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- Hidden on you is
a world you have never seen

overrun with bizarre
creatures that live on and in

every part of your body.

- It's an animal.

It's on your face and we
don't know very much about it.

- Yet they are affecting us

in ways we never imagined

but now for the first time

we can explore this unknown world.

- They're an absolutely essential
component of what we are.

- This is a
struggle of life and death.

- If we got rid of all
of the microbes on us

and inside us we would die.

- So doctors are even
reintroducing bugs into our bodies.

- Larvae are alive.

They're going through the skin.

It's Judy plus hookworm.

(laughing)

- You are more than human.

Each and everyone of us is a collection

of different life forms that call us home.

This is Life on Us.

(dramatic orchestra music)

(bouncy flute music)

You are mostly not you.

- Come on.

- You are home
to an astounding array

of life forms.

Some creatures hide inside your bowels.

Others prefer the view
from your eye brows.

There are gardens of fungi on your feet.

Alien tribes inhabit
the jungle of your hair.

Tiny mites borrow into your face

and you host more bacteria

than there are stars in the milky way.

You and your bugs form a web of life.

In fact bugs are us.

(baby crying)

Everyday this typical family is home

to 100 trillion hitchhikers

on their skin and inside their body.

(baby laughing)

These invisible colonizers
keep them healthy.

Sometimes make them ill.

- Hey!

- Mine!
- You played yesterday.

- No it's breakfast.

- And even
influence their behavior.

- Wait!

- Stop fighting!

- Yet until recently
we understood very little

about our microscopic residents.

(dramatic flourish)

Germs have a bad reputation.

We think of them as the cause of disease

but paradoxically we couldn't
survive without them.

- We have our tunnel vision.

- Bacteria are bad.

The archaeans are bad.

All this stuff growing on me is bad.

Let's just nuke it.

- And the majority of those organisms

are actually good for us.

They're assisting us.

They're not our enemies.

- Our obsession with bad bugs

left us blind to the good,

but now genetic tools allow us to see

what we've been missing.

- Molecular tools, sequencing DNA,

have allowed us to get a true picture

of what organisms are there

and there's a far richer
picture than we had previously

appreciated for our
culturing microorganisms.

- By decoding the genes

of these microscopic creatures

we can reveal a new microbial world.

- The genetic tools are kind
of like the new telescope.

- Think of it as a
geographer that might have

just been studying the fields

around Norway their whole career

and then somebody says, "Oh by the way

"we just discovered the
Americas and Australia,"

and nobody had ever heard of it before.

- For the first
time we can see the microbes

that live on us and inside us.

- It's a bit like a
gold rush at the moment.

- It really is a very thrilling thing.

- Scientists
have embarked on a journey

into the unexplored world of our own body.

They are discovering how we
are all shaped and kept alive

by the bugs that live on us.

As the crust covers planet Earth

the skin covers the body,

an impermeable barrier
between us and invading germs.

(sirens wailing)

But we only realize
just how important it is

when it's compromised.

- I see people's lives changed

in an instant on a daily basis.

But that tissue on the corner right

is not gonna stay.

- Fiona Wood is a
world leading burn specialist.

Her struggle to save lives is
all about beating pathogens.

The microbes that cause infections.

- We have bacteria and pathogens

all over us all the time.

When you have a breach in
your skin there's a way in

and that way in is going to be there

until we seal the wound.

So the longer the wound is open

the greater the risk of getting infected.

So what we want to do
is close that surface.

Seal the surface of the
wound as quickly as possible

while the waves of
infection keep coming over.

If you waterproof you will survive.

- And central to that survival

is the layer of microbes
that live on our skin.

Like the atmosphere
that protects our planet

our microbes form a shield
against alien invaders.

- If some pathogen arrives on your skin

it's not your immune system
that rises up to greet it.

The first thing that greets
it is this microbial layer.

This hairy invisible cloak.

(water gurgling)

- But where
do these bugs come from?

(triumphant orchestra music)

The answer lies in the miracle of birth.

(heart beating)

For the baby the womb is a solitary world,

but outside an army of
microbes awaits its arrival.

(clock ticking)

(sirens wailing)

(heavy breathing)

(slow piano music)

(moaning and wailing)

(baby crying)

- The moment you're born you're colonized

with your mother's microbes.

Until then you can be called 100% human

but after that moment you're really

just 10% human and 90% microbes.

- Which as a scientist
is very very exciting,

but as a parent is terrifying.

(baby cooing)

(camera shutters)

- Towards the end of pregnancy

the bacteria that live in the mother's gut

migrate to the vagina

ready for the baby to pick them up

as it slides through the birth canal.

(heart beating)

(baby crying)

Being covered in vagina microbes

may not seem much of a trait,

but it's a gift that lasts a lifetime.

These bugs not only
protect us from infections

they're essential for our overall health.

- They also have an important role

in regulating the immune system.

(dramatic music)

- The immune
system never rests.

Its cells constantly patrol our bodies

to eliminate pathogens,

but this power can also be dangerous.

- It can potentially
damage your own tissues

and therefore it must be controlled.

It must be turned down.

It must be regulated.

- The immune system
has an internal police force

keeping it under constant surveillance.

- If you don't have a properly
regulated immune system

it becomes trigger happy.

It's attacking people's brains.

It's attacking people's joints
and giving them arthritis

or it's attacking the contents of the gut

and then you have
inflammatory bowel disease,

or it's attacking trivial
quantities of pollen

or dog dandruff or whatever in the air

and that gives you
allergic airway disorders.

- And what keeps
our immune system in check

is our microbes.

- So that if you have
that organism in the gut

you have more, more policemen.

More regulation.

More control of the immune system

so it doesn't get trigger
happy and do crazy things.

- The supply of
these microbial regulators

doesn't stop at birth.

The mother continues to deliver hundreds

of species of bacteria in her breast milk.

- And it's only very recently
that it's become clear

that breast milk comes with
a whole suite of microbes

that have moved up
through the mother's body,

through the lymph, into the milk,

and come as part of what goes

into the baby with the breast milk.

- Breast milk
also contains sugars

that the infant can't digest.

These are like fertilizer for the baby's

rapidly developing gut flora.

- And the breast milk becomes
this really amazing example

of the way in which our
bodies actually evolved

to help these microbes
to the next generation.

(baby babbling)

- By the time
a child is two and a half

it will have developed a fully
mature microscopic community.

Collectively they're
known as our microbiome.

(dramatic music)

They're as much apart of us
as any of our own organs.

- We shouldn't think of them as a scary

part of our machinery.

They're an absolutely essential
component of what we are.

- Every one of
us is a finely tuned society

of many different life forms

relying on one another for survival,

but we're only just beginning
to discover new species

in the most unexpected places.

This little bug could
determine your health.

(enchanting orchestra music)

(birds chirping)

The Earth holds some spectacular habitats

and some retain their mystery,

but we know much less about the
eco systems of our own body.

Parts of the body are wet.

Others are dry.

(squishing)

Some are hot and dark.

Others are cold and exposed to light.

We are a world of different climate zones.

(birds chirping)

(dramatic music)

And just as on Earth,

on the human body too

life adapts to the environment.

- I started work in tropical forests

and every process I could
study in a tropical forest

is happening on my body
and your body right now.

You have species that are plants.

You have species that eat those plants

and you have species
that eat those species.

You have species that are predators.

You have species that are parasites.

There's active competition
just the way that tree roots

grow against tree roots

or ant colonies grow against ant colonies

that same thing is happening.

- Rob Dunn's
background in ecology

prepared him well for an exploration

of the wildlife of our bodies

and one of the most intriguing places

is the mysterious belly of smell,

the armpit.

- The armpit's this weird thing.

So why does it have hair?

Why does it smell funny?

What on Earth is going on with it?

- It is a pretty specialized environment.

It has high humidity levels

and there's human apocrine glands.

- And these are glands that
don't really produce sweat.

They produce what I and other people think

it's actually a food for microbes.

It is an odorless food and is released

in incredible density out of your armpit.

(heart beating and breathing)

Armpits in and of themselves have no odor.

Your hair has no odor.

Most of your body has no odor.

Those odors are all microbial.

(upbeat jazz music)

- Bacteria thrive
on the perspiration released

by our apocrine glands,

but they aren't active
until we reach puberty

which is why babies smell sweet,

- Good morning.

- But teenagers don't.

