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Do you ever stop to contemplate
the wonder of your body?

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No?

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No, neither do I.

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But, actually, it's the most
complicated piece of engineering

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known to us, and it throws up
some very puzzling questions.

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Why do I catch colds?

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Where does wind come from?

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And what will we look like
in 1,000 years?

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For the answers, stick with me,

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as we've uncovered the
Things You Need To Know
about the human body.

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Right, let's get this show on the
road, starting at the beginning...

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Daddy, where did I come from?

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So, your dad told you that he
and your mum loved each other,

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and decided to have a baby.

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Actually, it was much more
complicated than that.

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If your father was an average guy,
about 280 million of his sperm

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entered the race
to fertilise your mother's egg.

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They were blasted in
at an impressive 28mph,

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but almost instantly,
210 million had dropped out.

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What happened?

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Well, up to 70%
of human sperm is dodgy.

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Some have three tails.

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There are two-headed sperm
chasing their tails,

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and others with no tails at all.

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Humans compare pretty badly
with the animal kingdom.

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Let's compare me
with a rat and a pig.

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100% of the rat's sperm
will be strong swimmers

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compared with only
about 30% of mine.

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And the pig will produce
two pints of sperm,

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where as I will
produce about a teaspoonful.

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Anyway, back to the sperm's
voyage through your mother.

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Those that made it into her cervix
found themselves in a sticky maze.

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This mucus protects
a uterus from germs,

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but it's also a hostile
environment for sperm.

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Most will never get through.

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The 100,000 that did
then had to race across the uterus -

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an exhausting marathon.

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By the fallopian tubes,
we're down to just 200,

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and half of them
swim up the wrong tube.

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Meanwhile, the egg is only
fertile for 12 to 24 hours.

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Chemicals in the female body
encourage the sperm
to keep swimming.

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As they near the egg, they
turn up the wick and accelerate.

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But there can only be one winner.

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As one super-sperm enters the egg,

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a chemical message
seals its surface shut.

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So, if you ever feel down,
remember this -

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you are the product
of an Olympian sperm.

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Your father's sperm
and your mother's egg

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contained all the information
needed to make you.

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We are all unique products
of our parents' genetic codes.

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In which case...

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How did I get my granny's chin?

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Since way back when, families have
argued about who the kids look like.

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So, it was a nasty
shock for your parents

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when you were born with your
granny's smooth, pointy chin,

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instead of their elegant clefts.

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Your DNA is to blame.

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In 1953, James Watson and
Francis Crick discovered that DNA,

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or Deoxyribonucleic acid,

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is contained in a structure
called the double helix.

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Lying at the centre
of virtually all our cells.

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Within your DNA
are around 23,000 genes,

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which you inherited in two packs -

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one from your mother,
and one from your father.

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Your genes come in pairs,
one from each parent.

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Some pairs are what's
called dominant recessive.

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A dominant gene - like the one
that causes a cleft chin -

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always trumps its recessive pair,

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making sure its characteristic
is turned on.

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But hang on, if your parents both
have dominant cleft chins,

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then how can yours be smooth?

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Well, actually, we only inherit
half of each of our parents' genes.

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That's one gene from
each of their pairs.

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So we get half of our mum's genes
and half of our dad's,

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so it must follow that
we get a quarter of each
of our grandparents'.

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Now here comes the important bit -

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genes passed down
from our grandparents

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may be turned off in our parents,
but turned on again in us.

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To see how this works, let's take
a look at your family tree.

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Your dad got a dominant cleft
gene from your grandfather,

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with a paired recessive
gene from your grandmother.

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The same is true for your mother.

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So, in both of them, the dominant
cleft gene was switched on.

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The eggs and sperm your parents
produce could only carry

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one gene from each pair.

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It just so happened that the egg
and sperm that made you

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both got the recessive chin gene,

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so you could only get your
granny's pointy, smooth chin.

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The genetic mix your family
gave you is unique,

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but the genes themselves
aren't uniquely yours.

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That's because DNA is
the blueprint for all life,

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from bacteria to human beings.

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All your organs
are made up of cells,

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instructed by the genes within them
to work together to keep you alive.

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We share this basic method
of staying alive

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with every animal,
and plant, on earth.

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Which means you share
95% of your genes with rats,

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60% with chickens,

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and 50% with bananas.

