Original subtitles

♪♪

Garrod: SKIN.

WE ALL HAVE IT.

AND SO DOES EVERY VERTEBRATE ON THE PLANET.

IT KEEPS THE OUTSIDE OUT AND THE INSIDE IN.

ANIMALS MAY LOOK VERY DIFFERENT ON THE SURFACE,

BUT WE ALL SHARE THE SAME BASIC SKIN BLUEPRINT.

I'M BEN GARROD, PROFESSOR OF EVOLUTIONARY BIOLOGY,

AND I'M FASCINATED BY THIS OFTEN-OVERLOOKED

WONDER OF NATURE.

IT'S NOT JUST A CASE THAT IT'S HAIRLESS.

THE SKIN'S TOTALLY DIFFERENT.

NOW, GROUNDBREAKING NEW SCIENCE...

THIS IS REALLY QUITE REMARKABLE.

IT SHOULD BE A GAME CHANGER FOR SO MANY PEOPLE.

[ RATTLING ]THAT SOUND! OH!

IT MAKES THE HAIRS ON THE BACK OF YOUR NECK GO UP, DOESN'T IT?

...IS REVEALING SKIN'S MYSTERIES...

IT REALLY TRANSFORMS OUR UNDERSTANDING OF DINOSAURS.

I'M GOING TO EXPLORE THE NATURAL HISTORY

OF THE BODY'S LARGEST ORGAN.

...TO SEE HOW SKIN HAS ALLOWED ANIMALS

TO CONQUER EVERY HABITAT,

DISAPPEAR INTO THEIR SURROUNDINGS,

AND DEVELOP EXTRASENSORY ABILITIES.

WE'RE EVEN DISCOVERING THE COMPLEX ECOSYSTEM

LIVING ON OUR SKIN.

JIM, THAT'S AWFUL. IT REALLY IS.

IN THIS EPISODE, I'LL REVEAL HOW SKIN'S AMAZING VERSATILITY

HELPS FRIGATEBIRDS ATTRACT A MATE...

♪♪

...MEANS FROGS DON'T HAVE TO RELY

ON THEIR LUNGS TO BREATHE...

AND LETS MICROSCOPIC ANIMALS LIVE ON OUR FACES --

ANIMALS THAT COULD CHANGE THE STORY OF OUR EVOLUTION.

I'LL EXPLORE HOW SKIN'S UNIQUELY ADAPTABLE STRUCTURE

ALLOWS VERTEBRATES TO OVERCOME

SOME OF LIFE'S GREATEST CHALLENGES.

I'M GOING TO REVEAL THE SECRETS OF SKIN.

♪♪

THERE ARE MORE THAN 66,000 SPECIES

OF VERTEBRATES ALIVE ON THE PLANET TODAY.

THEY'VE CONQUERED THE WATER, LAND, AND AIR,

AND HAVE EVOLVED INTO A DAZZLING ARRAY OF SHAPES,

SIZES, AND COLORS.

AND IN MY OPINION, IT'S SKIN, THE LARGEST ORGAN IN ANY ANIMAL,

THAT HOLDS THE KEY TO THIS DIVERSITY AND SUCCESS.

OVER 500 MILLION YEARS OF VERTEBRATE EVOLUTION,

SKIN'S INCREDIBLE ADAPTABILITY

HAS ENABLED IT TO BECOME TOUGH...

FLEXIBLE...

SENSITIVE...

AND COLORFUL.

IT CAN GROW FEATHERS, SCALES, HAIR...

AND EVEN TEETH.

BUT THAT'S JUST THE TIP OF THE ICEBERG.

♪♪

THE KEY TO THIS INCREDIBLE VERSATILITY

IS A REMARKABLE BLUEPRINT

THAT FORMS THE BASIS OF VERTEBRATE SKIN.

FISH, REPTILES, AMPHIBIANS, MAMMALS, AND BIRDS

ALL SHARE THE SAME BASIC SKIN STRUCTURE.

ON THE SURFACE, THE EPIDERMIS,

MADE OF A FEW THIN LAYERS OF PROTECTIVE CELLS.

BENEATH THAT, THE DERMIS, RICH IN GLANDS,

NERVES, AND BLOOD VESSELS,

WHERE HAIR, FEATHERS, AND SCALES ARISE.

AND THEN FINALLY, THE SUBCUTANEOUS FAT LAYER,

A BED OF FATTY TISSUE THAT HELPS INSULATE THE BODY.

ADAPTATIONS IN THE FORM AND FUNCTION

OF THESE THREE BASIC LAYERS

HAVE LED TO THE DAZZLING RANGE OF SKIN TYPES

EXHIBITED BY VERTEBRATES TODAY.

