National Geographic: Mysteries of Mankind Page #3

---

without actually going back

in time and coming face to face

with our ancestors.

The end result is often

a surprise even to me.

I'm basing the restoration on

clues one by one

that I'm getting from the bony anatomy

and the cumulative effect

of those clues is often a surprise.

A face long lost to the tides of time

emerges out of plaster and clay.

We come face to face with one of

out earliest known relatives

across a chasm of three million years.

More than half a million years

before Lucy

and more than a thousand miles away,

a volcano erupted

spewing ash across

Tanzania's Serengeti Plain.

Then a moment was frozen in time.

An amazing sequence of

chance events created a record unique

in the pageant of prehistory.

Soon after the eruption the rain

clouds that had been threatening parted.

Then three hominids,

perhaps of the same species as Lucy,

walked by.

Their footprints left an impression

in the dampened ashfall.

Only because the sun then came out did

the footprints harden.

And only because continued eruptions

laid down yet other layers of ash

were the traces entombed more than

three and a half million years.

Today this area,

not far from Olduvai Gorge in

northern Tanzania, is called Laetoli.

Here, in 1978,

a team led by Dr. Mary Leakey

finds what is one of the most

astounding archaeological discoveries

of all time the very footprints

not seen on this earth

since the eruption of

one volcano millions of years ago.

Dr. Leakey and her team begin

the delicate process

of removing the cement hard rock.

To Dr. Leakey the prints

are more evocative than any fossil.

They tell a vivid story

of one fleeting moment in time.

The track of footprints that

you see here on my left

was a truly remarkable find

that we made this season.

It's a trail left by three people

who walked across a flat expanse

of volcanic ash

three and a half million years ago.

We can say they were relatively short.

We can estimate that their height was

probably between four and five feet.

We can say they had

this free striding walk.

One assumes they were

perhaps holding hands or

They are so evenly spaced, the tracks,

and they're keeping step,

always left foot for left foot

and right foot for right foot,

that it may, for all we know,

have been a family party.

The emotional impact of the footprints

is universal,

but scientifically they arouse debate:

Were these creatures related to Lucy,

and could their upright walk so long

ago have been the same as ours today?

Tim White helped excavate

the Laetoli footprints.

Now, to answer some of

the questions raised,

he has devised an experiment.

With our closest living relative,

he walks across an expanse of wet sand.

Its consistency is roughly the same

as damp volcanic ash.

Here we have my footprint

with a strong heel strike

and the big toe in line with

the other toes.

The chimpanzee's footprint is here and

the knuckle print is right behind it.

We see the chimpanzee's toe

is divergent,

whereas the human toe is

in line with the other toes.

The human foot also has

a dramatic arch to it.

The chimpanzee foot and

its print lacks this arch.

And at Laetoli we have evidence from

three and a half million years ago

of a large toe in line with the rest

of the toes and a longitudinal arch

and a strong heel strike.

In other words,

the human pattern has been established

three and a half million years ago

in Tanzania with these early hominids.

Some scientists feel that only by

studying the locomotion of apes

can we know how Lucy and our

other early ancestors actually walked.

At the state University

of New York at Stony Brook,

a team led by anatomists Randall Susman

and Jack Stern

videotapes the movements

of an orangutan.

They have also extensively

studied chimpanzees.

Come on.

Electrodes implanted in the arm

and leg muscles

send signals to monitoring equipment.

Clothing holds the transmitter

in place on the animal's back.

That's good bipedalism. Keep him going.

On their screen Susman and

Stern receive a superimposed image

of the electrical output

of the muscles as the animal moves.

One intriguing finding:

The hip muscles used by apes

in climbing are used in many

of the same ways as human hip muscles

are in walking.

So the transition from tree dweller

to ground walker

may have been relatively simple.

The pattern of muscle usage

was already in place.

Good boy.

But Susman and Stern, unlike Johanson,

White, and others,

believe that these ancestors

did not walk exactly as we do,

but more like an ape when it walks

on two legs.

They maintain that those creatures,

like apes,

still spent much time in the trees

and had not yet fully adapted

to life on the ground.

In earlier days,

anthropologists compared and

contrasted stones and bones,

but could only ponder questions

about behavior.

Today they can directly address

some of the fundamental issues

of our ancestry.

How did Lucy and the others live?

Where did they sleep?

What did they eat?

In the line of other Australopithecines

to which Lucy may have given rise,

there were smaller creatures

known as graciles

and robust ones

with puzzlingly massive iaws and teeth

The fossil teeth themselves hold clues

to what these hominids were eating.

Thousands or millions of years later,

the wear on the teeth remains.

Let's see if

we can't acquire that image.

Dr. Fred Grine, also at Stony Brook,

studies diet, using a scanning electron

microscope and computer graphics.

Different foods leave distinctively

different marks on teeth.

Comparing the two patterns

of a gracile

and robust australopithecine side

by side,

it becomes quite evident

that the wear patterns

are very dissimilar,

and that, therefore,

the foods they would have eaten would

have been dissimilar.

The scratches and

the polished surfaces found

on a gracile Australopithecine molar

would have been produced

by soft foods such as soft fruits

and leaves,

whereas the pitting which characterizes

a robust Australopithecine molar

would have been produced

by hard food obiects such as seeds

and nuts.

Shrouded in myth since their discovery

Australopithecines were

long characterized

as blood thirsty killer apes.

It now seems far more

likely they were vegetarians

who should be seen

in their more rightful place

in the human evolutionary drama.

Robust Australopithecines flourished

for well over a million years,

then disappeared an apparent

evolutionary dead end.

It is possible they lost out

in competition with another,

more intelligent species

a hominid tool user

a line that would eventually lead

to modern human beings.

Like the remains of their predecessors

the fossil bones of the tool users are

almost always discovered

in deposits formed along lake shores

or streams.

The areas around Lake Turkana

in northern Kenya have a record

of both human

and animal life that is

perhaps unmatched in the world.

Rate this script:0.0 / 0 votes