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Not all your features
are decided by a single gene.

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Genes are divided across structures
called chromosomes,

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and your eye colour, for example,
was created by genes

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from different chromosomes
working together in harmony.

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Now, this is very complex science,
but here is a simple question...

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How are you seeing this?

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In Ancient Greece,

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some people believed that eyes
worked by projecting beams of light.

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This idea was
knocked on the head

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by the 11th century scientist,
Alhazen.

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He figured out that we see
by the light entering our eyes.

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Objects reflect light rays
which are focused on to the retina,

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a layer at the back of the eyeball
that's packed with 125 million

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light receptor cells
called cones and rods.

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It's the red, blue and green cone
cells that give you colour vision.

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In total, we see ten
million different shades.

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What's more, your eyes are
perfectly positioned to give you

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two separate fields of vision.

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Each eye shows your brain the same
object from a different angle,

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allowing you to see in 3D
and judge distance and depth.

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Human eyes move at over 30 mph,

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giving you more information than
the rest of your senses combined.

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Impressive, till the sun drops

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and human vision starts to
look rather shoddy -

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something you'll have noticed
if you stub your toe

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when you get up to go to the lavvy
in the middle of the night,

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while your cat wanders around
as if he owns the place.

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Your eyes are missing something.

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Line up a human, a cat,
a sheep, a seal and a deer,

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and it's only human eyes
that don't glint at night.

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That's because the others have some
awesome night-vision technology -

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a layer of shiny cells called
the tapetum lucidum.

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When just a tiny bit of light
trickles into the eye,

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this layer reflects it back,

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giving the receptor cells a second
chance to pick up the light.

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So, it's a myth that your cat
sees in total darkness,

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but it can see in one-sixth
of the light that you can.

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I love cats.

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It's a pity
they don't really like me.

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Actually, they don't
really like anybody,

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they just want some food.

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Food is what keeps your cells
working and keeps you on the road.

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Cells need fuel - that's why we eat,
and this can cause pollution.

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So...

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where does wind come from?

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You eat 2,000 to 3,000
calories a day.

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You also let loose up to
two and half pints of wind.

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We're told the Emperor Claudius
thought releasing wind so important,

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he encouraged it at banquets.

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He was right - it's an essential
by-product of digestion.

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Within ten seconds of swallowing,

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your stomach is whisking your food
into a liquid called chyme,

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which is pushed into
your small intestine,

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where most of the goodness
is absorbed.

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The small intestine
is actually huge -

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a folded, 21-foot tube
which, pressed flat,

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would be bigger than a tennis court.

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So, while you're busy sipping
coffee after your dinner,

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your stomach is already churning
your shepherd's pie up into a soup,

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which your small intestine
can break down

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into nutrients your cells can use.

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Unfortunately...

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HE BREAKS WIND

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there are some leftovers.

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Two and a half pints
of watery gruel.

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This is poured into your
large intestine,

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home to billions of bacteria
known as gut flora.

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These account for over two pounds
of your body weight.

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To your bacteria,
this gruel is a feast.

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As it pours in, they set to work
digesting the plant fibres

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your small intestine can't and
extracting vitamins and fatty acids.

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This vital work produces gas,
including carbon dioxide,

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hydrogen, methane
and the odorous hydrogen sulphide...

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which builds up in your large
intestine, along with solid waste,

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up to 50% of which is dead bacteria
and cells from your own body.

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Your intestinal muscles
then squeeze

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to create a zone of high pressure
that moves the gas and waste

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down towards your rectum...

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forcing you to let out wind
around ten times a day.

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FART SOUNDS

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Embarrassing when not expected, but
at least you can do it on the move,

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whereas getting rid of
solid waste takes time.

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According to a recent survey,
by the end of our lives

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we'll have spent 90 days
sitting on the lavvy...

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STRAINING NOISES

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..giving us plenty of opportunities
for a nice quiet read.

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Now, if I'm Mr Average, I'm made
up of two stone of protein,

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two stone of fat,
and around eleven pints of blood.

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Sounds disgusting.

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But to other life forms,

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our bodies are actually an
irresistible all-day buffet,

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which begs a rather
unusual question...

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Is there life on me?

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As the proud owner of a human body,
you see yourself as an individual.

