > 1:04:50and the slime mould will find the quickest route through.
1:04:50 > 1:04:52But scientists started to wonder
1:04:52 > 1:04:55if the mould could do more than just perform clever tricks.
1:04:55 > 1:04:58You can set them lots of little tasks, and
1:04:58 > 1:05:01you can allow them to forage and connect up little
1:05:01 > 1:05:04- food sources to see what sort of network they would make.- OK.
1:05:04 > 1:05:07And a geometric shape, so a square or something more complicated,
1:05:07 > 1:05:10is interesting, but we wanted to see whether they would
1:05:10 > 1:05:14be able to solve a slightly more complex problem.
1:05:18 > 1:05:20Mark is recreating an experiment
1:05:20 > 1:05:24he worked on with colleagues at Tokyo University.
1:05:24 > 1:05:27He takes a blob of slime mould and then surrounds it with
1:05:27 > 1:05:31a pattern of oat flakes, an irresistible treat to slime mould.
1:05:34 > 1:05:39What happens next is recorded by a time-lapse camera.
1:05:42 > 1:05:48The slime mould locates the oat flakes by growing out in all directions.
1:05:49 > 1:05:53But within hours the slime mould shrinks back,
1:05:53 > 1:05:59leaving an intricate web of tubes that connect the oat flakes.
1:05:59 > 1:06:05It's these tubes that transfer nutrients around the slime mould.
1:06:05 > 1:06:10Incredibly, everything you can see is part of one single cell.
1:06:10 > 1:06:15It needs to build a network that is quite efficient, to transport all those resources.
1:06:15 > 1:06:19At the same time, that network mustn't cost too much.
1:06:19 > 1:06:22It mustn't take up too many of its own resources.
1:06:22 > 1:06:26And then the other problem it has is, it's going to be subject to damage.
1:06:26 > 1:06:29If there was only ever one connection,
1:06:29 > 1:06:31there's a risk it would break.
1:06:32 > 1:06:35The slime mould takes no chances.
1:06:35 > 1:06:39It grows back-up routes to make sure that its food supply isn't cut off.
1:06:42 > 1:06:48But there's something even more extraordinary about what the slime mould has done.
1:06:48 > 1:06:52Mark hasn't just laid out the flakes in a random pattern.
1:06:54 > 1:06:56The large blob in the middle is Tokyo
1:06:56 > 1:07:02and each of the food sources are positioned as cities nearby Tokyo.
1:07:02 > 1:07:05- So, it's a re-creation of the area around Tokyo?- Indeed.
1:07:05 > 1:07:10This is actually what it's based on, the rail network around Tokyo.
1:07:10 > 1:07:14We can superimpose that over. Ok, so we align it...
1:07:14 > 1:07:17That's identical! It's absolutely identical!
1:07:17 > 1:07:22You see a lot of these connections. It's formed the same sort of links, it's got a few extra ones in as well,
1:07:22 > 1:07:27- it's a slightly more resilient network than the ones the engineers designed...- Hold on!
1:07:27 > 1:07:29You're telling me, wait a minute,
1:07:29 > 1:07:33that this slime mould has built a better network...
1:07:33 > 1:07:35A remarkably similar network.
1:07:35 > 1:07:38- ..than the humans built.- Yes.
1:07:40 > 1:07:43The Tokyo rail system is one of the most efficient
1:07:43 > 1:07:45and well organised in the world.
1:07:45 > 1:07:50It took lots of skilled engineers using lots of brain power to plan.
1:07:50 > 1:07:54Yet, somehow, slime mould has achieved the same goal,
1:07:54 > 1:07:59how to efficiently link together multiple locations.
1:08:00 > 1:08:04Slime mould has also been put to work in other parts of world.
1:08:04 > 1:08:09Here it tackles some of Britain's major motorways.
1:08:09 > 1:08:13This is its take on the best routes around Spain.
1:08:15 > 1:08:21And here are some interesting alternatives to Americas Route 66.
1:08:22 > 1:08:25What is the slime mould actually displaying here?
1:08:25 > 1:08:28It's a sort of smart behaviour. It hasn't got a brain,
1:08:28 > 1:08:32it hasn't got a nervous system, but it still seems to be able to solve
1:08:32 > 1:08:34these sorts of complex problems with very simple rules.
1:08:34 > 1:08:39It's something the computer scientists we work with are getting very interested in,
1:08:39 > 1:08:44whether or not you can take inspiration from this system and apply it to other sorts of problems.
