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Decay.

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It happens to everything and everyone.

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We try to keep it out of our everyday lives.

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But decay is one of the most important forces in nature.

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It underpins all life on Earth.

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So what would we see, if we let it loose in our homes?

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To find out, we've built a home of our own

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inside this box.

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We've filled it with everything you might find in a typical kitchen

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and garden. And now we're going to let it all rot.

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Well, here it is.

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A team of engineers and scientists have spent eight months recreating

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a kitchen and garden. On the inside is all the food you'd expect,

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as if a family were just about to have a party.

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Also on the inside are the bacteria and fungal spores that are going

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to start the process of decay. I can't wait to see what happens next.

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Over eight weeks, we're going to track every step

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of the extraordinary process that breaks down and recycles our everyday things.

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The house will be our lab, as we reveal the unexpected order behind

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the chaos of decay, and will help us understand why

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life itself depends on this process.

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At times what we find might be disturbing and repellent...

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This is probably going to be absolutely atrocious.

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HE COUGHS

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But there will also be moments of surprise.

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The mould has just covered that entire box.

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..as we uncover hidden beauty.

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And I'll go beyond the box to see how decay affects our lives...

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Ah! Can't do it!

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..how we detect it...

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Do you remember seeing the film The Blob?

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..how we fight it.

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It's definitely the best two-year-old sandwich I've ever had.

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Something on this scale has never been attempted before,

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so things might not go according to plan.

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Ah! Now that's where all the flies went.

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But whatever happens, it will be a fascinating journey

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into the fate that awaits all living things.

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To be broken down.

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To be recycled. To be reborn.

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It's a surprising thought,

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life relies on death.

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Living things, us included, can only be made

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from the remains of dead things.

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And that's the incredible cycle we hope to capture,

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inside our After Life House.

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As a biologist, I can't wait to see what new life will emerge from these

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dead things by the time we're done.

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This is day one. We have eight weeks to go.

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This is my first chance to see inside the box.

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And a party was obviously just about to happen.

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Over here we've got cooked rice and chilli, there's cups of tea.

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Over in the corner there's a raw fish,

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that's going to get very smelly pretty fast.

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Cheese and a fruit bowl here, masses of fruit flies on that, probably,

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I mean, we don't know, it hasn't been tried before.

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A vegetable box over here, again, it all looks fresh,

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but that will, in a week or two, begin to rot down.

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And look at this, a raw chicken.

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Sausages, hamburgers, all this is

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going to attract flies like nobody's business.

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Out here in the garden you've got a whole pig on a spit.

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That's going to become very smelly.

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But it's not just food items out here in the garden.

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We have a compost heap. We have a woodpile.

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They'll rot down too.

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It'll be interesting to see how, as all the things decay,

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the wood and the plants and the pig, how they will interact.

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Over there in the corner we have a dead rat as well.

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In fact everything in here has been carefully arranged to help us

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unravel the underlying patterns of decay.

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We're going to keep an eye on how humid it is, and how hot it is.

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It's already up to 66% RH which will make things go really quite fast.

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I'm not sure if I'll be overcome by the heat, the stench or the flies.

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Insects are my own speciality.

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Together with moulds and bacteria, they are key agents of decay,

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things that will break all this down.

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To make sure they are all present in our house from the start,

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we're introducing a selection of common species.

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Look at that, straight underneath!

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These guys, blow flies, are going to be the ones

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to watch in the early stages.

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And there they go.

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Well, that's it. We're up and running

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and it's time to leave all this to the agents of decay.

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Now, for nearly two months,

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we're going to track every stage in the process of decay.

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And we're not the only ones following events.

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The box and its contents are on display to the public within

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Edinburgh zoo, to help explore our reactions to this

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little understood process.

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Oh my God, I've never seen anything like it

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That's a real pig.

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Ew, that's gross!

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Oh, there's a mouse.

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That's disgusting, eugh!

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Look at that fish.

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Can we go out now cos it's going to make us feel sick?

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THEY LAUGH

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I agree.

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For the first 24 hours of our project,

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visible signs of decay are subtle.

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But the agents of decay are already battling it out to decompose

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the food and get to the nutrients locked inside.

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I want to investigate who's got the advantage in this opening stage

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Well, it's the second day and it's really warm in here, it's 25 degrees.

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That's like a warm summer day, so some things are drying out

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the chilli con carne is already growing a layer of mould,

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and that shows that there are fungal spores drifting around in the atmosphere

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all the time and settling on food.

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Over here, the sandwiches which originally filled the box,

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up to the top, have sagged down to about half their height.

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But what's really interesting me is what's happening over here.

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The most obvious change so far has been on the surface of our chicken.

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Our time lapse cameras show these blotches appearing on its skin,

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over the course the past day.

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To find out what's producing them,

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I've asked Dr Clare Taylor, a microbiologist, to join me.

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Well, Clare, that chicken is beginning to look a bit discoloured.

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It smells a bit as well. There's beginning to be a slight whiff. What have you got on this?

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I tell you what I've got a UV light

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so we can take a look more closely at the surface.

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Now, ultraviolet I use for other things,

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but I'm interested to see what happens here.

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Now you can't see it. No, can't see anything.

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Take a look at that!

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It's glowing! So all these areas are glowing sort of blue.

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Exactly, so where you can see those glowing bits, that's bacteria.

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Any particular kind? That's likely to be pseudomonas.

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Pseudomonas is a common type of food spoilage bacteria.

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Our microscope shows a whole colony glowing under the UV light.

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There could be as many as a billion individual bacterial cells

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in this sample alone.

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In sheer number terms,

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bacteria are the most common agents of decay on the planet.

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And, on dead animals, they're the first to attack.

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Because they're already on the scene.

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All creatures carry bacteria while they're alive.

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These pseudomonas bacteria were on our chicken before it was killed,

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feeding on its skin secretions.

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Now it's dead, they've quickly switched to decomposing its flesh.

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With ample food, and enough moisture,

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they've multiplied rapidly.

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As colonies of bacteria like this expand, something surprising happens.

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The bacteria start to coordinate their actions.

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Working together to benefit the colony.

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The bacteria send signals to each other to direct what they do.

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So the bacteria are talking to each other, telling each other where they need to go.

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These E-coli bacteria have been genetically modified

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to allow us to see this in action.

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When the colony reaches a critical size all the bacteria start flashing in unison.

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Bacteria are constantly exchanging chemicals that allow them

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to sense their own numbers and those of rival colonies.

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They can even detect when they have the numbers

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to overwhelm a competitor.

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Back on our chicken, these tactics have allowed food spoilage bacteria to gain the upper hand.

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But their actions are setting off a chain of events

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that will attract a whole new set of decomposers.

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As they break down the cells of the chicken to feast on the protein inside,

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the bacteria are releasing strong smelling gases.

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blow flies can pick up the smell of decomposing flesh within minutes of an animal's death.

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So it's likely they've already laid eggs on the chicken and other meat throughout the box.

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We'll find out if we start seeing maggots in the next few days.

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These gases send a signal to us too.

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It's our most important clue that food spoilage bacteria have been at work.

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Right, let's see what folks make of these chicken drumsticks.

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I want to see how sensitive we are to even the smallest signs of decay.

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Hi, guys, would you care to have a smell of this?

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Erggh! I can smell it from here. Urgh!

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THEY LAUGH

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It's horrible. Stop it. It's not nice.

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So, if you found that in your house, what would you do?

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I wouldn't eat it. I think I'd put it in the bin.

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I'd throw it away immediately. Throw it out.

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It's disgusting.

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We fight a daily battle to keep this kind of decay out of our kitchens.

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Looking round the box already makes me think about what a challenge this really is.

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Decay is a relentless opponent.

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So, I'm interested in exploring what we've learnt about delaying its effects.

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And in America, there's a team that's taking on

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the ultimate food preservation challenge.

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GUNSHOTS

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Keep your head down or it's going to get shot off you!

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GUNSHOTS

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Now, this is not necessarily the first place I'd think of

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when it comes to the latest advances in food science,

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but the US army is right on the frontline in the war against decay.

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Feeding an army in the field has always presented a challenge.

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Soldiers need food that is quick to prepare,

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light to carry and long lasting.

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Traditionally, the US military uses vacuum packed food

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called MREs, meals ready to eat.

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Special packaging stops moisture and oxygen getting in

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so bacteria can't grow. MREs have a shelf life of three years.

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There's a problem though.

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MREs are not exactly popular with the people who have to eat them.

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Hands-down-worst MRE made is the veggie omelette.

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It's like eating a... I don't know.

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Wet, soggy cardboard is the best way I think you can describe it.

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If I had to eat an MRE every day, that would basically suck.

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GUNFIRE

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So, when the army went looking for ways to spruce up the menu,

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it wanted something more appealing.

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Something that was quick and easy to eat.

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And could deliver the huge amounts of energy that soldiers require.

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The solution was a surprise.

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A sandwich. But not just any sandwich.

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A sandwich that remains fresh and tasty in the field for up to three years,

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without refrigeration, freeze drying or the need to add water.

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That is extreme preservation.

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So how did they do it?

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Food scientist Michelle Richardson was part of the team that developed the sandwich.

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Her first challenge was to control the moisture you'd find in a typical sandwich.

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HE LAUGHS

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These sandwiches do not look very happy.

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They really don't.

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That's a ham and cheese wedge that's been in the car for three days.

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If we open it up, we'll just have a look at this thing

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cos if you had that in your backpack for three days...

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That was just a normal shop-bought sandwich.

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Urgh! It's soggy. It's really soggy. Look at that.

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You wouldn't really want to eat that in the field?

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You really wouldn't want to eat it for two reasons. It wouldn't taste good,

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because the texture is not what you typically get. And also

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because of that moisture excess you may have bacteria growing in it.

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If you can control the moisture, you can slow down the process of decay.

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Without water, bacteria cannot grow.

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That's why drying is the classic way to stop food decaying.

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But a sandwich without water would be inedible.

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So Michelle has taken inspiration from another classic preservation technique.

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Well, this right here is strawberry jam

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and as you can see in here, it's very firm. Yeah.

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It's made from strawberries. Most fruits and vegetables contain

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a lot of water, probably 95% water, but by adding different ingredients,

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what that does is it holds the water in very tightly.

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Right, so it's locked away in there? Yes.

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The sugar added to jam acts as what's called a humectant.

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It traps the water from the fruit inside the jam.

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That's why the jam is moist enough to spread,

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but doesn't make the bread soggy.

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Crucially for the battle against decay,

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the water is also now locked away from bacteria.

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The army's sandwiches deploy a whole range of ingredients

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that have these water-retaining properties.

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Honey, sugar and salt have all been enlisted.

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Bacteria need water to thrive. Most also need oxygen too.

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Michelle has found a way to cut off supplies of that as well.

248
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Now, when I opened the pack I found this inside

249
00:17:42,920 --> 00:17:45,720
and I assume that's not edible. No, it's not.

250
00:17:45,720 --> 00:17:47,560
What is this for?

251
00:17:47,560 --> 00:17:50,000
This is an oxygen scavenger.

252
00:17:50,000 --> 00:17:54,120
Basically what's contained in here are little iron shavings.

253
00:17:54,120 --> 00:17:57,160
Oh, right. Iron filings.

254
00:17:57,160 --> 00:18:02,040
If there is any oxygen or moisture still inside the packaging,

255
00:18:02,040 --> 00:18:06,600
they'll react with the iron filings, and become trapped in a layer of rust.

256
00:18:06,600 --> 00:18:11,200
This will prevent yeast and mould from growing as well as bacteria but

257
00:18:11,200 --> 00:18:15,880
it will also prevent chemical reactions that require oxygen from taking place.

258
00:18:15,880 --> 00:18:19,360
This is one seriously hi-tech sandwich!

259
00:18:19,360 --> 00:18:21,440
Yeah, it is.

260
00:18:21,440 --> 00:18:24,920
These simple but ingenious solutions have combined to make

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00:18:24,920 --> 00:18:29,040
a food that is highly resistant to decay.