AND THE STORY STARTS WITH THE OUTERMOST LAYER --

THE EPIDERMIS.

THE EPIDERMIS IS THE FINAL,

THIN BARRIER BETWEEN AN ANIMAL AND ITS ENVIRONMENT.

ON MY BODY, IT VARIES BETWEEN ONE MILLIMETER THICK

ON THE SOLES OF MY FEET

TO JUST 30 MICROMETERS HERE ON MY EYELIDS.

ON MY LITTLE FRIEND HERE, IT CAN BE EVEN THINNER,

BETWEEN 50 AND 12 MICROMETERS.

IT'S ESTIMATED THAT THE AVERAGE HUMAN EPIDERMIS

CONTAINS UP TO 180 BILLION CELLS.

ITS MAIN FUNCTION IS TO PROTECT US FROM THE OUTSIDE WORLD,

AND IT IS CONSTANTLY REPLACING ITSELF.

I'M LOSING 20 MILLION EPIDERMAL CELLS EVERY SINGLE HOUR.

AND IN ROUGHLY A MONTH'S TIME,

MY ENTIRE EPIDERMIS WILL EFFECTIVELY BE BRAND-NEW.

THIS MEANS MAMMAL SKIN IS A LITTLE BIT

LIKE A FLAKY CONVEYOR BELT.

THIS ENDLESS CYCLE OF EPIDERMAL RENEWAL HAS TWO BENEFITS.

DAMAGED SKIN FALLS AWAY TO BE REPLACED BY NEW, HEALTHY CELLS.

AND BECAUSE OUR EPIDERMIS IS CONSTANTLY RENEWING,

IT CAN GROW WITH US.

BUT THIS ISN'T THE CASE FOR ALL VERTEBRATES,

PARTICULARLY REPTILES, BECAUSE THEY HAVE A PROBLEM.

REPTILES' OUTER LAYER OF SKIN DOESN'T GROW WITH THEM,

SO THEY HAVE TO SHED THEIR ENTIRE EPIDERMIS IN ONE GO.

IT'S SIMPLY REPLACED BY A BIGGER VERSION GROWING UNDERNEATH.

♪♪

A SNAKE'S SIMPLER BODY SHAPE MAKES THIS PROCESS MUCH EASIER.

ADULT SNAKES DO THIS UP TO FOUR TIMES A YEAR,

ALTHOUGH YOUNG, FAST-GROWING INDIVIDUALS

CAN SHED EVERY TWO WEEKS.

THIS SNAKE HAS JUST SHED.

HER SKIN CAME OFF LIKE ONE BIG SOCK,

AND EVERY SINGLE BIT OF HER WAS REPLACED IN ONE GO,

INCLUDING THE SCALES OVER HER EYES.

LIZARDS AND SNAKES SHED LIKE THIS

BECAUSE REPTILE SKIN IS TOUGHENED

BY LARGE AMOUNTS OF A FIBER MADE IN THE EPIDERMIS --

KERATIN, A COMPLEX OF TWISTED PROTEINS.

IT'S ONE OF THE TOUGHEST NATURAL MATERIALS IN EXISTENCE.

FOUND IN ALL VERTEBRATES' SKIN, IT'S INCREDIBLY VERSATILE.

BUT JUST HOW TOUGH IS IT?

ONE PLACE KERATIN IS FOUND IN HIGH CONCENTRATIONS

IS THE HARD OUTER WALL OF A HORSE'S HOOF.

WILD STALLIONS USE THEIR HOOVES AS WEAPONS

IN VIOLENT BATTLES OVER MARES.

[ HORSE NEIGHS ]

THEY'RE CAPABLE OF DELIVERING A KICK

WITH A FORCE OF UP TO A TON, WITH BONE-SHATTERING RESULTS.

[ HORSES NEIGHING ]

WITH THIS IN MIND,

I NEED A SAFE WAY TO SEE THOSE TOUGH HOOVES CLOSE UP.

SO I'VE COME TO HILL LIVERY STABLES NEAR BRISTOL

TO MEET FARRIER DAN DOWNTON.

WHO HAVE WE GOT HERE?

THIS IS JASPER.

HE'S COME IN FOR A NEW SET OF SHOES.

I'M REALLY INTERESTED TO SEE HOW IT'S DONE.

SHALL WE GET ON WITH IT, THEN?YEAH. LET'S GIVE A GO.

SO, FIRST OF ALL, WE'RE GONNA TAKE THE SHOE OFF.

YEAH.

DAN, THAT LOOKS QUITE BRUTAL,

BUT JASPER'S NOT FEELING THAT, IS HE?