1:08:55 > 1:08:59How does one of the most simple life-forms on Earth,
1:08:59 > 1:09:04a single-celled amoeba that spends most of its time on woodland waste,
1:09:04 > 1:09:09match its wits against transport engineers and computer scientists?
1:09:13 > 1:09:17The clue seems to lie in its extraordinary biology.
1:09:21 > 1:09:25Professor Bruce Ing is a self confessed slime mould obsessive.
1:09:25 > 1:09:29He's going to help me track down some slime mould
1:09:29 > 1:09:33in one of its native habitats.
1:09:33 > 1:09:35Slime moulds aren't rare things?
1:09:35 > 1:09:39- Oh, no. They're very common, indeed. They're everywhere.- But overlooked?
1:09:39 > 1:09:42Overlooked because they are shy, not easy to find,
1:09:42 > 1:09:45- unless you know where to look. - Shy slime moulds!
1:10:01 > 1:10:05- Do you remember the film The Blob? - Yes.
1:10:05 > 1:10:09A giant mass of jelly, eating caravans?
1:10:09 > 1:10:12- It was a slime mould?- It was.
1:10:12 > 1:10:14But not one we'll find here.
1:10:14 > 1:10:17Not as big as that, I hope.
1:10:21 > 1:10:27Bruce's 54 years in the field prove vital as we hunt the elusive slime mould.
1:10:30 > 1:10:32After half an hour, he finds what we are looking for.
1:10:32 > 1:10:37- It's not quite the sheet I was hoping for.- No, indeed not.
1:10:37 > 1:10:41But it's still the real McCoy.
1:10:43 > 1:10:48This small patch of orange is creeping slime mould.
1:10:49 > 1:10:53Up close, you can see how it's constantly pulsating.
1:10:56 > 1:10:59When one part of it finds something it likes to eat,
1:10:59 > 1:11:02it pulses more rapidly.
1:11:02 > 1:11:06Scientists believe that it's this pulsating that helps transmit
1:11:06 > 1:11:08information across the entire cell,
1:11:08 > 1:11:12allowing the slime mould to move towards its food source.
1:11:17 > 1:11:21These pulsations control where and how they grow across the forest floor,
1:11:21 > 1:11:26or even around the oat flakes of the Tokyo rail map.
1:11:29 > 1:11:32What's so special about slime mould is that it can use
1:11:32 > 1:11:37this information to make multiple decisions, simultaneously.
1:11:37 > 1:11:40Pretty ingenious stuff for a single-celled organism.
1:11:45 > 1:11:49Slime moulds are what's known as self organising systems.
1:11:50 > 1:11:54It's not a unique phenomenon in nature.
1:11:54 > 1:11:56Flocks of birds work in a similar way.
1:11:56 > 1:11:59With no leader, no overall control,
1:11:59 > 1:12:03the flock nevertheless acts as a single unit.
1:12:03 > 1:12:07But slime mould can do something that flocks of birds could never do.
1:12:08 > 1:12:14Meet the Phi-Bot, the world's first slime mould controlled robot.
1:12:14 > 1:12:18The Phi-Bot is the brain child of Dr Soichiro Tsuda
1:12:18 > 1:12:22and Dr Klaus Peter Zauner from Southampton University.
1:12:22 > 1:12:28Their robot takes its orders from a tiny blob of slime mould.
1:12:28 > 1:12:31I sort of don't believe you, I want to...
1:12:31 > 1:12:33HE LAUGHS
1:12:33 > 1:12:34..I want to see it working. Prove it!
1:12:34 > 1:12:38THEY LAUGH Soichiro, flip the switch.
1:12:38 > 1:12:40It just seems almost unbelievable.
1:12:42 > 1:12:46It's not instant, is it? It's not instant... Oh!
1:12:46 > 1:12:50Wow! That's fantastic!
1:12:53 > 1:12:58The slime mould sits on an electronic chip, inside the robot.
1:12:58 > 1:13:02As it transmits information around its single-cell by pulsing,
1:13:02 > 1:13:05the robot detects these pulses and translates them
1:13:05 > 1:13:09into much larger movements across the surface of the table.
1:13:09 > 1:13:16How did you get the idea for having a live organism inside a robot?
1:13:16 > 1:13:20One inspiration source obviously from the Daleks, from Doctor Who?
1:13:20 > 1:13:23- This is inspired by a Dalek?- Yes.
1:13:23 > 1:13:25- Well, it's the same thing, isn't it?- Yeah exactly.
1:13:25 > 1:13:29You've got a live organism in the machine, which controls it.
1:13:29 > 1:13:33The Phi-Bot is pioneering a new approach to computing.
