0:00:05.000,0:00:06.240
Decay.

0:00:06.240,0:00:10.800
It happens to everything and everyone.

0:00:10.800,0:00:14.200
We try to keep it out of our everyday lives.

0:00:14.200,0:00:18.080
But decay is one of the most important forces in nature.

0:00:18.080,0:00:24.320
It underpins all life on Earth.

0:00:24.320,0:00:34.160
So what would we see, if we let it loose in our homes?

0:00:34.160,0:00:37.120
To find out, we've built a home of our own

0:00:37.120,0:00:43.000
inside this box.

0:00:43.000,0:00:46.680
We've filled it with everything you might find in a typical kitchen

0:00:46.680,0:00:54.760
and garden. And now we're going to let it all rot.

0:00:54.760,0:00:56.400
Well, here it is.

0:00:56.400,0:01:00.960
A team of engineers and scientists have spent eight months recreating

0:01:00.960,0:01:05.160
a kitchen and garden. On the inside is all the food you'd expect,

0:01:05.160,0:01:08.000
as if a family were just about to have a party.

0:01:08.000,0:01:12.080
Also on the inside are the bacteria and fungal spores that are going

0:01:12.080,0:01:17.960
to start the process of decay. I can't wait to see what happens next.

0:01:17.960,0:01:21.640
Over eight weeks, we're going to track every step

0:01:21.640,0:01:27.880
of the extraordinary process that breaks down and recycles our everyday things.

0:01:27.880,0:01:32.360
The house will be our lab, as we reveal the unexpected order behind

0:01:32.360,0:01:36.440
the chaos of decay, and will help us understand why

0:01:36.440,0:01:42.520
life itself depends on this process.

0:01:42.520,0:01:47.760
At times what we find might be disturbing and repellent...

0:01:47.760,0:01:51.840
This is probably going to be absolutely atrocious.

0:01:51.840,0:01:53.080
HE COUGHS

0:01:53.080,0:01:56.560
But there will also be moments of surprise.

0:01:56.560,0:02:01.360
The mould has just covered that entire box.

0:02:01.360,0:02:21.240
..as we uncover hidden beauty.

0:02:21.240,0:02:25.400
And I'll go beyond the box to see how decay affects our lives...

0:02:25.400,0:02:28.400
Ah! Can't do it!

0:02:28.400,0:02:30.280
..how we detect it...

0:02:30.280,0:02:33.520
Do you remember seeing the film The Blob?

0:02:33.520,0:02:35.280
..how we fight it.

0:02:35.280,0:02:39.640
It's definitely the best two-year-old sandwich I've ever had.

0:02:39.640,0:02:43.560
Something on this scale has never been attempted before,

0:02:43.560,0:02:46.880
so things might not go according to plan.

0:02:46.880,0:02:50.560
Ah! Now that's where all the flies went.

0:02:50.560,0:02:54.040
But whatever happens, it will be a fascinating journey

0:02:54.040,0:02:59.120
into the fate that awaits all living things.

0:02:59.120,0:03:01.280
To be broken down.

0:03:01.280,0:03:24.400
To be recycled. To be reborn.

0:03:24.400,0:03:26.520
It's a surprising thought,

0:03:26.520,0:03:32.440
life relies on death.

0:03:32.440,0:03:35.440
Living things, us included, can only be made

0:03:35.440,0:03:39.680
from the remains of dead things.

0:03:39.680,0:03:42.760
And that's the incredible cycle we hope to capture,

0:03:42.760,0:03:46.440
inside our After Life House.

0:03:46.440,0:03:50.960
As a biologist, I can't wait to see what new life will emerge from these

0:03:50.960,0:03:54.200
dead things by the time we're done.

0:03:54.200,0:04:02.720
This is day one. We have eight weeks to go.

0:04:02.720,0:04:07.200
This is my first chance to see inside the box.

0:04:07.200,0:04:10.440
And a party was obviously just about to happen.

0:04:10.440,0:04:13.800
Over here we've got cooked rice and chilli, there's cups of tea.

0:04:13.800,0:04:15.640
Over in the corner there's a raw fish,

0:04:15.640,0:04:18.520
that's going to get very smelly pretty fast.

0:04:18.520,0:04:22.920
Cheese and a fruit bowl here, masses of fruit flies on that, probably,

0:04:22.920,0:04:26.240
I mean, we don't know, it hasn't been tried before.

0:04:26.240,0:04:29.360
A vegetable box over here, again, it all looks fresh,

0:04:29.360,0:04:31.920
but that will, in a week or two, begin to rot down.

0:04:31.920,0:04:36.000
And look at this, a raw chicken.

0:04:36.000,0:04:37.800
Sausages, hamburgers, all this is

0:04:37.800,0:04:40.520
going to attract flies like nobody's business.

0:04:40.520,0:04:44.120
Out here in the garden you've got a whole pig on a spit.

0:04:44.120,0:04:46.760
That's going to become very smelly.

0:04:46.760,0:04:49.480
But it's not just food items out here in the garden.

0:04:49.480,0:04:51.640
We have a compost heap. We have a woodpile.

0:04:51.640,0:04:53.680
They'll rot down too.

0:04:53.680,0:04:56.440
It'll be interesting to see how, as all the things decay,

0:04:56.440,0:04:59.800
the wood and the plants and the pig, how they will interact.

0:04:59.800,0:05:03.040
Over there in the corner we have a dead rat as well.

0:05:03.040,0:05:07.480
In fact everything in here has been carefully arranged to help us

0:05:07.480,0:05:10.400
unravel the underlying patterns of decay.

0:05:10.400,0:05:15.200
We're going to keep an eye on how humid it is, and how hot it is.

0:05:15.200,0:05:20.680
It's already up to 66% RH which will make things go really quite fast.

0:05:20.680,0:05:28.200
I'm not sure if I'll be overcome by the heat, the stench or the flies.

0:05:28.200,0:05:31.840
Insects are my own speciality.

0:05:31.840,0:05:36.400
Together with moulds and bacteria, they are key agents of decay,

0:05:36.400,0:05:39.760
things that will break all this down.

0:05:39.760,0:05:43.480
To make sure they are all present in our house from the start,

0:05:43.480,0:05:47.080
we're introducing a selection of common species.

0:05:47.080,0:05:49.720
Look at that, straight underneath!

0:05:49.720,0:05:52.760
These guys, blow flies, are going to be the ones

0:05:52.760,0:05:54.680
to watch in the early stages.

0:05:54.680,0:05:56.240
And there they go.

0:05:56.240,0:05:58.920
Well, that's it. We're up and running

0:05:58.920,0:06:03.840
and it's time to leave all this to the agents of decay.

0:06:03.840,0:06:07.000
Now, for nearly two months,

0:06:07.000,0:06:11.480
we're going to track every stage in the process of decay.

0:06:11.480,0:06:14.120
And we're not the only ones following events.

0:06:14.120,0:06:18.160
The box and its contents are on display to the public within

0:06:18.160,0:06:21.000
Edinburgh zoo, to help explore our reactions to this

0:06:21.000,0:06:23.240
little understood process.

0:06:23.240,0:06:26.080
Oh my God, I've never seen anything like it

0:06:26.080,0:06:27.520
That's a real pig.

0:06:27.520,0:06:29.520
Ew, that's gross!

0:06:29.520,0:06:31.400
Oh, there's a mouse.

0:06:31.400,0:06:35.560
That's disgusting, eugh!

0:06:35.560,0:06:37.640
Look at that fish.

0:06:37.640,0:06:41.720
Can we go out now cos it's going to make us feel sick?

0:06:41.720,0:06:43.280
THEY LAUGH

0:06:43.280,0:06:55.400
I agree.

0:06:55.400,0:06:58.920
For the first 24 hours of our project,

0:06:58.920,0:07:02.440
visible signs of decay are subtle.

0:07:02.440,0:07:07.160
But the agents of decay are already battling it out to decompose

0:07:07.160,0:07:10.800
the food and get to the nutrients locked inside.

0:07:10.800,0:07:21.280
I want to investigate who's got the advantage in this opening stage

0:07:21.280,0:07:25.440
Well, it's the second day and it's really warm in here, it's 25 degrees.

0:07:25.440,0:07:28.800
That's like a warm summer day, so some things are drying out

0:07:28.800,0:07:31.520
the chilli con carne is already growing a layer of mould,

0:07:31.520,0:07:35.720
and that shows that there are fungal spores drifting around in the atmosphere

0:07:35.720,0:07:38.400
all the time and settling on food.

0:07:38.400,0:07:43.480
Over here, the sandwiches which originally filled the box,

0:07:43.480,0:07:46.960
up to the top, have sagged down to about half their height.

0:07:46.960,0:07:54.280
But what's really interesting me is what's happening over here.

0:07:54.280,0:07:58.520
The most obvious change so far has been on the surface of our chicken.

0:07:58.520,0:08:02.080
Our time lapse cameras show these blotches appearing on its skin,

0:08:02.080,0:08:07.240
over the course the past day.

0:08:07.240,0:08:09.680
To find out what's producing them,

0:08:09.680,0:08:19.240
I've asked Dr Clare Taylor, a microbiologist, to join me.

0:08:19.240,0:08:23.080
Well, Clare, that chicken is beginning to look a bit discoloured.

0:08:23.080,0:08:27.600
It smells a bit as well. There's beginning to be a slight whiff. What have you got on this?

0:08:27.600,0:08:30.000
I tell you what I've got a UV light

0:08:30.000,0:08:33.040
so we can take a look more closely at the surface.

0:08:33.040,0:08:35.600
Now, ultraviolet I use for other things,

0:08:35.600,0:08:38.360
but I'm interested to see what happens here.

0:08:38.360,0:08:41.160
Now you can't see it. No, can't see anything.

0:08:41.160,0:08:43.000
Take a look at that!

0:08:43.000,0:08:47.480
It's glowing! So all these areas are glowing sort of blue.

0:08:47.480,0:08:53.760
Exactly, so where you can see those glowing bits, that's bacteria.

0:08:53.760,0:09:03.120
Any particular kind? That's likely to be pseudomonas.

0:09:03.120,0:09:08.400
Pseudomonas is a common type of food spoilage bacteria.

0:09:08.400,0:09:16.920
Our microscope shows a whole colony glowing under the UV light.

0:09:16.920,0:09:20.360
There could be as many as a billion individual bacterial cells

0:09:20.360,0:09:25.360
in this sample alone.

0:09:25.360,0:09:27.400
In sheer number terms,

0:09:27.400,0:09:31.760
bacteria are the most common agents of decay on the planet.

0:09:31.760,0:09:35.400
And, on dead animals, they're the first to attack.

0:09:35.400,0:09:39.520
Because they're already on the scene.

0:09:39.520,0:09:43.720
All creatures carry bacteria while they're alive.

0:09:43.720,0:09:47.360
These pseudomonas bacteria were on our chicken before it was killed,

0:09:47.360,0:09:49.440
feeding on its skin secretions.

0:09:49.440,0:09:59.840
Now it's dead, they've quickly switched to decomposing its flesh.

0:09:59.840,0:10:02.400
With ample food, and enough moisture,

0:10:02.400,0:10:04.760
they've multiplied rapidly.

0:10:04.760,0:10:09.680
As colonies of bacteria like this expand, something surprising happens.

0:10:09.680,0:10:14.000
The bacteria start to coordinate their actions.

0:10:14.000,0:10:16.840
Working together to benefit the colony.

0:10:16.840,0:10:21.840
The bacteria send signals to each other to direct what they do.

