Pleistocene human footprints from the Willandra Lakes, southeastern Australia
Introduction
Pleistocene and earlier hominid foot impressions have been described previously from Africa (Deacon, 1966, Mountain, 1966, Leakey and Hay, 1979, Behrensmeyer and Laporte, 1981, Hay and Leakey, 1982, Roberts and Berger, 1997) and Eurasia (Facorellis et al., 2001, Zhang and Li, 2002, Mietto et al., 2003). Such prints are pivotal to current understanding of locomotor biomechanics in hominids, particularly with respect to the evolution of bipedality (Day and Wickens, 1980, Charteris et al., 1981, Mietto et al., 2003). They also preserve a record of hominid ecology, including subsistence patterns and social behavior. Despite the long occupation of Australia by humans (Roberts et al., 1990, Roberts et al., 1994, Turney et al., 2001), no Pleistocene footprints have previously been identified from the continent. The fossil trackways we describe were discovered in the Willandra Lakes region of western New South Wales during 2003 and are the largest known collection of Pleistocene human footprints in the world.
The Willandra Lakes system lies within the Murray Basin of southeastern Australia. It comprises 19 interconnected relict lake basins, which vary in surface area from 6 to 350 km2 (Fig. 1). These basins were filled by runoff from the Eastern Australian Highlands during the last glacial period, finally drying by ca. 18 ka (Bowler, 1998). Lunette dunes on the lake margins provide a record of this environmental change and preserve evidence of a human presence dating back at least 46,000 years (Webb, 1989, Bowler, 1998, Bowler et al., 2003). The oldest Australian human remains, Willandra Lakes Hominid 3, come from Lake Mungo, which has also provided the earliest human mitochondrial DNA in the world (Adcock et al., 2001; cf. Cooper et al., 2001). The region is Australia's foremost for the study of late Pleistocene human biology and archaeology.
Section snippets
Geomorphic setting
The footprints cover an area of approximately 700 m2 on an exposed indurated horizon, or hardpan, near the stranded shoreline of a small, relict lake basin between Lakes Garnpung and Leaghur (Fig. 2a). The hardpan lies within the swale of low sand dunes, part of an undulating terrain of lunettes and abandoned lakebeds formed during previous high water levels in the Willandra Lakes.
The hardpan unit is approximately 150 mm thick and composed of at least ten superimposed laminae of calcareous silty
Paleoenvironment of the footprint site
The thin, calcareous, silty-clay laminae of the hardpan probably accumulated from aeolian sediment that deflated from the floor of the nearby lake basin during arid phases. This material was blown onto the site and draped over the underlying dune. Approximately 1 km inland of the northwestern shore of Lake Garnpung, the hydrology of the small lake adjacent to the footprint site is likely to have become increasingly dominated by evaporitic processes as water levels in the Willandra Lakes waned
Implications and conclusions
The size of the prints and the pace lengths in most trackways indicate tall individuals who were able to achieve high running speeds. There are at least two particularly tall people in the group, suggesting adult males in keeping with skeletal remains previously studied from the region, and Lake Garnpung in particular (Webb, 1989, Johnston et al., 2003; S. Webb, unpublished data). Such remains typically display a robust set of characteristics, including thick cranial vaults and long bone
Acknowledgements
We thank the elders of the Barkindji, Mutthi Mutthi, and Ngiyampaa tribal groups of the Willandra Lakes World Heritage Area for their support. In particular, we thank Mary Pappin Jr., who discovered the first footprints during a site survey in August 2003. Michael Westaway of the Australian Department of Environment and Heritage and Harvey Johnston of the NSW Department of Environment and Conservation provided support and facilities. Jim Bowler and two anonymous referees made valuable comment
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