So why are we feeling
microbes in our armpits?

- We have hints.

We have parts of answers in other species.

Lemurs have these same glands

that kind of go across the chest

and in that case the
lemurs seem to use them

for identifying each other.

Are you my cousin or not my cousin?

- Body odor helps the lemur

to determine if a prospective partner

is too closely related.

Sexual attraction is
literally about chemistry.

Other mammals don't have
their glands in their armpits.

They're around their
anus and sexual organs.

- It looks like as we
started to stand up more

and as we interacted
with each other like this

that if we were gonna sniff each other

the hair and this smell had to move up.

- Meaning our
armpits have a major influence

on how we date and mate.

It's not just muscles or bikinis

that brings men and women together.

It's the smell of our personal wildlife.

(heart beating and slow breathing)

Bacteria thrive in every
nook and cranny of your body.

And one of the richest
eco systems is your navel.

It's a tiny crater.

A scar that we carry through life

and we barely give a thought to it,

but for scientists at the

North Carolina Museum of Natural Sciences

the navel is a place of infinite mystery.

This is the home of the Belly
Button Biodiversity Project.

Hundreds of volunteers have been recruited

to twirl a cotton swab
in their belly button

to help find new species.

- Hi, how are you?

- The power of our research

comes from the fact that
it will be able to sample

so many different citizens as scientists

and you kind of can't harness that power

unless people are engaged in a project.

- Welcome to the Daily Planet Theater.

- Brian Mellow bills himself

as a microbial comedian.

- We'll be talking about some
citizens science projects

and about the life that lives on us.

We'll be talking about tiny life

which is really fascinating.

An infectious disease walks into a bar.

The bartender says,

"We don't serves infectious
disease in this bar."

The infectious disease says,

"Well you're not a very good host."

(laughter)

If I can make you laugh maybe that'll

make you more open minded to the subject

and maybe it'll make it more memorable.

- And we want you to take this swab

and be really careful.

Just loosen it up, k?

Lift up, get it nice and good.

Get all the gunk out.
- Anything getting on here?

- All the microbes out.

- Yeah so while that's happening
you're actually getting

individual living organisms on that swab.

- Just by touching to it yeah.

- Not squirrels or anything,

but like bacteria, Archeanas, Proteus,

um, fungus
- Dogs, cats.

- Yeah, dogs are really unlikely

although it is a deep belly button

so I can't, yeah.
- Small dogs, chihuahuas,

- I can't rule anything out.
- not Great Danes.

- I'm not looking, I'm trying not to look,

but we'll see it if it's on the swab.

- No I keep it clean.

I probably don't have anything in there.

(water running)

- In fact, the belly button

is crawling with life.

It's protected from the
chemical warfare of soap

and it's usually covered up
from the ravages of weather.

All of which makes it a prime candidate

for the discovery of new species.

- Twirl it good.

- For a long time it's been argued

that the tropical rain forest
canopy is the last frontier

and it's true that we know
very little about that canopy,

but we know no more about our own bodies.

- The belly button survey

has revealed previously
unimagined species on our body.

One person was carrying
a form of archaic life

only ever seen before in the

most extreme environment on Earth.

In deep ocean fence.

(slow orchestra music)

- What's interesting is that if we look

at bacterial diversity
in the human belly button

we have a huge amount of variations

you know, among 60 individuals.

There was not one species of bacterium

that was found in all
60 of those individuals.

- Like our retinal patterns,

fingerprints,

and our DNA,

the wildlife in our
belly button is unique.

It's our microbial signature,

but it's in a constant state of flux.

The places we go

the food we eat

the people we meet

they all affect our microbial jungle.

- This is our Costa Rica, right?

This is our area where we go on the body

to really find our huge
amount of diversity.

Um, compared to the armpit
that's certainly true.

- So far
the North Carolina team

has identified 2,300 bacteria species.

That's four times the diversity

of all bird species in North America.

And this abundant harvest has come

from just 60 belly buttons.

- So on your body overall you
have thousands of species.

Most of them are not named.

- Some people maybe have
a lot less than others?

- Some people have hundreds of species

living in their belly button.

Some people have as few as six species

living in their belly button

and having fewer species is associated

with poorer health outcomes

and so it increases your
odds of getting sick.

- Maybe the words bacteria, microbes,

they have all sort of negative
connotations to most people

so maybe they need a re-branding.

- Diminutive super friends.

(laughing)

- Just as we need biodiversity

to support life on Earth

we need a variety of microorganisms

to guard the health of
our human ecosystems.

(bouncy flute music)

(water splashing gently)

On each square centimeter on your skin

there are more than a billion bacteria.

For them, it's a land of abundance

with plenty of food supplies.

(razor scraping skin)

You shed 30,000 to 40,000
dead skin cells every hour.

That's two kilograms in a year.

- Part of what they're consuming

is our dead skin, our dead bits,

and so there's some
decomposition happening there.

They're at war with each other

and so even our good bacteria

are actively fighting each other

producing antibiotics.

They're all trying to win.

I mean, none of them want to just

be confined to our armpit, right?

Each and every species,
they would all benefit

if they could colonize
us from head to toe.

- One of our
microscopic residents

engaged in chemical warfare
is Bacillus subtilis.

They patrol the skin
looking for fungi to attack.

Without them we'd wake up covered in mold.

Other microbes like
Staphylococcus epidermis

colonize our skin in numbers so vast

that there is little
room for invading rivals,

but the true power of bacteria
comes when they act together

and this coordination
requires a special language.

- Their genes are encoding proteins

that are allowing them
to talk with each other

and to detect each other

and to control each other's growth

and basically to allow other bacteria

that are more beneficial or
less competitive with them

you know, to grow in greater abundance.

(slow rock music)

- By tapping
into a cell to cell network

microbes conspire with their own species

and build alliances with other bacteria

to outsmart invaders.

Bacteria are the most
successful organisms on Earth

and part of their success is
that they're able to steal

the genes they need to adapt and thrive.

- They're able to change
their genomes very easily

and so this is why it's really important

to study the bacteria that
grow on and with us and in us

to understand in a sense like
what is the stable state,

because when a pathogen emerges

it's often one of these typical bacteria

that have co-evolved with us and have been

not a problem until ooh
they picked up something

perhaps from a virus,
from another bacterium,

who knows what?

And now they just change the game.

- This genetic flexibility

can transform our harmless microbes

from docile skin grazers
into vicious killers.

- I suddenly felt very ill

and I went to the gentleman's toilets

and basically I collapsed on the floor.

- But how can a tiny bacteria

destroy a healthy body
in just a few hours?

- Human or inhuman

not even the world's greatest
scientific minds can answer.

- Gentleman do you realize?

Try the light switch.

- When good bacteria go bad

the result can be scarier
than any science fiction.

(haunting music)

- For Andrew Ferguson a
visit to an Alpine resort

became a life and death
struggle with a rogue pathogen.

- I was vomiting and had
blood coming out of my mouth

and nose and all sorts of strange places.

- On arrival
Andrew had a quick swim

in the hotel pool.

Completely unaware that
a rare skin bacteria

had already entered his body.

(ominous music)

- The bug, the Strep
B bug, actually got in

through a cut on the leg and
I was having a rigors attack.

It's actually where the body
gets overwhelmed by bugs

and you go into a constant shaking

and I ended up at
Garmisch-Partenkirchen Hospital.

Over the next 12 hours I must have had

every test known to man.

They just didn't know
what the problem was.

Eventually after taking blood cultures

they discovered that I had
a Streptococcal B infection

and then over a period of three days

I was given increasing dosages

of different types of penicillin,

but nothing was working.

- It's like being in a canoe

and going down the Niagara River.

If we're in it early enough
someone can rescue us,

but if we're far enough down that river

eventually nothing is going to help us

and unfortunately that's
the situation we have

with these invasive infections

where at the very last moment
we have to get a surgeon

to get in and remove
that destroyed tissue.

- The surgeon said, "We're probably gonna

"have to amputate the leg.

"The infection is spreading
into a main artery

"and if we don't get it
it's gonna go to your heart

"and you'll be dead."

I remember saying to the surgeon

as I went into that operating theater,

"I can do without the leg,

"but I certainly can't
do without my life."

- Flesh eating disease

is an infection that
literally eats its way

through the layers of tissue
that surrounds the muscles

and it's fast.

It can cause death within 12 hours.

- It can spread amazingly quickly.