1:13:33 > 1:13:38Today's computers use a single central processing unit to do their thinking.
1:13:38 > 1:13:42But the slime mould has no need to ask a brain what to do,
1:13:42 > 1:13:46all parts of the cell just work together, for the good of the whole.
1:13:46 > 1:13:50The simple organism inside, processes information in a completely
1:13:50 > 1:13:53radically different way from our conventional computing technology.
1:13:53 > 1:13:57We want to learn more about how it can do that information processing.
1:13:58 > 1:14:03So slime mould could hold the secret to a revolution in computing.
1:14:03 > 1:14:07Or even the creation of artificial intelligence.
1:14:07 > 1:14:11Not bad for something you can find in your wood pile.
1:14:22 > 1:14:27There's only a week left to go in our project to study decay in a typical house and garden.
1:14:29 > 1:14:33The pace of change in the box is beginning to slow down.
1:14:33 > 1:14:38But, even now, decay is following an ordered sequence.
1:14:38 > 1:14:42What one decomposer leaves behind is food for others.
1:14:43 > 1:14:47Well, it's day 44 and the one thing that's immediately obvious,
1:14:47 > 1:14:53it doesn't smell nearly as bad in here. It's actually quite pleasant.
1:14:53 > 1:14:57The other thing that's obvious is there are very few flies now,
1:14:57 > 1:15:01the majority of the flies that hatched out have died.
1:15:01 > 1:15:04There aren't as many dead ones lying about as I'd expected, but
1:15:04 > 1:15:09it looks like a few flies might have got themselves stuck in this
1:15:09 > 1:15:14bottle of wine, as they searched for something to drink.
1:15:14 > 1:15:17This is solid. Uh!
1:15:17 > 1:15:20Look at this. Oh my God!
1:15:20 > 1:15:23Urgh! That is incredible.
1:15:25 > 1:15:27HE LAUGHS
1:15:27 > 1:15:29I can't get them all out.
1:15:29 > 1:15:35I've never seen so many flies in one bottle, in my life.
1:15:37 > 1:15:38I can barely get them out.
1:15:38 > 1:15:43That sort of explains why I wasn't seeing as many flies
1:15:43 > 1:15:46flying around, as I expected.
1:15:46 > 1:15:50It's because most of them were in here.
1:15:50 > 1:15:53Look at it. It's just incredible. It's thick.
1:15:55 > 1:15:57That's thick with flies.
1:16:04 > 1:16:07Conditions in the box are very dry.
1:16:07 > 1:16:13All that remains of the meat are hardened chunks of sinew and skin.
1:16:13 > 1:16:20Even if the flies had survived there's nothing left for another generation of maggots to feed on.
1:16:20 > 1:16:24But this is the perfect fodder for beetles.
1:16:24 > 1:16:28This dried meat gives off a far less pungent odour, but the smell
1:16:28 > 1:16:33it does produce gives them a signal that starts the next stage in decay.
1:16:36 > 1:16:44Decay happens in a series in waves, this fish is dry and hard,
1:16:44 > 1:16:48there are beetle larvae who will eat it. So there's no waste.
1:16:48 > 1:16:52That's what I'm hunting for now, I'm hunting for the larvae
1:16:52 > 1:16:58of a larder beetle and there's one right there.
1:17:00 > 1:17:05Larder beetle larvae are present in around half of all homes.
1:17:05 > 1:17:10They only colonise a carcass once it's become dried and desiccated.
1:17:10 > 1:17:14Their powerful jaws allow them to eat through flesh, hair and skin.
1:17:14 > 1:17:17And they can strip an animal down to the bone.
1:17:17 > 1:17:20This stage in decay moves slowly though.
1:17:20 > 1:17:24Larder beetle larvae take months to pupate into these adults.
1:17:24 > 1:17:30The job of recycling what remains in the box could take generations of them, years to complete.
1:17:35 > 1:17:38But another beetle in our box does allow us
1:17:38 > 1:17:41to see how effective these insects can be.
1:17:48 > 1:17:5236 days ago, two sexton beetles took less than 12 hours
1:17:52 > 1:17:54to bury our dead rat.
1:17:59 > 1:18:02What I'm aching to do now is a spot of archaeology.
1:18:02 > 1:18:05Because what has happened is, the sextons beetles have taken
1:18:05 > 1:18:10the rat down and they will have formed it into a ball,
1:18:10 > 1:18:15on which their larvae have fed and hopefully 36 days should be
1:18:15 > 1:18:19enough time. I should find a crypt in which the rat sits,
1:18:19 > 1:18:23surrounded by its own fur, which they smear on the outside.
