For several decades now, Brazilian sites like Pedra Furada have claimed archaeological material dating back as far as 30ky ago. That would be about double the age of the oldest securely dated archaeological material in the Americas.

I’ve commented on these sites before. My opinion so far is that the assemblages could very well have been formed by geological forces alone, or perhaps, as Fiedel (2019) and others have suggested, by capuchin monkeys, who live throughout the area, and are known to make stone tools for a number of applications. In any case, I have so far seen no argument or evidence that forces us to accept or even strongly suspect that these stone tool assemblages were made by humans.

Now, Agnolin and Agnolin (2022) claim to show that the very early stone tool assemblages at places like Pedra Furada are indeed the product of capuchin monkeys. They compare two claimed early archaeological sites to three known capuchin monkey stone tool assemblages.

This is very interesting work, and definitely a step in the right direction for evaluating the claims of very early archaeological sites in Brazil, but I would like to see a little bit more detail before I agree that they demonstrate that these assemblages are produced by capuchins.

The authors note that capuchin assemblages consist largely of unifacial cobble tools and flakes, some of which can show some retouch, but that they lack “hearths, blades, bifacially thinned stone tools and flakes, cut-marked bones, exotic raw materials, or traces of symbolic behavior, which would denote human activity. They also note that capuchin monkeys use locally available quartz and quartzite cobles (and sometimes anvils), sometimes transported over several tens of meters.

In their view, this above description fits both Pedra Furada and Sitio do Meio, the two claimed archaeological sites they are examining.

I agree with Agnolin and Agnolin that the very early Brazilian assemblages lack the distinctly human elements they list, at least going only by the published material I have seen. But I am not sure how strong a case the authors make for the capuchin connection specifically.

To be fair, the authors themselves do not claim a very strong demonstration. They conclude that they are “confident that the early archeological sites from Brazil may not be human-derived but may belong to capuchin monkeys.”

Figure 1 (c) from Agnolin and Agnolin 2022

Their only graph shows the proportions of kinds of lithic remains (flakes, partial flakes, anvils, etc) at known capuchin sites and at the two claimed early archaeological sites. Visual inspection of the figure is suggestive, but I would like to see some further attempt at quantitative analysis.

The rest of the argument is based on visual assessment of the published individual stone tools as similar to those made by capuchins. Personally, I would say that it is sufficient at this point to just say that the published tools don’t need to have been made by humans.

The only other quantitative argument in the article is that “the range and average of the weights of the Pedra Furada artifacts are within the variability registered for the assemblages used by primates.” Unfortunately, there is no accompanying graph or table, and I would love to see one added to the paper.

Agnolin and Agnolin definitely do not refute the idea that the claimed early archaeological assemblages in Brazil are the result of capuchin tool-making, and as a first test, this is a valid and welcome contribution. But they fall short of making a strong argument that the assemblages are indeed from capuchins.

I still haven’t been convinced by any of the published material that anything more than geological forces are needed to produce these assemblages, and that would be the real first step to take here. Then if someone shows that biological agents must have been, or were most likely involved, there are still a number of possibilities to rule out before concluding that these sites are archaeological.

The main possibility, and I would even say the main probability at this point, as Agnolin and Agnolin suggest, is that capuchins did it. But it isn’t case closed for now.


Agnolín AM and FL Agnolín 2022. Holocene capuchin-monkey stone tool deposits shed doubts on the human origin of archeological sites from the Pleistocene of Brazil. The Holocene, 0(0).

Fiedel SJ 2017. Did monkeys make the pre-Clovis pebble tools of Northeastern Brazil? PaleoAmerica 3: 6–12.

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