Sometimes we can even see
it before our very eyes.

- This bug
needs serious vigilance.

160,000 people are killed worldwide

by this bacterial onslaught every year.

- I still have my leg
and um, as you will see,

I'm actually still have it.

The aftermath of all of this is

I have to take penicillin twice a day

and that has its implications as well

because unfortunately
overuse of penicillin

tends to cause killing off the
good bugs that sit in the gut

and then I ended up
with other complications

as a result of that.

- These are dreadful infections.

To go from a perfectly
healthy person one day

to dying or only being saved
by very aggressive surgery

is an indication of these
bacteria's potential

for harm to us.

- But what
could turn Streptococcus,

usually no more dangerous
than a sore throat

into such an aggressive killer?

Microbiologist Professor Mark Walker

was intrigued by the mystery.

- It was quite a surprise
there being quite low levels

of very invasive diseases
caused by this bug.

- With some
ingenious genetic detective work

Professor Walker tracked the
origin of the deadly disease.

- In the mid 1980's in
the Rocky Mountain region

of the US there was an outbreak
of flesh eating disease

caused by Streptococcus.

This outbreak was investigated
and what was found

was that a new Group A Streptococcus

had come onto the scene

which was more virulent and better able

to cause invasive disease.

- This virulence
was caused by a virus

called bacteriophage
which invaded the strep

and modified its DNA.

- It inserts its genetic
information into the bacteria

and that's the reprogramming
that takes place

when a bacteriophage infects the bacteria.

- This modified
bacteria was so successful

that the clone of that single bacterium

spread across the world.

(radio chatter)

- And in other
news a young mother died.

- Hi
- Hi, how are you?

- I'm Sharon Lewin.

Nice to meet you.
- How are you?

- Tell us about what's happened to you

and what brought you to the Alfred?

- I arrived by ambulance.

I'm waking up from the anesthetic
from the first surgery.

Being told that I've lost my small toe

and quite a lot of flesh from my foot.

- Did you have any injury to the foot

or it just, it just came out of the blue?

- It just sort of come out of the blue.

Like even the cut, the
small cut that I had,

and then I've worked out
recently talking to the doctors

trying to investigate more
into this horrible bug

that um, basically you
can get it from coral.

You can get it from dirt.

You can get it from potting
mixes and things to my belief.

And I think I've got it through
walking around my garden.

- Think we can have a look?

- Absolutely.

Get ready!

So that's the flap as you can see.

- Where's the flap here?

- The flaps come from the your
whole top side of your back.

So I've got a massive
scar from under my armpit

right down basically to my bum.

- Yeah, from here to here.

- Luckily the
chance of catching such serious

invasive infection is still small.

- Usually we're able to
live with these bacteria

within our throat or on our
skin without getting disease.

So people should not be freaked out

the next time they have a sore throat

because that's just a normal event

and our immune system is able

to deal with it very adequately.

- But for those who cross paths

with the mutant form,
Streptococcus can be fatal.

(lighthearted music)

Most of the wildlife on
our bodies is harmless.

Even if we might horrified to discover

what they get up to.

Meet the tiny parasitic
mite called Demodex.

It takes up residence in your eyelashes

burrowing head first into your pores.

- They're these long
sort of narrow things.

They come out at night
when you're sleeping.

Come out onto your face and have sex

and then crawl back into the pores.

It's an animal.

It's on your face and we
don't know very much about it.

That's enough for me.

- Rob Dunn's
meet your mites project

is trying to shed light on one

of our most overlooked hangers on.

- We can ask questions
like how do the mites

in one human population relate to those

in another human population?

Pacific Islanders, they
have different mite species

as a function of the
relatively long isolation

from other people's.

Aboriginal people's of Australia,

what do their mites look like?

How have these mites changed
as our faces have changed?

It's super exciting.

People get to see whether
or not they have mites.

People get to see what they look like.

- Let's take those glasses off

because we're gonna try to
get in your sort of t-zone.

- What if you're wiping
the mites off right now?

- Well you know I don't think so

'cause I think they like to clink tight

to deep inside the pores on your face.

- That's always good to know,
they're clinging tightly.

- They're clinging on.

I think 'cause they
like to live in the oil

in your sebaceous glands

- Oh.
- And so

it just feels like home.

- Good oil out here.

- Yeah, exactly.
- Come and get it.

- They eat oil from our pores.

It'd probably eat microbes.

They probably have a pretty specific suite

of microbes in their guts which are just

you know, little hints
about what's going on there.

- Apart from eating, crawling,

and having sex on your
face while you sleep

Demodex may be linked to
a common skin problem,

rosacea.

- The connection hasn't
really been well defined,

but one of the hypotheses is that

is the bacteria inside the mite

that is what's causing the
flare up of the rosacea.

- I'm prone to rosacea.

- Oh.
- So if there's

a connection between mites and rosacea

lucky for you, I'm having
a flare up right now.

(mite clicking)

- But it's not
the mite that's the problem.

Like a Russian doll, there
are bugs within bugs,

and in this case they have no way out.

- So it turns out that
mites do not have an anus.

They have no exit.

- So they eat and eat and eat

and the feces just
accumulates in their back end

and eventually they sort of fill up

and then it's all over.

You know, we thing about what
our fate is determined by.

I'm grateful my fate is not determined by

how long it takes me
to fill out with shit.

- As it turned out

Brian's face mites have made

a significant contribution to science.

This is the first time mites

have ever been filmed giving birth.

They too are part of our private wildlife.

- The truth is, is you're
not really separate

from these critters.

Like who you are is defined
by your interactions

with other species.

- What would we be without them?

- Yeah, what would we be without them?

And who are we when we
have bad species on us?

So for example to take a
really extreme example.

A Toxoplasma gondii is this
Proteus that gets into the brain

and when it gets into our brain

it changes what happens in our brain.

(game beeping)

- Toxoplasma
gondii is a cunning parasite.

It's a real life zombie
bug and it's unmasking

is one of the strangest
stories in science.

(birds chirping)

(suspenseful orchestra music)

Normally a self respecting
mouse steers well clear

of anything that smells like a cat,

but for mice infected with the zombie bug

cats are like a magnet.

Mice pick up Toxoplasma from soil,

but to reproduce the
parasite has to find its way

into the intestines of a cat

and the best way to meet up with a cat

is to alter the mouses natural fear

and make felines fatally attractive.

The brainwashed rodent is now easy prey,

but it's Toxoplasma that's
the real winner here.

Once inside the cat it can reproduce.

(grass crushing)

The trail of the zombie bug led to Prague

and one of the world's
oldest universities.

Professor Jaroslav Flegr
is a renowned specialist

in the study of parasites.

By a complete coincidence

just as he was looking
for a new subject to study

he was tested for Toxoplasma
and the result was positive.

- I was not very happy to be
infected by some parasite,

but uh, at the same time it was very

hmm

interesting.

I mean this idea that it can explain

some behavioral pattern of me.

- Normally
Flegr was a cautious person

but he began to exhibit
some very risky habits.

Not unlike the mouse who
is attracted to cats.

- For example I'm not
very afraid in situation

when I should be afraid.

It's a

very strange behavior.

For example I was in Gorjestan

and there was a lot of shooting around

and I was quite calm.

And it's not the only situation.

Also my startle reactions
are a little bit unusual.

When somebody hits the horn
behind me in some traffic

I stay in the same place,
look slowly behind,

what has happened?

- Before
Flegr no one ever thought

of linking human behavior
to Toxoplasma infections

and if Flegr's hunt was right

it was messing with the brains
of many other people as well.

- I started to study this hypothesis

on the cheapest material
which is available here.

I mean on our students

and 25% of them were Toxoplasma infected.

- These studies
show that those infected

by the zombie bug were far more likely

to put themselves in risky situations.

- The risk of traffic accident

of Toxoplasma infected subject
is about 2.6 time higher

than the risk of traffic
accident of non-infected.

- The implications
of this discovery

are unsettling.

Toxoplasma is one of the
most common human parasites.

- We used to think that
our mind is really our,

but our results show
that maybe it's not true.

- We can be infected

by eating unwashed vegetables

and under-cooked meat.

(speaking foreign language)

In some countries it's rampant.

In France where barely
cooked meat is popular

infection rates are as high
as 55% of the population.

So the next time you meet
a reckless French driver

beware, it may be a zombie
bug behind the wheel.