NO. HE'S GOT QUITE A LOT OF FOOT THERE,

AND WE'RE NOT TOUCHING ANY SENSITIVE STRUCTURES,

SO IT'S FINE.

AND THAT'S THE NAIL WE CAN SEE THERE, ISN'T IT?

YEAH. SO THAT'S THE HOOF WALL.

THIS IS THE SOLE, AND THIS IS THE FROG.

OKAY.

A HORSE'S HOOF EVOLVED FROM A SINGLE TOENAIL,

LIKE ONE OF OURS.

AND ITS DENSE WALL OF KERATIN

GROWS OUT OF THE EPIDERMIS IN A SIMILAR WAY.

THE KERATIN IN AN UNSHOD HOOF

HAS TO WITHSTAND INCREDIBLE FORCES.

A GALLOPING HORSE CAN GENERATE 1,000 KILOGRAMS

THROUGH EACH FOOT.

GIVE THAT A RASP.

HE HASN'T GOT A LOT OF FOOT ON IT.

ONCE THE OLD SHOE'S OFF, DAN TRIMS THE HOOF.

SO THIS IS LIKE A BIG NAIL FILE?

SO YOU'VE BASICALLY GIVEN JASPER A HUGE MANICURE RIGHT NOW?

THAT'S IT.[ LAUGHS ]

Garrod: JUST LIKE OUR NAILS, A HORSE'S HOOVES

DON'T CONTAIN NERVES OR BLOOD VESSELS.

THE KERATIN WALL GROWS FROM THE SKIN

AT AROUND SIX MILLIMETERS A MONTH --

AN EVOLUTIONARY RESPONSE TO THE CONSTANT WEAR AND TEAR

HOOVES EXPERIENCE.

HOOVES ARE SO IMPORTANT

TO THE SURVIVAL AND WELL-BEING OF A HORSE

THAT FOR AT LEAST 2,000 YEARS,

WE'VE ENHANCED KERATIN'S TOUGHNESS WITH IRON,

SHOEING DOMESTICATED HORSES

TO MAINTAIN THE VITAL INTEGRITY OF THEIR HOOVES.

IT'S NOT JUST HORSES THAT RELY ON KERATIN'S DURABILITY.

MANY OTHER ANIMALS HAVE EXPLOITED

ITS AMAZING ATTRIBUTES.

♪♪

PANGOLINS, LIKE THIS ONE HERE,

ARE COVERED IN OVERLAPPING KERATIN SCALES.

THEY GROW OUT OF THE EPIDERMIS AND FORM THIS TOUGH,

BUT FLEXIBLE SUIT OF ARMOR.

IF THE PANGOLIN IS ATTACKED,

IT CURLS INTO A BALL TO PROTECT ITSELF.

AND EVEN A LION'S TEETH AND CLAWS CAN'T GET THROUGH

THOSE 2-MILLIMETER-THICK SCALES.

KERATIN ISN'T JUST PRODUCED FOR PROTECTION.

VERTEBRATES USE IT IN A HUGE RANGE OF SKIN-BASED STRUCTURES.

IT'S A KEY COMPONENT IN ALL HAIR AND QUILLS...

ALL FEATHERS AND SCALES...

AND CLAWS AND FINGERNAILS.

♪♪

THERE ARE 30 DIFFERENT FORMS OF KERATIN IN MAMMALS ALONE.

AT ITS MOST CHEMICALLY COMPLEX AND TOUGH,

IT TURNS A RHINO HORN INTO A BATTERING RAM.

[ RHINOS GRUNTING ]

♪♪

WHILE THE MAIN FUNCTION OF THE EPIDERMIS IS PROTECTION,

THE LAYER BELOW, THE DERMIS,

COMBINES INTENSE BIOLOGICAL ACTIVITY

WITH SOME EXTRAORDINARY PHYSICAL ATTRIBUTES.

[ FRIGATEBIRDS CALLING ]

THIS IS A MALE GREAT FRIGATEBIRD FROM THE GALAPAGOS ISLANDS.

HE'S JUST WON A HOTLY CONTESTED PATCH OF GROUND TO NEST ON.

NOW HE NEEDS A MATE.

FEMALE FRIGATEBIRDS ARE GLIDING OVERHEAD.

SOMEHOW, HE MUST ATTRACT THEIR ATTENTION

WITHOUT ABANDONING HIS HARD-WON BIT OF TURF.

♪♪

HIS SOLUTION IS THIS HUGE, INFLATED BALLOON OF SKIN

ON HIS THROAT.