0:10:21.840,0:10:27.320
So the bacteria are talking to each other, telling each other where they need to go.

0:10:27.320,0:10:31.600
These E-coli bacteria have been genetically modified

0:10:31.600,0:10:35.160
to allow us to see this in action.

0:10:35.160,0:10:43.080
When the colony reaches a critical size all the bacteria start flashing in unison.

0:10:43.080,0:10:47.240
Bacteria are constantly exchanging chemicals that allow them

0:10:47.240,0:10:53.400
to sense their own numbers and those of rival colonies.

0:10:53.400,0:10:56.400
They can even detect when they have the numbers

0:10:56.400,0:11:05.120
to overwhelm a competitor.

0:11:05.120,0:11:11.080
Back on our chicken, these tactics have allowed food spoilage bacteria to gain the upper hand.

0:11:11.080,0:11:15.160
But their actions are setting off a chain of events

0:11:15.160,0:11:20.160
that will attract a whole new set of decomposers.

0:11:20.160,0:11:24.280
As they break down the cells of the chicken to feast on the protein inside,

0:11:24.280,0:11:32.000
the bacteria are releasing strong smelling gases.

0:11:32.000,0:11:37.240
blow flies can pick up the smell of decomposing flesh within minutes of an animal's death.

0:11:37.240,0:11:45.560
So it's likely they've already laid eggs on the chicken and other meat throughout the box.

0:11:45.560,0:11:52.520
We'll find out if we start seeing maggots in the next few days.

0:11:52.520,0:11:55.800
These gases send a signal to us too.

0:11:55.800,0:12:01.680
It's our most important clue that food spoilage bacteria have been at work.

0:12:01.680,0:12:06.920
Right, let's see what folks make of these chicken drumsticks.

0:12:06.920,0:12:13.000
I want to see how sensitive we are to even the smallest signs of decay.

0:12:13.000,0:12:18.120
Hi, guys, would you care to have a smell of this?

0:12:18.120,0:12:20.640
Erggh! I can smell it from here. Urgh!

0:12:20.640,0:12:23.760
THEY LAUGH

0:12:23.760,0:12:29.680
It's horrible. Stop it. It's not nice.

0:12:29.680,0:12:32.920
So, if you found that in your house, what would you do?

0:12:32.920,0:12:36.160
I wouldn't eat it. I think I'd put it in the bin.

0:12:36.160,0:12:39.040
I'd throw it away immediately. Throw it out.

0:12:39.040,0:12:43.920
It's disgusting.

0:12:43.920,0:12:50.000
We fight a daily battle to keep this kind of decay out of our kitchens.

0:12:50.000,0:12:55.000
Looking round the box already makes me think about what a challenge this really is.

0:12:55.000,0:12:57.960
Decay is a relentless opponent.

0:12:57.960,0:13:04.200
So, I'm interested in exploring what we've learnt about delaying its effects.

0:13:04.200,0:13:07.440
And in America, there's a team that's taking on

0:13:07.440,0:13:11.080
the ultimate food preservation challenge.

0:13:11.080,0:13:15.880
GUNSHOTS

0:13:15.880,0:13:18.520
Keep your head down or it's going to get shot off you!

0:13:18.520,0:13:21.720
GUNSHOTS

0:13:21.720,0:13:25.680
Now, this is not necessarily the first place I'd think of

0:13:25.680,0:13:29.400
when it comes to the latest advances in food science,

0:13:29.400,0:13:35.120
but the US army is right on the frontline in the war against decay.

0:13:35.120,0:13:39.200
Feeding an army in the field has always presented a challenge.

0:13:39.200,0:13:42.400
Soldiers need food that is quick to prepare,

0:13:42.400,0:13:44.840
light to carry and long lasting.

0:13:44.840,0:13:48.760
Traditionally, the US military uses vacuum packed food

0:13:48.760,0:13:53.280
called MREs, meals ready to eat.

0:13:53.280,0:13:57.640
Special packaging stops moisture and oxygen getting in

0:13:57.640,0:14:04.320
so bacteria can't grow. MREs have a shelf life of three years.

0:14:04.320,0:14:06.160
There's a problem though.

0:14:06.160,0:14:12.160
MREs are not exactly popular with the people who have to eat them.

0:14:12.160,0:14:16.320
Hands-down-worst MRE made is the veggie omelette.

0:14:16.320,0:14:19.800
It's like eating a... I don't know.

0:14:19.800,0:14:23.840
Wet, soggy cardboard is the best way I think you can describe it.

0:14:23.840,0:14:28.400
If I had to eat an MRE every day, that would basically suck.

0:14:28.400,0:14:30.720
GUNFIRE

0:14:30.720,0:14:34.360
So, when the army went looking for ways to spruce up the menu,

0:14:34.360,0:14:37.840
it wanted something more appealing.

0:14:37.840,0:14:40.480
Something that was quick and easy to eat.

0:14:40.480,0:14:45.360
And could deliver the huge amounts of energy that soldiers require.

0:14:45.360,0:14:50.360
The solution was a surprise.

0:14:50.360,0:14:54.360
A sandwich. But not just any sandwich.

0:14:54.360,0:14:59.520
A sandwich that remains fresh and tasty in the field for up to three years,

0:14:59.520,0:15:03.440
without refrigeration, freeze drying or the need to add water.

0:15:03.440,0:15:05.880
That is extreme preservation.

0:15:05.880,0:15:10.000
So how did they do it?

0:15:10.000,0:15:15.640
Food scientist Michelle Richardson was part of the team that developed the sandwich.

0:15:15.640,0:15:22.920
Her first challenge was to control the moisture you'd find in a typical sandwich.

0:15:22.920,0:15:26.840
HE LAUGHS

0:15:26.840,0:15:29.520
These sandwiches do not look very happy.

0:15:29.520,0:15:31.680
They really don't.

0:15:31.680,0:15:38.080
That's a ham and cheese wedge that's been in the car for three days.

0:15:38.080,0:15:41.720
If we open it up, we'll just have a look at this thing

0:15:41.720,0:15:47.280
cos if you had that in your backpack for three days...

0:15:47.280,0:15:51.880
That was just a normal shop-bought sandwich.

0:15:51.880,0:15:56.480
Urgh! It's soggy. It's really soggy. Look at that.

0:15:56.480,0:16:00.160
You wouldn't really want to eat that in the field?

0:16:00.160,0:16:03.960
You really wouldn't want to eat it for two reasons. It wouldn't taste good,

0:16:03.960,0:16:07.080
because the texture is not what you typically get. And also

0:16:07.080,0:16:12.040
because of that moisture excess you may have bacteria growing in it.

0:16:12.040,0:16:16.760
If you can control the moisture, you can slow down the process of decay.

0:16:16.760,0:16:20.600
Without water, bacteria cannot grow.

0:16:20.600,0:16:24.920
That's why drying is the classic way to stop food decaying.

0:16:24.920,0:16:29.200
But a sandwich without water would be inedible.

0:16:29.200,0:16:34.200
So Michelle has taken inspiration from another classic preservation technique.

0:16:34.200,0:16:37.520
Well, this right here is strawberry jam

0:16:37.520,0:16:41.360
and as you can see in here, it's very firm. Yeah.

0:16:41.360,0:16:45.000
It's made from strawberries. Most fruits and vegetables contain

0:16:45.000,0:16:50.680
a lot of water, probably 95% water, but by adding different ingredients,

0:16:50.680,0:16:54.560
what that does is it holds the water in very tightly.

0:16:54.560,0:16:58.400
Right, so it's locked away in there? Yes.

0:16:58.400,0:17:03.480
The sugar added to jam acts as what's called a humectant.

0:17:03.480,0:17:06.920
It traps the water from the fruit inside the jam.

0:17:06.920,0:17:10.000
That's why the jam is moist enough to spread,

0:17:10.000,0:17:12.520
but doesn't make the bread soggy.

0:17:12.520,0:17:15.080
Crucially for the battle against decay,

0:17:15.080,0:17:18.800
the water is also now locked away from bacteria.

0:17:18.800,0:17:22.800
The army's sandwiches deploy a whole range of ingredients

0:17:22.800,0:17:25.840
that have these water-retaining properties.

0:17:25.840,0:17:29.280
Honey, sugar and salt have all been enlisted.

0:17:29.280,0:17:34.160
Bacteria need water to thrive. Most also need oxygen too.

0:17:34.160,0:17:38.400
Michelle has found a way to cut off supplies of that as well.

0:17:38.400,0:17:42.920
Now, when I opened the pack I found this inside

0:17:42.920,0:17:45.720
and I assume that's not edible. No, it's not.

0:17:45.720,0:17:47.560
What is this for?

0:17:47.560,0:17:50.000
This is an oxygen scavenger.

0:17:50.000,0:17:54.120
Basically what's contained in here are little iron shavings.

0:17:54.120,0:17:57.160
Oh, right. Iron filings.

0:17:57.160,0:18:02.040
If there is any oxygen or moisture still inside the packaging,

0:18:02.040,0:18:06.600
they'll react with the iron filings, and become trapped in a layer of rust.

0:18:06.600,0:18:11.200
This will prevent yeast and mould from growing as well as bacteria but

0:18:11.200,0:18:15.880
it will also prevent chemical reactions that require oxygen from taking place.

0:18:15.880,0:18:19.360
This is one seriously hi-tech sandwich!

0:18:19.360,0:18:21.440
Yeah, it is.

0:18:21.440,0:18:24.920
These simple but ingenious solutions have combined to make

0:18:24.920,0:18:29.040
a food that is highly resistant to decay.

0:18:29.040,0:18:32.480
But the ultimate test is whether anyone wants to eat it.

0:18:32.480,0:18:36.680
It's definitely the best two-year-old sandwich I've had. Better than a lot of new ones too.

0:18:36.680,0:18:38.800
I'm a big fan. I like the bread.

0:18:38.800,0:18:41.960
The bread just makes it, it's definitely great,

0:18:41.960,0:18:44.880
especially for two-years-old.

0:18:44.880,0:18:48.720
These sandwiches don't stay fresh for ever.

0:18:48.720,0:18:53.960
But they do show that, if you can reduce the moisture and oxygen that

0:18:53.960,0:19:08.000
bacteria thrive on, you can hold off decay for a very long time.

0:19:08.000,0:19:10.640
Back at the house, water and oxygen

0:19:10.640,0:19:19.000
certainly aren't in short supply, so bacteria are thriving.

0:19:19.000,0:19:22.640
And over the last eight days of decay we've started to see

0:19:22.640,0:19:25.480
the first maggots appearing in our pig.

0:19:25.480,0:19:30.520
I'd expect their numbers to rocket in a week or so.

0:19:30.520,0:19:33.800
Other insects have been busy around our dead rat.

0:19:33.800,0:19:36.640
These are sexton beetles.

0:19:36.640,0:19:39.880
In the wild they'll bury the carcasses of small mammals

0:19:39.880,0:19:42.440
to protect them from rival insects.

0:19:42.440,0:19:46.560
Their own larvae then break down the flesh.

0:19:46.560,0:19:50.200
But in our box, things are not quite going to plan.

0:19:50.200,0:19:55.000
Despite all the activity, our rat remains unburied.

0:19:55.000,0:20:01.680
So I'll try laying out a new rat and see if they prefer it.

0:20:01.680,0:20:05.320
But the most dramatic change has been in our kitchen.

0:20:05.320,0:20:23.360
It's been overrun by the next agent of decay, mould.

0:20:23.360,0:20:25.720
Moulds are masters of decay.