(upbeat French cafe music)

(tires screech)

(dramatic music)

- The hair on your head

is the equivalent of a rain forest.

Shaded, moist, and rich in nutrients.

It's the home for an
annoying little critter,

the head louse.

- There are really interesting
evolutionary stories

going on in our bodies.

And so hair lice in that
regard are fascinating.

Head lice are living fossils.

They are the ultimate survival machines.

- Lice approximately appeared on Earth

somewhere in the region of
115 to 130 million years ago.

- This means that they predate

the great extinction event
that killed off dinosaurs

and wiped out 75% of all species.

At London's natural history museum

Dr. Vincent Smith takes a special interest

in these blood sucking parasites.

- There are about 5,000
species of lice in total.

This one here is a human head louse.

This is a female.

It's highly adapted to living on humans.

So they have these thick sharp claws

and a groove under the
louse where the hair sits

so that they can cling on.

- Lice must live on their host.

If they fall off, that's it, they're dead.

- Right at the front is the mouth

where tiny sharp tubes get out

and they find a blood vessel
and they feed on the blood.

- Yet despite
these advanced features

lice can't walk, crawl, or fly.

They live lonely lives

until we come together.

(children playing and laughing)

When our body parts meet

lice don't miss the
opportunity to jump ship.

- One of the reasons why lice
spread particularly quickly

in young children is because many

of the social barriers that we
would normally have as adults

don't exist in young kids.

You'll see them touching,
hugging each other all the time,

and that is a perfect medium
for the transfer of lice.

- In a school room head lice

can pass over several
heads within an hour.

- The head lice can be really
difficult to get rid of.

Almost none of the traditional
insecticides will work

and you have to use other means

usually physical means
simply to get rid of lice.

- But lice are
more than just an irritation.

They've changed us in fundamental ways.

(heavy breathing)

(triumphant horn music)

One of the striking things
about the human body

is its hairlessness.

- Fur was an evolutionary breakthrough.

A warm hug on a cold day

that allowed mammals to live
in conditions too hostile

for reptiles and birds.

And once hair evolved
120 million years ago

it was rarely lost.

Yet we ended up virtually hairless.

Why?

- Some people think that it's

it was actually to help
lose our lousy infestations.

That there were fewer exoparasites,

lice, and fleas, and other things

because they can't really
cling to a naked skin.

- A furry coat is a safe haven

for ticks, lice, fleas,
and other blood suckers.

And they're not only annoying

but some of them can
carry lethal diseases.

- Lice and fleas and their kin

they don't kill us in and of themselves

but because most
exoparasites take our blood

they also have the capability
of transmitting disease.

And so that those
individuals who had less fur

were actually at a reduced risk of disease

from these exoparasites.

- Hairlessness
was an attractive sign

of good health.

Just like the bright plumage of birds

is an advertisement for
being free of parasites.

It was favored by sexual selection

and this ensured that the naked genes

were passed down to the next generation.

And ever since we've become
obsessed with removing hair.

We spend billions annually on razor blades

and getting waxed,

but some parts of our body are hairy.

This puzzled Professor Robin Weiss

at University College London.

- Why do we have pubic hair?

My guess, and this is just hand waving,

is that pubic hair isn't just a remnant

of when we were furry,

but it's an active evolutionary selection

of a big bush of hair.

- And if this idea is right

then we wouldn't expect to find pubic hair

on our furry cousins.

Professor Weiss wanted to find out.

- Well that was a great
excuse to go to the zoo

with two of my grandchildren

and while they were looking
at the antics of the apes

I was looking at the
ape's genital regions.

And sure enough they
don't have pubic hair.

They have some fur, but if anything,

amongst apes and monkeys
it's shorter and smoother

than on other parts of the body.

They're the very opposite of humans.

They have less hair
around the genital region.

- So if our primate
cousins don't have pubic hair

where does ours come from?

- Sexually immature humans,
children don't have it,

but males and females do.

- Could pubic
hair have evolved then

to indicate that mating could be fruitful?

The clue to this puzzle is
those pesky parasites, lice.

(salsa music)

It was assumed the pubic lice

were a close relative of head lice

which makes sense if they
both came from a time

when we were furry all over,

but on closer examination

the two couldn't be more different.

- The crabs or pubic lice
have these great big claws

to clasp around coarse hairs.

- They
couldn't live on our head

which means we got them and pubic hair

after we lost our fur.

- Closest known relative
to the humam pubic louse

is the gorilla hair louse.

Gorilla's have coarse hair and those lice

are already adapted to live on coarse hair

like pubic hair should
they get across to humans.

- And so it looks as though
around eight million years ago

an ancestor of modern gorillas

and one of our ancestors came
close enough to exchange lice.

- There must have been
some close physical contact

for us to have acquired that louse.

- What happened in that moment

only the gorilla ancestor
and our ancestor know.

I suspect it was a little bit tawdry.

- I mean the suggestion is it was sexual.

- One thing's for sure

one way or another we got crabs from them.

Since then, genital lice have
traveled the world with us,

but now we're getting our revenge.

(upbeat salsa music)

In 1987 seven Brazilian
women, the Padilha sisters,

opened the J. Sisters salon

to offer what they had
done, the Brazilian wax.

The complete removal of
hair from the pubic area.

- The first time I did it it
was a little uncomfortable,

but I noticed right away a lot of changes.

I sweat less in the summer.

- In only a few
years this form of waxing

has gone from the exotic to the everyday.

- It went like all over,
people coming from television,

from all over.

They wanted to know what is this?

- It's the
most successful innovation

in hairdressing since the permanent wave.

- I Get mine done about every five weeks

and I'm addicted to it.

- But this
addiction to the Brazilian

is actually threatening
pubic lice with extinction.

- You take away their habitat

and they can crawl on,
but they can't hold on.

- I feel very proud of ourselves

that they might be extinct.

It's ugly.

It's very ugly.

- Imagine a whole suite
of species like this

that were used to holding onto us

and then as our hair fell away

they lost their habitat.

- We evolved hairlessness

to rid ourselves of parasites.

Exposing our dark skin to the African sun,

but as we ventured to cooler climates

our skin became pale.

We owe these differences in our skin color

to our interaction with
the bugs that live on us.

- These are very fundamental aspects

of what it is to be us

that are plausibly linked
to these little organisms

that crawl around in our skin

and hang onto our fur.

(intense music)

- We are not alone.

Bugs have been our constant companions.

The hidden force behind your health,

your skin color, and even your behavior.

Whatever you are, you owe to them.

Microbes have been the making of us.

(dramatic music)

Life is an endless fight.

A battle for food and sex,

but often the winning strategy
is a balance of power.

A truce between rivals.

The same happens inside our bodies

where trillions of organisms
have evolved to share us.

(ants scratching)

There are worms in your bowel.

- You're nearly finished.
- Colonies of bacteria

on your teeth.

Fungi thrive in your lungs

and viruses embed themselves in your DNA.

Collectively this menagerie of bugs

is called your microbiome

and it's as much apart of you

as any of your organs.

We are essentially an assembly

of a lot of different
organisms, ourselves included.

- Microbes
have helped us to evolve.

They've made us who we are.

- They were there right from
the evolution of human beings

as hunter gatherers.

Even right back to the
evolution of mammals.

(spraying)

- But in the blink of an eye

we've cut ourselves adrift from nature.

(toothbrush brushing)

- We've gone from a daily
life in which we were exposed

to thousands and thousands of species

of many different kinds.

Where we ate food with dirt still on it.

Where we had worms

and then all of a sudden we
move into these environments

where we've convinced ourselves

that all other species aside from our dogs

and our lovers and our kids are bad.

- Believing
it makes us healthier

we do our best to scrub
bugs off our bodies.

We've unleashed a war on germs

and now we are paying the price.

(water pouring)

- Modern medicine is
about killing bad species.

We are really good at thinking

about medicine in that context.

You know, something bad makes us sick

we kill it, we get better,

but the idea that
something good is missing

and that that makes us sick

we don't have much of
a framework for that.

The medicine that would be required

to think about this in the right way

would need to think about
the body as an ecosystem.

- In this
revolution in medicine

it's the bugs that will save us.

This is a journey into the human body.

Your insides are a battle ground

and it's your health that's at stake.

(machine drilling)

Our tour begins at the mouth.

All is not well with the main entrance.

