So as you may have read from my last blog entry, I wasn’t very happy with the evidence produced by Roberts et al (2001)! And to back me up on my contention, I have come across an article by Field and Fullagar (2001) that basically reinforces what I have already said.
They use the Cuddie Springs site as a specific example, the oldest human levels that also contain megafaunal remains is dated at 36.4ka years. This was rejected by Roberts et al (2001), because of sediment mixing and the re-deposition of bones from older to younger sites. Field and Fullagar (2001) claim this is not a valid assertion because firstly the human and megafaunal overlap of remains is sealed at its upper and lower limits at the specific archaeological level by consolidated old land surfaces, meaning the movement of material from old sites is impossible. The next reason disputing Roberts et al (2001) rash conclusion is that the archaeological, faunal and geomorphologic data compiled at the site contradict sediment mixing, in particular pollen data can be an indicator of disturbance, yet the pollen records at the site show typical trends of increasing aridity leading up to the Last Glacial maximum.
Also through optically stimulated luminescence (OSL), they were able to tell ages for Cuddie Springs mixture of grains at the site. They found an increasing age with depth and are consistent with the established radiocarbon chronology, which is exactly what is expected of an archaeological site that has suffered no disturbance or mixing. Also another whole in Roberts et al (2001) study is that they never offered a process by which older megafaunal remains could reach the site.
So in conclusion, the study of Roberts et al (2001) is largely discredited, and although they did find sites with both human and megafaunal remains that were aged at 46.6ka years ago, they ignored a large proportion of them which were significantly younger. Therefore, this study can’t be used to harm the reputation of the environmental change hypothesis, which I still believe is a very strong explanation of the late Pleistocene extinctions in Australia.
Haha caught you out Roberts and friends!