All,
This one also almost fell between the cracks. In fact, given the controversial nature of the Kow Swamp remains (i.e., morphology and intial age estimates), I am surprised that this paper has not been given more visibility. That is, unless I have missed something.
Jacques Cinq-Mars
I am also surprised. It turns out I downloaded the paper a few weeks back. Here are some more tidbits for those who don't have access:
Implications
Genetic isolation caused by climatically-induced
population decline may explain the robust skeletal
morphology of the Kow Swamp people (Habgood,
1991). In Australia, this morphology is rarely
encountered after the LGM. The apparently
robust WLH-50 from Lake Garnpung has late
glacial ages obtained by TIMS and gamma
spectrometry U/Th (Simpson & Gru¨n, 1998). The
difficulty with this specimen is that its robust
calvaria may be pathological (Brown, 1989; 1992;
Webb, 1990; Stringer, 1998; cf. Hawks et al., 2000;
Wolpoff et al., 2001). The only certain robust
specimen from postglacial times is the Cossack
skull from Western Australia (Freedman &
Lofgren, 1979a, b). This had eroded from a mid-
Holocene coastal sand dune. Other robust
examples from Coobool Creek (Brown, 1987) and
Mossgiel (Freedman, 1985) in New South Wales are unprovenanced or poorly dated. The age of
6010125 yr BP for the Mossgiel skeleton is
from bone carbonate and is a minimum age only
(Freedman, 1985).
We propose that robust populations in
Australia did not recover from the LGM. Gracilization
after the LGM is related to postglacial
climatic amelioration (Brown, 1987). Increased
gene flow through previously marginal environments
could explain this trend (Habgood, 1991).
Some populations isolated from this gene flow for
longer may have preserved robust traits. The
Cossack skull could be an example of such an
isolated human (Habgood, 1991). The Kow
Swamp people, in contrast, are a large robust
population. Our dating suggests that they disappeared
at the close of the LGM and we find
scant evidence in the archaeological record of
southern Australia for robust humans younger
than the LGM.
Gracile humans represented by Mungo 1 and
Mungo 3 were present in southern Australia some
20,000 years before the Kow Swamp people
(Bowler et al., 2003). The emergence of morphological
diversity among Pleistocene humans
over the next 20,000 years coincided with signifi-
cant climate change. At Lake Mungo, water levels
fell suddenly around 40 ka, forcing the Mungo
people to adapt to increasing aridity (Bowler et al.,
2003). The morphological differences between the
Kow Swamp people and other Pleistocene humans
in Australia emerged as full glacial conditions
developed. These differences could have been
accentuated by the severity of the LGM (Stringer,
2002). The dating of the Kow Swamp people to
this period supports this view. It may even be that
robust traits were selected for by extremes of cold
or aridity (Wright, 1976).
The role of climate in shaping the Australian
landscape and its biota should not be underestimated.
Pleistocene human populations would
have been fragmented from the time they arrived
on the continent (Habgood, 1991). Yet the first
Pleistocene humans are blamed for the extinction
of the Australian megafauna some time between 50
and 40 ka (Flannery, 1999; Miller et al., 1999). The
period included a glacial advance in the southeastern
Highlands between 46 and 39 ka (Barrows et al., 2002). The most pronounced climatic stress
may have been felt closer to 40 ka (Bowler et al.,
2003). Pleistocene climates would have kept
human populations small and morphologically
diverse through genetic isolation. We cannot see
how small human groups could have caused
megafauna extinction on a continent-wide scale.
Conclusions
OSL dating of shoreline sediments at Kow
Swamp suggests that robust humans lived in
southern Australia around the time of the LGM.
Previous 14C ages placing the Kow Swamp people
in the period 15–9 ka may have been contaminated
by younger carbon. The new ages suggest that the
Kow Swamp people lived on the Kow Lake shore
between 22 and 19 ka. This period was one of
glacial advance and periglacial conditions in the
southeastern Highlands. The shellfish population
of Kow Lake became extinct around 19 ka coincident
with the onset of sand lunette formation. The
lake was abandoned by the Kow Swamp people
soon after.
Climatic deterioration from at least 40 ka may
be the cause of morphological diversity among
Pleistocene humans in Australia. The Mungo and
Kow Swamp people were part of a single evolving
population that had to adapt to a period of
climatic stress lasting more than 20,000 years. The
robust skeletal morphology of the Kow Swamp
people probably arose from increasing genetic
isolation, accentuated by the severity of the
LGM. Morphological diversity between human
populations decreases with postglacial climatic
amelioration. Robust human groups do not
appear to have recovered from the LGM.