- Dental decay in this world now

in talking about all countries is

uh, plague proportions.

- Tooth decay
now effects around 90%

of children worldwide and
can lead to serious diseases.

It's an epidemic of the modern age.

Compared to us our
ancestors had pearly whites

and they didn't even brush their teeth.

It's a mystery that
fascinated DNA detective

Professor Alan Cooper.

He's been studying teeth
throughout the ages.

- When you do look at the
hunter gatherer populations

you see very little
signs of dental caries,

the holes in your teeth.

They look in really good nick.

- But the closer
we come to modern people

the worse the teeth become.

- As soon as you start moving
from the hunter gatherer phase

into the farming phase
the teeth look terrible.

You know, there's dental carries.

There's gum disease 'cause of the bacteria

around the base of the teeth.

Um, nasty pathologies.

- And the consequences

are far more profound than bad teeth.

If Cooper could discover what's
gone wrong inside our mouths

it might help explain the rise

of some of our most serious diseases.

- We think oh well, we
get a bit of bleeding.

Gums, we have to go to the
dentist a bit, no big deal.

We got holes in our teeth.

What we don't realize is that the bacteria

are leaking down through
those inflamed gums

into our blood system

and stimulating all
sorts of immune responses

and these immune responses are
now being linked increasingly

to a huge range of
modern western diseases.

Cardiovascular disease,
diabetes, hypertension,

premature birth, cancer.

The list goes on and on.

- In one way or another

the key to it all is bacteria.

(soft piano music)

There are more than a
hundred million bacteria

in every drop of saliva.

An eco system of 700
hundred different species.

And there is no place they like better

than the wet surfaces of our teeth.

Here they form a layer or biofilm

that dentists call plaque.

- It happens every night
when we're sleeping.

The plaque, the layer of bacteria

on our teeth gets calcified

and slowly builds up over time.

This is what the dentist is removing.

- We provide
bacteria with a home

which is just as well because without them

we'd have no teeth.

The microbes in our mouth
protect us from the food we eat.

- We have evolved in
the presence of acids.

Most foods that we eat

most of our diet is essentially acidic.

At the same time the enamel

which makes up the outside
surface of the tooth

is inorganic and will dissolve in acid.

So here we've got this conundrum

trying to work out well
what's happening here?

How does a tooth stop
itself from dissolving?

- The answer is biofilm,

a dense layer of bacteria
that's stuck on our teeth.

As acid eats away at the enamel
bacteria fills in the holes.

- The tooth starts to dissolve

then the raw products of this process

get caught into the biofilm
and the right environment

get reused to heal the tooth.

- In a healthy mouth
everything works in balance

and the good bacteria
protects us from decay.

(spitting loudly)

(water running)

- These microscopic dentists
have looked after our teeth

for much of our evolution.

So what's changed?

- We can only judge that

if we've got an idea about what
it looked like before hand.

- But there was a problem.

There's no bacteria left alive

on the teeth of museum skulls.

- There seemed to be no way
that we could actually get

a look at what a bacterial microbiome

would look like in the past

until we thought about those
calcified plaque on the teeth.

- It was an ingenious solution

locked in the plaque of our ancestors

were the fossilized remains
of vast numbers of bacteria

and compared to us there
was a striking difference.

- Everything goes completely strange

when the industrial
revolution comes in 1850

and suddenly you're getting
large amounts of processed sugar

and flour become available.

And at that point the diversity

of the bacteria in the
mouth just drops away

and huge amounts of
these pathogenic bacteria

become very obvious in
everybody we look at.

- A bunch of
disease causing bacteria

has taken over our mouth.

They thrive on our modern
diet of processed food

and that's changed the game.

- These organisms tend to make,

be little acid factories

producing acid onto the tooth's surface

which then starts to
dissolve the enamel away

and lower the pH of the environment.

And they're able to withstand that low pH.

That harsh condition that other
microbes in the mouth have.

- And the good bacteria that don't

like living in acid conditions

good bacteria that normally keep

the bad bacteria under control

just like in the gut

then these die off.

- Our changing diet

unleashed a war inside our mouth

and the bad guys are winning.

Acidity in our mouth is a problem,

but there's one place where
we couldn't do without it,

our stomach.

- It's a filter that
kills lots of pathogens.

We eat food full of microbes

and one of the reasons
those don't just colonize

and take over our gut

is that we have this
stomach with adaptations

for dealing with the microbes.

- In fact healthy humans
can eat just about anything

because 99% of the bacteria in your food

are killed by the stomach acid.

It's certainly enough to dissolve nails

and you have these stories over the years

of people who try to kill themselves

by eating razor blades,
or nails, et cetera,

and a few months later
you look in this stomach

and you can only find a
few old rusty fragments.

It's almost totally digested.

- The only bacteria
that survives the acid bath

is the bug called the gastric demon,

Helicobacter pylori.

- Helicobacter is very very interesting.

It's somewhere in between a harmful one

and a harmless beneficial one.

(trumpet music)

- No one knows this bug

better than Australian Barry Marshall.

In 2005 he shared the Nobel Prize

with Robin Warren for
discovering its power over us.

- The reason people didn't look
for bacteria in the stomach

before the 1970's when
Dr. Warren first saw them

uh, was that

they knew that bacteria
could not live in acid.

It's too dangerous.

(sizzling)

- But we now know some bacteria

have learned to survive
in extreme environments.

And the gastric demon is one of them.

- So the question is then,

how do bacteria survive in acid?

And the next discovery was that

the bacteria can make ammonia

and ammonia neutralizes acid.

(haunting music)

- Helicobacter
has a nasty reputation.

It's called the gastric
demon for a reason.

It causes stomach cancer
and gastric ulcers.

(beeping)

Marshall and Warren were the first to show

that ulcers weren't triggered by stress

or spicy food as it was commonly thought

but by infection with Helicobacter.

- However we could never
get over this issue

that lots of people had the
bacteria and never got an ulcer

and so the skeptics could always say,

"You must be wrong because
I had lots of people

"with Helicobacter and they never

"had a days illness in their life."

(calypso music)

- And even more puzzling

is that in the developing world

where the gastric demon is rampant

hardly anyone gets ulcers.

Somehow a dangerous bacteria for the rich

is harmless for the poor

and the difference between
the two is another parasite,

worms.

- Helicobacter pylori causes ulcers

if you don't also have parasitic worms.

You can't just have a
part of the ecosystem.

You need the whole ecosystem.

- It's all
a question of balance.

The proportion of worms and bacteria

needs to be just right for a healthy body.

- But just to show how
subtle all of this is

if you remove Helicobacter pylori

which is what we're doing
nowadays with antibiotic

we get another problem.

- The eviction of Helicobacter

in the western world has contributed

to the rise of new diseases,

like asthma and allergies.

- So it's in this gray area.

Causes cancer or ulcers.

Possibly prevents asthma,

but the reason it prevents asthma

is possible more important than

all the terrible things it does.

(birds chirping)

- Helicobacter is an invader

that keeps our immune system busy

and if it's not present

we can overreact against harmless
stuff like pollen or pets.

- If you could find the correct strain

which you could control

then I think it would
resurrect Helicobacter

as a useful bacteria.

- If we could
tame the gastric demon

it might become a live
vaccine against allergies.

- So I think there are all
kinds of possibilities.

I'm quite excited about it

and we are already testing
Helicobacter products

in human volunteers at the
University of Western Australia.

(water splashing)

(dog barking)

- Bacteria, fungi, and worms,

are invading us all the time.

In fact they come as a side
order with every bit you take,

but some people can't get
enough of these nasty parasites.

They want more.

(bouncy guitar music)

(water pouring)

(sizzling)

Our food contains more
than we bargained for.

It's loaded with bacteria, fungi,

and sometimes the eggs of parasitic worms.

Richard Faulks loves his ham and eggs,

but this breakfast is being sacrificed

in the name of science.

Faulks built the world's
first artificial stomach

and today he is out to discover

if worm eggs survive the gut's acid test.

- This is my breakfast

and I'm now going to add just a pinch

of intestinal parasite eggs

and mix it before putting
it into the stomach.

(water pouring)

(bouncy guitar music)

- Ahead lies
a hydrochloric acid bath

that will kill just about anything.

- Everything was normal.

(liquid pouring)

The whole thing is operating
at 37 degrees centigrade

which is the same temperature as the body.

The first sample is
now just being ejected.