CALLED A GULAR SAC, IT'S ALMOST AS TALL AS HE IS

AND CLEARLY VISIBLE TO THE CIRCLING FEMALES.

[ FRIGATEBIRDS CALLING ]

HE ADDS TO THE DRAMATIC EFFECT BY SHAKING IT FROM SIDE TO SIDE

AND CLACKING HIS BEAK.

EVENTUALLY, HIS LONELY-HEARTS AD DOES THE TRICK

AND A FEMALE JOINS HIM AT THE NEST SITE.

♪♪

JOB DONE.

HIS GULAR SAC DEFLATES AND ALL BUT DISAPPEARS.

THE KEY TO A MALE FRIGATEBIRD'S AMAZINGLY STRETCHY SKIN

IS DOWN TO A FIBROUS PROTEIN

THAT'S FOUND IN THE DERMIS OF ALL VERTEBRATES.

IT'S CALLED ELASTIN.

NAMED FOR ITS ELASTIC PROPERTIES AND LOOKING AND BEHAVING

LIKE A MESH OF TIGHTLY COILED MICROSCOPIC SPRINGS,

ELASTIN PULLS STRETCHED SKIN BACK INTO SHAPE.

HUMAN ELASTIN PRODUCTION SLOWS DOWN AS WE GET OLDER.

AND THIS MEANS OUR SKIN NOT ONLY GETS LESS STRETCHY,

BUT STARTS TO DEVELOP WRINKLES.

♪♪

THE IMPRESSIVE ELASTICITY OF THE DERMIS

HAS LED TO SOME EXTRAORDINARY ADAPTATIONS

ACROSS THE VERTEBRATE WORLD,

FROM KANGAROO POUCHES TO BAT WINGS.

♪♪

AND NONE MORE SO THAN FROGS.

DURING THE BREEDING SEASON,

MALE FROGS' VOCAL SACS COMBINE ELASTIN

AND VERY THIN SKIN TO AMPLIFY THEIR MATING CALLS.

THE AMPHIBIAN DERMIS IS REMARKABLE FOR ANOTHER REASON.

♪♪

MORE THAN ANY OTHER VERTEBRATE,

THEY RELY ON THEIR SKIN FOR THE UPTAKE OF OXYGEN.

AMPHIBIANS, LIKE THIS AFRICAN BULLFROG,

USE THEIR THIN, PERMEABLE SKIN EFFECTIVELY TO BREATHE IN WATER

AS WELL AS ON LAND.

THEIR SKIN HAS EVOLVED TO LET OXYGEN PASS

THROUGH THE CELLS OF THE EPIDERMIS AND DERMIS

AND INTO THE BLOODSTREAM.

THEY CAN GET AS MUCH AS 20% OF THEIR OXYGEN THROUGH THEIR SKIN.

♪♪

[ LAUGHS ]

ONE FROG HAS TAKEN THIS TO THE EXTREME.

THE TITICACA FROG,

FOUND IN RIVERS AND LAKES HIGH IN THE ANDES,

IS COVERED IN FOLDS OF EXTRA SKIN.

A DENSE NETWORK OF CAPILLARIES IN THE DERMIS OF THESE FOLDS

ALLOWS THE FROG TO ABSORB ALL THE OXYGEN IT NEEDS

FROM THE WATER,

MEANING IT NEVER HAS TO SURFACE TO BREATHE.

BUT THERE ARE DRAWBACKS TO THIS TYPE OF RESPIRATION.

IN ORDER TO SURVIVE, AMPHIBIANS NEED TO LIVE IN DAMP PLACES,

WHERE THEIR SKIN REMAINS MOIST.

IF IT DRIES OUT, IT MEANS THAT GASES CAN'T DIFFUSE ACROSS IT

AND THEY SUFFOCATE.

ALONGSIDE ITS IMPRESSIVE PHYSICAL ATTRIBUTES,

THE DERMIS IS ALSO A HIVE OF BIOLOGICAL ACTIVITY.

SPECIALIZED GLANDS PRODUCE A HUGE ARRAY OF NATURAL COMPOUNDS,

WHICH FURTHER ENHANCE THE SKIN'S VERSATILITY.

AND I'VE GOT A NEAT, LOW-TECH WAY TO DEMONSTRATE THIS.

THESE ARE CAMPHOR BOATS,

AND A TINY CAMPHOR CRYSTAL ON THE BACK OF EACH ONE

HAS THEM SHOOTING ACROSS THE SURFACE OF THE WATER LIKE MAGIC.

OF COURSE IT'S NOT MAGIC.

CAMPHOR IS A PUNGENT CHEMICAL HARVESTED FROM CAMPHOR TREES.