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But, if an alien examined you,

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he'd see a walking zoo
of bacteria and parasites.

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Your bacteria outnumber
your cells ten to one.

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Numerically, you're 90% microbe.

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You house around 500 species
in your gut,

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128 in your lungs,

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and up to 200 in your mouth.

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Gross!

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But as we've seen in the intestine,
some bacteria are vital.

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More than you can say for...

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parasites.

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At some point, face mites will
almost certainly feed off your skin.

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Right now, they may
diving down into your follicles,

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using their needle-like mouths
to hoover up some
of the eight pounds

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of skin cells you lose every year.

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SOUND OF A VACUUM CLEANER

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Pull the plug, it's eating me alive!

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Scary, but better than
feeding bloodsucking bedbugs.

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Vampire fiction is,
of course, all the rage,

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00:13:50,000 --> 00:13:54,480
but the real twilight bloodsuckers
are rather less romantic.

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A few years ago, we believed
we had the bedbug beaten.

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But now, all across the world,
the bedbug is back.

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Bedbugs use their six legs
to scuttle out as you sleep.

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One feeding tube
administers anaesthetic

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to keep you in the land of nod,
while the other sucks your blood.

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Nasty.

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But nowhere near as bad
as hosting a tapeworm.

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The tapeworm gets in as larvae
in undercooked meat.

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Once inside,
it clings to your intestines,

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spending up to 25 years happily
bathing in your undigested food.

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By absorbing your nutrients through
its skin, it can grow up to 30 feet.

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With any luck you'll manage
to avoid tapeworm,

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unless you're one of those blokes
who believes he can do a barbecue.

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Viruses, on the other hand, are most
definitely going to get you,

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and when they do, they will give you
anything from a cold to Ebola.

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And yet, technically, viruses
have no life of their own,

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so why do they cause
so much trouble?

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More to the point...

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Why do I catch colds?

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See that guy with the blocked nose?

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00:15:20,960 --> 00:15:26,240
When he sneezes, 40,000 droplets
will fly twelve feet in the air,

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infecting up to 150 people.

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Ugh!

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You should have ducked.

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A cold virus just
can't live without you.

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WOMAN SCREAMS

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With no cells of its own,

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00:15:38,600 --> 00:15:41,280
it needs to take over
your cells and replicate.

242
00:15:41,280 --> 00:15:43,400
Here's something to think about -

243
00:15:43,400 --> 00:15:48,480
the virus can only travel around
inside a blob of mucus,

244
00:15:48,480 --> 00:15:51,360
and that means that
when you catch a sniffle,

245
00:15:51,360 --> 00:15:54,320
someone else's snot
has been up your nose.

246
00:15:54,320 --> 00:15:55,600
Anyway...

247
00:15:55,600 --> 00:16:00,480
your immune system is constantly on
the prowl for attackers like these.

248
00:16:00,480 --> 00:16:04,440
If it wasn't, you could
end up with fatal pneumonia.

249
00:16:06,040 --> 00:16:10,360
So, when it spots a viral invasion,
it grabs a sample

250
00:16:10,360 --> 00:16:14,200
and takes it to the nearest lymph
node, home of your killer T cells.

251
00:16:16,760 --> 00:16:20,320
Here, a T cell first
identifies the invader,

252
00:16:20,320 --> 00:16:25,480
and then deploys an army
of tailor-made immune cells
to your nose.

253
00:16:28,520 --> 00:16:30,280
These provide specialist backup

254
00:16:30,280 --> 00:16:34,640
for the standard immune cells
already fighting your cold.

255
00:16:35,880 --> 00:16:38,480
Your nose has become a battleground.

256
00:16:40,440 --> 00:16:43,760
Meanwhile, to stop infection
spreading to your lungs,

257
00:16:43,760 --> 00:16:46,960
you're manufacturing
a daily pint of mucus.

258
00:16:48,680 --> 00:16:53,920
This snot gives you a headache,
while the virus irritates your nose,

259
00:16:53,920 --> 00:16:57,120
so you have to blow it
around 45 times a day.

260
00:17:01,160 --> 00:17:05,200
Beating a cold takes you
about seven days,

261
00:17:05,200 --> 00:17:08,160
and you'll catch about four a year.

262
00:17:09,360 --> 00:17:12,480
This is the golden age
for the cold virus.