This is the material which
actually ends up going down

into the duodenum and into the intestine.

- But do the
parasites survive the journey?

(intense orchestra music)

- Well as we expected

most of these parasite
eggs seem to be viable.

- Worms are one
of nature's great survivors.

They thrive in some of the planet's

most inhospitable environments

including your insides.

The ones in our gut look like
aliens from a sci-fi movie

and incredibly they originally came

from the murky depths of the oceans.

They were able to come on land

by colonizing the guts of animals

including us.

They're after a rich food supply,

your blood.

Parasitic worms love us

and in turn we are
beginning to love them back.

- If I had Crohn's disease,
or ulcerative colitis,

or multiple sclerosis,

I would infect myself without hesitation.

- A colleague and I
gave ourselves hookworms

and my colleague had 20 hookworms

and I only had six

and being a competitive person

I thought well I'm going to get more.

I gather you've got--

- Dr. John
Croese and Alex Lucas

are hooked on worms.

- Worms are both bad and good.

In developed countries
where we are well nourished

worms are potentially good.

- The medical use of worms

is now being put to the test.

Hugh Sheardon is suffering
from celiac disease,

a nasty reaction to gluten

that causes severe diarrhea and pain.

He and Judy Noonan are part of
a pioneering clinical trial.

- We are experimentally infecting

these people with hookworms

to see if the infection
has a therapeutic benefit

on their Crohn's disease
or celiac disease.

- These are diseases where

the immune system attacks
the lining of the intestines

causing chronic inflammation.

So how can worms fix the problem?

- The last thing a worm wants to do

is have our immune system eject it.

They modulate the immune system

and send it in a direction

that just generally dampens inflammation

and that protects them.

Stops them from being attacked,

but the benefit of that
is that inflammation

in general is suppressed.

- As it turns
out it's the worms spit

that carries the magic ingredient.

- As a hookworm attaches
it releases all sorts

of salivary proteins

and some of those have immunized
suppressive properties.

(stove clicking)

- With worms on board

Hugh's immune system is turned down

and should stop overreacting
to gluten in pasta.

- The aim is to use hookworm

to change the immune response to gluten.

- For people
with celiac disease

any amount of pasta can be dangerous.

Six weeks with worms and
Hugh's reached a milestone.

It's a tiny morsel,

but previously even this
would have made him sick.

- When we reintroduce gluten to celiacs

who have hook work infection

that their response will be muted

and now start to tolerate
low doses of gluten.

- For Hugh Sheardon

the experiment was a success.

At the end of the trial he
could eat a full bowl of pasta.

- Live worm therapy is
a good proof of concept,

but I don't think it will ever become

a scalable, widely used method
of treating inflammation.

However if we can identify and harness

the actual molecules that are responsible

we can then turn those into a much more

conventional type of drug.

- But desperate
patients aren't willing to wait.

An approved drug will take
many years to develop.

- Nice to see you.

Come on.
- Nice to see you too.

- Come on please take a seat.

Welcome.

- So the seriously ill

are signing up for treatments
in the hookworm underground.

- Originally I was diagnosed
with ulcerative colitis.

- Yes.

- And because those medications
weren't working for me

they switched it to
irritable bowel syndrome.

- Can I have your arm please.

Just pull here.

- People should be allowed to
pursue alternative therapies.

Especially when the other
possibility seems not so great.

On the other hand if
it's not proven to work

then you don't know it works.

Then you're basically
just buying into a dream.

(calm guitar music)

- Valesquez-Manoff
is a science writer,

but his interest in alternative
therapy is very personal.

- My whole life I've had asthma.

I've had food allergies

and I've had, starting at age 11,

I have an auto immune disorder
called alopecia areata

which means my immune system
turned on my hair follicles

basically shutting them down.

- After researching
his health problems

Moises made arrangements to be inoculated

with the so called American murderer,

Necator americanus.

It's a parasite that has
plagued humanity for centuries.

Moises traveled to a
private clinic in Mexico

just across the border from the US

where using worms for medical
purposes remains illegal.

- Of course I was a little bit nervous

because I'm doing something that frankly

most people will tell you is
stupid and it probably is.

I wasn't that scared though 'cause I knew

that scientists around the
world had self infected

'cause the reality is you
can't study these things

unless you keep a colony alive somewhere.

They only live in humans

so they just have them in their own guts

and then when they need
them they cultivate them.

(slow guitar music)

- One of those
who cultivated his own worms

is the owner of the Mexican
clinic, Garin Aglietti.

- Parasitology has a story
tradition of self experimentation

and so what we're trying to do

is remove the barriers to access for this

because I don't want everyone
to have to do what I did

was basically when I became ill

and was looking for access,

you go to the professional scientists

and they can't help you.

They're bound by
institutional review boards

and professional standards

and appropriate treatment corridors.

- Garin
Aglietti's life was plagued

by chronic immune disorders.

Conventional medicine offered no help

so in desperation he turned to worms,

but first he had to find them.

(plane engine)

He traveled to Peru

where the American murderer was common.

Collecting worms is not
for the faint hearted.

The process requires doing something

called a latrine survey.

- A latrine survey basically means

just taking samples of soil and feces

and collecting it and cataloging it.

It's just about as much fun as it sounds.

I think it was the Ortiz family

was the one that turned
out to be the hottest one

and the thing that I wasn't prepared for

is that I had to beat the chickens

'cause the chickens were
going down to eat it

and if they got there first

then everything was gonna be gone

so I had to go me run around
trying to get to the chickens.

- After harvesting his medicine

Aglietti infested himself
with seven microscopic larvae

and the offspring of those worms

are now used by doctors to
treat patients in his clinic.

Once inside us the hookworms
face a perilous journey.

Yet they are well
adapted to the challenges

our body throws at them.

- If you apply 50 live
hookworm larvae to the skin

you can be assured that those 50 larvae

will get into the gut.

- The larvae
hitchhike aboard blood vessels

and flow through the bloodstream
like rafters on a river.

They will pass through the
heart before reaching the lung.

- They're going to irritate
the lung a little bit.

Lungs are going to produce
a little bit more phlegm.

The phlegm goes all the way to your throat

and you swallow it, okay?

So they got into the stomach
which is full of acid,

but the phlegm is actually
protecting the worm

so they don't get burned by the acid.

That's nature.

- Once the
worms reach the intestines

they announce themselves
to the immune system

by taking their first
bloody meal and that sucks.

- The side effect phase
was a bit of an experience

and had I not been so committed

to never doing a latrine survey again

I don't know if I would
have gotten through it.

- Those side
effects include cramps,

nausea, and diarrhea,

the body's natural response to shake

itself free of the parasites.

- They are painful to have.

Those symptoms sort of waned over time

and I also saw some benefits.

Like, about a few, let's say four months

after I took the parasites
was hay fever season.

For the first half of hay fever season

I completely lost my allergies.

It was amazing.

I never lost my food allergies.

I still had those.

(intense music)

- The worms can
manipulate our immune system

in a way that modern
medicine is yet to match.

- So I think just 'cause
you can kill all the worms

doesn't mean it's necessarily a good idea

to kill all the worms.

- It does work for some people.

It also doesn't work.

I interviewed some people who got worse.

So actually would not recommend it.

On the other hand it doesn't change

any of the evolutionary
argument that we're making here

and that is that our immune system

comes to expect stimuli like these

and we need to replace it somehow.

- These
therapies remain unproven,

but one way or another
worms are forcing us

to reconsider our approach
to treating western diseases,

but they are just one of
our microscopic tenants.

There are a hundred trillion more

in the most unloved place of our body,

the colon.

Gastroenterologist, Thomas Borody,

discovered the power of poo

and he's saving lives with it.

- Amongst the last
unexplored regions on Earth

are caves.

They hold species that
are unknown to science.

Yet they are no match for the
dark corridors of your bowel.

Here there are more bacteria on

just a single square centimeter

than all the humans who've ever lived.

- There's ten times more
living cells in the stool

than there is in our body.

So in effect we are 10% human and 90% poo.

- The microbes in the gut

aren't just along for the ride.

They are essential for the
development of the brain,

the immune system, our overall health,

and even our mood, and body shape.

- These bacteria depending
on the composition

can control weight gain, weight loss,

and develop in to have insulin resistance.

So there's a large sort of vast mechanisms

that are inside our bowel
flora that are responsible

which are just emerging.

