In the heat of our prehistoric past
when was the first braai (barbecue)?
 The
use of fire is one of the key tools that marked the difference between early ape
men, and their primate cousins. Fire also marked the start of mankind's long
march from being a common snack for predators to being the world's most
successful predator.
Not just any old fire would do. A random lightning strike, setting the long
grasses smouldering in the dry season, didn't count. But when an early man (or
woman) used his or her developing brain to think about the possibility of
capturing some of that fire safely, perhaps on a long branch of white stinkwood
or another tree, maybe even with one end dipped in water for safer handling, and
carried that fire to a communal living area - well, that was controlled fire,
and control of such a valuable tool has made all the difference to our history.
"Without the controlled use of fire it would not have been possible to
develop rocket technology," says Francis Thackeray of the Transvaal Museum
in Pretoria, South Africa. "Without a rocket it would not have been
possible for humans to have travelled to the moon." And it would not be
possible, without fire, for Americans to consider a mission to Mars.
Now a team of scientists – two South Africans, two Americans – have
confirmed that fire was first utilised on the African continent, not elsewhere.
Through the expensive technology of the modern age, and in particular electron
spin resonance, their results lead them to believe that the first small,
tentative technological steps that eventually led to the giant leap of lunar
exploration began in southern Africa more than 1 million years ago.
Swartkrans is a dark cave in the Cradle of Humankind, about a kilometre west
of Sterkfontein. (Sterkfontein is where the rare, virtually complete Little Foot
skeleton was discovered, and the Cradle of Humankind is one of the richest
palaeontological sites in the world).
In 1984 a treasure trove of more than 250 ancient burnt animal bones was
discovered at the site by Dr Bob Brain, then the Director of the Transvaal
Museum. These fossilised remains of antelope, at least one million years old –
and in some cases more than one million year old – were discovered in a
section identified as Member 3, in which the brescia - the deposits containing
the fossils - has been eroded into decalcified sands. As it erodes, the brescia
returns from a rock-hard type of cement back into its original sand. The problem
is, decalcified sand can make it more difficult for scientists to date
accurately the material found within it.
These antelope bones appeared to have been braaied - or to use a word more
commonly understood outside South Africa, the hominid bands sheltering in these
caves seemed to have enjoyed regular antelope barbecues. Brain worked with Dr
Andy Sillen, a chemist in the archaeometry laboratory at the University of Cape
Town, which specialised in the chemical detective work required to analyse these
frequently minute shards from both archaeological and palaeontological deposits.
Sillen and Brain recognised that the fossilised bones had been burnt by
undertaking chemical analyses (looking at ratios of carbon, nitrogen and
hydrogen), as well as by studying the structure of bone affected by heat. But
how hot? And how long ago?
Brain burnt modern bones of domesticated animals in a kiln at known
temperatures and compared them to the fossilised bones from Swartkrans.
Histological results – that is, the microscopic analysis of bone sections –
suggested that the heating temperatures experienced by the fossils had been
similar to those in campfires, and well above the temperatures experienced in
naturally-occurring grass fires which burn at relatively low temperatures (about
200 degrees Celsius). If confirmed, this would place the earliest controlled use
of fire between one million years ago, and one and a half million years ago.
(Previous to this, the earliest controlled use of fire was thought to date from
only about half a million years ago, from a site in China.)
But some palaeontologists questioned the validity of their claim. Many agreed
that the bones had been heated but some suggested that the fossils weren’t
over one million years old. So when newer technology presented an opportunity to
re-examine the issue of the heat, the scientists jumped at the chance.
"We decided to re-examine some of the Swartkrans bones to see if
electron spin resonance could serve as a palaeothermometer," explains Dr
Thackeray. The bones had been kept in storage in the Transvaal Museum. Dr Anne
Skinner of the Department of Chemistry at Williams College in Maryland in the
USA flew to South Africa to obtain a selection, which then accompanied her to
the USA. The electron spin resonance was done at Williams College.
"Preliminary results confirm that the bones fall into three general
categories: unheated, slightly heated, and calcined" says Dr Skinner.