263
00:17:14,920 --> 00:17:18,360
It hops on planes with its
human hosts, visits new cities,

264
00:17:18,360 --> 00:17:22,240
and finds hundreds of new homes
with every sneeze.

265
00:17:25,640 --> 00:17:28,160
As it replicates, it mutates,

266
00:17:28,160 --> 00:17:32,480
so by next year it may be
back in a different form.

267
00:17:32,480 --> 00:17:34,480
SNEEZING

268
00:17:34,480 --> 00:17:37,800
Children catch more colds
than adults

269
00:17:37,800 --> 00:17:41,440
because their immune systems
are less experienced.

270
00:17:41,440 --> 00:17:44,160
We also take ages to grow up -

271
00:17:44,160 --> 00:17:48,280
the human being is the only
species with a long adolescence -

272
00:17:48,280 --> 00:17:53,160
and this life phase developed
around 500,000 years ago,

273
00:17:53,160 --> 00:17:58,280
just before the human brain
developed into its current
large size.

274
00:17:58,280 --> 00:18:01,920
And all of this makes it much easier
to answer our next question...

275
00:18:01,920 --> 00:18:05,040
Why are teenagers so moody?

276
00:18:06,160 --> 00:18:08,520
At around eight or nine,
an alarm goes off

277
00:18:08,520 --> 00:18:10,840
in the hypothalamus
region of the brain,

278
00:18:10,840 --> 00:18:14,400
waking up powerful hormones
and triggering seismic changes,

279
00:18:14,400 --> 00:18:18,800
which eventually erupt as breasts,

280
00:18:18,800 --> 00:18:21,960
body hair, and bodily functions.

281
00:18:21,960 --> 00:18:23,040
GROANING

282
00:18:23,040 --> 00:18:26,480
Along with volcanic
surges of temper,

283
00:18:26,480 --> 00:18:30,640
which, until recently,
were also put down to hormones.

284
00:18:30,640 --> 00:18:34,200
Now experts believe
the brain is to blame.

285
00:18:34,200 --> 00:18:38,760
We used to think the human brain
was mature by 18 months.

286
00:18:40,360 --> 00:18:41,520
Not any more.

287
00:18:41,520 --> 00:18:44,200
When scientists used
magnetic resonance imaging

288
00:18:44,200 --> 00:18:46,720
to scan the brains of young
adolescents,

289
00:18:46,720 --> 00:18:49,760
they discovered
multiplying connections

290
00:18:49,760 --> 00:18:53,000
between the cells
of the prefrontal cortex.

291
00:18:56,080 --> 00:18:58,320
That's the bit of the brain

292
00:18:58,320 --> 00:19:01,320
that makes decisions
and controls emotion.

293
00:19:01,320 --> 00:19:04,000
So, what happens
when we ask a teenage

294
00:19:04,000 --> 00:19:07,560
and an adult brain
a straightforward question?

295
00:19:07,560 --> 00:19:12,760
The young brain's freshly grown
connections really slow it down.

296
00:19:12,760 --> 00:19:16,680
The teenage brain -
here's one we found earlier -

297
00:19:16,680 --> 00:19:20,320
finds it tough to control
impulses and emotions,

298
00:19:20,320 --> 00:19:24,680
and this explains why teenagers
think going out drinking

299
00:19:24,680 --> 00:19:28,600
with their mates is a viable
alternative to, say, exam revision,

300
00:19:28,600 --> 00:19:31,520
and that it explains why
they can't understand

301
00:19:31,520 --> 00:19:34,840
that this will
upset their parents.

302
00:19:34,840 --> 00:19:38,720
Because research show that young
adolescent brains struggle

303
00:19:38,720 --> 00:19:41,520
to read facial expressions.

304
00:19:41,520 --> 00:19:45,600
Thankfully, by adulthood,
the troublesome extra
connections are pruned.

305
00:19:47,520 --> 00:19:50,600
Mind you, hormones aren't
entirely off the hook

306
00:19:50,600 --> 00:19:52,760
when it comes to teenage moods.

307
00:19:52,760 --> 00:19:58,200
Hormones produce female curves
and male muscles,

308
00:19:58,200 --> 00:20:02,040
but also an oily substance
called sebum,

309
00:20:02,040 --> 00:20:05,560
which means 80% of teenage
skin suffers from...