262
00:18:29,040 --> 00:18:32,480
But the ultimate test is whether anyone wants to eat it.

263
00:18:32,480 --> 00:18:36,680
It's definitely the best two-year-old sandwich I've had. Better than a lot of new ones too.

264
00:18:36,680 --> 00:18:38,800
I'm a big fan. I like the bread.

265
00:18:38,800 --> 00:18:41,960
The bread just makes it, it's definitely great,

266
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especially for two-years-old.

267
00:18:44,880 --> 00:18:48,720
These sandwiches don't stay fresh for ever.

268
00:18:48,720 --> 00:18:53,960
But they do show that, if you can reduce the moisture and oxygen that

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bacteria thrive on, you can hold off decay for a very long time.

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00:19:08,000 --> 00:19:10,640
Back at the house, water and oxygen

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00:19:10,640 --> 00:19:19,000
certainly aren't in short supply, so bacteria are thriving.

272
00:19:19,000 --> 00:19:22,640
And over the last eight days of decay we've started to see

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00:19:22,640 --> 00:19:25,480
the first maggots appearing in our pig.

274
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I'd expect their numbers to rocket in a week or so.

275
00:19:30,520 --> 00:19:33,800
Other insects have been busy around our dead rat.

276
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These are sexton beetles.

277
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In the wild they'll bury the carcasses of small mammals

278
00:19:39,880 --> 00:19:42,440
to protect them from rival insects.

279
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Their own larvae then break down the flesh.

280
00:19:46,560 --> 00:19:50,200
But in our box, things are not quite going to plan.

281
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Despite all the activity, our rat remains unburied.

282
00:19:55,000 --> 00:20:01,680
So I'll try laying out a new rat and see if they prefer it.

283
00:20:01,680 --> 00:20:05,320
But the most dramatic change has been in our kitchen.

284
00:20:05,320 --> 00:20:23,360
It's been overrun by the next agent of decay, mould.

285
00:20:23,360 --> 00:20:25,720
Moulds are masters of decay.

286
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They're a form of fungi, the most versatile

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00:20:29,040 --> 00:20:32,080
and important decomposers on the planet.

288
00:20:32,080 --> 00:20:35,760
Fungi can rot almost anything.

289
00:20:35,760 --> 00:20:44,480
In our box, moulds are attacking our fruit and vegetables.

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00:20:44,480 --> 00:20:51,800
And they're also on our meat, battling with the bacteria for dominance.

291
00:20:51,800 --> 00:20:56,920
It'll be fascinating to see how that one plays out.

292
00:20:56,920 --> 00:21:02,880
The typical house will contain about 1,000 different species of mould.

293
00:21:02,880 --> 00:21:09,400
They can start to grow the moment their spores land on a suitable food source.

294
00:21:09,400 --> 00:21:19,400
I want to see which ones are at work in our box.

295
00:21:19,400 --> 00:21:24,720
Well, in the kitchen there is mould absolutely everywhere.

296
00:21:24,720 --> 00:21:27,360
The vegetables in the tray are covered in fungus.

297
00:21:27,360 --> 00:21:30,720
There's at least three sorts of fungus I can see.

298
00:21:30,720 --> 00:21:35,520
The hamburgers, sausages, even the hamburgers that are wrapped up are now covered in mould.

299
00:21:35,520 --> 00:21:39,480
That's looking quite... woah! That might blow at any time.

300
00:21:39,480 --> 00:21:43,400
The soft fruit in particular have been attacked.

301
00:21:43,400 --> 00:21:47,200
The peaches have gone and there's mould everywhere.

302
00:21:47,200 --> 00:21:50,920
The melon's just incredible, it's really been hammered.

303
00:21:50,920 --> 00:21:52,960
It's just covered, all over there.

304
00:21:52,960 --> 00:21:58,840
I'm a little bit nervous about taking this lid off.

305
00:21:58,840 --> 00:22:03,440
This is going to be... Urgh!

306
00:22:03,440 --> 00:22:06,760
Urgh! That's an incredible smell.

307
00:22:06,760 --> 00:22:13,880
It's almost sweet.

308
00:22:13,880 --> 00:22:19,080
It's an incredible sort of yeasty, smell.

309
00:22:19,080 --> 00:22:24,640
The mould has just covered the entire box.

310
00:22:24,640 --> 00:22:34,360
That's actually quite beautiful in a bizarre way.

311
00:22:34,360 --> 00:22:40,920
It's like just furry growths everywhere.

312
00:22:40,920 --> 00:22:51,400
That's amazing! That's only a week.

313
00:22:51,400 --> 00:23:06,280
In close up, the unexpected beauty of mould is even clearer.

314
00:23:06,280 --> 00:23:09,520
These networks of filaments we see on the surface of our bread

315
00:23:09,520 --> 00:23:26,800
are the mould's fruiting body.

316
00:23:26,800 --> 00:23:33,880
At the ends of the filaments are spore heads, each packed with individual spores,

317
00:23:33,880 --> 00:23:41,760
all waiting to be released to grow into new colonies.

318
00:23:41,760 --> 00:23:48,080
There are 500 spores in every cubic metre of air in the average home.

319
00:23:48,080 --> 00:24:03,600
So there's plenty of competition for the chance to attack our bread.

320
00:24:03,600 --> 00:24:08,560
I've asked Dr Patrick Hickey, our fungi expert to investigate

321
00:24:08,560 --> 00:24:12,200
which moulds have managed to gain control.

322
00:24:12,200 --> 00:24:16,120
Now, Patrick, it's only week one and we've got incredible fungal growth

323
00:24:16,120 --> 00:24:18,760
all over the kitchen. Particularly on the bread.

324
00:24:18,760 --> 00:24:22,440
Well, the bread is a perfect food source for the fungi.

325
00:24:22,440 --> 00:24:26,720
The spores probably landed on the bread when it was being prepared and

326
00:24:26,720 --> 00:24:31,400
they've grown quickly into the bread and they're taking up the nutrients.

327
00:24:31,400 --> 00:24:35,120
What we're actually seeing is two moulds meeting.

328
00:24:35,120 --> 00:24:38,080
In the background, we've got a dark green-grey mould

329
00:24:38,080 --> 00:24:41,800
that's penicilium. These bright dots in the front

330
00:24:41,800 --> 00:24:45,080
are the sporilating structures of aspergillus competing.

331
00:24:45,080 --> 00:24:47,960
So they're kind of trying to out compete each other for the bread,

332
00:24:47,960 --> 00:24:51,520
for the food resource.

333
00:24:51,520 --> 00:24:57,800
Each mould is trying to seize territory by out-growing its competitors.

334
00:24:57,800 --> 00:25:01,440
But they are also using powerful chemical weapons to try to

335
00:25:01,440 --> 00:25:07,600
kill off other moulds and rival decomposers, like bacteria.

336
00:25:07,600 --> 00:25:11,360
In the case of penicillium, the toxin it produces to win

337
00:25:11,360 --> 00:25:16,800
the battle for decay, has turned out to be highly beneficial to us.

338
00:25:16,800 --> 00:25:20,720
We call it penicillin.

339
00:25:20,720 --> 00:25:24,600
But not all moulds are good for us.

340
00:25:24,600 --> 00:25:28,040
Now, I have to admit, I sometimes cut the mould off bits of bread

341
00:25:28,040 --> 00:25:31,520
and toast it. Is that really harmful?

342
00:25:31,520 --> 00:25:34,960
Well, what you're scraping off is really the tip of the iceberg.

343
00:25:34,960 --> 00:25:38,240
The fungus grows deep into the bread and it also depends on what kind of

344
00:25:38,240 --> 00:25:41,440
mould is growing into the bread. You have various different moulds,

345
00:25:41,440 --> 00:25:45,720
some of which are harmless. Others like aspergillus produce deadly mycotoxins,

346
00:25:45,720 --> 00:25:49,960
these are toxic chemicals, which can rot your liver,

347
00:25:49,960 --> 00:25:51,600
they can give you cancer.

348
00:25:51,600 --> 00:25:54,320
So, what you're saying is, I shouldn't really do that.

349
00:25:54,320 --> 00:25:56,920
It's dangerous I should just throw it in the bin.

350
00:25:56,920 --> 00:26:00,800
Absolutely, the fungus penetrates quite deep into the bread you're

351
00:26:00,800 --> 00:26:06,680
not going to get rid of the toxins in the mould just by scraping it off.

352
00:26:06,680 --> 00:26:10,480
Most of us might prefer not to have to cope with mouldy bread

353
00:26:10,480 --> 00:26:18,720
in the first place. Moulds and other types of fungi are things that ruin our food, and may cause us harm.

354
00:26:18,720 --> 00:26:25,480
But fungi are vital to life on this planet.

355
00:26:25,480 --> 00:26:28,360
They're amongst the Earth's oldest life forms.

356
00:26:28,360 --> 00:26:35,280
On land, they pre-date plants by at least 300 million years.

357
00:26:35,280 --> 00:26:49,520
And they rise to almost any challenge.

358
00:26:49,520 --> 00:26:53,200
There is a fungus growing inside the brain of this ant.

359
00:26:53,200 --> 00:26:56,600
It's producing chemicals that control the ant's behaviour,

360
00:26:56,600 --> 00:27:00,280
forcing it to climb to the top of a plant.

361
00:27:00,280 --> 00:27:03,320
Then the killer fungus bursts out of the ant's head,

362
00:27:03,320 --> 00:27:12,240
allowing its spores to spread.

363
00:27:12,240 --> 00:27:16,920
Fungi have found ways to work on a microscopic level too.

364
00:27:16,920 --> 00:27:20,720
This one is lying in wait for tiny roundworms.

365
00:27:20,720 --> 00:27:25,640
At the right moment, it strangles them in a vice-like grip,

366
00:27:25,640 --> 00:27:33,800
then feeds on their flesh.

367
00:27:33,800 --> 00:27:37,640
But it's fungi's unrivalled ability to decay organic matter that

368
00:27:37,640 --> 00:27:41,280
makes them so important to us.

369
00:27:41,280 --> 00:27:43,840
A world where fungi couldn't decay things

370
00:27:43,840 --> 00:27:50,120
would be a very different place.

371
00:27:50,120 --> 00:27:54,200
To see just how different, we have to go back in Earth's history.

372
00:27:54,200 --> 00:27:57,320
To a period when a new form of organic matter emerged.

373
00:27:57,320 --> 00:28:04,760
One that challenged fungi's powers of decay.

374
00:28:04,760 --> 00:28:11,200
The fate of life on Earth, hung in the balance.

375
00:28:11,200 --> 00:28:14,640
Rewind 300 million years to the Carboniferous Period.

376
00:28:14,640 --> 00:28:17,680
A time when plants, struggling to compete for sunlight,

377
00:28:17,680 --> 00:28:24,160
had evolved into trees.

378
00:28:24,160 --> 00:28:27,760
That new organic material was wood.

379
00:28:27,760 --> 00:28:32,360
It gave plants the strength to grow taller.

380
00:28:32,360 --> 00:28:36,520
But this evolutionary leap left fungi behind.

381
00:28:36,520 --> 00:28:40,040
They weren't able to decompose wood.

382
00:28:40,040 --> 00:28:44,040
The delicate mechanism of decay had been upset.

383
00:28:44,040 --> 00:28:50,360
Without decay the trees grew, died and lay where they fell.

384
00:28:50,360 --> 00:28:56,200
The effect on the planet's climate was spectacular.

385
00:28:56,200 --> 00:29:00,160
Professor Lynne Boddy is an expert in the history of fungi.

386
00:29:00,160 --> 00:29:03,360
Trees absorb carbon dioxide from the air.

387
00:29:03,360 --> 00:29:05,600
They absorb nutrients from the soil.

388
00:29:05,600 --> 00:29:09,040
And then the carbon is locked up within the trees,

389
00:29:09,040 --> 00:29:14,520
so when they fall and die, the carbon is still locked up inside them.

