Speaker Report November - Extinction of the Australian Megafauna: What is the Evidence?

(Bryce Barker, Professor of Anthropology, University of Southern Queensland)

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)