(Bones may start off white, then progress to brown and black as they are burnt,
but in intense heat they return to a white colour and become very brittle. This
is what is meant by the term calcined.) "The presence of manganese in the
fossils makes comparisons with modern heated bone difficult, but there is some
evidence that the manganese electron spin resonance signal depends on
temperature, which would then provide a second measure of the degree of
heating."
Swartkrans is in fact named after the dark manganese deposited naturally
there, and is the Afrikaans word for a black hillside. Another problem facing
the first group of scientists was that manganese was being dissolved out of hill
and back into the deposits all the time. How to tell if the darker bones were
simply affected by manganese, or by fire? The new work by Anne Skinner, Joan
Lloyd and colleagues, using electron spin resonance, confirms the ideas of Brain
two decades earlier. These bones have gone through intense heat.
They found that the palaeotemperatures associated with many of the bones
exceed 500 degrees Celsius, which is the kind of temperature associated with
controlled fires in confined areas. 500 degrees Celsius is hot enough to change
both the structure and the chemistry of bone.
Whether you are heating organic materials such as bone or inorganic materials
such as rock, the heat produces free radicals, atoms which are temporarily
available for a chemical reaction to take place because they are not already
bound in a chemical marriage in a molecule. These molecules can be detected by
electron spin resonance. This process has been to look at heated flint, for
example, and stone. It has seldom been used to date bone. The type of free
radicals formed depends on the heating temperatures, with higher temperatures
resulting in simpler radicals. That particular group of free radicals is then
embedded in the bone as it slowly turns into a fossil, and has remained there
undetected until now. More tests are planned within the next year to get the
particular temperature for particular bones.
The burnt bones from Swartkrans are still thought by Thackeray and Skinner to
be between 1 and 1.5 million years old, although the electron spin resonance
technique was not used for dating. There is always difficulty in dating
palaeontological deposits in South Africa, which lacks the extremely useful
volcanic deposits in East Africa, which can be precisely measured. The figure of
one million years and greater is derived from the fossilised fauna found side by
side with the burnt antelope bones in the same layer of decalcified sand. These
animals can be matched with other members of their species in ancient sites
uncovered in Kenya and Tanzania.
Thackeray cautions, "we do not claim that distant human relatives such
as Homo ergaster or Homo erectus were making fires, but at least they were
probably using fire in a controlled manner. They could have collected burning
branches of trees that had been set alight by lightning after dry winters on the
highveld".
Whoever first used controlled fire had no thoughts about what this discovery
would unfold over the centuries. Indeed, whoever first used controlled fire
probably was hungry, infected with insects and desperately afraid of the big
cats and hunting hyenas which prowled the region. But out of a need for safety
comes the technologies which shape our lives, even today.
"Africa as a continent can be proud of the prehistoric technology which
contributed to the development of space age technology," says Dr Thackeray.
And if you want to touch base with some of humanity’s own history of
technological innovation, there are some burn fossilised antelope bones on
public display at the Transvaal Museum in Pretoria. It’s rather appropriate
that the off-white fossil fragments share a display cabinet with a piece of the
moon. Without the first fire, there would have been no moon rocket – and no
moon rock.
More information:
· The Transvaal Museum website can be accessed through the address for the
Northern Flagship Insitutions, which is www.nfi.co.za
· For more on Sterkfontein Caves, try www.cradleofhumankind.co.za
The scientific results of the recent study are not yet published. They were
presented in April at a meeting of the International Palaeoanthropology Society
in Montreal, Canada. Anne Skinner and Joan Lloyd are based in the Department of
Chemistry at Williams College in Maryland in the USA. C.K. Brain and Francis
Thackeray are associated with the Transvaal Museum (also known as the Northern
Flagship Institution) in Pretoria, South Africa.
Related articles:
 Mrs
Ples and our distant relatives
How
to extract information about diet from those ancient teeth and bones
Little
foot; big footprint
The
Earliest Human Ancestors: New Finds, New Interpretations
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