- Yet we are
damaging our gut flora

even before understanding it.

- We know that when you
take too many antibiotics

that one of the things that happens

is it puts you at extreme
risk for pathogens.

- It kills off all of the friendlies

and so then bad bacterium takes
over and the patient dies.

- So instead
of prescribing antibiotics

to kill the bacteria

Gastroenterologist Thomas
Borody does the opposite.

He adds bacteria.

Trillions of them.

- Start going forward.

- Professor
Borody is the pioneer

of fecal transplants.

To treat digestive diseases
he replaces infected gut flora

with healthy poo.

- Well it's still
disgusting to me as well.

I'm just like anybody else,

but you see the potential
because in its healthy form

with full diversity and lots of bacteria

is able to enter another person's bowel

and kill off bugs that cause disease.

- Despite all we've learned

of poo being smelly waste

for Borody it's medicine.

Our colon is a factory producing bacteria

that thrives on foods we can't digest.

- The bacteria eat them.

When bacteria eat them they multiply

so we have to let them out the other end

and that's why we defecate.

- And defecate we do.

An average person will produce

more than four tons of
feces in their lifetime.

(upbeat orchestra music)

Borody has opened a new
frontier in medicine.

Every morning healthy
donors arrive at his clinic

with a fresh supply to cater for people

with gastrointestinal diseases.

Kati Angelidis suffers from
debilitating bowel problems.

- I was used to that blank stare

you know when I'd ask them
what was wrong with me.

How can you help me?

When you have got issues you've been

to hell and back with your sympoms

so you will do anything to, you know,

get some kind of improvement.

- Professor Borody will perform

seven to ten treatments like this everyday

and many more would come
if they could afford it.

- The cost is prohibitive to get it done

in a clinic for them

so they're doing it at home

plenty of them.

A lot of parents doing
it for kids, you know,

with Crohn's disease or whatever

and they're desperate, they're helpless.

You know, they'll do anything.

So yeah it's a bit underground, isn't it?

But yeah it's happening.

- People are still trying to work out

the best way of doing it.

I mean do you put it in that way

or that way

(laughing)

or like radio controlled capsule

you just swallow and open up

with some sort of radio controlled signal

and then the capsule carries on?

You know, the technologies
are being developed.

There are going to be some
very clever ways of doing this.

- Tending our microbial garden

also helps with diseases
that having nothing to do

with digestive problems.

20 years ago William Kostopoulos

had his wisdom teeth removed.

It didn't go well.

- My body went into trauma.

They thought actually I had a stroke.

They sent me to a neurologist

and then they gave me an MRI scan

and um, after the MRI scan

they told me that I had a
mass multiple sclerosis.

- It was devastating news.

- There was times you feel
like just killing yourself.

Your life is revolving around medication,

and doctors,

and MRI scans,

and treatments,

and hospital.

- Realizing the
disease couldn't be beaten...

- Good to see you.

- He went to
see Professor Borody.

- We spoke about some sort of transplant.

A poo transplant as he puts it

and um, I was open to
anything at that stage

because I was suffering through

three and a half years, four years,

- William had the transplant

and incredibly he has
completely recovered.

- Things are fantastic.

Things couldn't be better.

I mean I'm 49 now.

I'm heading to 50 so, you know,

(scoffs)

but I don't feel 50.

I still feel like I'm 20.

(speaking lowly into recorder)

- That was a fortuitous finding

and we had three such patients

and we went on treating their MS

they did not come to us for that purpose.

We were treating the bowel disturbance.

- For now these
are anecdotal results.

Yet the treatment designed
for digestive diseases

seems to be having even more
intriguing side effects.

- We have had at least two patients

in whom profound depression
was able to be reversed

and I didn't notice that.

The patient said to me after he had

a transplant done for a different cause

he said, "My depression is gone."

I said to him, "What do you
mean your depression's gone?

"How can that be?"

He said, "Well I've had
depression for 25 years doc.

"I know when the depression is gone."

So I wasn't gonna argue with him.

- Gut microbes
influence our body and mind

in fundamental yet inexplicable ways.

There's so many changes
that we've seen patients

that are difficult to believe
when we change patients flora.

Why is this so?

There are so many
questions to be answered.

- If we can explain the links

between our microbial
ecosystem and chronic disease

it will revolutionize medicine.

As the first step microbiome explorers

are signing up volunteers
to donate a dollop of poop.

(toilet flushing)

- They're currently sequencing
lots of shit in the US

and I heard that's just
been expanded worldwide now.

So when we do the survey,
a very wide survey,

that's important too that we can see

across the whole human
population what the variety is

and we can see how that
relates to people's health

or lack of health.

- These initial surveys have

already revealed thousands of
bacteria we never knew before.

Our inner continent is terra incognita.

- Every person is colonized
with these species

that have an enormous
effect on how they live,

their health and well
being for their entire life

and in many cases we
can't give them names.

- But we've
already discovered bugs

that make us fat or thin.

A group of bacteria called Firnicutes

helps the absorption of fat by the body.

Depending on which ones you have

you may have absolutely
complete digestion of your food

and I suppose the theory is that

then you're one of these people

that has a small about of food
and puts on a kilo everyday.

Whereas other people
might eat the same amount

and not put on any weight.

- Having
these fat bugs on board

is the equivalent of eating
a slice of cake everyday.

- Historically if you
had a group of microbes

that gave you lots of
energy from your food

it would be enormously beneficial

because you could go longer
without food and survive.

You would need less food everyday

but now we're all fat.

- Luckily there is a bug

that helps keep you thin.

Accermansia may one day lead
to a treatment for obesity.

- I think we might have
yogurts in the future

or something like this which will give you

the sort of skinny
yogurt together with bugs

and I'll be eating a lot of those.

- Ultimately our
health will be determined

by the diversity of bugs in our gut

and the balance between
the beneficial and the bad

and that varies from
one culture to the next.

(children laughing)

- If you look at the gut flora

or for instance people living
in a little African village

and compare that with the gut flora

of people living in Italy
they are so different.

- People in
developing countries

have a richer and more balanced gut flora

than those in the west.

And that helps explain why the affluent

are more prone to modern diseases.

- Now one reason is clearly diet.

We eat crap.

(meat sizzling)

- When you eat
you don't only feed yourself.

You're also feeding your mirobes,

but in the west we are nourishing

the bugs that make us sick.

These bad bugs release toxins that trigger

a violent response from our immune system

and that causes inflammation.

- What happens when you eat junk food

is that you become immediately inflamed.

Your microbes actually inflame you

in the presence of junk food.

- And that inflammation runs

through your body like wildfire.

- And the higher that low level

of background inflammation is

the more susceptible you are
to all sorts of disorders.

- These are diseases

of an out of balance immune system

ranging from inflammatory bowel syndrome

to multiple sclerosis, Crohn's disease,

obesity, and allergies.

- Inflammation is at the
sort of root of all of them.

- Just as our mouth microbiome

has been disturbed by
eating too much carbohydrate

antibiotics and bad diet have
turned the bacteria in our gut

from friend into foe.

- We've moved in
incredibly few generations

from lives as hunter gatherers,

to lives as agriculturalists,

to lives in places like Hong Kong

where people live in 60 story buildings

and they're totally disconnected

from any of the wildlife around them.

This whole web, this
whole ecosystem, or biome,

it's changing and so what
we need moving forward

is to figure out how do we garden

the beneficial parts of this web?

- This idea of reconnecting us

to what we are missing
from the environment

is the life's work of British scientist,

Professor John Stanford.

He's found something in
an African mud puddle

that some are calling the wonder bug.

Cynthia Stanford had a rare condition

called Raynaud's disease.

Her fingers turn numb and
white when exposed to cold.

- Jobs in the kitchen were a problem

washing up or peeling
carrots, peeling potatoes.

My fingers used to go into
total white out and be unusable.

- By coincidence her husband

Professor John Stanford was testing

a new vaccine for leprosy.

It contained a bacteria he'd isolated

in a mud puddle in Uganda.

It was called M. vaccae.

- Since we were the ones
that were had developed it

we wanted to try it on ourselves first

before we gave it to anybody else.

- John and I had a dose each

and I realized that my Raynaud's disease

that I'd had since I was
a small girl had gone away

and so after that we lined up

all the rest of the family who
also had Raynaud's disease,

but they also had other things.

- The vaccine
appeared to be helpful

in dealing with the other
diseases that run in the family

including even cancer.

