Monday, 21 November 2011

Welcome to the 21st century and the current debate on the late Pleistocene extinctions in Australia!

So as I promised I am now going to focus on literature that is actually from the 21st century, and gives maybe a better bearing on the current development of the Late Pleistocene extinctions. 

I am starting with an article by Roberts et al (2001), who analysed burial ages for megafauna from 28 sites, and apparently infer the extinction in Australia occurring 46,400 years ago. He therefore rules out extreme climate change and aridity as the cause for the extinction, and poses that actually human induced changes were the main catalyst. Their reasoning for this assumption is that if the last megafaunal existence was probably between 51 to 40 ka years ago, then this was about 20 ka years before the height of the glacial maximum, and hence doesn’t correlate with the changing climate hypothesis. They go on to suggest that the megafauna vanished within 10-5 ka of human arrival, so obviously discounting the ‘blitzkrieg’ model of human extinction, but validating that perhaps humans gradually depleted the number of species leading to their final demise.

However, and trust me this is a pretty big however, this study must be taken with a pinch of salt. This is mainly because actually some of the sites and deposits have been ignored. This Roberts and the other researchers put down to the sites containing disarticulated remains they guessed had been derived from other locations of older units. They also put the emitting of some of the sites down to the fact that sediment mixing has occurred, for example at a site at Cuddie Springs, which has actually been found to have much younger deposits than the rest of Australia. So, in summary, Roberts et al (2001) claim ‘the young ages obtained for disarticulated remains and the indication of sediment mixing at Cuddie Springs are evidence that the remains are not in their primary depositional setting, but have been eroded from older units and re-deposited in younger units with contemporaneous sediment and charcoal.’

Mhmmm to be honest I’m not so sure myself, really can you just ignore certain sites because of supposed disarticulation and mixing. To me it just seems they are ignoring the evidence that doesn’t fit in with their dating methods and their hypothesis, which they probably had in mind before they started the research! But hey, maybe I am being cynical…but all I know is that I don’t see this as a strong argument against the environmental change hypothesis; I think all sites and all evidence must be taken into consideration to come up with a valid conclusion.

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