0:20:25.720,0:20:29.040
They're a form of fungi, the most versatile

0:20:29.040,0:20:32.080
and important decomposers on the planet.

0:20:32.080,0:20:35.760
Fungi can rot almost anything.

0:20:35.760,0:20:44.480
In our box, moulds are attacking our fruit and vegetables.

0:20:44.480,0:20:51.800
And they're also on our meat, battling with the bacteria for dominance.

0:20:51.800,0:20:56.920
It'll be fascinating to see how that one plays out.

0:20:56.920,0:21:02.880
The typical house will contain about 1,000 different species of mould.

0:21:02.880,0:21:09.400
They can start to grow the moment their spores land on a suitable food source.

0:21:09.400,0:21:19.400
I want to see which ones are at work in our box.

0:21:19.400,0:21:24.720
Well, in the kitchen there is mould absolutely everywhere.

0:21:24.720,0:21:27.360
The vegetables in the tray are covered in fungus.

0:21:27.360,0:21:30.720
There's at least three sorts of fungus I can see.

0:21:30.720,0:21:35.520
The hamburgers, sausages, even the hamburgers that are wrapped up are now covered in mould.

0:21:35.520,0:21:39.480
That's looking quite... woah! That might blow at any time.

0:21:39.480,0:21:43.400
The soft fruit in particular have been attacked.

0:21:43.400,0:21:47.200
The peaches have gone and there's mould everywhere.

0:21:47.200,0:21:50.920
The melon's just incredible, it's really been hammered.

0:21:50.920,0:21:52.960
It's just covered, all over there.

0:21:52.960,0:21:58.840
I'm a little bit nervous about taking this lid off.

0:21:58.840,0:22:03.440
This is going to be... Urgh!

0:22:03.440,0:22:06.760
Urgh! That's an incredible smell.

0:22:06.760,0:22:13.880
It's almost sweet.

0:22:13.880,0:22:19.080
It's an incredible sort of yeasty, smell.

0:22:19.080,0:22:24.640
The mould has just covered the entire box.

0:22:24.640,0:22:34.360
That's actually quite beautiful in a bizarre way.

0:22:34.360,0:22:40.920
It's like just furry growths everywhere.

0:22:40.920,0:22:51.400
That's amazing! That's only a week.

0:22:51.400,0:23:06.280
In close up, the unexpected beauty of mould is even clearer.

0:23:06.280,0:23:09.520
These networks of filaments we see on the surface of our bread

0:23:09.520,0:23:26.800
are the mould's fruiting body.

0:23:26.800,0:23:33.880
At the ends of the filaments are spore heads, each packed with individual spores,

0:23:33.880,0:23:41.760
all waiting to be released to grow into new colonies.

0:23:41.760,0:23:48.080
There are 500 spores in every cubic metre of air in the average home.

0:23:48.080,0:24:03.600
So there's plenty of competition for the chance to attack our bread.

0:24:03.600,0:24:08.560
I've asked Dr Patrick Hickey, our fungi expert to investigate

0:24:08.560,0:24:12.200
which moulds have managed to gain control.

0:24:12.200,0:24:16.120
Now, Patrick, it's only week one and we've got incredible fungal growth

0:24:16.120,0:24:18.760
all over the kitchen. Particularly on the bread.

0:24:18.760,0:24:22.440
Well, the bread is a perfect food source for the fungi.

0:24:22.440,0:24:26.720
The spores probably landed on the bread when it was being prepared and

0:24:26.720,0:24:31.400
they've grown quickly into the bread and they're taking up the nutrients.

0:24:31.400,0:24:35.120
What we're actually seeing is two moulds meeting.

0:24:35.120,0:24:38.080
In the background, we've got a dark green-grey mould

0:24:38.080,0:24:41.800
that's penicilium. These bright dots in the front

0:24:41.800,0:24:45.080
are the sporilating structures of aspergillus competing.

0:24:45.080,0:24:47.960
So they're kind of trying to out compete each other for the bread,

0:24:47.960,0:24:51.520
for the food resource.

0:24:51.520,0:24:57.800
Each mould is trying to seize territory by out-growing its competitors.

0:24:57.800,0:25:01.440
But they are also using powerful chemical weapons to try to

0:25:01.440,0:25:07.600
kill off other moulds and rival decomposers, like bacteria.

0:25:07.600,0:25:11.360
In the case of penicillium, the toxin it produces to win

0:25:11.360,0:25:16.800
the battle for decay, has turned out to be highly beneficial to us.

0:25:16.800,0:25:20.720
We call it penicillin.

0:25:20.720,0:25:24.600
But not all moulds are good for us.

0:25:24.600,0:25:28.040
Now, I have to admit, I sometimes cut the mould off bits of bread

0:25:28.040,0:25:31.520
and toast it. Is that really harmful?

0:25:31.520,0:25:34.960
Well, what you're scraping off is really the tip of the iceberg.

0:25:34.960,0:25:38.240
The fungus grows deep into the bread and it also depends on what kind of

0:25:38.240,0:25:41.440
mould is growing into the bread. You have various different moulds,

0:25:41.440,0:25:45.720
some of which are harmless. Others like aspergillus produce deadly mycotoxins,

0:25:45.720,0:25:49.960
these are toxic chemicals, which can rot your liver,

0:25:49.960,0:25:51.600
they can give you cancer.

0:25:51.600,0:25:54.320
So, what you're saying is, I shouldn't really do that.

0:25:54.320,0:25:56.920
It's dangerous I should just throw it in the bin.

0:25:56.920,0:26:00.800
Absolutely, the fungus penetrates quite deep into the bread you're

0:26:00.800,0:26:06.680
not going to get rid of the toxins in the mould just by scraping it off.

0:26:06.680,0:26:10.480
Most of us might prefer not to have to cope with mouldy bread

0:26:10.480,0:26:18.720
in the first place. Moulds and other types of fungi are things that ruin our food, and may cause us harm.

0:26:18.720,0:26:25.480
But fungi are vital to life on this planet.

0:26:25.480,0:26:28.360
They're amongst the Earth's oldest life forms.

0:26:28.360,0:26:35.280
On land, they pre-date plants by at least 300 million years.

0:26:35.280,0:26:49.520
And they rise to almost any challenge.

0:26:49.520,0:26:53.200
There is a fungus growing inside the brain of this ant.

0:26:53.200,0:26:56.600
It's producing chemicals that control the ant's behaviour,

0:26:56.600,0:27:00.280
forcing it to climb to the top of a plant.

0:27:00.280,0:27:03.320
Then the killer fungus bursts out of the ant's head,

0:27:03.320,0:27:12.240
allowing its spores to spread.

0:27:12.240,0:27:16.920
Fungi have found ways to work on a microscopic level too.

0:27:16.920,0:27:20.720
This one is lying in wait for tiny roundworms.

0:27:20.720,0:27:25.640
At the right moment, it strangles them in a vice-like grip,

0:27:25.640,0:27:33.800
then feeds on their flesh.

0:27:33.800,0:27:37.640
But it's fungi's unrivalled ability to decay organic matter that

0:27:37.640,0:27:41.280
makes them so important to us.

0:27:41.280,0:27:43.840
A world where fungi couldn't decay things

0:27:43.840,0:27:50.120
would be a very different place.

0:27:50.120,0:27:54.200
To see just how different, we have to go back in Earth's history.

0:27:54.200,0:27:57.320
To a period when a new form of organic matter emerged.

0:27:57.320,0:28:04.760
One that challenged fungi's powers of decay.

0:28:04.760,0:28:11.200
The fate of life on Earth, hung in the balance.

0:28:11.200,0:28:14.640
Rewind 300 million years to the Carboniferous Period.

0:28:14.640,0:28:17.680
A time when plants, struggling to compete for sunlight,

0:28:17.680,0:28:24.160
had evolved into trees.

0:28:24.160,0:28:27.760
That new organic material was wood.

0:28:27.760,0:28:32.360
It gave plants the strength to grow taller.

0:28:32.360,0:28:36.520
But this evolutionary leap left fungi behind.

0:28:36.520,0:28:40.040
They weren't able to decompose wood.

0:28:40.040,0:28:44.040
The delicate mechanism of decay had been upset.

0:28:44.040,0:28:50.360
Without decay the trees grew, died and lay where they fell.

0:28:50.360,0:28:56.200
The effect on the planet's climate was spectacular.

0:28:56.200,0:29:00.160
Professor Lynne Boddy is an expert in the history of fungi.

0:29:00.160,0:29:03.360
Trees absorb carbon dioxide from the air.

0:29:03.360,0:29:05.600
They absorb nutrients from the soil.

0:29:05.600,0:29:09.040
And then the carbon is locked up within the trees,

0:29:09.040,0:29:14.520
so when they fall and die, the carbon is still locked up inside them.

0:29:14.520,0:29:22.040
So huge changes simply because trees can't decay? Absolutely.

0:29:22.040,0:29:26.320
With fungi unable to break down wood, over time, more and more

0:29:26.320,0:29:30.480
carbon was removed from the air and locked up in dead trees.

0:29:30.480,0:29:37.520
The Earth's atmosphere began to change.

0:29:37.520,0:29:41.600
Oxygen levels shot up from 20% to 30%,

0:29:41.600,0:29:44.400
as carbon dioxide levels dropped.

0:29:44.400,0:29:51.480
This allowed insects to grow to gigantic proportions.

0:29:51.480,0:29:57.480
Spiders were as wide as a human head.

0:29:57.480,0:30:03.400
Dragonflies were ten times larger than they are today.

0:30:03.400,0:30:09.400
If the atmosphere had stayed like this, life on our planet would have looked very different.

0:30:09.400,0:30:14.000
The stumbling block for fungi was a molecule in trees called lignin.

0:30:14.000,0:30:16.680
It's what makes wood tough.

0:30:16.680,0:30:21.760
It took 50 million years for fungi to evolve a way to overcome it.

0:30:21.760,0:30:24.800
And Lynne is able to show me the modern descendents of

0:30:24.800,0:30:27.520
the fungi that solved the problem.

0:30:27.520,0:30:30.160
If you pick up that log we could have a better look.

0:30:30.160,0:30:32.240
No, the one underneath. That one, there.

0:30:32.240,0:30:34.560
The first thing I see about it, it's not heavy at all.

0:30:34.560,0:30:37.200
It's light as a feather. It hardly weighs anything.

0:30:37.200,0:30:40.440
Yes, it's been rotted and you can see that it's really white.

0:30:40.440,0:30:42.080
Why is it white?

0:30:42.080,0:30:46.440
It's white because the fungi have broken down the lignin in the wood.

0:30:46.440,0:30:48.880
Which was brown. Yes.

0:30:48.880,0:30:52.000
It's pretty easy to see what effect the fungi have had on the wood,

0:30:52.000,0:30:54.280
but can we actually see the fungi themselves?

0:30:54.280,0:30:56.480
We can't actually see them rotting the wood,

0:30:56.480,0:30:58.920
not with our naked eye because they're microscopic.

0:30:58.920,0:31:04.640
To show me the fungi in action, Lynne has grown this sample in soil.

0:31:04.640,0:31:08.200
That's pretty. What we've got here is a little bit of beech wood

0:31:08.200,0:31:11.280
that's got the fungus growing in it, and then you put the wood

0:31:11.280,0:31:14.400
on top of this soil, and the fungus has grown out of the wood,

0:31:14.400,0:31:21.080
looking for other pieces of wood that they can colonise and get food from.

0:31:21.080,0:31:29.320
The fungus sends out a network of tiny threads called hyphae.

0:31:29.320,0:31:34.080
They've aggregated together so we can actually see them with the naked eye.

