Monkey Tool Users

You may have never heard of a bearded capuchin monkey.  In many ways it is a typical New World monkey.  However, this particular species of monkey continues to impress primatologists because it is the only known non-ape primate to use tools.  Primatologists “discovered” this in the 1990’s, but knowledge of capuchin monkey tool-use has been a part of Brazilian folklore for over four centuries, if not longer.

Although more research needs to be conducted, it appears as though they have a limited “tool-kit” consisting of specialized stones that they use to crack nuts in different savanna-like environments (Ottoni & Izar, 2008).  Interestingly, there is a high degree of intentionality in both the stone selection process, and in the strategic use of stone tools (Visalberghi et al., 2009).  Furthermore, a paper published a few days ago revealed that they have the capacity to improve the efficiency of their tool use (Fragaszy et al., 2013). Here is an awesome video via the BBC of a capuchin using a tool to crack open a nut:

What is perhaps more remarkable, is that the capuchins lower skeletal structure is well adapted to walking bipedally while carrying stones.  This could mean that stone tool use has been an integral part of the bearded capuchin’s behavioural repertoire for thousands of years (if not much longer).

So what do these discoveries mean?  In terms of primate tool-use they appear to be an extreme phylogenetic outlier.  Chimpanzees, bonobos, gorillas, and orangutans make and use tools, but the lesser apes and all other monkeys in the wild do not.

When considering the fact that all great apes make and use tools, it seems reasonable to suspect that the common ancestor of all great apes also made and used tools.  That pushes back the origin of primitive tool use to perhaps as late as 14 million years ago.  Of course, as Adam Benton of EvoAnthhas pointed out, the first empirical evidence in the paleoanthropological record of stone tool construction is 2.5 million years old.  But the nature of the paleoanthropological record is fragmentary and all great ape tools would not preserve archaeologically; therefore it is also important to consider the possibility of tool-use being ancestral for great apes.

But where do the bearded capuchins fit into this picture?  These primates are displaying a type of technological ability that was thought to have emerged approximately 2 million years ago with the origin of our genus.  Is this simply an extreme and unexpected example of convergent evolution?

Capuchin stone tool-use wouldn’t represent the first time that animal behaviourists have been surprised by cultural and technological diversity in the animal kingdom.  Over the past few decades anthropologists and biologists have uncovered an unprecedented amount of cultural variety among cetaceans and birds, including New Caledonian crow tool use that appears to be cumulative (Hunt & Gray, 2003).

In my initial judgment of this perplexing situation, I would lean towards accepting the parsimonious conclusion: that capuchins have convergently evolved the ability to use stone tools.  However, some researchers have proposed that we must not rule out the alternatives.  It could be that stone tool-use among primates emerged 35 million years ago, with the origin of the first monkey species.  Or it could be the case that stone tool use has been adapted and then lost by several monkey and ape species over the past 35 million years.  If either of these scenarios is true, we must explain why all other known contemporary monkeys have no stone tool kits.

Either way, this is yet another great example of animals forcing us to question our relationship to the past and our own divergent behaviour.

Love evolution?  You can find more of Cadell’s thoughts on evolutionary anthropology via Twitter!

References:

Dean, L.G., et al.  2012.  Identification of the social and cognitive processes underlying human cumulative culture.  Science, 335: 1114-1118.

Fragaszy, D.M., Liu, Q., Wright, B.W., Allen, A., & Brown, C.W.  2013.  Wild bearded capuchin monkeys (Sapajus libidinosus) strategically place nuts in a stable position during nut-cracking.  PLoS ONE, 8: e56182.

Hunt, G.R. & Gray, R.D.  2003.  Diversification and cumulative evolution in New Caledonian crow tool manufacture.  Proceedings of the Royal Society, 270: 867-874.

Ottoni, E.B. & Izar, P.  2008.  Capuchin monkey tool use: Overview and implications.  Evolutionary Anthropology, 17: 171-178.

Visalberghi, E., Addessi, E., Truppa, V., Spagnoletti, N., Ottoni, E., Izar, P. & Fragaszy, D.  2009.  Selection of effective stone tools by wild bearded capuchin monkeys.  Current Biology, 19: 213-217.

Related Advanced Apes content:

Universality of Preadaptation for the Human Condition

The Evolution of Primate Sleep

Diurnality, Nocturnality, and Cathemerality

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About Cadell Last
I am a science educator, freelance science writer, and founder of The Advanced Apes based in Toronto, Ontario. In the past my academic research focused on the evolution, ecology, and behaviour of non-human primates (i.e., chimpanzees, gorillas, ring-tailed lemurs). Currently, my official blog, The Ratchet, can be found via The Advanced Apes and Svbtle. I enjoy exploring recent research in human evolutionary sciences, as well as biology, ecology, astronomy, physics, and computer science. My work has been featured in Scientific American, American Humanist, Richard Dawkins Foundation for Reason and Science, and Jane Goodall Institute of Canada. I am also exploring science popularization in new mediums in collaboration with PBS Digital Studios with an animated YouTube channel. You can contact me on Twitter (@cadelllast) or via email: cadell.last@gmail.com

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