The Australian megafauna lived during the time
known as the Pleistocene, colloquially termed the Ice Age, which
occurred between about 1.7 million to 10000 years ago. The megafauna are the
extinct ancestors of species which are today much smaller and were
characteristic of the Pleistocene not only in Australia, but also the Americas
and Eurasia. North America had mammoths, saber- toothed cats and giant sloths
for example, (as per my previous talk about the La Brea tarpits near Los
Angeles). Africa is the only continent still inhabited by megafauna.
The
Australian representatives included Megalania prisca, a seven
metre goanna; Diprotodon, at
two metres at the shoulder the largest marsupial to have ever existed; Procoptodon
goliah, the short faced kangaroo standing over two metres high; Thylacoleo
carnifex, termed the marsupial lion, and many others including seven metre
snakes and crocodiles, a 2.5 metre turtle and two toothed platypus species
double the size of today's species.
There is ongoing debate and controversy as to the
causes of extinction of these animals which occurred world-wide. Professor
Barker's presentation clearly examined the likely causes by comparing the
Australian research with findings from America and Europe.
Broadly, reasons for the
extinctions cover three main theories:
- The arrival of humans with their superior hunting
- The effect of humans on the landscape
- Climate change
It is possible that all three could have contributed, but Dr
Barker laid out the following points regarding human arrival:
1) Is there evidence of hunting technology
coinciding with extinctions?
2) Are there remains of megafauna in
association with human settlements?
3) Is there rock art depiction of hunting of
megafauna?
All three are found in America, Africa and Eurasia.
In North America the
earliest hunting technology is the stone projectile or knife, characterised by
the 'Clovis Point', a sharp tool knapped from suitable stone and associated
with the Clovis people. There are many bones of megafauna associated with these
people, and clear signs of penetration of or cuts to the bones (including those
of extinct megafaunal bison). So far, although stone tools are plentiful, there
is no confirmed evidence of mega-faunal bones associated with Humans in
Australian archaeology. Remains of post megafaunal species are how-ever common.
Eurasia also has many finds
associating stone projectiles with remains of extinct megafauna. Depiction of hunting seems universal in rock art and
is a feature common to all inhabited continents. The Lascaux and Chauvet caves
of France are famous, as are the many and widespread bushmen paintings in
Africa. So far there is no Australian rock art confirmed as depicting
megafauna. Many paintings previously thought to depict megafauna have been
dated to well post-extinction and are considered to be 'dreaming'
creatures...possibly passed down over many generations from an ancient memory.
Professor Barker then went on to describe a
truly remarkable and unique Australian site of human habituation, the Nawala Gabarnmang Rock Shelter, where he has carried out research.
Found only just over 10 years ago by two men overflying a remote area of
Arnhem land, Northern Territory, the site seemed almost lost to memory. One
elderly man recalled camping there with his father in the 1930s.
The shelter is part of an ancient shallow ocean
floor where deposits of sand laid down over time were compressed into
sandstone, then harder quartzite. When the structure was raised above the sea,
erosion of softer sandstone began, leaving pillars of quartzite supporting a
roof. About 50 000 years ago people began to use the shelter. The pillars would
have then been about a metre apart, and people began to modify the shelter by
chipping away some pillars with stone tools to increase space. This was carried
out over many generations and they also began to cover all surfaces with
paintings. There is layer after layer of paintings, some confirmed as being 28
000 years old! Blocks of broken pillar have been used for grinding coloured
ochres, others piled up as platforms for artists to sit or stand on.
No representations of megafauna
or their remains have been found at the site. The thylacine is clearly
depicted, but it is known that they occurred on the mainland until about 3 000
years ago (possibly displaced by the dingo). There is a painting at a nearby site, of what appears
to be a large flightless bird in which a spear is embedded. Research focused on
the giant Genyornis newtoni which became extinct about 40 000 years ago.
Humans and the bird may have co-existed for some thousands of years. However,
dating of the painting showed it to be only 14 000 years old, so it is probably
another 'dreaming' beast. It is now believed that only at most 14 species of
the original 90 megafauna species were still extant when humans arrived on this
continent. The evidence seems then to suggest that direct contact with humans
in Australia is an unlikely megafauna extinction culprit. However, many still
assert that hunting wiped out the megafauna.
The scientific research continues with ever more
sensitive dating techniques such as Optically Stimulated Luminescence OSL, (which
dates sediments by measuring when silica was last exposed to sunlight!) which
so far matches the older carbon dating. Meanwhile the controversies continue.
(Report by Cheryl Haxen)
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