1:18:23 > 1:18:26And there should just be bones left.
1:18:26 > 1:18:31This, for me, is about as exciting as it gets.
1:18:31 > 1:18:36I'm going to use a hoover to gently take away the soil.
1:18:38 > 1:18:41What is amazing about these insects is,
1:18:41 > 1:18:46they're one of the very few insects who look after their young.
1:18:46 > 1:18:51They take care of their young. Once they've dragged the prey down,
1:18:51 > 1:18:59and hidden it underground, they'll lay the eggs around the crypt,
1:18:59 > 1:19:03and then the larvae will move in and feed.
1:19:03 > 1:19:07And they'll help them to feed as well.
1:19:07 > 1:19:09We're beginning to see a shape here.
1:19:09 > 1:19:13This is very exciting. Turn that off.
1:19:15 > 1:19:17Wonder if I can free it.
1:19:20 > 1:19:23That is just fantastic.
1:19:30 > 1:19:34There look at that, that's all that remains of the rat.
1:19:34 > 1:19:40You can see the top part of the skull and the teeth.
1:19:40 > 1:19:43The rest of it has completely disappeared,
1:19:43 > 1:19:46there's nothing left of that rat.
1:20:02 > 1:20:07We're now at week eight. We're nearing the end of our project.
1:20:07 > 1:20:11But there is one final stage of decay I want to investigate.
1:20:11 > 1:20:14And it's probably the most important.
1:20:16 > 1:20:20We've watched as the nutrients, locked up in plant
1:20:20 > 1:20:23and animal remains, have been re-used by other organisms.
1:20:23 > 1:20:26In the process, complex things like chickens, rats and fruit,
1:20:26 > 1:20:33have become simpler ones, insects, fungi, bacteria.
1:20:33 > 1:20:37But the true power of decay is its ability to reduce complex things
1:20:37 > 1:20:41right back to the most basic building blocks of life.
1:20:43 > 1:20:45And all through the project,
1:20:45 > 1:20:49that's been quietly happening in a corner of the box.
1:20:51 > 1:20:57This is one of best places to see decay in action. We set this up
1:20:57 > 1:21:02eight weeks ago and it was piled to the top with plant material.
1:21:02 > 1:21:06It's now completely decayed down, we've been adding to it.
1:21:06 > 1:21:12What I really want to do, is have a look inside and see what's going on.
1:21:12 > 1:21:18Now, decay has been happening and the further you go down,
1:21:18 > 1:21:23the more advanced it is. There's a snail on the trowel handle.
1:21:27 > 1:21:30As all gardeners know, compost heaps turn dead plants
1:21:30 > 1:21:34into a form of nutrients that new plants can use.
1:21:37 > 1:21:43On the surface, animals like snails, slugs and worms begin the process
1:21:43 > 1:21:47by eating the remains of plants, helping to break them into pieces.
1:21:49 > 1:21:52The waste they excrete, and anything else left behind,
1:21:52 > 1:21:56is eaten by smaller creatures like these mites.
1:21:56 > 1:21:59Too tiny to be seen with the naked eye.
1:22:04 > 1:22:07And this process continues down through the compost.
1:22:07 > 1:22:09Ever smaller organisms,
1:22:09 > 1:22:13reducing the plant waste to ever smaller components.
1:22:13 > 1:22:19Until tiny fungi and bacteria are able to break down the very cells of the plant.
1:22:19 > 1:22:24A teaspoon of soil contains four billion micro-organisms.
1:22:24 > 1:22:27They finally release the nitrogen
1:22:27 > 1:22:32and other building blocks of organic life, back into the soil.
1:22:32 > 1:22:35What we end up with,
1:22:35 > 1:22:40is an incredibly very fine soil,
1:22:40 > 1:22:46the result of the breakdown processes of countless organisms.
1:22:48 > 1:22:56Having begun with a big pile of green material, you may think that is an end point, but it's not,
1:22:56 > 1:22:58it's just the beginning.
1:23:04 > 1:23:08From here, life can begin to rebuild.
1:23:08 > 1:23:13To me, this is the most amazing moment in the story of decay.
1:23:18 > 1:23:20When we began eight weeks ago,
1:23:20 > 1:23:24we wanted to demonstrate its significance in a unique way.
1:23:27 > 1:23:32This is probably one of the most important experiments we've set up in the box.
1:23:32 > 1:23:35These may look like ordinary plants but they're going to show us
1:23:35 > 1:23:40a part of the story that's absolutely crucial. These are the marigolds and radish seedlings
1:23:40 > 1:23:43I planted back at the beginning of the project.