0:31:34.080,0:31:39.160
And they're heading off to find other bits to eat? That's right.

0:31:39.160,0:31:43.240
The hyphae release powerful enzymes into the wood.

0:31:43.240,0:31:46.520
They are able to break down the lignin into nutrients

0:31:46.520,0:31:49.920
the fungi can then absorb.

0:31:49.920,0:31:54.800
This releases carbon from the wood, back into the air.

0:31:54.800,0:32:02.520
It was the evolution of these enzymes that allowed fungi to rebalance the Earth's atmosphere.

0:32:02.520,0:32:06.280
If those fungi weren't here today then decay would come to a grinding

0:32:06.280,0:32:09.800
halt and we would be in a similar position to what we were

0:32:09.800,0:32:15.680
in the Carboniferous period.

0:32:15.680,0:32:20.200
By evolving the ability to unlock the carbon in dead wood,

0:32:20.200,0:32:23.240
fungi saved the world.

0:32:23.240,0:32:27.520
We still rely on this delicate balance between all living things,

0:32:27.520,0:32:48.200
and the agents that can decompose them.

0:32:48.200,0:32:53.920
At the After Life house another eight days have gone by.

0:32:53.920,0:32:58.880
Just after my last visit we captured something extraordinary.

0:32:58.880,0:33:01.240
The new rat that I left out in the garden has been

0:33:01.240,0:33:06.880
buried by the sexton beetles, as I hoped it would be.

0:33:06.880,0:33:10.800
Despite their size, it took the two of them less than 12 hours to

0:33:10.800,0:33:18.480
get the whole carcass underground, and away from rival decomposers.

0:33:18.480,0:33:20.720
The female will lay her eggs in the rat

0:33:20.720,0:33:25.880
so her young will have food to eat when they hatch.

0:33:25.880,0:33:28.760
In about a month's time, we'll dig up the rat

0:33:28.760,0:33:38.560
and see what the beetle larvae have done.

0:33:38.560,0:33:40.200
Elsewhere in the box,

0:33:40.200,0:33:46.480
bacteria and mould are still battling it out on the meat.

0:33:46.480,0:33:50.400
The bacteria inside this sealed pack of burgers are hard at work,

0:33:50.400,0:33:53.400
producing this build up of gas.

0:33:53.400,0:34:02.280
I'm not looking forward to smelling that.

0:34:02.280,0:34:05.800
Where meat was left exposed to the air, like these sausages,

0:34:05.800,0:34:08.760
mould has been able to move in,

0:34:08.760,0:34:13.440
suggesting that the bacteria have been overwhelmed.

0:34:13.440,0:34:16.560
But just over two weeks in to our project,

0:34:16.560,0:34:21.840
and an army of even more voracious decomposers is taking control.

0:34:21.840,0:34:27.040
The maggot population has exploded.

0:34:27.040,0:34:30.600
Our pig is literally seething with them.

0:34:30.600,0:34:38.120
Maggots are some of decay's most effective operators.

0:34:38.120,0:34:41.160
The question is, how long will it take them

0:34:41.160,0:34:46.440
to munch their way through the contents of our house?

0:34:46.440,0:34:51.960
I haven't even got into the box and already I can see escaping maggots.

0:34:51.960,0:34:55.360
So, even though we try really carefully to keep

0:34:55.360,0:34:58.800
all the insects on the inside, some have escaped.

0:34:58.800,0:35:07.120
They can squeeze through the tiniest gap

0:35:07.120,0:35:10.880
The time-lapse cameras have shown a real fever pitch,

0:35:10.880,0:35:13.640
especially on the chicken and the fish.

0:35:13.640,0:35:17.960
I just want to show you the fish though. It's completely eaten out.

0:35:17.960,0:35:24.640
If I just... look at that, look at the inside of that.

0:35:24.640,0:35:26.440
Pwahh.

0:35:26.440,0:35:29.480
It's just a writhing mass of maggots

0:35:29.480,0:35:33.560
and the smell of ammonia is overpowering.

0:35:33.560,0:35:35.160
They've eaten everything.

0:35:35.160,0:35:40.480
All that remains is the dry skin on the outside and the bones.

0:35:40.480,0:35:43.960
These are the most efficient recyclers on the planet.

0:35:43.960,0:35:53.120
I think they are just amazing insects.

0:35:53.120,0:35:59.760
It's 15 days since I released about 100 blow flies into the box.

0:35:59.760,0:36:04.280
As soon as they mate, female flies look for a place to lay eggs.

0:36:04.280,0:36:08.560
Up to 300 at a time.

0:36:08.560,0:36:13.160
The gases given off in the very early stages of decomposition,

0:36:13.160,0:36:18.120
will have attracted them to the dead meat and fish.

0:36:18.120,0:36:20.840
They're the ideal food source for the maggots,

0:36:20.840,0:36:25.840
when they start to emerge, around 24 hours later.

0:36:25.840,0:36:29.720
Now they've hatched, these maggots have only one aim.

0:36:29.720,0:36:35.080
To eat. Non-stop.

0:36:35.080,0:36:38.280
Now, I've got the thermal image camera here

0:36:38.280,0:36:40.800
and this is actually quite a useful item.

0:36:40.800,0:36:45.480
It can show heat that's produced by organisms.

0:36:45.480,0:36:51.200
The fly larvae, when they feed en masse, do generate quite a bit of heat.

0:36:51.200,0:36:53.840
Now, I'm just shining it on the chicken drumsticks,

0:36:53.840,0:36:57.440
which are cold, they're not hot at all.

0:36:57.440,0:37:01.320
The chicken's not very hot. But wooo! Look at that!

0:37:01.320,0:37:04.040
The burgers are glowing like a beacon.

0:37:04.040,0:37:07.920
Now, that means that there are lots of fly larvae in there and they

0:37:07.920,0:37:19.600
are generating masses of heat, which actually makes them grow faster.

0:37:19.600,0:37:23.680
Our time lapse camera shows how maggots feed as a pack,

0:37:23.680,0:37:29.280
so they can share not just heat, but digestive enzymes too.

0:37:29.280,0:37:32.680
They carefully coordinate their movements.

0:37:32.680,0:37:37.240
As the meat in one burger runs out, the maggots move together, almost

0:37:37.240,0:37:46.480
as a single unit, over to the fresh supplies of the second burger.

0:37:46.480,0:37:49.720
Maggots are a perfectly adapted mechanism for turning

0:37:49.720,0:37:53.560
dead meat into flies.

0:37:53.560,0:37:59.000
At the head end, you've got these amazing hooks,

0:37:59.000,0:38:03.880
which are basically a pair of sharp, curved hooks

0:38:03.880,0:38:16.120
with which the maggot rasps its way through food.

0:38:16.120,0:38:19.440
As you move further down, you see it doesn't have legs.

0:38:19.440,0:38:22.720
There isn't any obvious head, thorax and abdomen.

0:38:22.720,0:38:27.640
It has got these bands of raised bumps,

0:38:27.640,0:38:30.880
they're like spikes for a grub.

0:38:30.880,0:38:34.520
They're bands of raised welts,

0:38:34.520,0:38:39.280
which help the maggot move through its food so it's essentially

0:38:39.280,0:38:41.600
in a pile of slop.

0:38:41.600,0:38:47.800
These welts enable it to undulate through the food.

0:38:47.800,0:38:51.560
Otherwise, it's very hard to move.

0:38:51.560,0:38:58.640
At the other end, let's go down to the back end.

0:38:58.640,0:39:03.800
These structures here are the breathing holes of the fly.

0:39:03.800,0:39:12.080
These are the spiracles through which it gets its air.

0:39:12.080,0:39:20.200
They're on the rear end. It has a pair of them, quite big.

0:39:20.200,0:39:25.520
So it's able to insert its head into wet food and still feed

0:39:25.520,0:39:29.680
while its rear end is in the air.

0:39:29.680,0:39:38.320
All in all, it is just about the perfect eating machine.

0:39:38.320,0:39:41.520
To me, maggots are the clearest example we've seen

0:39:41.520,0:39:45.760
so far of the fundamental principle behind decay.

0:39:45.760,0:39:48.800
Recycling the nutrients from dead animals,

0:39:48.800,0:39:50.920
and turning it into new life.

0:39:50.920,0:39:54.960
But, of course, for many of us they represent everything

0:39:54.960,0:39:58.240
that's disgusting about decay.

0:39:58.240,0:40:03.800
I'm intrigued as to what these strong feelings of revulsion are, so I've devised a little test.

0:40:03.800,0:40:07.240
I'm going to put a £5 note inside a plastic bag

0:40:07.240,0:40:13.400
and I'm going to hide it inside a tub, inside which I'm going to put

0:40:13.400,0:40:19.960
loads of maggots. We're going to end up with a pretty simple test,

0:40:19.960,0:40:22.280
which is essentially this,

0:40:22.280,0:40:26.080
a large box full of writhing maggots and a £5 note.

0:40:26.080,0:40:30.280
Now, I reckon only one person in ten will be able to

0:40:30.280,0:40:34.360
overcome their deep seated revulsion for maggots

0:40:34.360,0:40:44.720
and put their hand in to retrieve the fiver. Well, we'll find out.

0:40:44.720,0:40:50.400
Who would like to put their hand in a bucket of maggots for a fiver?

0:40:50.400,0:40:54.280
Oh, you would, would you?

0:40:54.280,0:40:58.120
It looks like my bin at home. THEY LAUGH

0:40:58.120,0:41:00.920
I can't do it! Five pound note.

0:41:00.920,0:41:02.920
No, I can't do it.

0:41:02.920,0:41:06.920
Maggots. Ew! SHE LAUGHS NERVOUSLY

0:41:06.920,0:41:09.760
Oh. It's a little gross, they're writhing on my fingers.

0:41:09.760,0:41:13.800
Oh, no! Oh! Oh! No, no.

0:41:13.800,0:41:17.240
No, I can't do it. Five pound note.

0:41:17.240,0:41:19.680
SHE SCREAMS

0:41:19.680,0:41:22.240
You're nearly there. I've got it! Ah!

0:41:22.240,0:41:25.160
You nearly got it. Yes!

0:41:25.160,0:41:29.080
THEY APPLAUD

0:41:29.080,0:41:34.320
This feeling of disgust is an emotion that evolved over thousands of years.

0:41:34.320,0:41:42.040
It's not just maggots. All signs of decay revolt us.

0:41:42.040,0:41:45.400
It's a great mechanism for stopping us

0:41:45.400,0:41:48.120
from eating food that might make us sick.

0:41:48.120,0:41:52.000
But it's also why we so rarely look at decay,

0:41:52.000,0:41:57.440
we're hardwired to be repulsed by it.

0:41:57.440,0:42:00.720
In the next few weeks, I hope our After Life house will start

0:42:00.720,0:42:05.800
to show why this disgusting process is so important.

0:42:05.800,0:42:11.400
Why decomposition is vital to life.

0:42:11.400,0:42:19.400
And there's one part of our box where we're attempting to demonstrate that, in a unique way.

0:42:19.400,0:42:23.640
These dead mustard plants are the starting point of an experiment

0:42:23.640,0:42:29.960
that will help me trace how new life emerges from old.

0:42:29.960,0:42:32.600
I've made liquid compost from the mustard

0:42:32.600,0:42:36.680
and fed it to these seedlings.

0:42:36.680,0:42:41.320
We plan to track individual nitrogen atoms from the dead mustard leaves,

0:42:41.320,0:42:46.880
to see if they are re-used in the new plants.