IT DISSOLVES IN WATER, ALTERING THE SURFACE TENSION

AND PUSHING THE LITTLE BOATS FORWARD.

ALL IT TAKES TO STOP THEM IS A THIN LAYER

OF GREASE ON THE WATER,

AND I KNOW JUST WHERE TO FIND SOME.

♪♪

IN COMMON WITH MOST MAMMALS,

MY SKIN IS COATED IN A THIN LAYER OF OIL.

THIS IS A WAXY SUBSTANCE CALLED SEBUM

THAT HELPS LUBRICATE AND WATERPROOF MY SKIN.

IT'S PRODUCED BY SEBACEOUS GLANDS

IN THE DERMIS OF ALL MAMMALS.

THESE ARE OFTEN FOUND NEXT TO HAIR FOLLICLES,

WHICH IS WHY OUR HAIR GETS GREASY.

WHILE WE HAVE AN ESTIMATED 2 MILLION SEBACEOUS GLANDS

ALL OVER OUR SKIN,

IT'S STILL A MYSTERY

WHY THEY'RE MOST ABUNDANT ON OUR SCALP AND FACES.

MAMMALS AREN'T THE ONLY VERTEBRATES

PRODUCING NATURAL OILS IN THE DERMIS.

BIRDS HAVE SEBACEOUS GLANDS, TOO.

BUT INSTEAD OF LOTS OF SMALL GLANDS ALL OVER THE SKIN,

THEY'VE EVOLVED ONE BIG ONE.

AND IF WE'RE REALLY CAREFUL, WE CAN LOOK AT THIS CONURE'S...

[ CONURE SQUAWKS ]BECAUSE -- HELLO! --

JUST AT THE TOP OF THE TAIL, YOU CAN SEE A LITTLE PATCH

THAT LOOKS LIKE IT'S A BUNCH OF SOGGY FEATHERS.

THAT'S THE PREEN GLAND.

AND IT'S THIS THAT PRODUCES OIL

WHICH THE BIRD THEN SPREADS AROUND ITS BODY

USING ITS BEAK AND HEAD.

BIRDS USE THIS DERMIS-PRODUCED OIL

FOR LOTS OF DIFFERENT REASONS --

KEEPING FEATHERS SUPPLE FOR FLYING,

SENDING ODOR-BASED CHEMICAL MESSAGES

TO POTENTIAL MATES OR RIVALS.

IT ALSO HELPS TO KEEP FEATHER COLORS VIVID.

MANY DIVING BIRDS HAVE LARGE PREEN GLANDS,

WHICH SUGGESTS IT ALSO PLAYS A VITAL ROLE

IN WATERPROOFING THEIR FEATHERS,

ALTHOUGH BIOLOGISTS ARE UNSURE OF EXACTLY HOW.

PREEN OIL IS AN IMPRESSIVE,

BUT MYSTERIOUS MULTIPURPOSE SUBSTANCE.

AND THE DERMIS STILL HAS MORE SURPRISES IN STORE.

♪♪

IN ANCIENT MAMMAL ANCESTORS

LIVING MORE THAN 250 MILLION YEARS AGO,

SCIENTISTS BELIEVE THE DERMIS EVOLVED

TO SECRETE SOMETHING EXTRAORDINARY -- MILK.

THERE ARE FOUR DIFFERENT TYPES OF GLAND

IN THE MAMMALIAN DERMIS,

AND IT'S THOUGHT AN ADAPTATION OF ONE, THE SWEAT GLAND,

LED TO THIS VITAL STEP IN MAMMAL EVOLUTION.

WE HAVE A ROUGH IDEA OF HOW THAT MIGHT HAVE WORKED

FROM PLATYPUS AND ECHIDNAS,

LIKE THIS LITTLE GUY HERE FROM AUSTRALIA.

NOW, THESE ARE UNUSUAL MAMMALS IN THAT THEY LAY EGGS,

AND THEY FEED THEIR OFFSPRING FROM MILK

THAT'S SECRETED TO THE SURFACE OF THE SKIN

BY COLLECTIONS OF PORES.

THIS MIGHT HAVE BEEN AN EARLY STEP INTO THE DEVELOPMENT

OF DEDICATED NIPPLES AND MAMMARY GLANDS

AS WE SEE IN MOST MAMMALS ALIVE TODAY.

THE VERSATILITY OF THE DERMIS

ALLOWS IT TO MAKE AN ARRAY OF UNIQUE COMPOUNDS

THAT HAVE SHAPED VERTEBRATE EVOLUTION.

AND THERE IS ONE MORE -- COLLAGEN,

A PROTEIN WITH INCREDIBLE TENSILE STRENGTH

WHICH IS FOUND IN EVERY VERTEBRATE DERMIS.

