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

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