National Geographic: Mysteries of Mankind Page #3
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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
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.
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,
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
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?
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
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.
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.
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,
that the wear patterns
are very dissimilar,
and that, therefore,
the foods they would have eaten would
have been dissimilar.
The scratches and
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
It now seems far more
likely they were vegetarians
who should be seen
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
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.
in northern Kenya have a record
of both human
and animal life that is
perhaps unmatched in the world.
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