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that continent. The inferred outcome in arid central Australia was a change from a
mosaic of trees, shrubs and grasslands adapted to drought to the modern fire-adapted
desert scrub.
Lopes dos Santos et al. (
2013
) sought to test these hypotheses by examining the
possible impact of extinction of the large marsupial fauna on the ecosystems of the
Murray-Darling Basin, which drains about one-fifth of the Australian continent. She
and her co-workers analysed a 140 ka marine sediment core obtained from a canyon
several hundred kilometres off the mouth of the Murray River in south-east Australia.
They used changes in accumulation rates of levoglucosan as a proxy for changes
in biomass burning and changes in the stable carbon isotopic composition of higher
plant wax
n
-alkanes as a measure of vegetation change inferred from changes in the
proportions of plants following the C
3
and C
4
photosynthetic pathways, as deduced
from the stable carbon isotopic record (see
Chapter 7
). The age control on the core
was of sufficient resolution to enable them to test the environmental changes in
the Murray-Darling Basin before and after the putative extinction of the Australian
megafauna between 48.9 and 43.6 ka. They found proxy evidence of an abrupt and
short-term decrease in the abundance of C
4
vegetation at around 43 ka, followed by an
increase in biomass burning lasting about 3,000 years. They concluded that because
these two events occurred after what they term the 'main period of human arrival'
and megafaunal extinction in Australia, the change in vegetation cannot have caused
the extinction but may have been a consequence of it, as initially hypothesised by
Flannery.
17.5.2 Late Pleistocene megafaunal extinctions in arid North America
In few parts of the desert world have late Pleistocene faunal extinctions received
as much scholarly attention as in North America, where the relatively late arrival
of sophisticated hunters (and makers of the Clovis spear points) is thought to have
brought about the rapid demise of the larger mammals (Martin and Wright,
1967
;
Martin,
1984
; Martin and Klein,
1984
). The apparent speed of the human occupation
of North America, as well as that of the faunal extinctions, prompted Martin (
1967
)
to invoke the World War II German military metaphor for invasion and warfare at
lightning speed (
Blitzkrieg
) as a description of the process. Although seductive in its
simplicity, this interpretation has been rejected or at least modified by those who point
out that the terminal Pleistocene was also a time of rapid climatic change in North
America (and, indeed, elsewhere), with substantial modification of plant communities
and a continent-wide repatterning of food supplies.
Several recent studies have cast doubt on the Blitzkrieg model. Haile et al. (
2009
)
investigated ancient DNA and concluded that mammoths and horses survived in
interior Alaska until at least 10.5 ka, or thousands of years after the initial arrival
of humans in North America. Lorenzen et al. (
2011
) summarised studies of ancient