0:42:46.880,0:42:53.120
No-one has ever followed the cycle of life in this way before.

0:42:53.120,0:42:56.600
In a couple of weeks time we can come back and, with any luck,

0:42:56.600,0:43:15.640
we'll be able to track this vital part of the cycle from death and decay to new life.

0:43:15.640,0:43:20.480
It's the 23rd day in the After Life house.

0:43:20.480,0:43:24.600
The first waves of decay have now passed.

0:43:24.600,0:43:28.680
Vegetables and soft fruit have been consumed by mould.

0:43:28.680,0:43:32.920
In some places there's not much left for them to feed on.

0:43:32.920,0:43:40.520
They'll need to find new supplies.

0:43:40.520,0:43:43.280
Anything with a hard skin, like this orange,

0:43:43.280,0:43:48.480
remains apparently unaffected.

0:43:48.480,0:43:51.560
Maggot activity too has begun to die down,

0:43:51.560,0:43:55.680
leaving behind a sort of meat slurry in our burger packet,

0:43:55.680,0:44:04.800
where a few late developers eke out a meal from the remains.

0:44:04.800,0:44:07.840
Most of the maggots have started to pupate,

0:44:07.840,0:44:10.480
the next stage before they turn into adults.

0:44:10.480,0:44:16.800
So we should soon see an explosion in our fly numbers.

0:44:16.800,0:44:20.320
And our chicken has gone through an alarming metamorphosis.

0:44:20.320,0:44:26.280
Bacteria continue to rot away at it, releasing gases as they feed.

0:44:26.280,0:44:29.840
This week the carcass bloated to even more grotesque proportions

0:44:29.840,0:44:34.840
before deflating as the gases escaped.

0:44:34.840,0:44:38.280
One month into the project and our house really isn't somewhere

0:44:38.280,0:44:41.000
you'd want to visit, unless you had to.

0:44:41.000,0:44:47.080
Every time I go into the box there's one thing that hits me.

0:44:47.080,0:44:55.640
That is, the all-pervading, hideous stink of decay.

0:44:55.640,0:44:58.840
Imagine sticking your nose deep into a rubbish bin.

0:44:58.840,0:45:01.880
That's the smell I'm talking about.

0:45:01.880,0:45:04.520
But if you can get beyond your revulsion,

0:45:04.520,0:45:09.840
the smell of decay gives real clues to its underlying mechanisms.

0:45:09.840,0:45:16.040
And the different ways plants and animals are broken down.

0:45:16.040,0:45:19.120
I want to share some of these smells with our audience.

0:45:19.120,0:45:20.800
I've got two tubs.

0:45:20.800,0:45:25.360
One's got far gone vegetables and this one meat that's far gone.

0:45:25.360,0:45:35.760
I want to find out which our visitors find most disgusting.

0:45:35.760,0:45:42.080
This is decaying vegetables. Have a smell of that. See what you think.

0:45:42.080,0:45:46.680
It smells like vegetables, still. Have a good sniff.

0:45:46.680,0:45:49.440
THEY LAUGH It's not that bad, is it?

0:45:49.440,0:45:51.760
That's not terrible.

0:45:51.760,0:45:56.800
I think it's only fair to warn you, this is not nice.

0:45:56.800,0:46:00.200
Have a smell of that.

0:46:00.200,0:46:04.040
That smells like a pig barn!

0:46:04.040,0:46:08.120
THEY LAUGH

0:46:08.120,0:46:12.800
As expected, the meat gets the same response every time.

0:46:12.800,0:46:15.040
That's pretty grim, isn't it?

0:46:15.040,0:46:18.880
His eyes are watering!

0:46:18.880,0:46:20.320
Ew!

0:46:20.320,0:46:24.040
Rotting meat is far more dangerous to us than rotting vegetables.

0:46:24.040,0:46:27.480
So we're programmed to find it more offensive.

0:46:27.480,0:46:31.080
But what are we actually smelling?

0:46:31.080,0:46:34.320
Plant cells are largely made up of starches and sugars.

0:46:34.320,0:46:37.160
So when fruit and veg decay, they ferment,

0:46:37.160,0:46:40.400
turning the sugars into alcohol, and releasing

0:46:40.400,0:46:43.080
volatile compounds which have a sweet odour.

0:46:43.080,0:46:47.120
But fish and meat are going to produce really smelly gases

0:46:47.120,0:46:51.040
like hydrogen sulphide, sulphur dioxide and ammonia

0:46:51.040,0:46:53.040
so I'm just going to extract

0:46:53.040,0:46:57.640
some of the gases from the inside of this decaying chicken,

0:46:57.640,0:47:00.320
suck it up into this syringe

0:47:00.320,0:47:05.600
and blow it over a gas analyser and see what happens.

0:47:05.600,0:47:07.640
LOUD BEEPING

0:47:07.640,0:47:13.320
Look at that! The hydrogen sulphide shot up to 10%.

0:47:13.320,0:47:16.760
That really is smelly.

0:47:16.760,0:47:18.640
Oh, God.

0:47:18.640,0:47:23.520
HE COUGHS

0:47:23.520,0:47:28.360
Unlike plant cells, animal cells are made up largely of proteins.

0:47:28.360,0:47:30.600
The foul smelling gases are produced

0:47:30.600,0:47:34.560
when these proteins are broken down into amino acids.

0:47:34.560,0:47:38.520
To understand more about that process, and why the smell

0:47:38.520,0:47:42.880
it generates is such an important part of decay, I am going to

0:47:42.880,0:47:57.920
experience rotting flesh on a scale that even the box can't provide.

0:47:57.920,0:48:01.680
At a secret location in north-west England

0:48:01.680,0:48:07.560
a grotesque but important experiment is taking place.

0:48:07.560,0:48:16.920
65 pig carcasses are being left to rot.

0:48:16.920,0:48:20.760
They're part of an investigation into exactly how

0:48:20.760,0:48:28.760
flesh decomposes, under different conditions.

0:48:28.760,0:48:35.840
And the smell of death is everywhere.

0:48:35.840,0:48:41.240
Well, I haven't been here very long and there's a real whiff of dead animal.

0:48:41.240,0:48:46.360
Sometimes the wind changes direction and it catches your nose.

0:48:46.360,0:48:51.800
I'm used to dealing with smells and excrement and stuff but I'm

0:48:51.800,0:49:00.400
wondering if I'm up to this. There's a lot of dead animals around here.

0:49:00.400,0:49:04.040
The pigs are stand-ins for human remains.

0:49:04.040,0:49:06.880
The aim of the experiment is to help police forensic teams

0:49:06.880,0:49:12.800
establish an accurate time of death, based on the state of decomposition.

0:49:12.800,0:49:16.640
Dr Tal Simmons is the research director for the project.

0:49:16.640,0:49:19.080
And she's going to help me understand how

0:49:19.080,0:49:23.320
the different stages of decay account for what we smell.

0:49:23.320,0:49:25.760
Good morning, Tal. Good morning, George.

0:49:25.760,0:49:29.000
I won't shake hands. Possibly not. What's happening here?

0:49:29.000,0:49:32.760
Let's move the cage and we'll be able to see a bit better.

0:49:32.760,0:49:37.240
Well, we've got a pig we put out four days ago.

0:49:37.240,0:49:40.560
He's just begun to really show some of the early stages of decomposition.

0:49:40.560,0:49:45.800
The first thing that's obvious to me, it's swollen up there.

0:49:45.800,0:49:48.040
He's beginning to bloat

0:49:48.040,0:49:54.400
and he'll bloat more in the next couple of days and that's due to the cellular breakdown, inside the body.

0:49:54.400,0:49:58.440
All those cells are starting to collapse, the cell membrane is going.

0:49:58.440,0:50:01.000
It's exuding all the fluids inside the cell.

0:50:01.000,0:50:03.600
A lot of those contain digestive enzymes.

0:50:03.600,0:50:06.400
He's starting to eat himself from the inside.

0:50:06.400,0:50:09.840
The moment blood stops flowing in an animal,

0:50:09.840,0:50:13.040
this process of cell death begins.

0:50:13.040,0:50:17.160
As each cell membrane splits, enzymes inside are released

0:50:17.160,0:50:20.000
and begin to break down other cells.

0:50:20.000,0:50:24.000
Bacteria then start to feed on these protein rich contents,

0:50:24.000,0:50:28.360
releasing the gases that are bloating the pig.

0:50:28.360,0:50:32.360
All of these gases produced inside are coming up the digestive tract.

0:50:32.360,0:50:37.520
So that smell is actually coming out and that's what attracts the flies?

0:50:37.520,0:50:43.120
We can't smell it but flies can. It's not obvious at all. No.

0:50:43.120,0:50:47.040
But, as I know from the rotting meat and fish in the box,

0:50:47.040,0:50:53.280
it doesn't take long for the smell to become something we can detect.

0:50:53.280,0:50:54.920
HE COUGHS

0:50:54.920,0:50:57.360
Oh, that's a lot worse.

0:50:57.360,0:50:59.600
Let's pull this off.

0:50:59.600,0:51:02.440
Oh, dear!

0:51:02.440,0:51:05.040
He's much more advanced, as you can see.

0:51:05.040,0:51:06.680
HE COUGHS

0:51:06.680,0:51:10.720
We're now smelling a cocktail of highly volatile gases and

0:51:10.720,0:51:15.000
liquids produced, not just by the break down of the animal proteins,

0:51:15.000,0:51:19.200
but by the agents of decay themselves.

0:51:19.200,0:51:23.240
The body is largely composed of water, so as the cells break down

0:51:23.240,0:51:27.240
and the cell walls go, you get the liquid coming from that,

0:51:27.240,0:51:30.320
you get the liquid that was part of the organs, and you get the liquid

0:51:30.320,0:51:34.120
that the maggots are excreting as part of their digestive process too.

0:51:34.120,0:51:37.160
If you look at it really closely, it's actually rather interesting.

0:51:37.160,0:51:39.440
It's a fascinating process.

0:51:39.440,0:51:44.880
I wouldn't say it's attractive. I wouldn't go that far either!

0:51:44.880,0:51:48.840
Many of the molecules in this cocktail of decomposition fluids

0:51:48.840,0:51:55.560
have a particular property, they are highly electrically charged.

0:51:55.560,0:51:58.720
It's a bit like when you rub a balloon on a woollen jumper.

0:51:58.720,0:52:02.360
The molecules of the balloon pick up a charge, which means they stick to

0:52:02.360,0:52:05.000
other materials they come into contact with.

0:52:05.000,0:52:09.880
Which is why the smell of decay can literally stick to our clothes.

0:52:09.880,0:52:13.120
And it also explains why decay can leave a trace

0:52:13.120,0:52:16.360
that lingers far longer than you might think.

0:52:16.360,0:52:17.840
Top off.

0:52:17.840,0:52:21.440
Tal's colleague Peter Cross is measuring what effect

0:52:21.440,0:52:28.360
the decomposing pigs are having on the surrounding earth.

0:52:28.360,0:52:31.400
Just draw the water up. It's even frothing.

0:52:31.400,0:52:33.840
It's foaming. Yeah.

0:52:33.840,0:52:38.520
Well, it's clearly not fresh.

0:52:38.520,0:52:41.640
Argh!

0:52:41.640,0:52:44.680
That's pretty bad!

0:52:44.680,0:52:50.520
This is soil water taken from the site of a buried pig carcass.

0:52:50.520,0:52:54.360
This machine is passing an electrical current through the soil water

0:52:54.360,0:52:58.840
and then measuring how well that soil water conducts electricity.

