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Stone anvil damage by wild bearded capuchins (Sapajus libidinosus) during pounding tool use: a field experiment.

Haslam M, Cardoso RM, Visalberghi E, Fragaszy D - PLoS ONE (2014)

Bottom Line: We found that new pits were formed with approximately every 10 nuts cracked, (corresponding to an average of 38 strikes with a stone tool), and that adult males were the primary initiators of new pit positions on the anvil.Visible anvil damage was rapid, occurring within a day of the anvil's introduction to the field laboratory.Destruction of the anvil through use has continued for three years since the experiment, resulting in both a pitted surface and a surrounding archaeological debris field that replicate features seen at natural FBV anvils.

View Article: PubMed Central - PubMed

Affiliation: Research Laboratory for Archaeology and the History of Art, University of Oxford, Oxford, United Kingdom.

ABSTRACT
We recorded the damage that wild bearded capuchin monkeys (Sapajus libidinosus) caused to a sandstone anvil during pounding stone tool use, in an experimental setting. The anvil was undamaged when set up at the Fazenda Boa Vista (FBV) field laboratory in Piauí, Brazil, and subsequently the monkeys indirectly created a series of pits and destroyed the anvil surface by cracking palm nuts on it. We measured the size and rate of pit formation, and recorded when adult and immature monkeys removed loose material from the anvil surface. We found that new pits were formed with approximately every 10 nuts cracked, (corresponding to an average of 38 strikes with a stone tool), and that adult males were the primary initiators of new pit positions on the anvil. Whole nuts were preferentially placed within pits for cracking, and partially-broken nuts outside the established pits. Visible anvil damage was rapid, occurring within a day of the anvil's introduction to the field laboratory. Destruction of the anvil through use has continued for three years since the experiment, resulting in both a pitted surface and a surrounding archaeological debris field that replicate features seen at natural FBV anvils.

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Results of the stone-drop use-wear experiment: (a) pit width and depth relative to length (piaçava and tucum results combined); (b) ratio of pit length∶depth for three piaçava nuts, and one tucum nut (the tucum nut has sixty strikes, the others 100 strikes).
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pone-0111273-g006: Results of the stone-drop use-wear experiment: (a) pit width and depth relative to length (piaçava and tucum results combined); (b) ratio of pit length∶depth for three piaçava nuts, and one tucum nut (the tucum nut has sixty strikes, the others 100 strikes).

Mentions: Results of the stone drop experiment performed by a human are very similar to those from the BN study involving capuchins. Three pits were created while processing piaçava, and these show consistent formation rates (Figure 6a). One piaçava nut, measuring 61×40 mm, was used for this experiment (it did not crack); the final pit sizes exceed these values, likely resulting from slight nut movement at the moment of impact. The tucum nuts fractured after an average of 33 strikes for each nut, which is a much lower fracture rate than that typically seen among the monkeys [23], supporting the conservative assumption of lower energy input from the stone drop experiment. One aspect that differed between the BN and stone drop studies is that the stone drop protocol did not also involve striking nuts placed beside the pits, which explains the perhaps unrealistic greater maximum pit depth (close to 40 mm) and the high number of strikes to crack tucum attained in the latter study. Placing nuts beside the pits would likely have abraded that surface and therefore slightly increased the length and width of the pits already present, while decreasing their relative depth. Although they did not attain the same maximum size in this study, pits resulting from tucum processing were not distinguishable via measurement ratios from those created by piaçava nuts (Figure 6b).


Stone anvil damage by wild bearded capuchins (Sapajus libidinosus) during pounding tool use: a field experiment.

Haslam M, Cardoso RM, Visalberghi E, Fragaszy D - PLoS ONE (2014)

Results of the stone-drop use-wear experiment: (a) pit width and depth relative to length (piaçava and tucum results combined); (b) ratio of pit length∶depth for three piaçava nuts, and one tucum nut (the tucum nut has sixty strikes, the others 100 strikes).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4221011&req=5

pone-0111273-g006: Results of the stone-drop use-wear experiment: (a) pit width and depth relative to length (piaçava and tucum results combined); (b) ratio of pit length∶depth for three piaçava nuts, and one tucum nut (the tucum nut has sixty strikes, the others 100 strikes).
Mentions: Results of the stone drop experiment performed by a human are very similar to those from the BN study involving capuchins. Three pits were created while processing piaçava, and these show consistent formation rates (Figure 6a). One piaçava nut, measuring 61×40 mm, was used for this experiment (it did not crack); the final pit sizes exceed these values, likely resulting from slight nut movement at the moment of impact. The tucum nuts fractured after an average of 33 strikes for each nut, which is a much lower fracture rate than that typically seen among the monkeys [23], supporting the conservative assumption of lower energy input from the stone drop experiment. One aspect that differed between the BN and stone drop studies is that the stone drop protocol did not also involve striking nuts placed beside the pits, which explains the perhaps unrealistic greater maximum pit depth (close to 40 mm) and the high number of strikes to crack tucum attained in the latter study. Placing nuts beside the pits would likely have abraded that surface and therefore slightly increased the length and width of the pits already present, while decreasing their relative depth. Although they did not attain the same maximum size in this study, pits resulting from tucum processing were not distinguishable via measurement ratios from those created by piaçava nuts (Figure 6b).

Bottom Line: We found that new pits were formed with approximately every 10 nuts cracked, (corresponding to an average of 38 strikes with a stone tool), and that adult males were the primary initiators of new pit positions on the anvil.Visible anvil damage was rapid, occurring within a day of the anvil's introduction to the field laboratory.Destruction of the anvil through use has continued for three years since the experiment, resulting in both a pitted surface and a surrounding archaeological debris field that replicate features seen at natural FBV anvils.

View Article: PubMed Central - PubMed

Affiliation: Research Laboratory for Archaeology and the History of Art, University of Oxford, Oxford, United Kingdom.

ABSTRACT
We recorded the damage that wild bearded capuchin monkeys (Sapajus libidinosus) caused to a sandstone anvil during pounding stone tool use, in an experimental setting. The anvil was undamaged when set up at the Fazenda Boa Vista (FBV) field laboratory in Piauí, Brazil, and subsequently the monkeys indirectly created a series of pits and destroyed the anvil surface by cracking palm nuts on it. We measured the size and rate of pit formation, and recorded when adult and immature monkeys removed loose material from the anvil surface. We found that new pits were formed with approximately every 10 nuts cracked, (corresponding to an average of 38 strikes with a stone tool), and that adult males were the primary initiators of new pit positions on the anvil. Whole nuts were preferentially placed within pits for cracking, and partially-broken nuts outside the established pits. Visible anvil damage was rapid, occurring within a day of the anvil's introduction to the field laboratory. Destruction of the anvil through use has continued for three years since the experiment, resulting in both a pitted surface and a surrounding archaeological debris field that replicate features seen at natural FBV anvils.

Show MeSH
Related in: MedlinePlus