Saturday, March 14, 2009

Saturday Morning Musings- Australian prehistory

I have suggested before that it is a pity that current Australians do not seem to have full access to the long history of human occupation on this continent.

It is not known when the Australian Aborigines first arrived in Sahul, the name given to the broader land mass including Australia and New Guinea that existed during the Pleistocene period when sea levels were much lower than today. Based on current evidence, the best estimate seems to be 40,000 to 50,000 years ago, although it could be longer.

The question as to whether there was one or several waves of human settlement with later waves replacing earlier groups still seems to be open to question. Based on the discussion in John Mulvaney and Johan Kamminga's Prehistory of Australia, my gut judgement would be that the early arrivals quickly built up a population mass such that later arrivals probably melded in. I base this in part on difficulties of transportation; people probably came in small groups.

40,000 to 50,000 years is a very long time in human terms, long enough for the human occupants of the continent to experience major environmental changes.

At the time the first humans arrived in what would become Australia, sea levels were somewhere between 60 and 85 metres below current levels. Sea levels fluctuated considerably between 40,000 and 50,000 years ago, so the level depends upon the exact time the first small groups landed on what would become Australian shores.

Lower sea levels meant that Sahul was considerably larger than the modern continent. Neither Torres Strait nor Bass Strait existed. The northern shore line swept in a north easterly direction from well west of current Darwin up to modern New Guinea. The current Gulf of Carpentaria was well inland, with a large lake in the centre.

For those who love interactive maps, Monash University has a fun interactive map that allows you to look at the impact of past changes in sea levels on the continent.

If you look at the chart on the top of the map, you will see that 120,000 or so years ago sea levels peaked at around 3 metres higher than current levels. There was then a long downward trend, but with marked fluctuations around the trend. This meant while sea levels were falling, this fall was constantly interrupted by significant rises.

Around 30,000 years ago, the world entered a sudden cold snap that lasted at least 10,000 years. Note that all dates are approximate, plus or minus thousands of years. Sea levels dropped to perhaps 130 metres plus below current levels. Small glaciers emerged in Tasmania and on the Snowy Mountains.

Sea levels then began to rise slowly. Around 13,000 years ago there was a major surge; sea levels rose 25 metres in 1,000 years, 2.5 metres every century, 25 millimetres a year. At 10,000 years BP (Before Present), Mulvaney & Kamminga suggest that there was another surge as the Antarctic ice sheet fragmented. The Monash site suggests that 10,000 years ago sea levels at Sydney were perhaps two metres higher than now.

There are uncertainties and variations in all this that increase as we narrow our date focus. However, there appears to be agreement as to overall patterns.

The long history of human occupation of Australia, together with the continent's relative isolation, means that Australian prehistory provides a remarkable if still only partially understood story of the adaptation of people to environmental change.

Expressed in human terms, the changes would generally have appeared slow, taking place over generations.

This was not always the case. Mulvaney and Kamminga suggest that on the flat Great Australian Bight and Arafura Shelf between 13,000 to 11,000 years ago, the rate of marine transgression reached one metre a week, 110 kilometres in 2,000 years. Each high tide would have exceeded the previous one.

This would have had a major impact; ten years, 520 metres of territory gone; thirty years 1,560 metres gone; those living on the sea's edge would have had to move, triggering consequential effects.

As rising sea levels stabilised, the continent pushed back. Rivers deposited sediment, forming deltas. Dunes formed, linking higher land with lakes behind. The lakes filled with sediment, extending land areas. The coastline as we know it today came into existence.

As land extended, it was colonised by plants and animals. New, richer, ecosystems formed. People moved in, re-occupying previously lost areas.

Sea level changes were associated with changes in climate that are reflected in the archaeological record. I do not want to write about these in detail, I am not sure that I understand them yet, but I can illustrate with a few examples.

Along the Murray River, a high population environment because of the richness of the riverine resources, semi-arid land crept to within a few hundred metres of much of the river. The Murray Aborigines became isolated, mixing along the river. Clan boundaries shrank, life became more sedentary, more intensive. Analysis of human remains shows evidence of periodic malnutrition associated with dry times. There is also evidence of intestinal parasites.

In the high country of the Snow Mountains and the New England, very harsh country during the colder periods, people re-occupied the land around 2,000 years ago as the climate became warmer. Population numbers were not high, but the human presence returned.

We do not fully understand these changes. We never will. However, the evolving study of the Australian past has slowly pushed back barriers, bringing the long past back to the present.

I did my honours thesis - largely an ethnohistorical study - on the traditional structure of Aboriginal economic life in Northern NSW - in 1967. When I compare what was known then with Mulvaney and Kamminga's 1999 publication, a time period of only 22 years, I can see how far we have come. Yet so much remains to be done.

Unfortunately, the present affects the study of the past. I have to be very careful how I phrase this to avoid getting caught in the wrong arguments.

When I look at Australian prehistory I am struck by two things. I stand to be corrected on both.

The first is the way that the discipline has been, as I see it, twisted by current needs.

There has been a huge increase in archaeological studies, but this has been driven by things such as heritage or rescue studies commissioned to meet particular needs. The quantum devoted to study of our prehistoric past for the sake of knowledge has shrunk. This certainly holds in relative terms and may hold in absolute terms as well.

The second is the way in which study has been restricted by the need to take into account the views of particular indigenous groups. This is the really touchy one.

Take the study of human remains as an example. These provide invaluable evidence of the past. How much weight should be placed on the views of current Aborigines who may (but in some cases clearly may not) have some form of historical linkage to those remains?

The long history of human occupation of the Australian continent is, I think, a very interesting topic in its own right, as well as something directly relevant to all Australians. I wonder why so few Australians are interested?


Neil had a useful comment on this post. He said:
It really is quite recent for Australian history books to go back any further than the first European navigators... That certainly was the history I learned in school.
Neil is right and it's all a matter of perspective. When Neil and I went to school the basic information wasn't there. That was why I found Australian prehistory so much fun at university - it was all new.

This no longer holds. The material is there.

A year or so back a book was published on Indigenous building and construction. It was reviewed more or less along the lines this is new, it shows that the Aborigines built things.

This was clear when I did my thesis in 1967, although I was surprised at the scale. Then I was entitled to be surprised. That is no longer true. There have been a number of books since including Prehistory of Australia that show this.

My question remains.

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