310
00:20:07,120 --> 00:20:09,400
whiteheads, blackheads,

311
00:20:09,400 --> 00:20:11,440
yellow, pus-sy pimples,

312
00:20:11,440 --> 00:20:15,080
and, if they're really unlucky,
bulging nodules.

313
00:20:15,080 --> 00:20:18,160
At the exact moment
they want to look attractive,

314
00:20:18,160 --> 00:20:20,240
teenagers start resembling pizza.

315
00:20:20,240 --> 00:20:22,280
And if they do manage to get a date,

316
00:20:22,280 --> 00:20:25,160
their brains are
so emotionally inept

317
00:20:25,160 --> 00:20:27,920
they're almost bound to mess it up.

318
00:20:27,920 --> 00:20:32,320
Teenagers can be forgiven for not
being able to handle alcohol.

319
00:20:32,320 --> 00:20:35,320
Adults, you'd think,
would know better,

320
00:20:35,320 --> 00:20:39,520
but I'm afraid we don't,
because every day in Britain,

321
00:20:39,520 --> 00:20:45,000
500,000 of us go to work
with a hangover.

322
00:20:45,000 --> 00:20:47,120
Although, mind you,
it's not just us.

323
00:20:47,120 --> 00:20:49,560
Human beings have been
boozing like mad

324
00:20:49,560 --> 00:20:52,040
for thousands
and thousands of years,

325
00:20:52,040 --> 00:20:56,480
which gives my next question truly
international significance.

326
00:20:57,680 --> 00:20:58,880
Mmm.

327
00:21:00,240 --> 00:21:04,400
Why am I hung-over?

328
00:21:04,400 --> 00:21:05,840
Headache?

329
00:21:05,840 --> 00:21:06,880
Dizziness?

330
00:21:06,880 --> 00:21:07,920
Nausea?

331
00:21:07,920 --> 00:21:10,320
The evidence suggests you
drink alcohol.

332
00:21:10,320 --> 00:21:16,000
On average, we each sink more than
a gallon of pure alcohol a year.

333
00:21:16,000 --> 00:21:20,520
Worldwide, this adds up to
a trillion pints of beer,

334
00:21:20,520 --> 00:21:24,320
or 250 billion bottles of wine,

335
00:21:24,320 --> 00:21:26,680
or 100 billion bottles of vodka.

336
00:21:28,440 --> 00:21:33,160
To find out how it makes you feel
so bad, we need to flash back.

337
00:21:33,160 --> 00:21:36,880
90 seconds after your first sip,
the alcohol hit your brain,

338
00:21:36,880 --> 00:21:40,920
and interfered
with your neurotransmitters,

339
00:21:40,920 --> 00:21:44,480
making you talkative
and self-confident.

340
00:21:44,480 --> 00:21:48,160
By drink two, your inhibitions
were really dropping.

341
00:21:48,160 --> 00:21:49,560
Back inside your brain,

342
00:21:49,560 --> 00:21:53,600
a chemical called vasopressin would
normally be sending a signal

343
00:21:53,600 --> 00:21:57,320
to your kidneys, to tell them
how much water take from your blood.

344
00:21:59,120 --> 00:22:01,640
Alcohol switches this chemical off.

345
00:22:02,960 --> 00:22:07,280
So, your kidneys started channelling
most of the water to your bladder.

346
00:22:07,280 --> 00:22:13,120
For every drink, you expelled
four times as much in urine.

347
00:22:13,120 --> 00:22:16,440
By now, you were also
tired and emotional.

348
00:22:16,440 --> 00:22:20,720
Thankfully, someone took you home,
where you crashed out.

349
00:22:20,720 --> 00:22:22,240
And slept really badly.

350
00:22:22,240 --> 00:22:26,800
That's because alcohol suppresses
the production of glutamine,

351
00:22:26,800 --> 00:22:29,560
one of the body's
natural stimulants.

352
00:22:29,560 --> 00:22:33,000
When you stopped drinking,
production revved up again,

353
00:22:33,000 --> 00:22:36,520
so you spent the night
tossing and turning.

354
00:22:36,520 --> 00:22:41,200
Overnight, your dehydrated liver had
to process the alcohol toxins,

355
00:22:41,200 --> 00:22:44,320
so it stole water from your brain,
which shrank

356
00:22:44,320 --> 00:22:48,320
and began to pull on the membranes
attaching it to your skull.

357
00:22:48,320 --> 00:22:52,200
Which is why you just woke up with
a pounding head, dry mouth,

358
00:22:52,200 --> 00:22:56,480
and nausea from the after-effects
of the toxins.

359
00:22:56,480 --> 00:22:59,480
A hangover can last
for up to 24 hours,

360
00:22:59,480 --> 00:23:04,400
giving you plenty of time to
think about what you did last night.

361
00:23:04,400 --> 00:23:09,280
If you can face it,
a cooked breakfast might help.

362
00:23:09,280 --> 00:23:11,040
But chances are you can't,

363
00:23:11,040 --> 00:23:14,920
so you'll just have to spend
the day feeling like death.

364
00:23:14,920 --> 00:23:16,800
But then one day you'll be ill

365
00:23:16,800 --> 00:23:19,440
and your body won't be able
to make you better,

366
00:23:19,440 --> 00:23:23,320
and that brings us to
the greatest question in life...

367
00:23:23,320 --> 00:23:26,280
Why do I have to die?

368
00:23:26,280 --> 00:23:30,040
For most of history, human life
has been dangerous and short.

369
00:23:30,040 --> 00:23:33,640
Natural selection favoured
the genes that made you strong,

370
00:23:33,640 --> 00:23:36,600
not the ones that
helped you get old.

371
00:23:36,600 --> 00:23:40,280
Our bodies still peak
between 20 and 35.

372
00:23:40,280 --> 00:23:43,480
After that,
it's a slippery slope to the grave.

373
00:23:45,280 --> 00:23:49,440
To find out why, scientists
are investigating our cells.

374
00:23:49,440 --> 00:23:53,200
When you're young and healthy,
your cells divide and replicate

375
00:23:53,200 --> 00:23:56,080
50 billion times every day.

376
00:23:56,080 --> 00:24:00,480
But each individual cell
can only split 50 times.

377
00:24:00,480 --> 00:24:03,240
When it hits this magic number,
it's retired.

378
00:24:06,040 --> 00:24:09,680
As you age, cell death starts
to outpace cell birth.

379
00:24:11,360 --> 00:24:16,320
And ageing cells are more
vulnerable to attackers.

380
00:24:16,320 --> 00:24:19,200
Amongst the worst are
free radicals -

381
00:24:19,200 --> 00:24:22,440
unstable oxygen molecules
which stabilize themselves

382
00:24:22,440 --> 00:24:25,040
by stealing electrons
from your cells...

383
00:24:27,840 --> 00:24:32,880
inflicting damage that
can cause diseases like cancer.

384
00:24:32,880 --> 00:24:34,800
Free radicals aren't
the only problem -

385
00:24:35,440 --> 00:24:38,120
old cells just get tired.

386
00:24:38,120 --> 00:24:42,320
The elderly cell enlarges,
and becomes less efficient

387
00:24:42,320 --> 00:24:45,640
at turning oxygen and
nutrients into energy.

388
00:24:45,640 --> 00:24:48,200
A bit like a person, really.

389
00:24:48,200 --> 00:24:51,200
You can see the results
of ageing in your skin.

390
00:24:51,200 --> 00:24:55,200
Inside your body,
the same thing is going on.

391
00:24:55,200 --> 00:24:59,000
At 40, your nervous system
becomes less co-ordinated,

392
00:24:59,000 --> 00:25:02,120
giving you heartburn
and constipation.

393
00:25:02,120 --> 00:25:08,760
By 60, your eyes let in two-thirds
less light than they did at 20.

394
00:25:08,760 --> 00:25:14,120
And at 85, your heart can only beat
a fifth as fast as a 20-year-old's.

395
00:25:14,120 --> 00:25:15,840
At which point, well,

396
00:25:15,840 --> 00:25:20,280
you and your magnificent body
are just about to hit journey's end.

397
00:25:21,440 --> 00:25:25,600
Although science is helping
more of us to live to be old,

398
00:25:25,600 --> 00:25:28,600
humans have a natural lifespan.

399
00:25:28,600 --> 00:25:30,600
85 is about it, really,

400
00:25:30,600 --> 00:25:34,920
and conventional medicine isn't
likely to extend this very much.

401
00:25:34,920 --> 00:25:39,360
But of course, medicine is becoming
more and more unconventional,

402
00:25:39,360 --> 00:25:44,200
so for our descendants, life
and death may be very different.

403
00:25:44,200 --> 00:25:48,720
So what will we look
like in 1,000 years' time?

404
00:25:48,720 --> 00:25:53,680
Two million years ago,
Homo habilis made stone tools.

405
00:25:53,680 --> 00:25:57,560
These days, Homo sapiens
design computer chips.

406
00:25:57,560 --> 00:26:01,160
Next, we'll be taking
charge of our own evolution.

407
00:26:01,160 --> 00:26:05,600
In 2008, scientists announced
that they had taken a rat's heart,

408
00:26:05,600 --> 00:26:11,640
stripped it to its scaffolding,
and re-seeded it with cardiac cells.

409
00:26:11,640 --> 00:26:15,000
Within four days, the cells
were contracting.

410
00:26:15,000 --> 00:26:17,440
Within eight,
they had begun to pump.

411
00:26:17,440 --> 00:26:21,600
This was a big step on the road
to replacement organs.

412
00:26:22,680 --> 00:26:26,680
Also in the pipeline are eyes,
lungs and limbs.

413
00:26:27,840 --> 00:26:30,600
This technology could
make us immortal

414
00:26:30,600 --> 00:26:34,680
IF we can also work out how
to regenerate our brains.

415
00:26:35,920 --> 00:26:38,160
But that will take a while,

416
00:26:38,160 --> 00:26:42,440
because the brain is
a mind-bogglingly complex thing.

417
00:26:42,440 --> 00:26:46,200
Inside here there are
a hundred billion cells,

418
00:26:46,200 --> 00:26:50,680
all communicating through
tiny waves of electricity.

419
00:26:50,680 --> 00:26:54,400
And somewhere within all those cells
and all those connections

420
00:26:54,400 --> 00:26:58,440
is the mind,
the essence of you and me.

421
00:27:00,200 --> 00:27:05,480
Scientists are determined
to unlock the mysteries of the mind.

422
00:27:05,480 --> 00:27:08,520
When they do,
we may achieve not just immortality,

423
00:27:08,520 --> 00:27:11,840
but a higher intelligence
than we can imagine.

424
00:27:11,840 --> 00:27:14,000
Here's how -

425
00:27:14,000 --> 00:27:17,040
in 2004, a computer chip
was implanted

426
00:27:17,040 --> 00:27:20,240
into the brain
of a paralysed man.

427
00:27:20,240 --> 00:27:23,680
When he wanted to watch TV,
the chip read his thoughts,

428
00:27:23,680 --> 00:27:25,280
and switched the channels.

429
00:27:26,480 --> 00:27:30,840
By 2050, it's predicted that
computer-brain interaction

430
00:27:30,840 --> 00:27:35,520
will be so advanced, that we'll use
PCs to store our surplus memories.

431
00:27:36,840 --> 00:27:40,040
Beyond that, we'll aim to
devise technology to merge

432
00:27:40,040 --> 00:27:44,440
the creativity of human thought
with the speed of computers.

433
00:27:44,440 --> 00:27:48,160
So, while your descendants
might choose to look human,

434
00:27:48,160 --> 00:27:51,440
inside they could be
more machine than man.

435
00:27:54,160 --> 00:27:57,120
So, back to my first question -

436
00:27:57,120 --> 00:28:01,080
do you ever contemplate
the wonder of your body?

437
00:28:01,080 --> 00:28:03,280
Well, we just have,

438
00:28:03,280 --> 00:28:05,760
and now I'm incredibly
proud to own one,

439
00:28:05,760 --> 00:28:09,520
a marvellous vehicle in which to
journey through life.

440
00:28:09,520 --> 00:28:12,280
And one day that journey
may last forever,

441
00:28:12,280 --> 00:28:15,360
but I'm afraid you and I
were born too early for that.

442
00:28:15,360 --> 00:28:18,920
All we can do is sit back
and enjoy the rest of the ride.

443
00:28:44,720 --> 00:28:46,760
Subtitles by Red Bee Media Ltd

444
00:28:46,760 --> 00:28:48,800
E-mail subtitling@bbc.co.uk