ONLY NOW ARE WE UNDERSTANDING THE FAR-REACHING EFFECT

IT COULD HAVE ON OUR LIVES.

I'M GOING TO SEE BIOENGINEER DR. CLAIRE HIGGINS.

SHE'S TESTING A DISC OF HUMAN FOOT SKIN

TO SEE HOW IT RESPONDS TO A BIT OF WEAR AND TEAR.

Higgins: SO, THE MACHINE COMPRESSES THE PIECE OF SKIN,

AND WE MEASURE THE AMOUNT OF DEFORMATION IN THE TISSUE

AS TO HOW MUCH THE TISSUE IS CHANGING SHAPE.

THE DISC OF FOOT SKIN IS REPEATEDLY SQUASHED

UP AND DOWN AND SIDE TO SIDE,

MIMICKING THE FORCES PRODUCED BY WALKING.

AND WHAT HAVE THE RESULTS SHOWN SO FAR?

SO WITH COMPRESSION, FOOT SKIN DEFORMS BY ABOUT 15%

WHEREAS BODY SKIN CHANGES SHAPE BY ABOUT 25%.

AND THEN, WHEN WE LOOK AT SHEAR FORCES,

FOOT SKIN DEFORMS BY ABOUT 40%,

WHILE LEG SKIN ACTUALLY DEFORMS BY AS MUCH AS 150%.

CLAIRE'S TESTS REVEAL THAT

WHEN IT COMES TO DEALING WITH WEAR AND TEAR,

THE SKIN ON OUR FEET SIGNIFICANTLY OUTPERFORMS

THE SKIN ON THE REST OF OUR BODIES.

TO FIND OUT WHAT MAKES FOOT SKIN SO RESILIENT,

CLAIRE'S USING LASER MICROSCOPY.

SO WE'RE ACTUALLY IMAGING COLLAGEN FIBERS,

AND WE'RE INTERESTED IN COLLAGEN

BECAUSE IT MAKES UP ABOUT 90% OF THE SKIN DERMIS,

AND IT'S REALLY THE STRUCTURAL PROTEIN

THAT CONTRIBUTES TO THE INTEGRITY OF THE SKIN.

FIBERS OF COLLAGEN RUNNING THROUGH THE DERMIS

ARE WHAT GIVE VERTEBRATE SKIN ITS TENSILE STRENGTH.

SO YOU CAN SEE, IN THIS IMAGE HERE,

THIS IS COLLAGEN IN FOOT SKIN.MM-HMM.

AND THIS IMAGE ON THE RIGHT IS COLLAGEN IN LEG SKIN.

THE FOOT SKIN OWES ITS IMPRESSIVE TOUGHNESS

TO THIS DENSE NETWORK OF COLLAGEN.

THE IMAGES SHOW THAT THE COLLAGEN FIBERS IN FOOT SKIN

ARE MUCH THICKER THAN THE ONES IN LEG SKIN.

THEY'RE ALSO ABOUT FOUR TIMES BRIGHTER, WHICH IS SIGNIFICANT.

THAT BRIGHTNESS ACTUALLY IS AN INDICATION OF TENSILE STATE.

THE FIBERS IN FOOT SKIN ARE PRETENSED ALMOST.

SO BASICALLY THESE ARE EVER READY LITTLE BUNDLES OF COLLAGEN

IN ANTICIPATION FOR THIS HEAVY WEAR AND TEAR

THAT WE'RE NOT SEEING ELSEWHERE IN THE BODY?

♪♪

CLAIRE'S GROUNDBREAKING RESEARCH HAS REVEALED

THAT OUR SKIN STRUCTURE VARIES WITH THE JOB IT HAS TO DO.

HER ULTIMATE AIM IS TO REPLICATE

THE DURABILITY OF FOOT SKIN

IN SKIN ON OTHER PARTS OF THE BODY,

CHANGING LIVES IN THE PROCESS.

THERE ARE SOME CIRCUMSTANCES, SUCH AS AFTER AMPUTATION,

THAT SKIN ON A STUMP IS REQUIRED TO BE LOAD-BEARING,

BUT IT'S NOT DESIGNED TO BE.

SO WE'RE HOPING THAT WE CAN TRY TO RE-ENGINEER SKIN,

SUCH AS STUMP SKIN, TO MAKE IT STRONGER

AND MAKE IT CAPABLE OF BEING LOAD-BEARING.

SO YOU'RE TALKING ABOUT DEVELOPING SKIN ON PEOPLE

WITH DISABILITIES OR INJURIES HERE?