0:52:58.840,0:53:03.720
The contaminated water is 30 times more conductive than

0:53:03.720,0:53:06.760
soil water taken from ten metres away.

0:53:06.760,0:53:10.440
This is the trace that decay leaves behind.

0:53:10.440,0:53:12.640
We think that because of all the electrolytes

0:53:12.640,0:53:16.080
that are leaching into the soil water from the decomposing pig,

0:53:16.080,0:53:19.560
that they are changing the electrical properties of the soil water.

0:53:19.560,0:53:21.000
How long will that remain?

0:53:21.000,0:53:24.640
I'd expect conductivity to continue increasing for up to two years.

0:53:24.640,0:53:27.880
So that really is a fingerprint of death, isn't it?

0:53:27.880,0:53:37.440
Absolutely, yes.

0:53:37.440,0:53:41.200
And it's a fingerprint that allows scientists to detect

0:53:41.200,0:53:45.560
signs of decay, not just over years, but over centuries.

0:53:45.560,0:53:48.600
OK, Chris, do you want to grab the remote probes?

0:53:48.600,0:53:52.480
Dr Jamie Pringle is a forensic geophysicist.

0:53:52.480,0:53:57.840
Today he's using the conductive qualities of decomposition fluids

0:53:57.840,0:54:01.800
to identify unmarked graves in this churchyard.

0:54:01.800,0:54:07.320
Some are estimated to be 200-years-old.

0:54:07.320,0:54:12.800
Jamie's kit sends an electrical current into the ground to measure conductivity.

0:54:12.800,0:54:16.440
It can detect electrically charged molecules

0:54:16.440,0:54:21.920
left behind by the bodies buried centuries ago.

0:54:21.920,0:54:22.840
BEEPING

0:54:22.840,0:54:31.120
Oh, that's interesting, lads. Looks like it's going down there.

0:54:31.120,0:54:33.520
I've just downloaded the data from the machine

0:54:33.520,0:54:38.280
and the results show there's one, two, three, four, five areas

0:54:38.280,0:54:41.680
of blue, which means it's high conductivity results,

0:54:41.680,0:54:45.280
which suggests to me that's where the graves are going to be located

0:54:45.280,0:54:49.320
and where the decompositional fluids have been retained in the soil.

0:54:49.320,0:54:53.800
This technology opens up new possibilities in forensic science.

0:54:53.800,0:54:57.560
Not only can it be used for unmarked graves, it can be used for

0:54:57.560,0:55:02.120
other things as well, such as looking for buried murder victims.

0:55:02.120,0:55:06.480
For crime fighters, the powerful lingering effect of decay,

0:55:06.480,0:55:28.520
turns out to be one of its most useful qualities.

0:55:28.520,0:55:32.640
We're more than halfway through our investigation of what happens

0:55:32.640,0:55:38.280
when decay is allowed to run its course in a typical home.

0:55:38.280,0:55:42.320
We set out to see how quickly its contents would be broken down

0:55:42.320,0:55:46.320
and transformed into new life.

0:55:46.320,0:55:53.760
One month in, we have our most striking result yet.

0:55:53.760,0:56:04.800
The clue is in our rapidly increasing fly numbers.

0:56:04.800,0:56:10.000
These flies are the first generation to be born and bred in the box.

0:56:10.000,0:56:17.320
Two weeks ago, they were the maggots that were so active in all the meat.

0:56:17.320,0:56:20.720
Once a maggot has fed enough, it pupates.

0:56:20.720,0:56:26.400
Within about seven days, the adult blow fly emerges.

0:56:26.400,0:56:42.680
It inflates a soft spongy sack on the top of its head to help push itself out.

0:56:42.680,0:56:46.320
Then blood pumps into the wings, spreading them out

0:56:46.320,0:57:04.760
ready for take off.

0:57:04.760,0:57:07.840
There isn't anything better than flies to illustrate

0:57:07.840,0:57:10.520
the transformative power of decay.

0:57:10.520,0:57:13.800
The fly larvae have eaten this pig. I want to show you

0:57:13.800,0:57:17.320
just how little is left behind.

0:57:17.320,0:57:24.240
If I get this torn back without cutting my finger, it's quite tough.

0:57:24.240,0:57:30.600
The outer surface of the skin is now quite dry. Look at that.

0:57:30.600,0:57:36.160
Oh! The smell of ammonia is quite overpowering.

0:57:36.160,0:57:40.440
If I peel it back...

0:57:40.440,0:57:43.640
What we've got here is basically dried skin

0:57:43.640,0:57:47.680
and a few bits of fat All the meat has gone.

0:57:47.680,0:57:51.920
The fly larvae have eaten this pig out completely

0:57:51.920,0:57:55.000
All that's left are some ribs and fat.

0:57:55.000,0:57:59.440
All that meat that was once pig is now flying around this room.

0:57:59.440,0:58:11.720
Who says pigs can't fly?

0:58:11.720,0:58:24.320
Seven days later and the number of blow flies is becoming a problem inside the house.

0:58:24.320,0:58:27.280
Well, it's a week since I was here before

0:58:27.280,0:58:31.400
and, as I predicted, the numbers of flies have absolutely sky rocketed,

0:58:31.400,0:58:33.440
they've gone through the roof.

0:58:33.440,0:58:40.080
I'm going to wear an all-in-one suit for a bit of protection this week.

0:58:40.080,0:58:45.120
I reckon there could be as many as 10,000 flies inside.

0:58:45.120,0:58:48.400
Because our box is sealed, they can't escape to find

0:58:48.400,0:58:52.280
new sources of food and places to lay their eggs.

0:58:52.280,0:59:01.000
I'm worried that their sheer numbers may disrupt the natural course of decay elsewhere in the box.

0:59:01.000,0:59:07.520
There are now simply too many flies here, it's becoming quite unpleasant.

0:59:07.520,0:59:11.400
It's causing a problem because of the fly speck, that's the excrement,

0:59:11.400,0:59:14.200
which they leave on the surfaces, inside the glass.

0:59:14.200,0:59:19.400
So, it's time I tried to reduce them a bit...

0:59:19.400,0:59:21.320
manually.

0:59:21.320,0:59:28.000
The trouble is, they're flying quite low and sitting on surfaces.

0:59:28.000,0:59:31.640
It's hard to get them.

0:59:31.640,0:59:37.120
Half the flies are drunk because

0:59:37.120,0:59:40.440
the fruit bowl has become alcoholic

0:59:40.440,0:59:44.760
and the flies are flying under the influence at the moment.

0:59:44.760,0:59:48.920
It's probably why there are so many on the floor.

0:59:48.920,0:59:52.320
You can hear them.

0:59:52.320,0:59:54.400
A constant buzz.

0:59:54.400,0:59:56.880
This is pretty unpleasant.

0:59:56.880,1:00:03.720
Oh! Look at this!

1:00:03.720,1:00:06.360
It's no wonder that flies are so hard to capture.

1:00:06.360,1:00:11.000
Their compound eyes give them 360 degree vision.

1:00:11.000,1:00:15.320
So they can respond to movement in less than 30 milliseconds.

1:00:15.320,1:00:19.800
Me and my net can only do so much.

1:00:19.800,1:00:23.680
It will be hunger that kills off these flies in the remaining weeks,

1:00:23.680,1:00:27.720
as food supplies in the box run out.

1:00:27.720,1:00:30.760
Their role in our project is coming to an end.

1:00:30.760,1:00:34.760
We should start to see other insects moving in to carry on

1:00:34.760,1:00:42.800
the process of breaking down what's left of the meat.

1:00:42.800,1:00:53.720
In the meantime, the flies need for food is affecting one of our other agents of decay.

1:00:53.720,1:00:58.240
Six weeks in, mould is still ravaging the sandwich box.

1:00:58.240,1:01:00.640
It's even grown out from under the lid.

1:01:00.640,1:01:08.160
And it's attracted the attention of our starving flies.

1:01:08.160,1:01:13.480
Now, this to me, is one of the most amazing things I've ever seen.

1:01:13.480,1:01:20.120
Patrick Hickey has returned to investigate what's been happening to the moulds in our house.

1:01:20.120,1:01:22.600
How many actual species of fungus are here?

1:01:22.600,1:01:26.120
At least 20 or 30, maybe more.

1:01:26.120,1:01:29.640
20 or 30 species of fungus! I can't wait to have a sort of...

1:01:29.640,1:01:33.960
It's the perfect environment. Some of them are fairly dangerous.

1:01:33.960,1:01:40.560
One of the moulds here, aspergillus flavus, a greeny-yellow one,

1:01:40.560,1:01:45.320
can produce a nasty toxin. So, you want to be careful.

1:01:45.320,1:01:49.600
Look at this, it's a solid mat.

1:01:49.600,1:01:53.080
There are the layers of sandwich.

1:01:53.080,1:01:58.320
It's completely through. There aren't any flies, of course.

1:01:58.320,1:02:02.920
It was sealed in the box so the flies couldn't get in.

1:02:02.920,1:02:07.480
Big contrast to the fruit bowl, which was left open.

1:02:07.480,1:02:13.000
A couple of weeks ago it was covered in thick layers of fungus and

1:02:13.000,1:02:16.000
the flies have stripped it bare.

1:02:16.000,1:02:21.440
They've eaten the fungus and spores and recycled the fungi.

1:02:21.440,1:02:25.720
Fruit has become mould. Mould has become flies. Flies fly off.

1:02:25.720,1:02:31.400
And, if they were outside, they'd be eaten by something.

1:02:31.400,1:02:33.120
Outside in the garden,

1:02:33.120,1:02:37.120
other forms of fungi rely on insects to help them do their job.

1:02:37.120,1:02:41.720
This is the fruiting body of a stinkhorn fungus.

1:02:41.720,1:02:45.320
The rest of the fungus is below the soil,

1:02:45.320,1:02:48.280
feeding on wood and plant matter in the soil.

1:02:48.280,1:02:52.160
These stalks emerge when the fungus is ready to fruit,

1:02:52.160,1:03:01.720
growing up to 15cms in less than 24 hours.

1:03:01.720,1:03:05.360
When they break through the top layer of soil,

1:03:05.360,1:03:09.880
they release an intense smell that flies find irresistible,

1:03:09.880,1:03:13.960
the smell of dead and decaying meat.

1:03:13.960,1:03:17.320
The flies strip the jelly-like flesh from the mushroom,

1:03:17.320,1:03:21.160
and help spread its spores.

1:03:21.160,1:03:24.240
Even after 30 years of studying biology,

1:03:24.240,1:03:33.840
I'm still amazed by the complex behaviour of these simple organisms.

1:03:33.840,1:03:40.640
But stinkhorns aren't the strangest things feeding on the decaying wood in our garden.

1:03:40.640,1:03:47.400
Hidden away in our woodpile is something even more intriguing.

1:03:47.400,1:03:52.560
This is a slime mould.

1:03:52.560,1:03:56.040
It's the largest single-celled organism on Earth.

1:03:56.040,1:04:07.320
It can grow to more than three square metres.

1:04:07.320,1:04:10.760
Scientists have recently discovered that these primitive life forms

1:04:10.760,1:04:26.600
have some rather sophisticated talents.

1:04:26.600,1:04:29.840
At Oxford University, Dr Mark Fricker is one of a team of

1:04:29.840,1:04:34.440
botanists and computer scientists studying a species of slime mould

1:04:34.440,1:04:37.160
called Physarum Polycephalum.

1:04:37.160,1:04:40.400
For years slime moulds have fascinated scientists

1:04:40.400,1:04:45.400
with their remarkable ability to solve simple mazes.