1:23:43 > 1:23:46They've flourished into mature plants.
1:23:46 > 1:23:49I've been feeding them with a special liquid compost
1:23:49 > 1:23:54made from plants grown using chemically labelled nitrogen atoms.
1:23:54 > 1:23:57If everything has gone according to plan,
1:23:57 > 1:24:01we should be able to track how individual atoms of nitrogen
1:24:01 > 1:24:05are transferred from the mustard plant to our seedlings.
1:24:06 > 1:24:08From death to life.
1:24:12 > 1:24:16We sent samples of our plants to Professor Malcolm Clench.
1:24:16 > 1:24:20It's time to find out if our experiment has worked.
1:24:21 > 1:24:24The first one is from the marigold.
1:24:24 > 1:24:29What can you see at the moment is a photograph of the marigold leaf.
1:24:29 > 1:24:34He's able to pinpoint exactly where the labelled nitrogen has ended up.
1:24:34 > 1:24:39As I start to play the video clip, we'll come up with
1:24:39 > 1:24:43an overlay that shows the nitrogen in high abundance.
1:24:43 > 1:24:47- That's really clear. - Yes, very clear.
1:24:50 > 1:24:53Each one of these dots shows where we found traces of the labelled
1:24:53 > 1:24:57nitrogen from the mustard plant in our marigold leaf.
1:24:59 > 1:25:02White areas show where it's concentrated.
1:25:05 > 1:25:12How can we be 100% sure that labelled nitrogen has come from our experiment and nowhere else?
1:25:12 > 1:25:18The form of nitrogen we're using is only 0.3% naturally abundant.
1:25:18 > 1:25:22We can see areas of high intensity and they can only have come from
1:25:22 > 1:25:26the mustard that was grown with the labelled nitrogen in.
1:25:26 > 1:25:32- So, that is the definitive proof of the cycle of life?- Indeed.
1:25:32 > 1:25:36I think you're going to be pleased with the radish results.
1:25:36 > 1:25:38We can see first off a very nice radish.
1:25:38 > 1:25:41One that you prepared earlier.
1:25:42 > 1:25:43Wow look at that!
1:25:43 > 1:25:47That is absolutely cast iron proof,
1:25:47 > 1:25:53that we have transferred material, an element in this case,
1:25:53 > 1:25:57from one plant, dead and decayed, fed to something else and it takes it up.
1:25:57 > 1:25:59Yes, it's incontrovertible.
1:26:01 > 1:26:04This is what I hoped we'd see when we began our project.
1:26:04 > 1:26:07It's the fundamental principle of decay,
1:26:07 > 1:26:10revealed in front of our eyes.
1:26:10 > 1:26:12For me, this is as good as it gets.
1:26:20 > 1:26:24Two months of decay have transformed the After Life box.
1:26:27 > 1:26:30Little is left of the fresh food we began with.
1:26:31 > 1:26:37And what remains will continue its inexorable journey back to the basic building blocks of life.
1:26:40 > 1:26:43But, as our plant experiment so dramatically demonstrated,
1:26:43 > 1:26:47what we have witnessed in the box is a process of renewal.
1:26:49 > 1:26:50That we are all part of.
1:26:58 > 1:27:01It's a real snap-shot of everyone's life.
1:27:01 > 1:27:05To see things changing, as they do, is a fantastic experiment.
1:27:06 > 1:27:09We'd be in a horrible mess if we didn't have decay.
1:27:09 > 1:27:13When you see what nature can do to get rid of all the dead things in the world...
1:27:15 > 1:27:20We need that decay to happen in order for life to go on, I guess.
1:27:20 > 1:27:23- Oh, my God!- Look at that.
1:27:23 > 1:27:28We tend to think of life as a linear process, with a beginning and end.
1:27:28 > 1:27:30Things go from life to death.
1:27:30 > 1:27:34I hope the box has shown this process in a new light.
1:27:34 > 1:27:36Life is an ever repeating cycle.
1:27:36 > 1:27:41One that's not just happening here, but everywhere on the planet.
1:27:41 > 1:27:47The plants and animals of Earth's ecosystems rely on this continuing cycle.
1:27:47 > 1:27:50Even the atoms that make us up are recycled.
1:27:50 > 1:27:53They come from the food we eat, the air we breathe,
1:27:53 > 1:27:56they're in our flesh, blood and bones.
1:27:56 > 1:27:58They've been used millions of times before,
1:27:58 > 1:28:01and they'll be used millions of times again.
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