Australia: The Land Where Time Began

A biography of the Australian continent 

Cuddie Springs and Pleistocene Fauna – Extinction not by Overkill

The bones of megafaunal animals from Cuddie Springs were studied by Judith Field for more than 15 years, a site which Hiscock suggests illustrates the nature of archaeological evidence for the extinction of megafauna. Evidence was found by Field at Cuddie Springs that was significant because it indicated that megafauna and humans coexisted for a long time, and no evidence was found that the megafauna had been pushed to extinction by overkill.

Cuddie Springs is on a riverine plain, and at present it is a small claypan which at times fill and for short periods forms a small swamp. The area surrounding Cuddie Springs is a semiarid landscape at present which receives rainfall that is highly variable, and supports woodland of eucalypts, saltbush and grasses. At the time represented by the excavations Cuddie Springs was a large, full lake which was surrounded by shrublands that provided good conditions for large animals such as Diprotodon (Dodson et al., 1993). Humans and many species of marsupial megafauna shared this landscape for long periods of time.

In stratum 6, a series of silt and clay lenses dating to about 33,000-40,000 BP, and 1-2 m below the present surface (Field & Dodson, 1999; Field et al., 2001; Field et al., 2002) stone artefacts were found that provided evidence of early human occupation at Cuddie Springs. Bones of many large species, which included Diprotodon, Genyornis, Sthenurus, and Macropus giganteus titan, the giant kangaroo, were recovered from the deposit by Field and her team. It has been contended by some scientists that at the site the bones had been jumbled stratigraphically (Roberts et al., 2001; Gillespie & Brook, 2006), though Hiscock suggests these concerns were not warranted (Field & Fullagar, 2001; Trueman et al., 2005). Stone artefacts and bones were not found spread throughout a homogenised deposit, they were found sealed together in ancient land surfaces that are well-defined which are rich in rocks, and according to Hiscock it would be rare for post-depositional movement of objects to occur. It is indicated by pollen, charcoal and even rare elements, that the broad stratigraphic sequence is real, though it is dated imprecisely. Human artefacts and bones of megafauna animals are contained in stratum 6 which were deposited over a period of possibly7,000 years, and this evidenced has been interpreted as showing that animals such as Diprotodon and Genyornis coexisted with humans for hundreds of generations (Field & Dodson, 1999); Trueman et al., 2005).

When droughts occurred the lake partially dried out and became marshy, and at this time animals that came to drink were trapped in the mud. Hiscock suggests that when large animals such as Diprotodon and Genyornis were trapped they may have died naturally in the mud, so were not killed by humans. It was suggested (Field & Dodson, 1999) it is not likely all the remains of large animals could be explained in this way; though there is no evidence they were killed in this manner. On the contrary, it is indicated by partially articulated skeletons and tooth marks in the bones that were made by carnivores that humans were only minimally involved in the deaths. Archaeological evidence, such as low numbers of artefacts that have been recovered at this site, is consistent with early occupation by humans being of low intensity; the foragers visiting the site only occasionally, in which case many of the animals found at the site may have died after being stranded in between visits by humans. It has been suggested by researchers working on the site that it is highly likely that humans scavenged meat from these huge carcasses, even if they did not hunt the animals. Stone artefacts that were used to cut meat were present scattered among the bones of megafaunal species, though no cut marks made by a stone tool have been found on the bones of any of the Diprotodon or Genyornis. The absence of cut marks may indicate that humans visited the site infrequently, or that there was so much meat on the carcasses that the meat was rarely cut deeply enough to mark the bones. Whichever was the case, based on existing information from Cuddie Springs it is suggested that humans did not hunt or scavenge these large animals intensively. Evidence has been found at Cuddie Springs that humans and megafauna coexisted for a prolonged period, but it is not a kill site that documented over-hunting. In order to understand the context of extinctions, assuming they were not caused by humans, Field and her colleagues studied the environment in which humans lived and megafauna died at the site.

The circumstances in which megafaunal species went extinct is the most remarkable evidence from Cuddie Springs.  A record of animals that died at Cuddie Springs prior to the arrival of humans is preserved by the deep bone deposit at the site. Many species of megafauna were already extinct by the time humans arrived in the local region of Cuddie Springs. Examples are the bones of  Megalania, a reptile, Zygomaturus, a marsupial the size of a cow, and Palorchestes, a marsupial browser, have all been recorded at Cuddie Springs from strata that pre-date the arrival of humans at the site, though in the archaeological levels these animals are not present in the vary large bone collections. Over the last million years a trend that has been found throughout Australia is illustrated by this, of the ongoing extinction of large animals, particularly over the last 200,000 years (Wroe et al., 2004; Wroe & Field, 2006). As humans were not present for much of that time, those extinctions were the result of environmental changes.

Also, following the arrival of humans at Cuddie Springs, extinctions of megafauna occurred over thousands of years. Some species, such as Protemnodon, are found only in the lowest archaeological level, while Genyornis, Diprotodon, Procoptodon, Sthenurus and  Macropus giganteus titan were present in later stratigraphic levels, which documents the progressive extinction of megafauna species during a period when climate change has been ongoing.

The vegetation around Cuddie Springs had undergone significant changes long before the beginning of the LGM. Chenopodiaceae pollen, which is an indicator of shrubland, was being replaced gradually by the pollen of grass, herbs and aquatic plants from 40,000 BP to 35,000 BP. This has been interpreted by Field as progressive transformation of local environments from dry shrublands to grasslands, which are moister (Field et al., 2002). Grazers such as red kangaroos (Macropus rufus) and flexible feeders such as Emus (Dromaius novaehollandiae), have both persisted in the region to the present. Large species of marsupial, such as Diprotodon and Genyornis were not well equipped for a grassland environment that was increasingly dominating the area, and they became extinct locally.

It is demonstrated by evidence from Cuddie Springs that extinctions of megafauna such as Diprotodon did not occur immediately after the arrival of humans at Cuddie Springs or during the LGM when the environment was extremely arid. The phase of the extinctions of large marsupials actually occurred throughout the intervening period (40,000-30,000 BP) as habitats were reconfigured into grasslands. It was the more subtle and gradual dynamics of habitat transformations which resulted in environmental conditions that were favourable to some species and unfavourable to others, and not the extraordinary, rapid events such as the arrival of humans or the LGM. Hiscock suggests this lesson helps to consider the role played by environmental change in the extinction of Australian megafauna.

Hiscock, Peter, 2008, Archaeology of Ancient Australia, Taylor & Francis.