- My mother had cancer at the same time

as her Raynaud's disease

which disappeared including
spinal secondaries.

- She had her M. vaccae injection

and then a month or so afterward

when she went for radiological assessment

before having the radiation

they say, "Well they've disappeared."

- These results
were entirely anecdotal,

but the bacterial treatment began

to have surprising results elsewhere too.

- I asked an Indian doctor
who was doing leprosy work

if he would look out for
any other indications

that it seemed to be helpful with.

- The first one that he noticed

which was really quite important

was a patient with leprosy and cirrhosis.

Remarkably the cirrhosis got better.

He was so pleased that when
we were out there visiting

he brought us um, a small
goat to give us in exchange

for the good that we've done to him.

- Stanford's discovery

is now being tested in clinical trials

and one of the most
promising is for depression.

- Drugs that are commonly
used to treat depression

have anti inflammatory effects

and so one of the ways that they

may be improving the health
of depressed patients

is by suppressing the inflammation

which is exactly what
microbacteria M. vaccae does.

(flute and bell music)

- Inflammatory diseases

are problems of the immune system,

but how could something so complex

be controlled by a bacterium from Africa?

- Humans co-evolved with these bacteria

throughout evolution
and so it's thought that

until about the last 50 years or so

we would have consumed
milligram quantities

of these bacteria.

- So the immune system began to rely

on the presence of these things

to turn on the police force if you'd like

of the immune system.

(intense music)

- Without
microbes like M. vaccae

the immune system becomes overactive

and causes constant inflammation.

- You spend all this time thinking

about our immune system as this machine

that repelled microbes.

That just zapped them left and right

like one of those fly zappers

and it turns out that the immune system

that we thought had
evolved to kill microbes

is actually controlled by microbes.

- Our modern lives however

are isolating us from the very thing

we need to stay healthy.

- Now of course we don't
consume these bacteria

because we have sterilized
water and sterilized food

and it's thought that the
lack of these bacteria

is contributing to an increase in disease.

Specifically diseases that
are related to inflammations.

- The evidence
now strongly suggests

that the rise in these diseases

is a result of our isolation from

the microbes we've evolved with.

Soon we may be able to
treat immune disorders

by putting the bugs back into our bodies,

but the potential of bacterial
treatments goes even further.

Australian scientists are
now injecting bacteria

into mosquitoes to prevent
us from getting sick.

(crickets chirping)

Mozzies are annoying at the best of times.

(mosquito buzzing)

They've developed elaborate weapons

to get the food they need to survive,

our blood.

- Mosquitoes need blood
for protein to make eggs.

Only the female mosquito feeds on blood

and without it she really won't
develop enough eggs to lie.

- But these
syringes don't only draw blood.

They also often inject us with
potentially lethal parasites

causing serious infections
like dengue fever.

- Dengue is actually cause by
four quite different viruses

and each of them has quite a
different effect on the host.

- So you literally have to have

four vaccines rolled into one.

- But scientists
at Monash University

have discovered an elegant
way to combat the disease.

Instead of vaccinating humans

they are vaccinating the mosquitoes.

These mosquito eggs are being injected

with a powerful bacteria called Wolbachia.

(enchanting music)

Professor Scott O'Neill has
spent much of his career

studying this intriguing bacteria.

- I got introduces to
it at a very early age

and it hooked me enough.

Been studying it my whole life.

And so one of the most
amazing things about wolbachia

is just how common it is.

If you were to look in a bush
land environment like this

and look at the insects within it

around 70% of those insects

would all carry wolbachia natrually.

And when you think on the planet

that there are to to five million

different species of
insect that's a huge number

that naturally carry wolbachia.

- Just as gut
bacteria can be good for us

wolbachia is beneficial to insects.

Protecting them against
invading parasites.

- By having wolbachia within
the body of the insect

it's acting like a probiotic
for the insect if you'd like.

It's making the insect healthier

and makes it able to fend off
some of these other pathogens

like dengue viruses.

- But there's a catch.

Mozzies that spread diseases like dengue

don't have wolbachia.

So the challenge was to
find a way to infect them.

- In fact, you know, we
spent years and years

trying to do that experiment.

Had many poor students
fail in that endeavor

until finally we were able to
succeed about four years ago.

(suspenseful music)

- These
mosquitoes host wolbachia.

They are so precious that volunteers

will gladly sacrifice
their ankles to feed them.

- We're rearing thousands,
occasionally tens of thousands,

hundreds of thousands of
mosquitoes and releasing them.

Not killing them.

- There have
been outbreaks of dengue

in Australia's tropical
north in recent years.

So to test their theory researchers

have been releasing the
vaccinated mosquitoes in Cairns.

Once released wolbachia spreads quickly.

Every week they monitor how many

of the wild mosquitoes
now have the bacteria

and the results are paying off.

- The releases that we did in 2011

are close to 100% infected with wolbachia.

- Wherever the mosquitoes

have been released dengue has
been stopped in its tracks.

Following the success in Cairns

new trials have begun all over the world.

But even super bacteria
like wolbachia have enemies.

Like all living things it's prey

for the ultimate parasite, viruses.

They are all around us.

In the air, in the soil, in the oceans,

and right now three
trillion are inside you.

- Most of them are probably
doing us no harm at all,

but a few of them are deadly,
cause deadly diseases.

- From flu,
to AIDS, to smallpox,

viruses have killed
untold millions of people,

but some viruses, the retroviruses,

have an even more extraordinary power.

They have found a way into
the very core of us, our DNA.

- On occasion the virus will infect cells

of what we call the germ line.

Those are the cells that are destined

to become eggs in females
and sperm in males

and if they infect those cells
and get into the chromosomes

then these retroviruses get a free ride

to the next generation.

- Robin Weiss
was the first to prove

that viruses not only cause disease

they can become genes.

- It was an eureka moment to realize

that something that we think
of as an infectious agent

as a virus going form
one person to another

can be part of the normal inheritance.

- This was a
mind blowing discovery.

By transforming into genes retroviruses

can replicate for millions of years.

They are the ultimate survivors.

- Their reason for living
is to replicate themselves

so if you can embed
yourself into another host

that's going to replicate
your genome for you

you've probably reached nirvana.

- These viral
invasions of DNA are rare events

occurring perhaps once in a million years.

Yet amazingly one is unfolding right now

in front of our eyes.

Veterinarian John Hanger
noticed that something unusual

was killing the Australian icon,

the koala.

- It seemed almost inevitable

if they rang me up and said,
"Oh we've got a sick koala,"

nine times out of ten it
was a koala that was sick

with leukemia or lymphoma.

It was so common.

- When he investigated

Hanger discovered a retrovirus
in the cancerous tissues.

- Every single koala that we looked at

and every single tissue that we isolated

some DNA from and tested

they were all positive for the retrovirus.

- It's the first time we see it.

On the other hand it's an example

of what we know has been happening

during evolution in any case.

(slow guitar music)

- We are the
survivors of viral invasions

like the one that is waging war on koalas.

Human DNA is littered
with the fossil remains

of these ancient battles.

- It's amazing really

about 8% of our DNA sequences

in our human DNA

is derived from retroviruses.

We are chock a block
with fossil retroviruses.

- Until recently these genes

were considered insignificant,
nothing more than junk,

but we now understand
that these genetic fossils

have actually played a
key role in evolution.

In fact without them we couldn't be born.

The same trick a virus
uses to infect cells

now allows a mother and
fetus to fuse together

through the placenta.

- This makes a very good efficient barrier

between the mother and the fetus

that is protective but allows nutrients

and oxygen to get across.

Thanks to a protein that was
once millions of years ago

a protein used by the
virus to infect cells.

- We shouldn't think of them

as a scary part of our machinery.

They're an absolutely essential
component of what we are.

- An ancient
retrovirus now intimately bonds

with every person on Earth

and it's just one of the trillions

of organisms that call us home.

Microbes define our life

and even our evolution.

- Would your personality be different

without all your microbes?

I think probably.

Would what you get from
your food be different?

Certainly.

Would you differ in other ways
we haven't yet thought about?

Almost assuredly.

And so our existence is part
of this complexity of life.

(intense music)

(baby crying)

- We are not alone.

From the moment we are born until we die

we live in a delicately
balanced relationship

with our private wildlife.

We are more than human.

Together we have become superhuman.

(high intensity music)