Natural Science Forum / Biology / Paleontology / January 2007

Gavin Prideaux and colleagues have published two papers in the last
few weeks describing the faunal composition of cave deposits formed
over hundreds of thousands of years during the Pleistocene in
Australia.  Here's a link to a news story on the latest:

http://www.theaustralian.news.com.au/story/
0,20867,21123766-30417,00.html

The argument that the cave studies bear on the causes of megafauna
extinction (which happened, in Australia, about 45,000 years ago, i.e.
long after these particular caves stopped accumulating remains) is
just a teeny bit indirect, i.e. understanding it requires holding two
or more items in consciousness at the same time.

So I suggest you don't bother trying to understand if you are, for
example, a brain-dead malignant paranoid delusional psychotic, since
maintaining that pose will already be keeping you quite busy enough.

1) The new studies show that there was little change in the number and
identity of megafaunal and other mammal species present at these sites
(i.e. in the surrounding countryside of southern Australia) while the
climate swung between warm, wet interglacials and cold, dry glacial
maxima.

2) The major extinction event in the Australian Pleistocene is known
from other studies to have occurred in relatively warm and wet times
(~40-45Ka) before the last glacial maximum.

3) Therefore, glacial maxima - including the last one, even if it was
'worse' than the others - do not explain the extinction.

4) The earliest evidence of humans in Australia is less than 50,000
years old, and other recent studies of 14C (near its practical limits
here) and other dating methods (Uranium-series, OSR etc. as used in
the cave studies) have concluded a most likely overlap between humans
and megafauna of 4,000 years.

5) According to reasonable demographic models, that's plenty of time
to wipe out a bunch of big slow-breeding browse-dependent animal
species just by eating the odd juvenile - let alone setting fire to
the woodland and heath every time you go for a walk, leaving a lot of
grass and the odd nation-sized patch of blowing sand.