YEAH, RE-ENGINEERING SKIN ON THE STUMP, ESSENTIALLY.

THIS IS REALLY QUITE REMARKABLE,

AND IT SHOULD BE A GAME CHANGER FOR SO MANY PEOPLE.

OH, WE HOPE SO. YEAH, ABSOLUTELY.

CLAIRE'S DISCOVERIES ARE SHEDDING NEW LIGHT,

NOT JUST ON THE POTENTIAL OF HUMAN SKIN,

BUT THE VERSATILITY OF SKIN ITSELF.

IT'S ALSO A CLEAR DEMONSTRATION

OF JUST HOW MUCH WE STILL HAVE TO LEARN.

ANOTHER REMARKABLE DISCOVERY ABOUT HUMAN SKIN

COULD CHANGE OUR VIEW OF EVOLUTION.

IT INVOLVES LOOKING FOR AN ANIMAL

THAT LIVES ON AND IN OUR SKIN.

THEY'RE SO SMALL THAT YOU CAN'T FEEL THEM

OR SEE THEM WITH THE NAKED EYE,

BUT MOST OF US DO HAVE THEM.

SO I'M OFF TO SEE WHETHER I CAN FIND MINE.

THEY'RE SKIN MITES.

AND I'VE COME TO MEET DR. DAVE PATTON,

WHO'S GOING TO HELP ME TRACK MINE DOWN.

HI, DAVE. HELLO.

SO WE'RE GONNA LOOK FOR MITES ON MY FACE, ARE WE?

YEAH. WE'RE GONNA USE AN INTERESTING TECHNIQUE

INVOLVING SUPERGLUING YOUR HEAD TO A GLASS SLIDE.

[ LAUGHS ]

YOU SAY IT LIKE IT'S SUCH A COMMON THING.

OKAY, SO WE'VE LITERALLY GOT A GLASS SLIDE AND SOME SUPERGLUE.

YES.

OKAY. RIGHT.

SO ALL WE DO IS PUT SOME GLUE ON THE SLIDE

AND THEN PRESS IT ONTO YOUR FOREHEAD FOR A MINUTE.

THEN IT'LL REMOVE SOME OF YOUR FOREHEAD

AND HOPEFULLY SOME SKIN MITES.

NOT MUCH OF MY FOREHEAD, THOUGH, RIGHT?

UM...A MILLIMETER.

[ CHUCKLES ]

MITES LIVE IN GREATER CONCENTRATIONS ON OUR FACES

THAN ANYWHERE ELSE,

PARTICULARLY ON OUR CHEEKS AND FOREHEADS.

YOU READY? I THINK SO.

RIGHT, OKAY.

OKAY. CAN YOU HOLD THAT IN PLACE?

YEAH.

WHILE THE 60 SECONDS COUNT DOWN, I WANT TO CHECK SOMETHING.

HAVE YOU DONE THIS TO YOURSELF?

YES. YES.

HAVE YOU FOUND ANY?

WE HAVE FOUND ONE. [ LAUGHS ]

THAT'S NOT A VERY HIGH HIT RATE.

SO TO BE ON THE SAFE SIDE, WE'LL NEED SOME BACKUP SAMPLES.

I THINK IN THAT CASE, THEN, WHAT I MIGHT DO

IS TO GET SLIDES AND SAMPLES FROM ALL THE CREW, AS WELL.

WHY NOT? [ LAUGHS ]

COME ON, GUYS! [ CHUCKLES ]

AND SO THE CREW BRAVELY SUBMITS TO THE SUPERGLUE TREATMENT.

JUST PRESS THAT ON. THANK YOU.

THANK YOU.

♪♪

AAH!

SORRY.THAT DIDN'T HURT.

WE HAVE GOT A NICE VARIETY OF PEELED SKIN ON THERE RIGHT NOW.

SO NOW WE'VE PUT THOSE UNDER A MICROSCOPE

AND WE SEE WHETHER WE CAN FIND

THESE LITTLE FACE MITES STUCK ON THE SUPERGLUE?

YEAH. THAT'S THE PLAN.

WELL, LET'S SEE IF WE CAN FIND SOME.

GOOD LUCK, TEAM.

♪♪

DAVE PUTS MY SAMPLE IN A SCANNING ELECTRON MICROSCOPE,

AND WITHIN MINUTES,

I'M LOOKING AT THE INSIDE OF MY SKIN MAGNIFIED 200 TIMES.

IT'S LIKE A REALLY HORRIBLE TREASURE TRAIL,

'CAUSE I DON'T WANT TO FIND WHAT'S HIDING.