390
00:29:14,520 --> 00:29:22,040
So huge changes simply because trees can't decay? Absolutely.

391
00:29:22,040 --> 00:29:26,320
With fungi unable to break down wood, over time, more and more

392
00:29:26,320 --> 00:29:30,480
carbon was removed from the air and locked up in dead trees.

393
00:29:30,480 --> 00:29:37,520
The Earth's atmosphere began to change.

394
00:29:37,520 --> 00:29:41,600
Oxygen levels shot up from 20% to 30%,

395
00:29:41,600 --> 00:29:44,400
as carbon dioxide levels dropped.

396
00:29:44,400 --> 00:29:51,480
This allowed insects to grow to gigantic proportions.

397
00:29:51,480 --> 00:29:57,480
Spiders were as wide as a human head.

398
00:29:57,480 --> 00:30:03,400
Dragonflies were ten times larger than they are today.

399
00:30:03,400 --> 00:30:09,400
If the atmosphere had stayed like this, life on our planet would have looked very different.

400
00:30:09,400 --> 00:30:14,000
The stumbling block for fungi was a molecule in trees called lignin.

401
00:30:14,000 --> 00:30:16,680
It's what makes wood tough.

402
00:30:16,680 --> 00:30:21,760
It took 50 million years for fungi to evolve a way to overcome it.

403
00:30:21,760 --> 00:30:24,800
And Lynne is able to show me the modern descendents of

404
00:30:24,800 --> 00:30:27,520
the fungi that solved the problem.

405
00:30:27,520 --> 00:30:30,160
If you pick up that log we could have a better look.

406
00:30:30,160 --> 00:30:32,240
No, the one underneath. That one, there.

407
00:30:32,240 --> 00:30:34,560
The first thing I see about it, it's not heavy at all.

408
00:30:34,560 --> 00:30:37,200
It's light as a feather. It hardly weighs anything.

409
00:30:37,200 --> 00:30:40,440
Yes, it's been rotted and you can see that it's really white.

410
00:30:40,440 --> 00:30:42,080
Why is it white?

411
00:30:42,080 --> 00:30:46,440
It's white because the fungi have broken down the lignin in the wood.

412
00:30:46,440 --> 00:30:48,880
Which was brown. Yes.

413
00:30:48,880 --> 00:30:52,000
It's pretty easy to see what effect the fungi have had on the wood,

414
00:30:52,000 --> 00:30:54,280
but can we actually see the fungi themselves?

415
00:30:54,280 --> 00:30:56,480
We can't actually see them rotting the wood,

416
00:30:56,480 --> 00:30:58,920
not with our naked eye because they're microscopic.

417
00:30:58,920 --> 00:31:04,640
To show me the fungi in action, Lynne has grown this sample in soil.

418
00:31:04,640 --> 00:31:08,200
That's pretty. What we've got here is a little bit of beech wood

419
00:31:08,200 --> 00:31:11,280
that's got the fungus growing in it, and then you put the wood

420
00:31:11,280 --> 00:31:14,400
on top of this soil, and the fungus has grown out of the wood,

421
00:31:14,400 --> 00:31:21,080
looking for other pieces of wood that they can colonise and get food from.

422
00:31:21,080 --> 00:31:29,320
The fungus sends out a network of tiny threads called hyphae.

423
00:31:29,320 --> 00:31:34,080
They've aggregated together so we can actually see them with the naked eye.

424
00:31:34,080 --> 00:31:39,160
And they're heading off to find other bits to eat? That's right.

425
00:31:39,160 --> 00:31:43,240
The hyphae release powerful enzymes into the wood.

426
00:31:43,240 --> 00:31:46,520
They are able to break down the lignin into nutrients

427
00:31:46,520 --> 00:31:49,920
the fungi can then absorb.

428
00:31:49,920 --> 00:31:54,800
This releases carbon from the wood, back into the air.

429
00:31:54,800 --> 00:32:02,520
It was the evolution of these enzymes that allowed fungi to rebalance the Earth's atmosphere.

430
00:32:02,520 --> 00:32:06,280
If those fungi weren't here today then decay would come to a grinding

431
00:32:06,280 --> 00:32:09,800
halt and we would be in a similar position to what we were

432
00:32:09,800 --> 00:32:15,680
in the Carboniferous period.

433
00:32:15,680 --> 00:32:20,200
By evolving the ability to unlock the carbon in dead wood,

434
00:32:20,200 --> 00:32:23,240
fungi saved the world.

435
00:32:23,240 --> 00:32:27,520
We still rely on this delicate balance between all living things,

436
00:32:27,520 --> 00:32:48,200
and the agents that can decompose them.

437
00:32:48,200 --> 00:32:53,920
At the After Life house another eight days have gone by.

438
00:32:53,920 --> 00:32:58,880
Just after my last visit we captured something extraordinary.

439
00:32:58,880 --> 00:33:01,240
The new rat that I left out in the garden has been

440
00:33:01,240 --> 00:33:06,880
buried by the sexton beetles, as I hoped it would be.

441
00:33:06,880 --> 00:33:10,800
Despite their size, it took the two of them less than 12 hours to

442
00:33:10,800 --> 00:33:18,480
get the whole carcass underground, and away from rival decomposers.

443
00:33:18,480 --> 00:33:20,720
The female will lay her eggs in the rat

444
00:33:20,720 --> 00:33:25,880
so her young will have food to eat when they hatch.

445
00:33:25,880 --> 00:33:28,760
In about a month's time, we'll dig up the rat

446
00:33:28,760 --> 00:33:38,560
and see what the beetle larvae have done.

447
00:33:38,560 --> 00:33:40,200
Elsewhere in the box,

448
00:33:40,200 --> 00:33:46,480
bacteria and mould are still battling it out on the meat.

449
00:33:46,480 --> 00:33:50,400
The bacteria inside this sealed pack of burgers are hard at work,

450
00:33:50,400 --> 00:33:53,400
producing this build up of gas.

451
00:33:53,400 --> 00:34:02,280
I'm not looking forward to smelling that.

452
00:34:02,280 --> 00:34:05,800
Where meat was left exposed to the air, like these sausages,

453
00:34:05,800 --> 00:34:08,760
mould has been able to move in,

454
00:34:08,760 --> 00:34:13,440
suggesting that the bacteria have been overwhelmed.

455
00:34:13,440 --> 00:34:16,560
But just over two weeks in to our project,

456
00:34:16,560 --> 00:34:21,840
and an army of even more voracious decomposers is taking control.

457
00:34:21,840 --> 00:34:27,040
The maggot population has exploded.

458
00:34:27,040 --> 00:34:30,600
Our pig is literally seething with them.

459
00:34:30,600 --> 00:34:38,120
Maggots are some of decay's most effective operators.

460
00:34:38,120 --> 00:34:41,160
The question is, how long will it take them

461
00:34:41,160 --> 00:34:46,440
to munch their way through the contents of our house?

462
00:34:46,440 --> 00:34:51,960
I haven't even got into the box and already I can see escaping maggots.

463
00:34:51,960 --> 00:34:55,360
So, even though we try really carefully to keep

464
00:34:55,360 --> 00:34:58,800
all the insects on the inside, some have escaped.

465
00:34:58,800 --> 00:35:07,120
They can squeeze through the tiniest gap

466
00:35:07,120 --> 00:35:10,880
The time-lapse cameras have shown a real fever pitch,

467
00:35:10,880 --> 00:35:13,640
especially on the chicken and the fish.

468
00:35:13,640 --> 00:35:17,960
I just want to show you the fish though. It's completely eaten out.

469
00:35:17,960 --> 00:35:24,640
If I just... look at that, look at the inside of that.

470
00:35:24,640 --> 00:35:26,440
Pwahh.

471
00:35:26,440 --> 00:35:29,480
It's just a writhing mass of maggots

472
00:35:29,480 --> 00:35:33,560
and the smell of ammonia is overpowering.

473
00:35:33,560 --> 00:35:35,160
They've eaten everything.

474
00:35:35,160 --> 00:35:40,480
All that remains is the dry skin on the outside and the bones.

475
00:35:40,480 --> 00:35:43,960
These are the most efficient recyclers on the planet.

476
00:35:43,960 --> 00:35:53,120
I think they are just amazing insects.

477
00:35:53,120 --> 00:35:59,760
It's 15 days since I released about 100 blow flies into the box.

478
00:35:59,760 --> 00:36:04,280
As soon as they mate, female flies look for a place to lay eggs.

479
00:36:04,280 --> 00:36:08,560
Up to 300 at a time.

480
00:36:08,560 --> 00:36:13,160
The gases given off in the very early stages of decomposition,

481
00:36:13,160 --> 00:36:18,120
will have attracted them to the dead meat and fish.

482
00:36:18,120 --> 00:36:20,840
They're the ideal food source for the maggots,

483
00:36:20,840 --> 00:36:25,840
when they start to emerge, around 24 hours later.

484
00:36:25,840 --> 00:36:29,720
Now they've hatched, these maggots have only one aim.

485
00:36:29,720 --> 00:36:35,080
To eat. Non-stop.

486
00:36:35,080 --> 00:36:38,280
Now, I've got the thermal image camera here

487
00:36:38,280 --> 00:36:40,800
and this is actually quite a useful item.

488
00:36:40,800 --> 00:36:45,480
It can show heat that's produced by organisms.

489
00:36:45,480 --> 00:36:51,200
The fly larvae, when they feed en masse, do generate quite a bit of heat.

490
00:36:51,200 --> 00:36:53,840
Now, I'm just shining it on the chicken drumsticks,

491
00:36:53,840 --> 00:36:57,440
which are cold, they're not hot at all.

492
00:36:57,440 --> 00:37:01,320
The chicken's not very hot. But wooo! Look at that!

493
00:37:01,320 --> 00:37:04,040
The burgers are glowing like a beacon.

494
00:37:04,040 --> 00:37:07,920
Now, that means that there are lots of fly larvae in there and they

495
00:37:07,920 --> 00:37:19,600
are generating masses of heat, which actually makes them grow faster.

496
00:37:19,600 --> 00:37:23,680
Our time lapse camera shows how maggots feed as a pack,

497
00:37:23,680 --> 00:37:29,280
so they can share not just heat, but digestive enzymes too.

498
00:37:29,280 --> 00:37:32,680
They carefully coordinate their movements.

499
00:37:32,680 --> 00:37:37,240
As the meat in one burger runs out, the maggots move together, almost

500
00:37:37,240 --> 00:37:46,480
as a single unit, over to the fresh supplies of the second burger.

501
00:37:46,480 --> 00:37:49,720
Maggots are a perfectly adapted mechanism for turning

502
00:37:49,720 --> 00:37:53,560
dead meat into flies.

503
00:37:53,560 --> 00:37:59,000
At the head end, you've got these amazing hooks,

504
00:37:59,000 --> 00:38:03,880
which are basically a pair of sharp, curved hooks

505
00:38:03,880 --> 00:38:16,120
with which the maggot rasps its way through food.

506
00:38:16,120 --> 00:38:19,440
As you move further down, you see it doesn't have legs.

507
00:38:19,440 --> 00:38:22,720
There isn't any obvious head, thorax and abdomen.

508
00:38:22,720 --> 00:38:27,640
It has got these bands of raised bumps,

509
00:38:27,640 --> 00:38:30,880
they're like spikes for a grub.

510
00:38:30,880 --> 00:38:34,520
They're bands of raised welts,

511
00:38:34,520 --> 00:38:39,280
which help the maggot move through its food so it's essentially

512
00:38:39,280 --> 00:38:41,600
in a pile of slop.

513
00:38:41,600 --> 00:38:47,800
These welts enable it to undulate through the food.

514
00:38:47,800 --> 00:38:51,560
Otherwise, it's very hard to move.

515
00:38:51,560 --> 00:38:58,640
At the other end, let's go down to the back end.

516
00:38:58,640 --> 00:39:03,800
These structures here are the breathing holes of the fly.

