This month in Archaeology: Stone hatchets as nut-cracking tools

Why are there pits on ground stone hatchets? These are wood working tools, but could they have been used for cracking seeds and nuts as well? How to find out? Do experiments! For this month in archaeology, we discuss the recent experimental archaeology paper, led by Dr Nina Kononenko.

By studying the marks on a stone tool, we can see what that tool was used for. In Australia, stone artefacts such as hammerstones and hatchets often have pits on the surface. These pits are produced when these tools are used as anvils for stone-working or opening hard-cased foods such as shell-fish. But could they have been used for plant processing as well?

The recently published paper in the Journal of Archaeological Science: Reports by Dr Nina Kononenko, Val Attenbrow, Peter White, Robin Torrence and Brit Amussen set up a series of experiments to ask – could these pits be formed from nut-cracking?

What nuts could have been cracked in Australia?

There are many edible endemic nuts and hard seeds in Australia including Quandong nuts (Pardoe et al. 2019), Macrozamia seeds and Macadamia nuts (Asmussen, 2011; Beck et al., 1988; Ferrier and Cosgrove, 2012; Field et al., 2009).

What nuts did they use in this experiment?

In these experiments they used macrozamia and macadamia nuts. Macrozamia seeds have a red-fleshy outer layer. Under this is a hard, woody shell which has to be cracked open to get the soft starchy kernel on the inside. This kernel is highly toxic and must be leached in water for many days to remove the toxin before it can be eaten.

Macadamia nuts have a hard, smooth outer-shell, which can be crushed by resting the nut on an anvil and hitting it with a hammerstone.

What experiments did they do?

The authors conducted a series of experiments with different stones and nuts to test damage marks; specifically, if the marks caused by nut-cracking were different to the marks formed by other activities, such stone knapping. The tools tested were stone tools (anvils and hammers) made from basalt, quartzite and sandstone. In Australia basalt is used to make hatchets and sandstone is used to make grinding stones.

What were the results?

They found that cracking seeds and nuts produces diagnostic wear traits on stone hammers and anvils. One of the key traits of nut-cracking is the presence of ‘distinctive sub-circular or oval patches with surface alteration in the form of localised, dense, shallow impact marks and cracks’.

The authors found that this diagnostic use-wear is only produced after several hours of nut cracking.

What does this mean for Australian archaeology?

To test what this means for Australian stone tools, the authors compared their results with 11 pitted stone artefacts. Kononenko, lead author, highlighted that: ‘Similarities between wear traces produced in the experiments and those preserved on prehistoric stone artefacts made it possible to confirm the re-use of stone hatchets for cracking seeds and nuts’ (Kononenko et al. 2021:2).

It had previously been assumed that ground-edge hatchets were only used for chopping wood. But this study shows that Australian ground-edged stone hatchet heads were used for plant processing and nut-cracking, in addition to wood chopping. Importantly, this shows that many ground-edge hatchets were used for ‘multiple activities and had long and complex use lives’ (Kononenko et al. 2021:2). This shows that the well-know artefact type, the stone hatchet, actually had many more functions.

Dr Amy Way, Scientific Officer, Archaeology, Australian Museum Research Institute; and Conjoint Lecturer, School of Philosophical and Historical Inquiry, Faculty of Arts and Social Sciences, University of Sydney.

Dr Nina Kononenko, Research Associate, Geosciences and Archaeology, Australian Museum Research Institute.