Bower et al recently proposed archaeological evidence of a 120ky old human presence at the Moyjil in Australia. The oldest well-established archaeological material in Australia is currently just under 60ky old. As Bowler acknowledges in an interview, “That is a big jump to make”. How far do they get?
It has become normal for the geological and environmental dating of these claimed surprisingly early archaeological contexts to be unimpeachable. This is no exception. The stratigraphy, the regional geological contextualization, and the thermoluminescence dates are all very convincing. Unfortunately, we have become much better at dating stuff, than at deciding whether it was put there by people.
The claim and the conclusion
Like all sites associated with claims of surprisingly early presence, this one lacks human skeletal remains. It is unusual though, in that it also lacks claimed stone tools. Normally, early presence claims feature stones that may or may not be the result of tool-making by people. So no eoliths here. In fact, the absence of eoliths in the report is what first caught my attention. It does, however, have claimed hearths and shell fragments which would be the result of human subsistence activity.
Through a combination of experimental archaeology and excavation, Bower et al argue that the deposits, which are clearly about 120ky old, are likely to be the result of human activity. After reviewing the evidence, they conclude that “On the basis of present evidence, human agency is a viable explanation”. This is a refreshing change from other such studies, which often claim that there is no other possible explanation than human activity for the evidence they present. Bower et al. claim that human activity could explain their evidence. That much is true. I don’t follow them as far as probability, but they certainly show possibility.
In a companion paper, McNiven et al give a more systematic review of alternative explanations for the hearthlike features. They conclude that they can’t determine whether they have a natural or cultural origin.
The two claimed hearths pictured in the article certainly look like the real thing. If they were in a clearly archaeological context, I would have no trouble accepting them. The fire-cracked rock, which litters many sites around the world in frustrating quantities, and which many archaeologists affectionately call FCR, looks convincing.
In another companion paper, Sherwood et al. examine the shell assemblage. They conclude that they can’t determine statistically whether it was produced by humans or by seabirds, and that it shares characteristics with both types.
If there were clear stone tools, good zooarchaeological remains, or more obvious structural features, the hearths and FCR would certainly be accepted as archaeological. In the absence of these other lines of evidence, I can’t conclude that they are. But that’s ok. Let’s see why.
What they get right
Bower et al. are careful never to over-reach their evidence in their conclusions. Everything they report is consistent with human activity, but nothing makes it an unavoidable conclusion, or even, as far as I am concerned, a likely one. The centerpiece of the paper is a series of experiments to determine whether the FCR is the result of combustion. They note that many other agents can produce FCR-like remains: “weathering, algal or other biological films”, and any combination of them, among others.
The experiments focus on a corollary of the hypothesis that fire produced the FCR. If the change in coloration is due to heat, the magnetic susceptibility of the rocks will be changed as well. These experiments establish that “Fire remains the most likely cause of the wide variety of darkened stones”. However, the authors very properly never claim that no other processes could account for their finds. They use experimental archaeology the way it is supposed to be used, to rule out proposed explanations. They fail to rule out that fire produced the FCR and the hearth-like features, but they don’t claim that they have therefore excluded other possibilities.
But, they ask: When is “a place of fire” really a “fireplace” produced by people? How do we know? Natural fires can produce remains very similar to human hearths, especially when stumps burn deep in the ground. In certain soils, you don’t even need fire to get a concentration of wood that looks “burned”. The authors acknowledge that “definitive hearth structures remains elusive”.
Here, they have few answers apart from circumstantial evidence, for example that fuel for natural fires could have been scarce in that place at that time, or that the rocks in question are “transported”, although it is never specified from where or from how far. Fairly weak stuff, but again, that’s ok because there is no over-reaching.
The overall conclusion is as careful as the rest of the paper: “For some, an acceptance of human presence in Australia 120,000 years ago as a possibility may now tentatively advance to one of probability”. I am not one of those yet, but I certainly appreciate the way in which the authors present their case. In summary, the claims are consistent with the evidence, experimental archaeology is used properly, and the problem of equifinality is fully acknowledged in the examination of all lines of evidence.
What could be improved
There are three fairly glaring omissions in the paper. The experiments on the FCR are interesting, but the results are presented in very summary fashion. This section of the paper badly needs a graph showing the relationship between colour alteration and changes in magnetic susceptibility (MS) in the experimental and field samples. Spot values are reported, but no overall results. I suspect it is some kind of crime against science to report that “In summary, the correlation between small dark samples and high MS values reflects a change consistent with progressive heating”, and then not report correlation and probability values.
The central claim of the paper, that the FCR and hearth concentrations are consistent with fireplaces created by humans, would be much stronger if we had a clearer sense that the fires are unlikely to be natural. The reader could form a better opinion if the paper included a regional fire history for the appropriate time-frame, drawn from charcoal signals in at least a few local cores. How frequent were natural fires? How were they distributed in the region? The paper does include a schematic environmental history of the region, but a more detailed ecological history, including pollen profiles would tell us more about the likelihood of natural fires at various times.
Finally, I was surprised that the paper gives no information about local knowledge of the past. It is clear that the authors work closely with local agencies, but there is no information on the perspective of local descendent communities on these claimed remains.
I have no reason to reject the idea of a human presence in Australia at 120kya, but this particular paper does not increase my confidence that there currently are archaeological remains of that age in the region. However, it is a great example of how to present and discuss a claim of early presence. Unfortunately, those very strengths make this type of treatment unattractive to major journals, when it is exactly the sort of material they should be seeking.
References
Bowler JM, DM Price, JE Sherwood, SP Carey 2019. The Moyjil site, south-west Victoria, Australia: fire and environment in a 120,000-year coastal midden – nature or people? Proceedings of the Royal Society of Victoria 130:71-93.
Carey SP, JE Sherwood, M Kay, IJ McNiven, JM Bowler 2019. The Moyjil site, south-west Victoria, Australia: stratigraphic and geomorphic context, Proceedings of the Royal Society of Victoria 130:14-31.
McNiven IJ, J Crouch, JM Bowler, JE Sherwood, N Dolby, JE Dunn, J Stanisic 2019. The Moyjil site, south-west Victoria, Australia: excavation of a Last Interglacial charcoal and burnt stone feature – is it a hearth? Proceedings of the Royal Society of Victoria 130:94-116.
Sherwood JE, JM Bowler, SP Carey, J Hellstrom, IJ McNiven, CV Murray-Wallace, JR Prescott, DG Questiaux, NA Spooner, FM Williams, JD Woodhead 2019. The Moyjil site, south-west, Victoria, Australia: Chronology, Proceedings of the Royal Society of Victoria 130:32-49.
Sherwood JE, IJ McNiven, L Laurenson 2019, The Moyjil site, south-west Victoria, Australia: shells as evidence of the deposit’s origin, Proceedings of the Royal Society of Victoria 130:50-70.
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