517
00:39:03,800 --> 00:39:12,080
These are the spiracles through which it gets its air.

518
00:39:12,080 --> 00:39:20,200
They're on the rear end. It has a pair of them, quite big.

519
00:39:20,200 --> 00:39:25,520
So it's able to insert its head into wet food and still feed

520
00:39:25,520 --> 00:39:29,680
while its rear end is in the air.

521
00:39:29,680 --> 00:39:38,320
All in all, it is just about the perfect eating machine.

522
00:39:38,320 --> 00:39:41,520
To me, maggots are the clearest example we've seen

523
00:39:41,520 --> 00:39:45,760
so far of the fundamental principle behind decay.

524
00:39:45,760 --> 00:39:48,800
Recycling the nutrients from dead animals,

525
00:39:48,800 --> 00:39:50,920
and turning it into new life.

526
00:39:50,920 --> 00:39:54,960
But, of course, for many of us they represent everything

527
00:39:54,960 --> 00:39:58,240
that's disgusting about decay.

528
00:39:58,240 --> 00:40:03,800
I'm intrigued as to what these strong feelings of revulsion are, so I've devised a little test.

529
00:40:03,800 --> 00:40:07,240
I'm going to put a £5 note inside a plastic bag

530
00:40:07,240 --> 00:40:13,400
and I'm going to hide it inside a tub, inside which I'm going to put

531
00:40:13,400 --> 00:40:19,960
loads of maggots. We're going to end up with a pretty simple test,

532
00:40:19,960 --> 00:40:22,280
which is essentially this,

533
00:40:22,280 --> 00:40:26,080
a large box full of writhing maggots and a £5 note.

534
00:40:26,080 --> 00:40:30,280
Now, I reckon only one person in ten will be able to

535
00:40:30,280 --> 00:40:34,360
overcome their deep seated revulsion for maggots

536
00:40:34,360 --> 00:40:44,720
and put their hand in to retrieve the fiver. Well, we'll find out.

537
00:40:44,720 --> 00:40:50,400
Who would like to put their hand in a bucket of maggots for a fiver?

538
00:40:50,400 --> 00:40:54,280
Oh, you would, would you?

539
00:40:54,280 --> 00:40:58,120
It looks like my bin at home. THEY LAUGH

540
00:40:58,120 --> 00:41:00,920
I can't do it! Five pound note.

541
00:41:00,920 --> 00:41:02,920
No, I can't do it.

542
00:41:02,920 --> 00:41:06,920
Maggots. Ew! SHE LAUGHS NERVOUSLY

543
00:41:06,920 --> 00:41:09,760
Oh. It's a little gross, they're writhing on my fingers.

544
00:41:09,760 --> 00:41:13,800
Oh, no! Oh! Oh! No, no.

545
00:41:13,800 --> 00:41:17,240
No, I can't do it. Five pound note.

546
00:41:17,240 --> 00:41:19,680
SHE SCREAMS

547
00:41:19,680 --> 00:41:22,240
You're nearly there. I've got it! Ah!

548
00:41:22,240 --> 00:41:25,160
You nearly got it. Yes!

549
00:41:25,160 --> 00:41:29,080
THEY APPLAUD

550
00:41:29,080 --> 00:41:34,320
This feeling of disgust is an emotion that evolved over thousands of years.

551
00:41:34,320 --> 00:41:42,040
It's not just maggots. All signs of decay revolt us.

552
00:41:42,040 --> 00:41:45,400
It's a great mechanism for stopping us

553
00:41:45,400 --> 00:41:48,120
from eating food that might make us sick.

554
00:41:48,120 --> 00:41:52,000
But it's also why we so rarely look at decay,

555
00:41:52,000 --> 00:41:57,440
we're hardwired to be repulsed by it.

556
00:41:57,440 --> 00:42:00,720
In the next few weeks, I hope our After Life house will start

557
00:42:00,720 --> 00:42:05,800
to show why this disgusting process is so important.

558
00:42:05,800 --> 00:42:11,400
Why decomposition is vital to life.

559
00:42:11,400 --> 00:42:19,400
And there's one part of our box where we're attempting to demonstrate that, in a unique way.

560
00:42:19,400 --> 00:42:23,640
These dead mustard plants are the starting point of an experiment

561
00:42:23,640 --> 00:42:29,960
that will help me trace how new life emerges from old.

562
00:42:29,960 --> 00:42:32,600
I've made liquid compost from the mustard

563
00:42:32,600 --> 00:42:36,680
and fed it to these seedlings.

564
00:42:36,680 --> 00:42:41,320
We plan to track individual nitrogen atoms from the dead mustard leaves,

565
00:42:41,320 --> 00:42:46,880
to see if they are re-used in the new plants.

566
00:42:46,880 --> 00:42:53,120
No-one has ever followed the cycle of life in this way before.

567
00:42:53,120 --> 00:42:56,600
In a couple of weeks time we can come back and, with any luck,

568
00:42:56,600 --> 00:43:15,640
we'll be able to track this vital part of the cycle from death and decay to new life.

569
00:43:15,640 --> 00:43:20,480
It's the 23rd day in the After Life house.

570
00:43:20,480 --> 00:43:24,600
The first waves of decay have now passed.

571
00:43:24,600 --> 00:43:28,680
Vegetables and soft fruit have been consumed by mould.

572
00:43:28,680 --> 00:43:32,920
In some places there's not much left for them to feed on.

573
00:43:32,920 --> 00:43:40,520
They'll need to find new supplies.

574
00:43:40,520 --> 00:43:43,280
Anything with a hard skin, like this orange,

575
00:43:43,280 --> 00:43:48,480
remains apparently unaffected.

576
00:43:48,480 --> 00:43:51,560
Maggot activity too has begun to die down,

577
00:43:51,560 --> 00:43:55,680
leaving behind a sort of meat slurry in our burger packet,

578
00:43:55,680 --> 00:44:04,800
where a few late developers eke out a meal from the remains.

579
00:44:04,800 --> 00:44:07,840
Most of the maggots have started to pupate,

580
00:44:07,840 --> 00:44:10,480
the next stage before they turn into adults.

581
00:44:10,480 --> 00:44:16,800
So we should soon see an explosion in our fly numbers.

582
00:44:16,800 --> 00:44:20,320
And our chicken has gone through an alarming metamorphosis.

583
00:44:20,320 --> 00:44:26,280
Bacteria continue to rot away at it, releasing gases as they feed.

584
00:44:26,280 --> 00:44:29,840
This week the carcass bloated to even more grotesque proportions

585
00:44:29,840 --> 00:44:34,840
before deflating as the gases escaped.

586
00:44:34,840 --> 00:44:38,280
One month into the project and our house really isn't somewhere

587
00:44:38,280 --> 00:44:41,000
you'd want to visit, unless you had to.

588
00:44:41,000 --> 00:44:47,080
Every time I go into the box there's one thing that hits me.

589
00:44:47,080 --> 00:44:55,640
That is, the all-pervading, hideous stink of decay.

590
00:44:55,640 --> 00:44:58,840
Imagine sticking your nose deep into a rubbish bin.

591
00:44:58,840 --> 00:45:01,880
That's the smell I'm talking about.

592
00:45:01,880 --> 00:45:04,520
But if you can get beyond your revulsion,

593
00:45:04,520 --> 00:45:09,840
the smell of decay gives real clues to its underlying mechanisms.

594
00:45:09,840 --> 00:45:16,040
And the different ways plants and animals are broken down.

595
00:45:16,040 --> 00:45:19,120
I want to share some of these smells with our audience.

596
00:45:19,120 --> 00:45:20,800
I've got two tubs.

597
00:45:20,800 --> 00:45:25,360
One's got far gone vegetables and this one meat that's far gone.

598
00:45:25,360 --> 00:45:35,760
I want to find out which our visitors find most disgusting.

599
00:45:35,760 --> 00:45:42,080
This is decaying vegetables. Have a smell of that. See what you think.

600
00:45:42,080 --> 00:45:46,680
It smells like vegetables, still. Have a good sniff.

601
00:45:46,680 --> 00:45:49,440
THEY LAUGH It's not that bad, is it?

602
00:45:49,440 --> 00:45:51,760
That's not terrible.

603
00:45:51,760 --> 00:45:56,800
I think it's only fair to warn you, this is not nice.

604
00:45:56,800 --> 00:46:00,200
Have a smell of that.

605
00:46:00,200 --> 00:46:04,040
That smells like a pig barn!

606
00:46:04,040 --> 00:46:08,120
THEY LAUGH

607
00:46:08,120 --> 00:46:12,800
As expected, the meat gets the same response every time.

608
00:46:12,800 --> 00:46:15,040
That's pretty grim, isn't it?

609
00:46:15,040 --> 00:46:18,880
His eyes are watering!

610
00:46:18,880 --> 00:46:20,320
Ew!

611
00:46:20,320 --> 00:46:24,040
Rotting meat is far more dangerous to us than rotting vegetables.

612
00:46:24,040 --> 00:46:27,480
So we're programmed to find it more offensive.

613
00:46:27,480 --> 00:46:31,080
But what are we actually smelling?

614
00:46:31,080 --> 00:46:34,320
Plant cells are largely made up of starches and sugars.

615
00:46:34,320 --> 00:46:37,160
So when fruit and veg decay, they ferment,

616
00:46:37,160 --> 00:46:40,400
turning the sugars into alcohol, and releasing

617
00:46:40,400 --> 00:46:43,080
volatile compounds which have a sweet odour.

618
00:46:43,080 --> 00:46:47,120
But fish and meat are going to produce really smelly gases

619
00:46:47,120 --> 00:46:51,040
like hydrogen sulphide, sulphur dioxide and ammonia

620
00:46:51,040 --> 00:46:53,040
so I'm just going to extract

621
00:46:53,040 --> 00:46:57,640
some of the gases from the inside of this decaying chicken,

622
00:46:57,640 --> 00:47:00,320
suck it up into this syringe

623
00:47:00,320 --> 00:47:05,600
and blow it over a gas analyser and see what happens.

624
00:47:05,600 --> 00:47:07,640
LOUD BEEPING

625
00:47:07,640 --> 00:47:13,320
Look at that! The hydrogen sulphide shot up to 10%.

626
00:47:13,320 --> 00:47:16,760
That really is smelly.

627
00:47:16,760 --> 00:47:18,640
Oh, God.

628
00:47:18,640 --> 00:47:23,520
HE COUGHS

629
00:47:23,520 --> 00:47:28,360
Unlike plant cells, animal cells are made up largely of proteins.

630
00:47:28,360 --> 00:47:30,600
The foul smelling gases are produced

631
00:47:30,600 --> 00:47:34,560
when these proteins are broken down into amino acids.

632
00:47:34,560 --> 00:47:38,520
To understand more about that process, and why the smell

633
00:47:38,520 --> 00:47:42,880
it generates is such an important part of decay, I am going to

634
00:47:42,880 --> 00:47:57,920
experience rotting flesh on a scale that even the box can't provide.

635
00:47:57,920 --> 00:48:01,680
At a secret location in north-west England

636
00:48:01,680 --> 00:48:07,560
a grotesque but important experiment is taking place.

637
00:48:07,560 --> 00:48:16,920
65 pig carcasses are being left to rot.

638
00:48:16,920 --> 00:48:20,760
They're part of an investigation into exactly how

639
00:48:20,760 --> 00:48:28,760
flesh decomposes, under different conditions.

640
00:48:28,760 --> 00:48:35,840
And the smell of death is everywhere.

641
00:48:35,840 --> 00:48:41,240
Well, I haven't been here very long and there's a real whiff of dead animal.

642
00:48:41,240 --> 00:48:46,360
Sometimes the wind changes direction and it catches your nose.

643
00:48:46,360 --> 00:48:51,800
I'm used to dealing with smells and excrement and stuff but I'm

644
00:48:51,800 --> 00:49:00,400
wondering if I'm up to this. There's a lot of dead animals around here.

645
00:49:00,400 --> 00:49:04,040
The pigs are stand-ins for human remains.

646
00:49:04,040 --> 00:49:06,880
The aim of the experiment is to help police forensic teams

647
00:49:06,880 --> 00:49:12,800
establish an accurate time of death, based on the state of decomposition.

648
00:49:12,800 --> 00:49:16,640
Dr Tal Simmons is the research director for the project.

649
00:49:16,640 --> 00:49:19,080
And she's going to help me understand how

650
00:49:19,080 --> 00:49:23,320
the different stages of decay account for what we smell.

651
00:49:23,320 --> 00:49:25,760
Good morning, Tal. Good morning, George.

652
00:49:25,760 --> 00:49:29,000
I won't shake hands. Possibly not. What's happening here?

653
00:49:29,000 --> 00:49:32,760
Let's move the cage and we'll be able to see a bit better.

654
00:49:32,760 --> 00:49:37,240
Well, we've got a pig we put out four days ago.

655
00:49:37,240 --> 00:49:40,560
He's just begun to really show some of the early stages of decomposition.

656
00:49:40,560 --> 00:49:45,800
The first thing that's obvious to me, it's swollen up there.

657
00:49:45,800 --> 00:49:48,040
He's beginning to bloat

658
00:49:48,040 --> 00:49:54,400
and he'll bloat more in the next couple of days and that's due to the cellular breakdown, inside the body.

659
00:49:54,400 --> 00:49:58,440
All those cells are starting to collapse, the cell membrane is going.

660
00:49:58,440 --> 00:50:01,000
It's exuding all the fluids inside the cell.

661
00:50:01,000 --> 00:50:03,600
A lot of those contain digestive enzymes.

662
00:50:03,600 --> 00:50:06,400
He's starting to eat himself from the inside.

663
00:50:06,400 --> 00:50:09,840
The moment blood stops flowing in an animal,

664
00:50:09,840 --> 00:50:13,040
this process of cell death begins.

665
00:50:13,040 --> 00:50:17,160
As each cell membrane splits, enzymes inside are released

666
00:50:17,160 --> 00:50:20,000
and begin to break down other cells.

667
00:50:20,000 --> 00:50:24,000
Bacteria then start to feed on these protein rich contents,

668
00:50:24,000 --> 00:50:28,360
releasing the gases that are bloating the pig.

669
00:50:28,360 --> 00:50:32,360
All of these gases produced inside are coming up the digestive tract.

670
00:50:32,360 --> 00:50:37,520
So that smell is actually coming out and that's what attracts the flies?

671
00:50:37,520 --> 00:50:43,120
We can't smell it but flies can. It's not obvious at all. No.

672
00:50:43,120 --> 00:50:47,040
But, as I know from the rotting meat and fish in the box,

673
00:50:47,040 --> 00:50:53,280
it doesn't take long for the smell to become something we can detect.

674
00:50:53,280 --> 00:50:54,920
HE COUGHS

675
00:50:54,920 --> 00:50:57,360
Oh, that's a lot worse.

676
00:50:57,360 --> 00:50:59,600
Let's pull this off.

677
00:50:59,600 --> 00:51:02,440
Oh, dear!

678
00:51:02,440 --> 00:51:05,040
He's much more advanced, as you can see.

679
00:51:05,040 --> 00:51:06,680
HE COUGHS

680
00:51:06,680 --> 00:51:10,720
We're now smelling a cocktail of highly volatile gases and

681
00:51:10,720 --> 00:51:15,000
liquids produced, not just by the break down of the animal proteins,

682
00:51:15,000 --> 00:51:19,200
but by the agents of decay themselves.

683
00:51:19,200 --> 00:51:23,240
The body is largely composed of water, so as the cells break down

684
00:51:23,240 --> 00:51:27,240
and the cell walls go, you get the liquid coming from that,

685
00:51:27,240 --> 00:51:30,320
you get the liquid that was part of the organs, and you get the liquid

686
00:51:30,320 --> 00:51:34,120
that the maggots are excreting as part of their digestive process too.

687
00:51:34,120 --> 00:51:37,160
If you look at it really closely, it's actually rather interesting.

688
00:51:37,160 --> 00:51:39,440
It's a fascinating process.

689
00:51:39,440 --> 00:51:44,880
I wouldn't say it's attractive. I wouldn't go that far either!

690
00:51:44,880 --> 00:51:48,840
Many of the molecules in this cocktail of decomposition fluids

691
00:51:48,840 --> 00:51:55,560
have a particular property, they are highly electrically charged.

692
00:51:55,560 --> 00:51:58,720
It's a bit like when you rub a balloon on a woollen jumper.

693
00:51:58,720 --> 00:52:02,360
The molecules of the balloon pick up a charge, which means they stick to

694
00:52:02,360 --> 00:52:05,000
other materials they come into contact with.

695
00:52:05,000 --> 00:52:09,880
Which is why the smell of decay can literally stick to our clothes.

696
00:52:09,880 --> 00:52:13,120
And it also explains why decay can leave a trace

697
00:52:13,120 --> 00:52:16,360
that lingers far longer than you might think.

698
00:52:16,360 --> 00:52:17,840
Top off.

699
00:52:17,840 --> 00:52:21,440
Tal's colleague Peter Cross is measuring what effect

700
00:52:21,440 --> 00:52:28,360
the decomposing pigs are having on the surrounding earth.

701
00:52:28,360 --> 00:52:31,400
Just draw the water up. It's even frothing.

702
00:52:31,400 --> 00:52:33,840
It's foaming. Yeah.

703
00:52:33,840 --> 00:52:38,520
Well, it's clearly not fresh.

704
00:52:38,520 --> 00:52:41,640
Argh!

705
00:52:41,640 --> 00:52:44,680
That's pretty bad!

706
00:52:44,680 --> 00:52:50,520
This is soil water taken from the site of a buried pig carcass.

707
00:52:50,520 --> 00:52:54,360
This machine is passing an electrical current through the soil water

708
00:52:54,360 --> 00:52:58,840
and then measuring how well that soil water conducts electricity.

709
00:52:58,840 --> 00:53:03,720
The contaminated water is 30 times more conductive than

710
00:53:03,720 --> 00:53:06,760
soil water taken from ten metres away.

711
00:53:06,760 --> 00:53:10,440
This is the trace that decay leaves behind.

712
00:53:10,440 --> 00:53:12,640
We think that because of all the electrolytes

713
00:53:12,640 --> 00:53:16,080
that are leaching into the soil water from the decomposing pig,

714
00:53:16,080 --> 00:53:19,560
that they are changing the electrical properties of the soil water.

715
00:53:19,560 --> 00:53:21,000
How long will that remain?

716
00:53:21,000 --> 00:53:24,640
I'd expect conductivity to continue increasing for up to two years.

717
00:53:24,640 --> 00:53:27,880
So that really is a fingerprint of death, isn't it?

718
00:53:27,880 --> 00:53:37,440
Absolutely, yes.

719
00:53:37,440 --> 00:53:41,200
And it's a fingerprint that allows scientists to detect

720
00:53:41,200 --> 00:53:45,560
signs of decay, not just over years, but over centuries.

721
00:53:45,560 --> 00:53:48,600
OK, Chris, do you want to grab the remote probes?

722
00:53:48,600 --> 00:53:52,480
Dr Jamie Pringle is a forensic geophysicist.

723
00:53:52,480 --> 00:53:57,840
Today he's using the conductive qualities of decomposition fluids

724
00:53:57,840 --> 00:54:01,800
to identify unmarked graves in this churchyard.

725
00:54:01,800 --> 00:54:07,320
Some are estimated to be 200-years-old.

726
00:54:07,320 --> 00:54:12,800
Jamie's kit sends an electrical current into the ground to measure conductivity.

727
00:54:12,800 --> 00:54:16,440
It can detect electrically charged molecules

728
00:54:16,440 --> 00:54:21,920
left behind by the bodies buried centuries ago.

729
00:54:21,920 --> 00:54:22,840
BEEPING

730
00:54:22,840 --> 00:54:31,120
Oh, that's interesting, lads. Looks like it's going down there.

731
00:54:31,120 --> 00:54:33,520
I've just downloaded the data from the machine

732
00:54:33,520 --> 00:54:38,280
and the results show there's one, two, three, four, five areas

733
00:54:38,280 --> 00:54:41,680
of blue, which means it's high conductivity results,

734
00:54:41,680 --> 00:54:45,280
which suggests to me that's where the graves are going to be located

735
00:54:45,280 --> 00:54:49,320
and where the decompositional fluids have been retained in the soil.

736
00:54:49,320 --> 00:54:53,800
This technology opens up new possibilities in forensic science.

737
00:54:53,800 --> 00:54:57,560
Not only can it be used for unmarked graves, it can be used for

738
00:54:57,560 --> 00:55:02,120
other things as well, such as looking for buried murder victims.

739
00:55:02,120 --> 00:55:06,480
For crime fighters, the powerful lingering effect of decay,

740
00:55:06,480 --> 00:55:28,520
turns out to be one of its most useful qualities.

741
00:55:28,520 --> 00:55:32,640
We're more than halfway through our investigation of what happens

742
00:55:32,640 --> 00:55:38,280
when decay is allowed to run its course in a typical home.

743
00:55:38,280 --> 00:55:42,320
We set out to see how quickly its contents would be broken down

744
00:55:42,320 --> 00:55:46,320
and transformed into new life.

745
00:55:46,320 --> 00:55:53,760
One month in, we have our most striking result yet.

746
00:55:53,760 --> 00:56:04,800
The clue is in our rapidly increasing fly numbers.

747
00:56:04,800 --> 00:56:10,000
These flies are the first generation to be born and bred in the box.

748
00:56:10,000 --> 00:56:17,320
Two weeks ago, they were the maggots that were so active in all the meat.

749
00:56:17,320 --> 00:56:20,720
Once a maggot has fed enough, it pupates.

750
00:56:20,720 --> 00:56:26,400
Within about seven days, the adult blow fly emerges.

751
00:56:26,400 --> 00:56:42,680
It inflates a soft spongy sack on the top of its head to help push itself out.

752
00:56:42,680 --> 00:56:46,320
Then blood pumps into the wings, spreading them out

753
00:56:46,320 --> 00:57:04,760
ready for take off.

754
00:57:04,760 --> 00:57:07,840
There isn't anything better than flies to illustrate

755
00:57:07,840 --> 00:57:10,520
the transformative power of decay.

756
00:57:10,520 --> 00:57:13,800
The fly larvae have eaten this pig. I want to show you

757
00:57:13,800 --> 00:57:17,320
just how little is left behind.

758
00:57:17,320 --> 00:57:24,240
If I get this torn back without cutting my finger, it's quite tough.

759
00:57:24,240 --> 00:57:30,600
The outer surface of the skin is now quite dry. Look at that.

760
00:57:30,600 --> 00:57:36,160
Oh! The smell of ammonia is quite overpowering.

761
00:57:36,160 --> 00:57:40,440
If I peel it back...

762
00:57:40,440 --> 00:57:43,640
What we've got here is basically dried skin

763
00:57:43,640 --> 00:57:47,680
and a few bits of fat All the meat has gone.

764
00:57:47,680 --> 00:57:51,920
The fly larvae have eaten this pig out completely

765
00:57:51,920 --> 00:57:55,000
All that's left are some ribs and fat.

766
00:57:55,000 --> 00:57:59,440
All that meat that was once pig is now flying around this room.

767
00:57:59,440 --> 00:58:11,720
Who says pigs can't fly?

768
00:58:11,720 --> 00:58:24,320
Seven days later and the number of blow flies is becoming a problem inside the house.

769
00:58:24,320 --> 00:58:27,280
Well, it's a week since I was here before

770
00:58:27,280 --> 00:58:31,400
and, as I predicted, the numbers of flies have absolutely sky rocketed,

771
00:58:31,400 --> 00:58:33,440
they've gone through the roof.

772
00:58:33,440 --> 00:58:40,080
I'm going to wear an all-in-one suit for a bit of protection this week.

773
00:58:40,080 --> 00:58:45,120
I reckon there could be as many as 10,000 flies inside.

774
00:58:45,120 --> 00:58:48,400
Because our box is sealed, they can't escape to find

775
00:58:48,400 --> 00:58:52,280
new sources of food and places to lay their eggs.

776
00:58:52,280 --> 00:59:01,000
I'm worried that their sheer numbers may disrupt the natural course of decay elsewhere in the box.

777
00:59:01,000 --> 00:59:07,520
There are now simply too many flies here, it's becoming quite unpleasant.

778
00:59:07,520 --> 00:59:11,400
It's causing a problem because of the fly speck, that's the excrement,

779
00:59:11,400 --> 00:59:14,200
which they leave on the surfaces, inside the glass.

780
00:59:14,200 --> 00:59:19,400
So, it's time I tried to reduce them a bit...

781
00:59:19,400 --> 00:59:21,320
manually.

782
00:59:21,320 --> 00:59:28,000
The trouble is, they're flying quite low and sitting on surfaces.

783
00:59:28,000 --> 00:59:31,640
It's hard to get them.

784
00:59:31,640 --> 00:59:37,120
Half the flies are drunk because

785
00:59:37,120 --> 00:59:40,440
the fruit bowl has become alcoholic

786
00:59:40,440 --> 00:59:44,760
and the flies are flying under the influence at the moment.

787
00:59:44,760 --> 00:59:48,920
It's probably why there are so many on the floor.

788
00:59:48,920 --> 00:59:52,320
You can hear them.

789
00:59:52,320 --> 00:59:54,400
A constant buzz.

790
00:59:54,400 --> 00:59:56,880
This is pretty unpleasant.

791
00:59:56,880 --> 01:00:03,720
Oh! Look at this!

792
01:00:03,720 --> 01:00:06,360
It's no wonder that flies are so hard to capture.

793
01:00:06,360 --> 01:00:11,000
Their compound eyes give them 360 degree vision.

794
01:00:11,000 --> 01:00:15,320
So they can respond to movement in less than 30 milliseconds.

795
01:00:15,320 --> 01:00:19,800
Me and my net can only do so much.

796
01:00:19,800 --> 01:00:23,680
It will be hunger that kills off these flies in the remaining weeks,

797
01:00:23,680 --> 01:00:27,720
as food supplies in the box run out.

798
01:00:27,720 --> 01:00:30,760
Their role in our project is coming to an end.

799
01:00:30,760 --> 01:00:34,760
We should start to see other insects moving in to carry on

800
01:00:34,760 --> 01:00:42,800
the process of breaking down what's left of the meat.

801
01:00:42,800 --> 01:00:53,720
In the meantime, the flies need for food is affecting one of our other agents of decay.

802
01:00:53,720 --> 01:00:58,240
Six weeks in, mould is still ravaging the sandwich box.

803
01:00:58,240 --> 01:01:00,640
It's even grown out from under the lid.

804
01:01:00,640 --> 01:01:08,160
And it's attracted the attention of our starving flies.

805
01:01:08,160 --> 01:01:13,480
Now, this to me, is one of the most amazing things I've ever seen.

806
01:01:13,480 --> 01:01:20,120
Patrick Hickey has returned to investigate what's been happening to the moulds in our house.

807
01:01:20,120 --> 01:01:22,600
How many actual species of fungus are here?

808
01:01:22,600 --> 01:01:26,120
At least 20 or 30, maybe more.

809
01:01:26,120 --> 01:01:29,640
20 or 30 species of fungus! I can't wait to have a sort of...

810
01:01:29,640 --> 01:01:33,960
It's the perfect environment. Some of them are fairly dangerous.

811
01:01:33,960 --> 01:01:40,560
One of the moulds here, aspergillus flavus, a greeny-yellow one,

812
01:01:40,560 --> 01:01:45,320
can produce a nasty toxin. So, you want to be careful.

813
01:01:45,320 --> 01:01:49,600
Look at this, it's a solid mat.

814
01:01:49,600 --> 01:01:53,080
There are the layers of sandwich.

815
01:01:53,080 --> 01:01:58,320
It's completely through. There aren't any flies, of course.

816
01:01:58,320 --> 01:02:02,920
It was sealed in the box so the flies couldn't get in.

817
01:02:02,920 --> 01:02:07,480
Big contrast to the fruit bowl, which was left open.

818
01:02:07,480 --> 01:02:13,000
A couple of weeks ago it was covered in thick layers of fungus and

819
01:02:13,000 --> 01:02:16,000
the flies have stripped it bare.

820
01:02:16,000 --> 01:02:21,440
They've eaten the fungus and spores and recycled the fungi.

821
01:02:21,440 --> 01:02:25,720
Fruit has become mould. Mould has become flies. Flies fly off.

822
01:02:25,720 --> 01:02:31,400
And, if they were outside, they'd be eaten by something.

823
01:02:31,400 --> 01:02:33,120
Outside in the garden,

824
01:02:33,120 --> 01:02:37,120
other forms of fungi rely on insects to help them do their job.

825
01:02:37,120 --> 01:02:41,720
This is the fruiting body of a stinkhorn fungus.

826
01:02:41,720 --> 01:02:45,320
The rest of the fungus is below the soil,

827
01:02:45,320 --> 01:02:48,280
feeding on wood and plant matter in the soil.

828
01:02:48,280 --> 01:02:52,160
These stalks emerge when the fungus is ready to fruit,

829
01:02:52,160 --> 01:03:01,720
growing up to 15cms in less than 24 hours.

830
01:03:01,720 --> 01:03:05,360
When they break through the top layer of soil,

831
01:03:05,360 --> 01:03:09,880
they release an intense smell that flies find irresistible,

832
01:03:09,880 --> 01:03:13,960
the smell of dead and decaying meat.

833
01:03:13,960 --> 01:03:17,320
The flies strip the jelly-like flesh from the mushroom,

834
01:03:17,320 --> 01:03:21,160
and help spread its spores.

835
01:03:21,160 --> 01:03:24,240
Even after 30 years of studying biology,

836
01:03:24,240 --> 01:03:33,840
I'm still amazed by the complex behaviour of these simple organisms.

837
01:03:33,840 --> 01:03:40,640
But stinkhorns aren't the strangest things feeding on the decaying wood in our garden.

838
01:03:40,640 --> 01:03:47,400
Hidden away in our woodpile is something even more intriguing.

839
01:03:47,400 --> 01:03:52,560
This is a slime mould.

840
01:03:52,560 --> 01:03:56,040
It's the largest single-celled organism on Earth.

841
01:03:56,040 --> 01:04:07,320
It can grow to more than three square metres.

842
01:04:07,320 --> 01:04:10,760
Scientists have recently discovered that these primitive life forms

843
01:04:10,760 --> 01:04:26,600
have some rather sophisticated talents.

844
01:04:26,600 --> 01:04:29,840
At Oxford University, Dr Mark Fricker is one of a team of

845
01:04:29,840 --> 01:04:34,440
botanists and computer scientists studying a species of slime mould

846
01:04:34,440 --> 01:04:37,160
called Physarum Polycephalum.

847
01:04:37,160 --> 01:04:40,400
For years slime moulds have fascinated scientists

848
01:04:40,400 --> 01:04:45,400
with their remarkable ability to solve simple mazes.

849
01:04:45,400 --> 01:04:47,560
Put food at the end of a maze

850
01:04:47,560 --> 01:04:51,080
and the slime mould will find the quickest route through.

851
01:04:51,080 --> 01:04:53,040
But scientists started to wonder

852
01:04:53,040 --> 01:04:56,440
if the mould could do more than just perform clever tricks.

853
01:04:56,440 --> 01:04:59,280
You can set them lots of little tasks, and

854
01:04:59,280 --> 01:05:02,160
you can allow them to forage and connect up little

855
01:05:02,160 --> 01:05:05,240
food sources to see what sort of network they would make. OK.

856
01:05:05,240 --> 01:05:08,880
And a geometric shape, so a square or something more complicated,

857
01:05:08,880 --> 01:05:11,720
is interesting, but we wanted to see whether they would

858
01:05:11,720 --> 01:05:18,960
be able to solve a slightly more complex problem.

859
01:05:18,960 --> 01:05:21,240
Mark is recreating an experiment

860
01:05:21,240 --> 01:05:25,200
he worked on with colleagues at Tokyo University.

861
01:05:25,200 --> 01:05:28,160
He takes a blob of slime mould and then surrounds it with

862
01:05:28,160 --> 01:05:35,680
a pattern of oat flakes, an irresistible treat to slime mould.

863
01:05:35,680 --> 01:05:43,840
What happens next is recorded by a time-lapse camera.

864
01:05:43,840 --> 01:05:50,920
The slime mould locates the oat flakes by growing out in all directions.

865
01:05:50,920 --> 01:05:54,360
But within hours the slime mould shrinks back,

866
01:05:54,360 --> 01:06:00,320
leaving an intricate web of tubes that connect the oat flakes.

867
01:06:00,320 --> 01:06:06,720
It's these tubes that transfer nutrients around the slime mould.

868
01:06:06,720 --> 01:06:11,520
Incredibly, everything you can see is part of one single cell.

869
01:06:11,520 --> 01:06:16,840
It needs to build a network that is quite efficient, to transport all those resources.

870
01:06:16,840 --> 01:06:20,560
At the same time, that network mustn't cost too much.

871
01:06:20,560 --> 01:06:23,240
It mustn't take up too many of its own resources.

872
01:06:23,240 --> 01:06:27,280
And then the other problem it has is, it's going to be subject to damage.

873
01:06:27,280 --> 01:06:29,920
If there was only ever one connection,

874
01:06:29,920 --> 01:06:33,360
there's a risk it would break.

875
01:06:33,360 --> 01:06:36,440
The slime mould takes no chances.

876
01:06:36,440 --> 01:06:43,760
It grows back-up routes to make sure that its food supply isn't cut off.

877
01:06:43,760 --> 01:06:50,000
But there's something even more extraordinary about what the slime mould has done.

878
01:06:50,000 --> 01:06:55,400
Mark hasn't just laid out the flakes in a random pattern.

879
01:06:55,400 --> 01:06:57,560
The large blob in the middle is Tokyo

880
01:06:57,560 --> 01:07:03,120
and each of the food sources are positioned as cities nearby Tokyo.

881
01:07:03,120 --> 01:07:06,760
So, it's a re-creation of the area around Tokyo? Indeed.

882
01:07:06,760 --> 01:07:11,160
This is actually what it's based on, the rail network around Tokyo.

883
01:07:11,160 --> 01:07:15,240
We can superimpose that over. Ok, so we align it...

884
01:07:15,240 --> 01:07:18,640
That's identical! It's absolutely identical!

885
01:07:18,640 --> 01:07:23,760
You see a lot of these connections. It's formed the same sort of links, it's got a few extra ones in as well,

886
01:07:23,760 --> 01:07:28,000
it's a slightly more resilient network than the ones the engineers designed... Hold on!

887
01:07:28,000 --> 01:07:30,320
You're telling me, wait a minute,

888
01:07:30,320 --> 01:07:34,080
that this slime mould has built a better network...

889
01:07:34,080 --> 01:07:36,000
A remarkably similar network.

890
01:07:36,000 --> 01:07:41,240
..than the humans built. Yes.

891
01:07:41,240 --> 01:07:44,120
The Tokyo rail system is one of the most efficient

892
01:07:44,120 --> 01:07:46,440
and well organised in the world.

893
01:07:46,440 --> 01:07:51,800
It took lots of skilled engineers using lots of brain power to plan.

894
01:07:51,800 --> 01:07:55,880
Yet, somehow, slime mould has achieved the same goal,

895
01:07:55,880 --> 01:08:01,320
how to efficiently link together multiple locations.

896
01:08:01,320 --> 01:08:05,520
Slime mould has also been put to work in other parts of world.

897
01:08:05,520 --> 01:08:10,000
Here it tackles some of Britain's major motorways.

898
01:08:10,000 --> 01:08:16,760
This is its take on the best routes around Spain.

899
01:08:16,760 --> 01:08:23,280
And here are some interesting alternatives to Americas Route 66.

900
01:08:23,280 --> 01:08:25,880
What is the slime mould actually displaying here?

901
01:08:25,880 --> 01:08:29,200
It's a sort of smart behaviour. It hasn't got a brain,

902
01:08:29,200 --> 01:08:33,000
it hasn't got a nervous system, but it still seems to be able to solve

903
01:08:33,000 --> 01:08:36,080
these sorts of complex problems with very simple rules.

904
01:08:36,080 --> 01:08:40,920
It's something the computer scientists we work with are getting very interested in,

905
01:08:40,920 --> 01:08:56,920
whether or not you can take inspiration from this system and apply it to other sorts of problems.

906
01:08:56,920 --> 01:09:01,040
How does one of the most simple life-forms on Earth,

907
01:09:01,040 --> 01:09:05,400
a single-celled amoeba that spends most of its time on woodland waste,

908
01:09:05,400 --> 01:09:14,040
match its wits against transport engineers and computer scientists?

909
01:09:14,040 --> 01:09:21,960
The clue seems to lie in its extraordinary biology.

910
01:09:21,960 --> 01:09:26,440
Professor Bruce Ing is a self confessed slime mould obsessive.

911
01:09:26,440 --> 01:09:30,400
He's going to help me track down some slime mould

912
01:09:30,400 --> 01:09:34,120
in one of its native habitats.

913
01:09:34,120 --> 01:09:36,520
Slime moulds aren't rare things?

914
01:09:36,520 --> 01:09:40,440
Oh, no. They're very common, indeed. They're everywhere. But overlooked?

915
01:09:40,440 --> 01:09:43,280
Overlooked because they are shy, not easy to find,

916
01:09:43,280 --> 01:10:02,760
unless you know where to look. Shy slime moulds!

917
01:10:02,760 --> 01:10:06,480
Do you remember the film The Blob? Yes.

918
01:10:06,480 --> 01:10:10,680
A giant mass of jelly, eating caravans?

919
01:10:10,680 --> 01:10:13,720
It was a slime mould? It was.

920
01:10:13,720 --> 01:10:15,760
But not one we'll find here.

921
01:10:15,760 --> 01:10:22,320
Not as big as that, I hope.

922
01:10:22,320 --> 01:10:30,960
Bruce's 54 years in the field prove vital as we hunt the elusive slime mould.

923
01:10:30,960 --> 01:10:33,800
After half an hour, he finds what we are looking for.

924
01:10:33,800 --> 01:10:38,360
It's not quite the sheet I was hoping for. No, indeed not.

925
01:10:38,360 --> 01:10:44,320
But it's still the real McCoy.

926
01:10:44,320 --> 01:10:50,720
This small patch of orange is creeping slime mould.

927
01:10:50,720 --> 01:10:57,320
Up close, you can see how it's constantly pulsating.

928
01:10:57,320 --> 01:11:00,240
When one part of it finds something it likes to eat,

929
01:11:00,240 --> 01:11:03,080
it pulses more rapidly.

930
01:11:03,080 --> 01:11:07,000
Scientists believe that it's this pulsating that helps transmit

931
01:11:07,000 --> 01:11:09,600
information across the entire cell,

932
01:11:09,600 --> 01:11:18,560
allowing the slime mould to move towards its food source.

933
01:11:18,560 --> 01:11:22,800
These pulsations control where and how they grow across the forest floor,

934
01:11:22,800 --> 01:11:30,240
or even around the oat flakes of the Tokyo rail map.

935
01:11:30,240 --> 01:11:33,800
What's so special about slime mould is that it can use

936
01:11:33,800 --> 01:11:38,040
this information to make multiple decisions, simultaneously.

937
01:11:38,040 --> 01:11:46,560
Pretty ingenious stuff for a single-celled organism.

938
01:11:46,560 --> 01:11:51,880
Slime moulds are what's known as self organising systems.

939
01:11:51,880 --> 01:11:55,120
It's not a unique phenomenon in nature.

940
01:11:55,120 --> 01:11:57,800
Flocks of birds work in a similar way.

941
01:11:57,800 --> 01:12:00,000
With no leader, no overall control,

942
01:12:00,000 --> 01:12:04,320
the flock nevertheless acts as a single unit.

943
01:12:04,320 --> 01:12:09,720
But slime mould can do something that flocks of birds could never do.

944
01:12:09,720 --> 01:12:15,440
Meet the Phi-Bot, the world's first slime mould controlled robot.

945
01:12:15,440 --> 01:12:19,760
The Phi-Bot is the brain child of Dr Soichiro Tsuda

946
01:12:19,760 --> 01:12:23,640
and Dr Klaus Peter Zauner from Southampton University.

947
01:12:23,640 --> 01:12:29,440
Their robot takes its orders from a tiny blob of slime mould.

948
01:12:29,440 --> 01:12:32,400
I sort of don't believe you, I want to...

949
01:12:32,400 --> 01:12:33,960
HE LAUGHS

950
01:12:33,960 --> 01:12:35,920
..I want to see it working. Prove it!

951
01:12:35,920 --> 01:12:39,200
THEY LAUGH Soichiro, flip the switch.

952
01:12:39,200 --> 01:12:43,600
It just seems almost unbelievable.

953
01:12:43,600 --> 01:12:47,520
It's not instant, is it? It's not instant... Oh!

954
01:12:47,520 --> 01:12:54,800
Wow! That's fantastic!

955
01:12:54,800 --> 01:12:59,520
The slime mould sits on an electronic chip, inside the robot.

956
01:12:59,520 --> 01:13:03,520
As it transmits information around its single-cell by pulsing,

957
01:13:03,520 --> 01:13:06,480
the robot detects these pulses and translates them

958
01:13:06,480 --> 01:13:10,760
into much larger movements across the surface of the table.

959
01:13:10,760 --> 01:13:17,160
How did you get the idea for having a live organism inside a robot?

960
01:13:17,160 --> 01:13:21,760
One inspiration source obviously from the Daleks, from Doctor Who?

961
01:13:21,760 --> 01:13:24,000
This is inspired by a Dalek? Yes.

962
01:13:24,000 --> 01:13:26,480
Well, it's the same thing, isn't it? Yeah exactly.

963
01:13:26,480 --> 01:13:30,160
You've got a live organism in the machine, which controls it.

964
01:13:30,160 --> 01:13:34,280
The Phi-Bot is pioneering a new approach to computing.

965
01:13:34,280 --> 01:13:39,520
Today's computers use a single central processing unit to do their thinking.

966
01:13:39,520 --> 01:13:43,560
But the slime mould has no need to ask a brain what to do,

967
01:13:43,560 --> 01:13:47,360
all parts of the cell just work together, for the good of the whole.

968
01:13:47,360 --> 01:13:51,320
The simple organism inside, processes information in a completely

969
01:13:51,320 --> 01:13:54,640
radically different way from our conventional computing technology.

970
01:13:54,640 --> 01:13:59,880
We want to learn more about how it can do that information processing.

971
01:13:59,880 --> 01:14:04,880
So slime mould could hold the secret to a revolution in computing.

972
01:14:04,880 --> 01:14:08,800
Or even the creation of artificial intelligence.

973
01:14:08,800 --> 01:14:23,320
Not bad for something you can find in your wood pile.

974
01:14:23,320 --> 01:14:30,080
There's only a week left to go in our project to study decay in a typical house and garden.

975
01:14:30,080 --> 01:14:34,400
The pace of change in the box is beginning to slow down.

976
01:14:34,400 --> 01:14:39,360
But, even now, decay is following an ordered sequence.

977
01:14:39,360 --> 01:14:44,320
What one decomposer leaves behind is food for others.

978
01:14:44,320 --> 01:14:48,160
Well, it's day 44 and the one thing that's immediately obvious,

979
01:14:48,160 --> 01:14:54,680
it doesn't smell nearly as bad in here. It's actually quite pleasant.

980
01:14:54,680 --> 01:14:58,320
The other thing that's obvious is there are very few flies now,

981
01:14:58,320 --> 01:15:02,160
the majority of the flies that hatched out have died.

982
01:15:02,160 --> 01:15:05,680
There aren't as many dead ones lying about as I'd expected, but

983
01:15:05,680 --> 01:15:10,120
it looks like a few flies might have got themselves stuck in this

984
01:15:10,120 --> 01:15:15,400
bottle of wine, as they searched for something to drink.

985
01:15:15,400 --> 01:15:18,440
This is solid. Uh!

986
01:15:18,440 --> 01:15:21,280
Look at this. Oh my God!

987
01:15:21,280 --> 01:15:26,160
Urgh! That is incredible.

988
01:15:26,160 --> 01:15:28,480
HE LAUGHS

989
01:15:28,480 --> 01:15:30,440
I can't get them all out.

990
01:15:30,440 --> 01:15:37,960
I've never seen so many flies in one bottle, in my life.

991
01:15:37,960 --> 01:15:39,960
I can barely get them out.

992
01:15:39,960 --> 01:15:44,560
That sort of explains why I wasn't seeing as many flies

993
01:15:44,560 --> 01:15:47,280
flying around, as I expected.

994
01:15:47,280 --> 01:15:51,080
It's because most of them were in here.

995
01:15:51,080 --> 01:15:56,600
Look at it. It's just incredible. It's thick.

996
01:15:56,600 --> 01:16:05,160
That's thick with flies.

997
01:16:05,160 --> 01:16:08,680
Conditions in the box are very dry.

998
01:16:08,680 --> 01:16:14,320
All that remains of the meat are hardened chunks of sinew and skin.

999
01:16:14,320 --> 01:16:21,000
Even if the flies had survived there's nothing left for another generation of maggots to feed on.

1000
01:16:21,000 --> 01:16:25,400
But this is the perfect fodder for beetles.

1001
01:16:25,400 --> 01:16:29,760
This dried meat gives off a far less pungent odour, but the smell

1002
01:16:29,760 --> 01:16:37,640
it does produce gives them a signal that starts the next stage in decay.

1003
01:16:37,640 --> 01:16:44,960
Decay happens in a series in waves, this fish is dry and hard,

1004
01:16:44,960 --> 01:16:49,480
there are beetle larvae who will eat it. So there's no waste.

1005
01:16:49,480 --> 01:16:53,520
That's what I'm hunting for now, I'm hunting for the larvae

1006
01:16:53,520 --> 01:17:01,200
of a larder beetle and there's one right there.

1007
01:17:01,200 --> 01:17:06,280
Larder beetle larvae are present in around half of all homes.

1008
01:17:06,280 --> 01:17:11,040
They only colonise a carcass once it's become dried and desiccated.

1009
01:17:11,040 --> 01:17:14,960
Their powerful jaws allow them to eat through flesh, hair and skin.

1010
01:17:14,960 --> 01:17:18,120
And they can strip an animal down to the bone.

1011
01:17:18,120 --> 01:17:21,120
This stage in decay moves slowly though.

1012
01:17:21,120 --> 01:17:25,320
Larder beetle larvae take months to pupate into these adults.

1013
01:17:25,320 --> 01:17:36,080
The job of recycling what remains in the box could take generations of them, years to complete.

1014
01:17:36,080 --> 01:17:39,160
But another beetle in our box does allow us

1015
01:17:39,160 --> 01:17:49,360
to see how effective these insects can be.

1016
01:17:49,360 --> 01:17:53,080
36 days ago, two sexton beetles took less than 12 hours

1017
01:17:53,080 --> 01:18:00,440
to bury our dead rat.

1018
01:18:00,440 --> 01:18:03,680
What I'm aching to do now is a spot of archaeology.

