Little foot; big footprint
 Little
Foot has been lying there, with his weary skull resting on an out-stretched left
arm, in the humid shadows and hard-as-concrete soil of the Sterkfontein Caves,
for a long time. A very long time. 4.17 million years, according to a
breakthrough new method of analyzing the age of the soil around the body. Which
makes Little Foot - the famous, virtually complete skeleton of a South African
caveman - almost a million years older than was first estimated.
This new date puts the little man - big for an Australopithecus, small by our
standards - in the running for the title of Grandfather of the human species.
"If nothing else, his bones talk to us of a time very near the beginning of
the road to humanity," says geologist Professor Tim Partridge, one of the
experts working on the Little Foot case, who has spent much of his life
searching for new ways to make our shadowy prehistory a more exact science.
The important new date obtained by a team of South African and American
scientists is being reported on in the prestigious weekly, Science.
Knowing the problems Wits University was encountering in calculating the age of
the
fragile figure, Purdue University geomorphologist Darryl Granger offered to
try a new dating method. Used only twice, it's called the cosmogenic burial
technique. Each grain in the soil surrounding a deeply buried body can be
analysed.
Nuclear physicist Marc Caffee assisted with the laborious and time -
consuming process of measuring the activity of decaying radioactive metallic
elements in each grain, in wildly expensive nuclear accelerators at California's
Lawrence Livermore defense and security laboratory. It's not Chernobyl-style
radioactivity, but the minute amounts occurring naturally
that he was monitoring.
Because physicists know how long it takes these elements to decay, they can
work out the age of Little Foot's surroundings - but only if they have access to
state-of-the-art technology.
As a result of the Americans' hard work, Wits University academics Professor
Tim Partridge and Dr Ron Clarke were able to narrow down the date of Little
Foot's brief life and important death quite dramatically: 4.17 million years,
give or take fifteen thousand decades.
Partridge can't give the exact date on which the short male decided to go
running across the hillocks and bumps of what is now part of Gauteng
province. Perhaps a large carnivore, like the terrifying long-legged hunting
hyena whose bones lie nearby, was searching for a tasty bit of hominid lunch.
What seems very likely is that Little Foot accidentally tripped and fell
down one of the many vertical shafts through the soft dolomite, shafts now
either fenced off by man or filled in by Mother Nature.
"Fractures crisscross his arms and legs," says Professor Partidge.
"Some of
those clearly happened after death, as parts of the cave fell in on him, but
some of them may have been from the fall."
Today there are steps and tunnels carved into Sterkfontein. Four million
years ago, there was no way out for a wounded ancestor. No way out, until his
bones spoke to palaeo-anthropologist Dr Ron Clarke, who was rummaging through a
box of bones stored at Wits, labelled as primate
relics from chunks of fossil-bearing breccia blasted out by limestone miners
in the 1920s.
Clarke found the little bones of two feet, one left, one right. When rivers
wash down fossils, or carnivores drag and scatter their meaty meals, the
leftovers are not normally found in neat, matched pairs, like shoes in a closet.
So Clarke went to Steven Motsumi and Nkwane Molefe, technical assistants at
the dig, and asked them to search. He saw how a fragment of leg bone fitted into
the foot bones, and knew those feet were made for walking on the ground, not
moving in trees. Early human ancestor - an ape, not a monkey. And two feet meant
the possibility of two legs, connected to the hip bones, a ribcage, arms,
collarbone and skull.
Motsumi and Molefe, the fossil hunters, found what they were looking for
within an astonishing 48 hours. As soon as the findings were published, disputes
over the age of Little Foot began. Certain scientists suggested that Little Foot
was younger than the paper suggested. But now the new research places Little
Foot's age at being almost a million years older than originally suggested.
South Africa may yet turn out to be the cradle of humanity but its geology
doesn't make it easy for anyone to prove this.
In Kenya, the famous Leakey family had an advantage when it came to dating
the East African lake and river fossil deposits. Their ally: volcanoes.
They used an unstable version of the common element potassium, present in
crystals in the volcanic ash, to date the bones of early hominids
sandwiched between layers of lava from volcanoes along the Rift Valley. As
the potassium decays into another element, argon, over incredibly
long timespans, dates could be established.
Without volcanic materials in South Africa, scientists relied on examining
animal fossils found alongside the remains of early humans and comparing them to
similar animal fossils dated in Kenya.
Because radiocarbon dating is only accurate to about 50,000 years ago, it
couldn't be used to date Little Foot. Other scientists dated the site by looking
at the signature left in the white flowstone that separates layers of breccia, a
signature scrawled by the periodic switching of the North Pole and the South
Pole. This magnetic reversal technique was used in 1999 when Clarke, Partridge
and others insisted that Little Foot was 3.3 million years old. It turns out
they were only off by a million years or so. They'd missed two magnetic
reversals. But at least they erred on the right side.
It's a great detective story, starting with the death of one sturdy member
of the australopithecine lineage, which successfully colonised much of Africa
for at least two million years, considerably longer than modern humans have been
around.
And the story's not over yet. For a start, scientists will query every aspect
of the dating. It's their right. For another, Little Foot is still partially
locked into the unyielding soil at Sterkfontein. His bones are practically putty
compared to the rock-hard compacted earth in which he has been resting, so the
process of removing him from his grave will continue for years.
But enough painstaking work has been done to show that those four million
year old hands might have been good for climbing trees but they were also
powerful like ours. Those four million year old arms are similar in length
to the legs rather than long like a knuckle-walking ape. Little Foot's
facial anatomy, with the orange earth of Sterkfontein delicately scraped
off, doesn't look like a chimpanzee or a gorilla. He has a smaller brain
than ours but his teeth are not like that of other apes.
The tender loving care shown by the palaeo-anthropologists tending Little
Foot isn't simply the result of fear and wonder for something old, unique
and vulnerable. It's a recognition of a common link. This is a fellow member
of the extended family called humanity.
More bones of other ancestors lie waiting for their chance to talk. In the
Science article, it's noted that the previously-unexplored Jacovec cavern
has yielded bone bits and pieces from three different early people, almost
as old as Little Foot.
"And much of Sterkfontein has yet to be excavated," Partridge says
with
glee.
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