[ BOTH LAUGHING ]

RIGHT, SO, TO SEARCH, I'M JUST GOING TO MOVE

ONE SCREEN AT A TIME.

AND WE'RE LOOKING FOR A LITTLE HEAD

THAT'S POPPING OUT NEXT TO THE HAIR ITSELF, AREN'T WE?

YEAH, IN THE SAME PORE, SO, LIKE, PARALLEL TO THE HAIR,

LOOKING VERY SIMILAR TO THE HAIR.

BUT HOWEVER HARD WE SEARCH,

WE JUST DON'T FIND ANY SIGNS OF LIFE.

SO WHAT I THINK WE SHOULD DO IS HAVE A LOOK

AT SOME OF THE OTHER FILM CREW MEMBERS

TO SEE WHAT THEIR SKIN'S LIKE.

SO WHO HAVE WE GOT HERE, THEN, DAVE?

ANDY, THE SOUND MAN.

THERE'S A PORE THERE WITH HAIR COMING OUT OF IT.

IT'S PROBABLY JUST A BIG BIT OF FOLLICLE THERE

BELONGING TO THIS HAIR.

♪♪

DAVE LOOKS EVEN CLOSER, AND BINGO.

THAT'S TEMPTING. LOOK. LOOK AT THAT.

THERE APPEAR TO BE 1, 2, 3 DEMODEX.

ANDY NOT ONLY HAS MITES. HE'S GOT LOADS OF THEM.

SO YOU'VE GOT EVIDENCE

OF THREE LITTLE MITES ON ONE HAIR STRAND

FROM ANDY'S SAMPLE HERE?

IT LOOKS LIKE IT.

WHAT WE'VE FOUND ARE DEMODEX MITES --

TINY, HARMLESS ARACHNIDS THAT LIVE ON MY,

YOUR, AND ANDY THE SOUND MAN'S SKIN.

THEIR LONG, THIN BODIES HELP THEM SLIDE

INSIDE OUR HAIR FOLLICLES,

WHERE THEY CLING ON WITH EIGHT STUMPY CLAWS.

THEY SPEND THEIR TIME HIDDEN AWAY,

FEEDING ON OILS MADE IN THE DERMIS

AND ALL THOSE DEAD EPIDERMAL CELLS.

IF THAT WASN'T BAD ENOUGH,

THESE LITTLE ANIMALS ARE LIGHT-SENSITIVE

AND ONLY COME OUT AT NIGHT,

WHEN THEY MATE ON OUR FACES.

♪♪

THE ONLY TIME WE DON'T HAVE DEMODEX MITES

IS WHEN WE'RE IN THE WOMB.

ONCE YOU'RE BORN, A FEW SNUGGLES FROM YOUR MUM OR DAD

AND YOU'VE PROBABLY GOT MITES.

♪♪

WHILE THIS IS BOTH FASCINATING AND DISTURBING,

IT JUST GOES TO SHOW THAT OUR SKIN ISN'T JUST AN ORGAN.

IT'S AN ENTIRE ECOSYSTEM.

THIS DISCOVERY HAS OPENED UP

A WHOLE NEW LINE OF SCIENTIFIC INQUIRY.

BY TESTING MITE DNA FROM AROUND THE GLOBE,

SCIENTISTS REVEALED IN 2015 THAT DIFFERENT HUMAN POPULATIONS

HAVE DIFFERENT MITE POPULATIONS,

HANDED DOWN THROUGH THE GENERATIONS.

THIS MEANS WE CAN MAP WHICH CONTINENT

A PERSON'S ANCESTORS CAME FROM

BY STUDYING THE MITES ON THEIR SKIN.

WE MAY EVEN BE ABLE TO TRACE ANCIENT HUMAN-MIGRATION PATTERNS

BY STUDYING MITE DNA,

SHEDDING NEW LIGHT ON OUR EVOLUTION.

AND THE EXTRAORDINARY STORY DOESN'T END THERE.

EVERY MAMMAL SPECIES TESTED SO FAR

HAS ITS OWN FAMILIAL DEMODEX MITES --

PROOF THAT SKIN STILL HAS ITS SECRETS.

♪♪

WHEN IT COMES TO HELPING VERTEBRATES THRIVE

IN AN UNPREDICTABLE WORLD,

SKIN, WHICH IS BOTH RESOURCEFUL AND ADAPTABLE,

IS THE ULTIMATE MULTIPURPOSE TOOL,

HELPING ANIMALS DEFEND THEMSELVES,

DISGUISE THEMSELVES, EVEN COMMUNICATE.

AND IT'S STILL FULL OF SURPRISES.

--Captions by VITAC-- www.vitac.com

CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS