16.12.2017 - 00:24
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Human and Chimpanzee Natural Cognition

By Christophe Boesch

Philosophers, anthropologists, psychologists and others have been addressing the question of “What makes us humans?” for centuries. However, we have always been limited in our ability to answer that question by the fact that in most comparative studies either humans and/or chimpanzees, our closest living relatives, have been placed in species unnatural conditions or have been tested in species untypical situations. Thereby, either species were facing a systematic disadvantage that has hampered our ability to understand “What makes us humans?”

In theory, the solution to this quandary is rather straightforward, as it would “only” require to select some natural tasks that are performed by both species and to compare them in situ. My goal in this project is to do exactly this and compare humans with chimpanzees solving two similar natural tasks: Finding food producing trees in their natural environment and cracking wild nuts.

By making the human / chimpanzee comparison with natural populations solving similar natural daily tasks with all their local and historical accumulated knowledge of the technical challenge, we hope to be able to detect more precisely species differences that are only affected by the specie-specific way to solve such ecological challenges.

 

Finding food producing trees

Finding food sources is a basic challenge that all animals, including humans, have to solve. Finding sources such as trees may be complicated by the visibility conditions prevailing in different environments. Therefore, we are comparing the food tree finding strategies of the Mbendjele foragers in the Republic of Congo, living in a closed tropical rainforest, similar to those of the Taï chimpanzees in Côte d’Ivoire, both populations facing similar challenges to find their food.

As in previous studies (Normand et al. 2009a, b, Janmaat et al. 2013, 2014, 2016, Ban et al. 2016), we adopted exactly the same methodology for a similar natural task which should allow us to improve our knowledge of the similarities and differences between humans and chimpanzees, as well as understand the impact of ecological differences. Karline Janmaat and Haneul Jang have spent three seasons in the forest with the Mbendjele women following individual women in the same way than we did previously with Taï chimpanzee females to collect the best possible comparative data.

 

Cracking wild nuts

Central African forest hunter-gatherers have traditionally been dependent to a large extent on the many wild foods produced by the forest. One of these resources, hard-shelled wild nuts, is especially promising for comparing human and chimpanzee technological skills. More specifically, the Aka foragers in the Central African Republic and the Mbendjele foragers in the Republic of Congo rely for many months of the year on the nuts they find and crack in the forest, and many of these nut species are the same than the ones cracked by the Taï chimpanzees in Côte d’Ivoire. This facilitates comparison of the techniques used, the tools used and made, the transport of tools, the efficiencies reached with the tools and techniques, and the cognitive skills required in both species.

Christophe Boesch has been studying the nut-cracking behaviour of the chimpanzees for many years (e.g. Boesch and Boesch 1981, 1982, 1984a, b, Boesch and Boesch-Achermann 2000, Boesch 1991, 2012). Adopting for this comparative project the same methodology while following women foraging in the forest, we could make some very detailed comparison of the similarities and the differences of the two species when facing extremely similar natural challenges involving tools. Boesch et al. (in press) could show that the degree of cooperation during the nut-cracking varies from a more individualistic enterprise in chimpanzees to a more cooperative endeavour in the Mbendjele women. Intriguingly, although by using sharp-cutting metal tools the Aka and Mbendjele women were able to crack open more species of nuts than the Taï chimpanzees, the chimpanzees were sometimes more efficient than the women.

Figure 1: A Taï chimpanzee mother cracking a Coula nut within the forest with a wooden hammer and a root as anvil, while her infant is looking intently at what she is doing
Figure 2: An Aka mother cracking a Panda nut within the forest with her wooden hammer and an axe as anvil while her baby is looking over her shoulder at what she is doing.
Figure 3: Group of Mbendjele women cracking Panda nuts