1019
01:18:03,680 --> 01:18:06,800
Because what has happened is, the sextons beetles have taken

1020
01:18:06,800 --> 01:18:11,080
the rat down and they will have formed it into a ball,

1021
01:18:11,080 --> 01:18:16,040
on which their larvae have fed and hopefully 36 days should be

1022
01:18:16,040 --> 01:18:20,640
enough time. I should find a crypt in which the rat sits,

1023
01:18:20,640 --> 01:18:24,320
surrounded by its own fur, which they smear on the outside.

1024
01:18:24,320 --> 01:18:27,560
And there should just be bones left.

1025
01:18:27,560 --> 01:18:32,560
This, for me, is about as exciting as it gets.

1026
01:18:32,560 --> 01:18:39,560
I'm going to use a hoover to gently take away the soil.

1027
01:18:39,560 --> 01:18:42,400
What is amazing about these insects is,

1028
01:18:42,400 --> 01:18:47,080
they're one of the very few insects who look after their young.

1029
01:18:47,080 --> 01:18:52,880
They take care of their young. Once they've dragged the prey down,

1030
01:18:52,880 --> 01:19:00,440
and hidden it underground, they'll lay the eggs around the crypt,

1031
01:19:00,440 --> 01:19:04,520
and then the larvae will move in and feed.

1032
01:19:04,520 --> 01:19:07,960
And they'll help them to feed as well.

1033
01:19:07,960 --> 01:19:10,400
We're beginning to see a shape here.

1034
01:19:10,400 --> 01:19:16,280
This is very exciting. Turn that off.

1035
01:19:16,280 --> 01:19:21,800
Wonder if I can free it.

1036
01:19:21,800 --> 01:19:31,040
That is just fantastic.

1037
01:19:31,040 --> 01:19:35,920
There look at that, that's all that remains of the rat.

1038
01:19:35,920 --> 01:19:41,040
You can see the top part of the skull and the teeth.

1039
01:19:41,040 --> 01:19:44,320
The rest of it has completely disappeared,

1040
01:19:44,320 --> 01:20:03,160
there's nothing left of that rat.

1041
01:20:03,160 --> 01:20:08,320
We're now at week eight. We're nearing the end of our project.

1042
01:20:08,320 --> 01:20:12,840
But there is one final stage of decay I want to investigate.

1043
01:20:12,840 --> 01:20:17,480
And it's probably the most important.

1044
01:20:17,480 --> 01:20:21,520
We've watched as the nutrients, locked up in plant

1045
01:20:21,520 --> 01:20:24,760
and animal remains, have been re-used by other organisms.

1046
01:20:24,760 --> 01:20:27,800
In the process, complex things like chickens, rats and fruit,

1047
01:20:27,800 --> 01:20:34,080
have become simpler ones, insects, fungi, bacteria.

1048
01:20:34,080 --> 01:20:38,840
But the true power of decay is its ability to reduce complex things

1049
01:20:38,840 --> 01:20:44,440
right back to the most basic building blocks of life.

1050
01:20:44,440 --> 01:20:46,480
And all through the project,

1051
01:20:46,480 --> 01:20:52,760
that's been quietly happening in a corner of the box.

1052
01:20:52,760 --> 01:20:58,000
This is one of best places to see decay in action. We set this up

1053
01:20:58,000 --> 01:21:03,160
eight weeks ago and it was piled to the top with plant material.

1054
01:21:03,160 --> 01:21:07,000
It's now completely decayed down, we've been adding to it.

1055
01:21:07,000 --> 01:21:13,880
What I really want to do, is have a look inside and see what's going on.

1056
01:21:13,880 --> 01:21:19,000
Now, decay has been happening and the further you go down,

1057
01:21:19,000 --> 01:21:28,240
the more advanced it is. There's a snail on the trowel handle.

1058
01:21:28,240 --> 01:21:31,360
As all gardeners know, compost heaps turn dead plants

1059
01:21:31,360 --> 01:21:38,880
into a form of nutrients that new plants can use.

1060
01:21:38,880 --> 01:21:44,040
On the surface, animals like snails, slugs and worms begin the process

1061
01:21:44,040 --> 01:21:50,480
by eating the remains of plants, helping to break them into pieces.

1062
01:21:50,480 --> 01:21:53,520
The waste they excrete, and anything else left behind,

1063
01:21:53,520 --> 01:21:57,160
is eaten by smaller creatures like these mites.

1064
01:21:57,160 --> 01:22:05,320
Too tiny to be seen with the naked eye.

1065
01:22:05,320 --> 01:22:08,320
And this process continues down through the compost.

1066
01:22:08,320 --> 01:22:10,560
Ever smaller organisms,

1067
01:22:10,560 --> 01:22:14,360
reducing the plant waste to ever smaller components.

1068
01:22:14,360 --> 01:22:21,120
Until tiny fungi and bacteria are able to break down the very cells of the plant.

1069
01:22:21,120 --> 01:22:25,560
A teaspoon of soil contains four billion micro-organisms.

1070
01:22:25,560 --> 01:22:28,040
They finally release the nitrogen

1071
01:22:28,040 --> 01:22:33,280
and other building blocks of organic life, back into the soil.

1072
01:22:33,280 --> 01:22:36,160
What we end up with,

1073
01:22:36,160 --> 01:22:41,240
is an incredibly very fine soil,

1074
01:22:41,240 --> 01:22:49,200
the result of the breakdown processes of countless organisms.

1075
01:22:49,200 --> 01:22:57,080
Having begun with a big pile of green material, you may think that is an end point, but it's not,

1076
01:22:57,080 --> 01:23:05,600
it's just the beginning.

1077
01:23:05,600 --> 01:23:09,200
From here, life can begin to rebuild.

1078
01:23:09,200 --> 01:23:19,240
To me, this is the most amazing moment in the story of decay.

1079
01:23:19,240 --> 01:23:21,440
When we began eight weeks ago,

1080
01:23:21,440 --> 01:23:28,160
we wanted to demonstrate its significance in a unique way.

1081
01:23:28,160 --> 01:23:32,960
This is probably one of the most important experiments we've set up in the box.

1082
01:23:32,960 --> 01:23:36,400
These may look like ordinary plants but they're going to show us

1083
01:23:36,400 --> 01:23:41,200
a part of the story that's absolutely crucial. These are the marigolds and radish seedlings

1084
01:23:41,200 --> 01:23:44,320
I planted back at the beginning of the project.

1085
01:23:44,320 --> 01:23:47,280
They've flourished into mature plants.

1086
01:23:47,280 --> 01:23:50,480
I've been feeding them with a special liquid compost

1087
01:23:50,480 --> 01:23:55,760
made from plants grown using chemically labelled nitrogen atoms.

1088
01:23:55,760 --> 01:23:58,840
If everything has gone according to plan,

1089
01:23:58,840 --> 01:24:02,120
we should be able to track how individual atoms of nitrogen

1090
01:24:02,120 --> 01:24:07,120
are transferred from the mustard plant to our seedlings.

1091
01:24:07,120 --> 01:24:13,280
From death to life.

1092
01:24:13,280 --> 01:24:17,840
We sent samples of our plants to Professor Malcolm Clench.

1093
01:24:17,840 --> 01:24:22,720
It's time to find out if our experiment has worked.

1094
01:24:22,720 --> 01:24:25,280
The first one is from the marigold.

1095
01:24:25,280 --> 01:24:30,160
What can you see at the moment is a photograph of the marigold leaf.

1096
01:24:30,160 --> 01:24:35,600
He's able to pinpoint exactly where the labelled nitrogen has ended up.

1097
01:24:35,600 --> 01:24:40,280
As I start to play the video clip, we'll come up with

1098
01:24:40,280 --> 01:24:44,680
an overlay that shows the nitrogen in high abundance.

1099
01:24:44,680 --> 01:24:50,960
That's really clear. Yes, very clear.

1100
01:24:50,960 --> 01:24:54,880
Each one of these dots shows where we found traces of the labelled

1101
01:24:54,880 --> 01:25:00,120
nitrogen from the mustard plant in our marigold leaf.

1102
01:25:00,120 --> 01:25:05,960
White areas show where it's concentrated.

1103
01:25:05,960 --> 01:25:13,520
How can we be 100% sure that labelled nitrogen has come from our experiment and nowhere else?

1104
01:25:13,520 --> 01:25:19,480
The form of nitrogen we're using is only 0.3% naturally abundant.

1105
01:25:19,480 --> 01:25:23,520
We can see areas of high intensity and they can only have come from

1106
01:25:23,520 --> 01:25:27,000
the mustard that was grown with the labelled nitrogen in.

1107
01:25:27,000 --> 01:25:33,680
So, that is the definitive proof of the cycle of life? Indeed.

1108
01:25:33,680 --> 01:25:37,040
I think you're going to be pleased with the radish results.

1109
01:25:37,040 --> 01:25:39,680
We can see first off a very nice radish.

1110
01:25:39,680 --> 01:25:43,040
One that you prepared earlier.

1111
01:25:43,040 --> 01:25:44,760
Wow look at that!

1112
01:25:44,760 --> 01:25:48,240
That is absolutely cast iron proof,

1113
01:25:48,240 --> 01:25:54,200
that we have transferred material, an element in this case,

1114
01:25:54,200 --> 01:25:58,480
from one plant, dead and decayed, fed to something else and it takes it up.

1115
01:25:58,480 --> 01:26:01,960
Yes, it's incontrovertible.

1116
01:26:01,960 --> 01:26:05,600
This is what I hoped we'd see when we began our project.

1117
01:26:05,600 --> 01:26:08,240
It's the fundamental principle of decay,

1118
01:26:08,240 --> 01:26:11,040
revealed in front of our eyes.

1119
01:26:11,040 --> 01:26:21,040
For me, this is as good as it gets.

1120
01:26:21,040 --> 01:26:27,960
Two months of decay have transformed the After Life box.

1121
01:26:27,960 --> 01:26:32,640
Little is left of the fresh food we began with.

1122
01:26:32,640 --> 01:26:41,120
And what remains will continue its inexorable journey back to the basic building blocks of life.

1123
01:26:41,120 --> 01:26:44,600
But, as our plant experiment so dramatically demonstrated,

1124
01:26:44,600 --> 01:26:50,080
what we have witnessed in the box is a process of renewal.

1125
01:26:50,080 --> 01:26:59,600
That we are all part of.

1126
01:26:59,600 --> 01:27:02,440
It's a real snap-shot of everyone's life.

1127
01:27:02,440 --> 01:27:07,960
To see things changing, as they do, is a fantastic experiment.

1128
01:27:07,960 --> 01:27:10,520
We'd be in a horrible mess if we didn't have decay.

1129
01:27:10,520 --> 01:27:16,280
When you see what nature can do to get rid of all the dead things in the world...

1130
01:27:16,280 --> 01:27:21,040
We need that decay to happen in order for life to go on, I guess.

1131
01:27:21,040 --> 01:27:24,560
Oh, my God! Look at that.

1132
01:27:24,560 --> 01:27:28,880
We tend to think of life as a linear process, with a beginning and end.

1133
01:27:28,880 --> 01:27:31,160
Things go from life to death.

1134
01:27:31,160 --> 01:27:35,080
I hope the box has shown this process in a new light.

1135
01:27:35,080 --> 01:27:37,600
Life is an ever repeating cycle.

1136
01:27:37,600 --> 01:27:42,200
One that's not just happening here, but everywhere on the planet.

1137
01:27:42,200 --> 01:27:48,040
The plants and animals of Earth's ecosystems rely on this continuing cycle.

1138
01:27:48,040 --> 01:27:51,000
Even the atoms that make us up are recycled.

1139
01:27:51,000 --> 01:27:54,120
They come from the food we eat, the air we breathe,

1140
01:27:54,120 --> 01:27:57,080
they're in our flesh, blood and bones.

1141
01:27:57,080 --> 01:27:59,840
They've been used millions of times before,

1142
01:27:59,840 --> 01:28:36,720
and they'll be used millions of times again.

1143
01:28:36,720 --> 01:28:39,720
Subtitles by Red Bee Media Ltd

1144
01:28:39,720 --> 99:59:59,999
E-mail subtitling@bbc.co.uk