1:04:45.400,1:04:47.560
Put food at the end of a maze

1:04:47.560,1:04:51.080
and the slime mould will find the quickest route through.

1:04:51.080,1:04:53.040
But scientists started to wonder

1:04:53.040,1:04:56.440
if the mould could do more than just perform clever tricks.

1:04:56.440,1:04:59.280
You can set them lots of little tasks, and

1:04:59.280,1:05:02.160
you can allow them to forage and connect up little

1:05:02.160,1:05:05.240
food sources to see what sort of network they would make. OK.

1:05:05.240,1:05:08.880
And a geometric shape, so a square or something more complicated,

1:05:08.880,1:05:11.720
is interesting, but we wanted to see whether they would

1:05:11.720,1:05:18.960
be able to solve a slightly more complex problem.

1:05:18.960,1:05:21.240
Mark is recreating an experiment

1:05:21.240,1:05:25.200
he worked on with colleagues at Tokyo University.

1:05:25.200,1:05:28.160
He takes a blob of slime mould and then surrounds it with

1:05:28.160,1:05:35.680
a pattern of oat flakes, an irresistible treat to slime mould.

1:05:35.680,1:05:43.840
What happens next is recorded by a time-lapse camera.

1:05:43.840,1:05:50.920
The slime mould locates the oat flakes by growing out in all directions.

1:05:50.920,1:05:54.360
But within hours the slime mould shrinks back,

1:05:54.360,1:06:00.320
leaving an intricate web of tubes that connect the oat flakes.

1:06:00.320,1:06:06.720
It's these tubes that transfer nutrients around the slime mould.

1:06:06.720,1:06:11.520
Incredibly, everything you can see is part of one single cell.

1:06:11.520,1:06:16.840
It needs to build a network that is quite efficient, to transport all those resources.

1:06:16.840,1:06:20.560
At the same time, that network mustn't cost too much.

1:06:20.560,1:06:23.240
It mustn't take up too many of its own resources.

1:06:23.240,1:06:27.280
And then the other problem it has is, it's going to be subject to damage.

1:06:27.280,1:06:29.920
If there was only ever one connection,

1:06:29.920,1:06:33.360
there's a risk it would break.

1:06:33.360,1:06:36.440
The slime mould takes no chances.

1:06:36.440,1:06:43.760
It grows back-up routes to make sure that its food supply isn't cut off.

1:06:43.760,1:06:50.000
But there's something even more extraordinary about what the slime mould has done.

1:06:50.000,1:06:55.400
Mark hasn't just laid out the flakes in a random pattern.

1:06:55.400,1:06:57.560
The large blob in the middle is Tokyo

1:06:57.560,1:07:03.120
and each of the food sources are positioned as cities nearby Tokyo.

1:07:03.120,1:07:06.760
So, it's a re-creation of the area around Tokyo? Indeed.

1:07:06.760,1:07:11.160
This is actually what it's based on, the rail network around Tokyo.

1:07:11.160,1:07:15.240
We can superimpose that over. Ok, so we align it...

1:07:15.240,1:07:18.640
That's identical! It's absolutely identical!

1:07:18.640,1:07:23.760
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,

1:07:23.760,1:07:28.000
it's a slightly more resilient network than the ones the engineers designed... Hold on!

1:07:28.000,1:07:30.320
You're telling me, wait a minute,

1:07:30.320,1:07:34.080
that this slime mould has built a better network...

1:07:34.080,1:07:36.000
A remarkably similar network.

1:07:36.000,1:07:41.240
..than the humans built. Yes.

1:07:41.240,1:07:44.120
The Tokyo rail system is one of the most efficient

1:07:44.120,1:07:46.440
and well organised in the world.

1:07:46.440,1:07:51.800
It took lots of skilled engineers using lots of brain power to plan.

1:07:51.800,1:07:55.880
Yet, somehow, slime mould has achieved the same goal,

1:07:55.880,1:08:01.320
how to efficiently link together multiple locations.

1:08:01.320,1:08:05.520
Slime mould has also been put to work in other parts of world.

1:08:05.520,1:08:10.000
Here it tackles some of Britain's major motorways.

1:08:10.000,1:08:16.760
This is its take on the best routes around Spain.

1:08:16.760,1:08:23.280
And here are some interesting alternatives to Americas Route 66.

1:08:23.280,1:08:25.880
What is the slime mould actually displaying here?

1:08:25.880,1:08:29.200
It's a sort of smart behaviour. It hasn't got a brain,

1:08:29.200,1:08:33.000
it hasn't got a nervous system, but it still seems to be able to solve

1:08:33.000,1:08:36.080
these sorts of complex problems with very simple rules.

1:08:36.080,1:08:40.920
It's something the computer scientists we work with are getting very interested in,

1:08:40.920,1:08:56.920
whether or not you can take inspiration from this system and apply it to other sorts of problems.

1:08:56.920,1:09:01.040
How does one of the most simple life-forms on Earth,

1:09:01.040,1:09:05.400
a single-celled amoeba that spends most of its time on woodland waste,

1:09:05.400,1:09:14.040
match its wits against transport engineers and computer scientists?

1:09:14.040,1:09:21.960
The clue seems to lie in its extraordinary biology.

1:09:21.960,1:09:26.440
Professor Bruce Ing is a self confessed slime mould obsessive.

1:09:26.440,1:09:30.400
He's going to help me track down some slime mould

1:09:30.400,1:09:34.120
in one of its native habitats.

1:09:34.120,1:09:36.520
Slime moulds aren't rare things?

1:09:36.520,1:09:40.440
Oh, no. They're very common, indeed. They're everywhere. But overlooked?

1:09:40.440,1:09:43.280
Overlooked because they are shy, not easy to find,

1:09:43.280,1:10:02.760
unless you know where to look. Shy slime moulds!

1:10:02.760,1:10:06.480
Do you remember the film The Blob? Yes.

1:10:06.480,1:10:10.680
A giant mass of jelly, eating caravans?

1:10:10.680,1:10:13.720
It was a slime mould? It was.

1:10:13.720,1:10:15.760
But not one we'll find here.

1:10:15.760,1:10:22.320
Not as big as that, I hope.

1:10:22.320,1:10:30.960
Bruce's 54 years in the field prove vital as we hunt the elusive slime mould.

1:10:30.960,1:10:33.800
After half an hour, he finds what we are looking for.

1:10:33.800,1:10:38.360
It's not quite the sheet I was hoping for. No, indeed not.

1:10:38.360,1:10:44.320
But it's still the real McCoy.

1:10:44.320,1:10:50.720
This small patch of orange is creeping slime mould.

1:10:50.720,1:10:57.320
Up close, you can see how it's constantly pulsating.

1:10:57.320,1:11:00.240
When one part of it finds something it likes to eat,

1:11:00.240,1:11:03.080
it pulses more rapidly.

1:11:03.080,1:11:07.000
Scientists believe that it's this pulsating that helps transmit

1:11:07.000,1:11:09.600
information across the entire cell,

1:11:09.600,1:11:18.560
allowing the slime mould to move towards its food source.

1:11:18.560,1:11:22.800
These pulsations control where and how they grow across the forest floor,

1:11:22.800,1:11:30.240
or even around the oat flakes of the Tokyo rail map.

1:11:30.240,1:11:33.800
What's so special about slime mould is that it can use

1:11:33.800,1:11:38.040
this information to make multiple decisions, simultaneously.

1:11:38.040,1:11:46.560
Pretty ingenious stuff for a single-celled organism.

1:11:46.560,1:11:51.880
Slime moulds are what's known as self organising systems.

1:11:51.880,1:11:55.120
It's not a unique phenomenon in nature.

1:11:55.120,1:11:57.800
Flocks of birds work in a similar way.

1:11:57.800,1:12:00.000
With no leader, no overall control,

1:12:00.000,1:12:04.320
the flock nevertheless acts as a single unit.

1:12:04.320,1:12:09.720
But slime mould can do something that flocks of birds could never do.

1:12:09.720,1:12:15.440
Meet the Phi-Bot, the world's first slime mould controlled robot.

1:12:15.440,1:12:19.760
The Phi-Bot is the brain child of Dr Soichiro Tsuda

1:12:19.760,1:12:23.640
and Dr Klaus Peter Zauner from Southampton University.

1:12:23.640,1:12:29.440
Their robot takes its orders from a tiny blob of slime mould.

1:12:29.440,1:12:32.400
I sort of don't believe you, I want to...

1:12:32.400,1:12:33.960
HE LAUGHS

1:12:33.960,1:12:35.920
..I want to see it working. Prove it!

1:12:35.920,1:12:39.200
THEY LAUGH Soichiro, flip the switch.

1:12:39.200,1:12:43.600
It just seems almost unbelievable.

1:12:43.600,1:12:47.520
It's not instant, is it? It's not instant... Oh!

1:12:47.520,1:12:54.800
Wow! That's fantastic!

1:12:54.800,1:12:59.520
The slime mould sits on an electronic chip, inside the robot.

1:12:59.520,1:13:03.520
As it transmits information around its single-cell by pulsing,

1:13:03.520,1:13:06.480
the robot detects these pulses and translates them

1:13:06.480,1:13:10.760
into much larger movements across the surface of the table.

1:13:10.760,1:13:17.160
How did you get the idea for having a live organism inside a robot?

1:13:17.160,1:13:21.760
One inspiration source obviously from the Daleks, from Doctor Who?

1:13:21.760,1:13:24.000
This is inspired by a Dalek? Yes.

1:13:24.000,1:13:26.480
Well, it's the same thing, isn't it? Yeah exactly.

1:13:26.480,1:13:30.160
You've got a live organism in the machine, which controls it.

1:13:30.160,1:13:34.280
The Phi-Bot is pioneering a new approach to computing.

1:13:34.280,1:13:39.520
Today's computers use a single central processing unit to do their thinking.

1:13:39.520,1:13:43.560
But the slime mould has no need to ask a brain what to do,

1:13:43.560,1:13:47.360
all parts of the cell just work together, for the good of the whole.

1:13:47.360,1:13:51.320
The simple organism inside, processes information in a completely

1:13:51.320,1:13:54.640
radically different way from our conventional computing technology.

1:13:54.640,1:13:59.880
We want to learn more about how it can do that information processing.

1:13:59.880,1:14:04.880
So slime mould could hold the secret to a revolution in computing.

1:14:04.880,1:14:08.800
Or even the creation of artificial intelligence.

1:14:08.800,1:14:23.320
Not bad for something you can find in your wood pile.

1:14:23.320,1:14:30.080
There's only a week left to go in our project to study decay in a typical house and garden.

1:14:30.080,1:14:34.400
The pace of change in the box is beginning to slow down.

1:14:34.400,1:14:39.360
But, even now, decay is following an ordered sequence.

1:14:39.360,1:14:44.320
What one decomposer leaves behind is food for others.

1:14:44.320,1:14:48.160
Well, it's day 44 and the one thing that's immediately obvious,

1:14:48.160,1:14:54.680
it doesn't smell nearly as bad in here. It's actually quite pleasant.

1:14:54.680,1:14:58.320
The other thing that's obvious is there are very few flies now,

1:14:58.320,1:15:02.160
the majority of the flies that hatched out have died.

1:15:02.160,1:15:05.680
There aren't as many dead ones lying about as I'd expected, but

1:15:05.680,1:15:10.120
it looks like a few flies might have got themselves stuck in this

1:15:10.120,1:15:15.400
bottle of wine, as they searched for something to drink.

1:15:15.400,1:15:18.440
This is solid. Uh!

