Saturday, 12 November 2011

A bit more on Horton...

I decided to look at some other work by Horton, just to get a fuller picture of his theory behind the late Pleistocene extinction in Australia. 

In another paper of his, he studies the possible impacts of Aborigine populations and their fire regimes (1980). In this paper, he considers the ‘fire stick farming’ model, which suggests that Aborigines changed the frequency and nature of fires in order to manipulate animals and plant resources. He various evidence to disclaim this theory, one piece of evidence being from Kangaroo Island, who lived on the island until 2,500 year BP, but their living there had little effect on the vegetation, and the only change in vegetation was at 4,800 years BP, which can be attributed to the climate. Horton blames the fire starting on thunder storms, Cheal, Day and Meredith (1979) prove that at least 54% of the fires in North West Victoria are started by lightening, and give figures as high as 97% for New South Wales between 1974-75, seeming a possible cause of large scale fires, rather than human intervention.

Also he points to the fact that under the ‘fire stick farming’, most of the vegetation early stages of growth, not having reached anywhere near maturity, which would in turn have meant the mass extinctions of small species, which did not occur (1980). He also looks at the human side of it as well and points out that if they did keep relighting these fires it would have in fact been very bad for the soils and been detrimental to the Aborigine populations who relied heavily on these soils for food and livelihood. But the main point he highlights that shows that this model is obsolete, is that this model requires Aborigine populations to change the nature, season and frequency of the fires in Australia, but this would have been impossible because the natural fire potential of Australian vegetation cannot be changed. Although Aborigine populations may have provided an ‘alternative of fire’ they didn’t change the fire regime, these interacting fire cycles had continued for at least 2 million years and were probably unaffected by the human arrival (1980). I have to agree with Horton here, and think that nature is a lot stronger than people give it credit for, and these people couldn’t have changed the vegetative community in Australia, unless they were large groups of settlers with growing populations of both livestock and populations, which we know they were not.

In another one of his papers, based on evidence from Southeast Australia, he presents evidence from excavations of the Australian swamp, Lancefield. Here, a bone bed dating about 26,000 years was found containing possibly 10,000 giant extinct megafaunal species (1978). This, in line with the first human appearance in Australia, highlights that animals and humans co-inhabited Australia for 7,000 years, reducing the human predations theory credibility. If human predation was the main cause of the extinction, then surely the extinctions would have happened much earlier, when humans first arrived, not 7,000 years later. And remember, the timing of the extinctions was perfectly in line with the most dramatic shift in climate in the late Pleistocene; this could not surely just be coincidence?

I think people forget about the fact that humans were also restricted during the arid times in Australia. Humans rely on free water as well so would have followed the same concentric distribution around water sources as megafauna did (see last blog for more information). Humans would have had an economy based on principle resource, determined by balance between economic return and effort required (Jones 1980) – catching megafauna would have been high return and high effort, something humans would not have risked when there was so little water. Hence another reason why human predation did not have a big impact, humans probably lived more off fish and small mammals. And this is proven in the fossils is it not? There are very few, in fact only one site where human and megafaunal fossils are found together, discrediting the both the 'blitzkrieg' and 'overkill hypothesis' somewhat!

So I think these other studies of Horton's re-enforce the  hypothesis that actually humans had very little impact on the extinctions and certainly didn't cause them. However, I feel like I have been a bit biased with articles I'm picking, so on my next blog I will review an article by Martin, who was actually the one who first proposed the 'blitzkrieg' model of human predation. Then after that as I've promised, I will go onto more recent research and see how the argument has developed and if there are any new or updated theories knocking around.

Because they're not available online:

P. D. Cheal, Day, J. C. and Meredith, C. W (1979) 'Fire in the National Parks of North West Victoria', National Parks Service: Victoria.

Jones, R. and J. M. Bowler (1980) 'Struggle for the Savannah: northern Australia in ecological and prehistoric perspective', in R. Jones (ed) Northern Australia: Options and Implications, Canberra: Australian National University, 3-31.

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