National Geographic: The Body Changers

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In the beginning,

there is the fertilized egg.

Its form couldn't be simpler.

But this will change.

It's a piece of work to craft

a creature from a single cell.

By the time it enters the world,

every living thing has experienced

an odyssey of alteration.

Change doesn't stop

with hatching or birth.

Growing up is also

a story of transformation.

A newborn kangaroo can grow

over 50,000 times in weight.

Some creatures do far more than

simply grow up.

They reinvent themselves.

A fish can start life as a female

but end up as a male.

A bird can grow or shrink a brain area

for song to suit the season.

Polliwogs become frogs.

Caterpillars turn into butterflies.

We learn few more curious facts

than these.

But it's easy to lose sight of just

how astonishing these changes are!

And even weirder transformers

live among us.

Turn and face the strange.

Meet the body changers.

"Hey, Emma, come here!"

Compared to the epic alteration

of a caterpillar,

our own changes may seem subtle.

But there's no denying that

kids change shape

as they turn into grown-ups.

The brain kicks off our own

sexual transformations.

Girls tend to get curvier

from estrogen and other hormones.

A child's body,

and that of many other young creatures,

changes shape when it reaches

the age for reproduction.

These alterations prepare us

to compete for mates,

to have babies,

and to care for them.

Boys change in their own way.

They add muscle.

Shoulders become broader.

The body gets hairier.

Vocal cords lengthen as does the jaw.

A child's journey to adulthood

is a long one.

A grown-up is not just

a scaled-up kid,

but one rebuilt from head to toe.

Look back at

the odyssey of growing up,

and we see that

even our faces change shape,

starting in infancy with small chins,

huge eyes, and plump cheeks.

We are all body changers

when it comes to growing up

and growing old.

It may be no accident that

many baby animals have different

face shapes from their parents.

Adults find baby features irresistible,

a hard-wired system

that promotes infant care.

Silvered leaf monkeys

have Day-Glo offspring.

No one knows why,

unless it's a reminder

to rough-and-tumble mothers

to handle the baby with care.

The young and old of many animals

have different colors,

sometimes to conceal newborns

that are less able to flee danger.

A young, sexually mature male orangutan

has a distinguished, mournful visage.

But in middle age,

his face changes shape.

His new jowly look

is a badge of power.

Changes in our own faces

tell many stories.

A face that forms symmetrically

in the womb

and stays that way through adulthood

can be a mark of good nutrition

and resistance to disease.

Is it any wonder we are highly attuned

to symmetry and find it beautiful?

Old age brings new changes

as our faces transform again,

keeping a faithful record

of wear and tear, loves and losses.

As we change ourselves in the

subtle ways that human beings do,

we're surrounded by creatures

that become entirely new.

Around us are animals

that live out the youthful fantasy of

sprouting wings and flying like a bird.

But we also share the world

with animals

whose stories of change

echo darker myths.

Hercules' enemy,

the many-headed Hydra,

sprouted two new heads

for every one lopped off.

Nature nearly matches legend.

The salamander has powers of

regeneration bordering on the magical.

It will need these talents,

for it lives not in a fairy tale,

but rather in a world of real dangers.

A red-eared slider enters the stream.

The salamander picks

an unlucky moment for a swim.

It's a vulnerable creature,

unarmored and undisguised.

The turtle has nipped off

the salamander's hind leg.

Over three months, the creature

miraculously transforms itself

back to an earlier stage of life.

The genes that grew the leg

in the first place are activated again.

The new leg will be indistinguishable

from the original.

Unique among animals with backbones,

the salamander can regrow

not just limbs

but the lens of the eye

and even part of the brain.

This beast can survive

a bite to the head!

The Hydra lives.

The power to change shape or color

offers a special edge in life.

Some creatures change

to stay hidden.

Others transform

to find new kinds of food.

Still other animals change

for upward mobility,

for the chance to fly or leap

to another pond.

This lake is home to two body changers

that can be lifelong rivals.

A dragonfly nymph spends the first

part of its life beneath the surface.

Everything about this creature

seems honed for water.

It is tapered for speed.

Its head has powerful jaws and huge

eyes-the better to catch prey with.

It breathes through an anal gill,

also handy for jet propulsion.

It's hard to believe

that this pond predator,

sleek as a torpedo, accurate and deadly,

will one day take to the air.

Wings are already forming.

An amazing makeover is beginning.

But the dragonfly will not be able to

complete its body change

without regular meals.

Sharing the pond are

gray treefrog tadpoles.

You can't get any fishier than this

without actually being a fish.

A tadpole breathes through

internal gills.

Its long flat tail propels it

like a fish's tail.

Inside, powerful front legs have formed

and are nearly ready to burst out.

But not every ungainly swimmer will

live to be reborn as an elegant leaper.

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