1:15:18.440,1:15:21.280
Look at this. Oh my God!

1:15:21.280,1:15:26.160
Urgh! That is incredible.

1:15:26.160,1:15:28.480
HE LAUGHS

1:15:28.480,1:15:30.440
I can't get them all out.

1:15:30.440,1:15:37.960
I've never seen so many flies in one bottle, in my life.

1:15:37.960,1:15:39.960
I can barely get them out.

1:15:39.960,1:15:44.560
That sort of explains why I wasn't seeing as many flies

1:15:44.560,1:15:47.280
flying around, as I expected.

1:15:47.280,1:15:51.080
It's because most of them were in here.

1:15:51.080,1:15:56.600
Look at it. It's just incredible. It's thick.

1:15:56.600,1:16:05.160
That's thick with flies.

1:16:05.160,1:16:08.680
Conditions in the box are very dry.

1:16:08.680,1:16:14.320
All that remains of the meat are hardened chunks of sinew and skin.

1:16:14.320,1:16:21.000
Even if the flies had survived there's nothing left for another generation of maggots to feed on.

1:16:21.000,1:16:25.400
But this is the perfect fodder for beetles.

1:16:25.400,1:16:29.760
This dried meat gives off a far less pungent odour, but the smell

1:16:29.760,1:16:37.640
it does produce gives them a signal that starts the next stage in decay.

1:16:37.640,1:16:44.960
Decay happens in a series in waves, this fish is dry and hard,

1:16:44.960,1:16:49.480
there are beetle larvae who will eat it. So there's no waste.

1:16:49.480,1:16:53.520
That's what I'm hunting for now, I'm hunting for the larvae

1:16:53.520,1:17:01.200
of a larder beetle and there's one right there.

1:17:01.200,1:17:06.280
Larder beetle larvae are present in around half of all homes.

1:17:06.280,1:17:11.040
They only colonise a carcass once it's become dried and desiccated.

1:17:11.040,1:17:14.960
Their powerful jaws allow them to eat through flesh, hair and skin.

1:17:14.960,1:17:18.120
And they can strip an animal down to the bone.

1:17:18.120,1:17:21.120
This stage in decay moves slowly though.

1:17:21.120,1:17:25.320
Larder beetle larvae take months to pupate into these adults.

1:17:25.320,1:17:36.080
The job of recycling what remains in the box could take generations of them, years to complete.

1:17:36.080,1:17:39.160
But another beetle in our box does allow us

1:17:39.160,1:17:49.360
to see how effective these insects can be.

1:17:49.360,1:17:53.080
36 days ago, two sexton beetles took less than 12 hours

1:17:53.080,1:18:00.440
to bury our dead rat.

1:18:00.440,1:18:03.680
What I'm aching to do now is a spot of archaeology.

1:18:03.680,1:18:06.800
Because what has happened is, the sextons beetles have taken

1:18:06.800,1:18:11.080
the rat down and they will have formed it into a ball,

1:18:11.080,1:18:16.040
on which their larvae have fed and hopefully 36 days should be

1:18:16.040,1:18:20.640
enough time. I should find a crypt in which the rat sits,

1:18:20.640,1:18:24.320
surrounded by its own fur, which they smear on the outside.

1:18:24.320,1:18:27.560
And there should just be bones left.

1:18:27.560,1:18:32.560
This, for me, is about as exciting as it gets.

1:18:32.560,1:18:39.560
I'm going to use a hoover to gently take away the soil.

1:18:39.560,1:18:42.400
What is amazing about these insects is,

1:18:42.400,1:18:47.080
they're one of the very few insects who look after their young.

1:18:47.080,1:18:52.880
They take care of their young. Once they've dragged the prey down,

1:18:52.880,1:19:00.440
and hidden it underground, they'll lay the eggs around the crypt,

1:19:00.440,1:19:04.520
and then the larvae will move in and feed.

1:19:04.520,1:19:07.960
And they'll help them to feed as well.

1:19:07.960,1:19:10.400
We're beginning to see a shape here.

1:19:10.400,1:19:16.280
This is very exciting. Turn that off.

1:19:16.280,1:19:21.800
Wonder if I can free it.

1:19:21.800,1:19:31.040
That is just fantastic.

1:19:31.040,1:19:35.920
There look at that, that's all that remains of the rat.

1:19:35.920,1:19:41.040
You can see the top part of the skull and the teeth.

1:19:41.040,1:19:44.320
The rest of it has completely disappeared,

1:19:44.320,1:20:03.160
there's nothing left of that rat.

1:20:03.160,1:20:08.320
We're now at week eight. We're nearing the end of our project.

1:20:08.320,1:20:12.840
But there is one final stage of decay I want to investigate.

1:20:12.840,1:20:17.480
And it's probably the most important.

1:20:17.480,1:20:21.520
We've watched as the nutrients, locked up in plant

1:20:21.520,1:20:24.760
and animal remains, have been re-used by other organisms.

1:20:24.760,1:20:27.800
In the process, complex things like chickens, rats and fruit,

1:20:27.800,1:20:34.080
have become simpler ones, insects, fungi, bacteria.

1:20:34.080,1:20:38.840
But the true power of decay is its ability to reduce complex things

1:20:38.840,1:20:44.440
right back to the most basic building blocks of life.

1:20:44.440,1:20:46.480
And all through the project,

1:20:46.480,1:20:52.760
that's been quietly happening in a corner of the box.

1:20:52.760,1:20:58.000
This is one of best places to see decay in action. We set this up

1:20:58.000,1:21:03.160
eight weeks ago and it was piled to the top with plant material.

1:21:03.160,1:21:07.000
It's now completely decayed down, we've been adding to it.

1:21:07.000,1:21:13.880
What I really want to do, is have a look inside and see what's going on.

1:21:13.880,1:21:19.000
Now, decay has been happening and the further you go down,

1:21:19.000,1:21:28.240
the more advanced it is. There's a snail on the trowel handle.

1:21:28.240,1:21:31.360
As all gardeners know, compost heaps turn dead plants

1:21:31.360,1:21:38.880
into a form of nutrients that new plants can use.

1:21:38.880,1:21:44.040
On the surface, animals like snails, slugs and worms begin the process

1:21:44.040,1:21:50.480
by eating the remains of plants, helping to break them into pieces.

1:21:50.480,1:21:53.520
The waste they excrete, and anything else left behind,

1:21:53.520,1:21:57.160
is eaten by smaller creatures like these mites.

1:21:57.160,1:22:05.320
Too tiny to be seen with the naked eye.

1:22:05.320,1:22:08.320
And this process continues down through the compost.

1:22:08.320,1:22:10.560
Ever smaller organisms,

1:22:10.560,1:22:14.360
reducing the plant waste to ever smaller components.

1:22:14.360,1:22:21.120
Until tiny fungi and bacteria are able to break down the very cells of the plant.

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A teaspoon of soil contains four billion micro-organisms.

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They finally release the nitrogen

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and other building blocks of organic life, back into the soil.

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What we end up with,

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is an incredibly very fine soil,

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the result of the breakdown processes of countless organisms.

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Having begun with a big pile of green material, you may think that is an end point, but it's not,

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it's just the beginning.

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From here, life can begin to rebuild.

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To me, this is the most amazing moment in the story of decay.

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When we began eight weeks ago,

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we wanted to demonstrate its significance in a unique way.

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This is probably one of the most important experiments we've set up in the box.

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These may look like ordinary plants but they're going to show us

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a part of the story that's absolutely crucial. These are the marigolds and radish seedlings

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I planted back at the beginning of the project.

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They've flourished into mature plants.

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I've been feeding them with a special liquid compost

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made from plants grown using chemically labelled nitrogen atoms.

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If everything has gone according to plan,

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we should be able to track how individual atoms of nitrogen

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are transferred from the mustard plant to our seedlings.

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From death to life.

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We sent samples of our plants to Professor Malcolm Clench.

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It's time to find out if our experiment has worked.

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The first one is from the marigold.

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What can you see at the moment is a photograph of the marigold leaf.

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He's able to pinpoint exactly where the labelled nitrogen has ended up.

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As I start to play the video clip, we'll come up with

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an overlay that shows the nitrogen in high abundance.

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That's really clear. Yes, very clear.

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Each one of these dots shows where we found traces of the labelled

1:24:54.880,1:25:00.120
nitrogen from the mustard plant in our marigold leaf.

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White areas show where it's concentrated.

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How can we be 100% sure that labelled nitrogen has come from our experiment and nowhere else?

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The form of nitrogen we're using is only 0.3% naturally abundant.

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We can see areas of high intensity and they can only have come from

1:25:23.520,1:25:27.000
the mustard that was grown with the labelled nitrogen in.

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So, that is the definitive proof of the cycle of life? Indeed.

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I think you're going to be pleased with the radish results.

1:25:37.040,1:25:39.680
We can see first off a very nice radish.

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One that you prepared earlier.

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Wow look at that!

1:25:44.760,1:25:48.240
That is absolutely cast iron proof,

1:25:48.240,1:25:54.200
that we have transferred material, an element in this case,

1:25:54.200,1:25:58.480
from one plant, dead and decayed, fed to something else and it takes it up.

1:25:58.480,1:26:01.960
Yes, it's incontrovertible.

1:26:01.960,1:26:05.600
This is what I hoped we'd see when we began our project.

1:26:05.600,1:26:08.240
It's the fundamental principle of decay,

1:26:08.240,1:26:11.040
revealed in front of our eyes.

1:26:11.040,1:26:21.040
For me, this is as good as it gets.

1:26:21.040,1:26:27.960
Two months of decay have transformed the After Life box.

1:26:27.960,1:26:32.640
Little is left of the fresh food we began with.

1:26:32.640,1:26:41.120
And what remains will continue its inexorable journey back to the basic building blocks of life.

1:26:41.120,1:26:44.600
But, as our plant experiment so dramatically demonstrated,

1:26:44.600,1:26:50.080
what we have witnessed in the box is a process of renewal.

1:26:50.080,1:26:59.600
That we are all part of.

1:26:59.600,1:27:02.440
It's a real snap-shot of everyone's life.

1:27:02.440,1:27:07.960
To see things changing, as they do, is a fantastic experiment.

1:27:07.960,1:27:10.520
We'd be in a horrible mess if we didn't have decay.

1:27:10.520,1:27:16.280
When you see what nature can do to get rid of all the dead things in the world...

1:27:16.280,1:27:21.040
We need that decay to happen in order for life to go on, I guess.

1:27:21.040,1:27:24.560
Oh, my God! Look at that.

1:27:24.560,1:27:28.880
We tend to think of life as a linear process, with a beginning and end.

1:27:28.880,1:27:31.160
Things go from life to death.

1:27:31.160,1:27:35.080
I hope the box has shown this process in a new light.

1:27:35.080,1:27:37.600
Life is an ever repeating cycle.

1:27:37.600,1:27:42.200
One that's not just happening here, but everywhere on the planet.

1:27:42.200,1:27:48.040
The plants and animals of Earth's ecosystems rely on this continuing cycle.

1:27:48.040,1:27:51.000
Even the atoms that make us up are recycled.

1:27:51.000,1:27:54.120
They come from the food we eat, the air we breathe,

1:27:54.120,1:27:57.080
they're in our flesh, blood and bones.

1:27:57.080,1:27:59.840
They've been used millions of times before,

1:27:59.840,1:28:36.720
and they'll be used millions of times again.

1:28:36.720,1:28:39.720
Subtitles by Red Bee Media Ltd

1:28:39.720,9:59:59.000
E-mail subtitling@bbc.co.uk