for more information:
Herrmann, E., Hare, B., Call, J., & Tomasello, M. (2010). Differences in the Cognitive Skills of Bonobos and Chimpanzees PLoS ONE, 5 (8) DOI: 10.1371/journal.pone.0012438
We humans shouldn't forget that our species has been around only a relatively short time (geologically speaking), and we have much in common with other animals on the planet we share. Migration out of Africa less than 200,000 years ago isn't when we diverged from other animals; we diverged from chimpanzees and bonobos roughly 6 million years ago.
In other words, although we're distinct from them, we're nevertheless closely related. Chimpanzees and bonobos are even more similar to each other, sharing an ancestor from 1 or 2 million years ago.
There are many similarities between chimpanzees and bonobos. In addition to ecological and genetic similarities, their cognitive abilities are also very similar, e.g. communication via gestures and a grasp of numbers.
On the other hand, bonobos are less dependent on tools, and more tolerant, passive, and cautious than chimpanzees. These are the places to look for differences in cognition.
Even though one or two million years may seem like a long time, it's a relatively short time for major differences in cognitive ability to emerge. Understanding cognitive similarities and differences between chimpanzees and bonobos may help scientists understand cognitive development in humans.
Esther Herrmann (Max Planck Institute for Evolutionary Anthropology, Germany) and coworkers have carried out research in this direction. Comparing and contrasting chimpanzee and bonobo cognition, their research suggests that chimpanzees have a superior grasp of physical causality, while bonobos have a superior grasp of social causality.
The apes.
The bonobos in this research (34 of them, 13 females, no infants, on average 8.5 years old) were from the Lola ya Bonobo Sanctuary in the Democratic Republic of Congo. The chimpanzees (106 of them, 53 females, no infants, on average 9.8 years old) were from either the Ngamba Island chimpanzee sanctuary in Uganda or the Tchimpounga chimpanzee sanctuary in the Republic of Congo.
The overwhelming majority of the apes had access to a large outdoor forest area during the day, and all of them came back to indoor enclosures during the night. They all had access to plenty of food and water.
Each one of them was a rescued orphan from the "bushmeat" trade, and was raised together with humans as well as with their peers (they lived in social groups by the time of the experiments). Their participation was voluntary; they were never deprived of food for any reason.
Testing the apes.
The apes were tested on the Primate Cognition Test Battery. This is a collection of 16 physical and social cognition tests across a range of abilities: social learning, space, quantities, theory of mind, tools and causality, and communication.
For example, the apes were tested against their ability to understand the relationship between a noise and a hidden reward, and their use of communicative gestures to retrive a hidden reward. None of the apes had participated in similar experiments, and they each participated in these experiments between three and five hours each day for several days.
Cognitive differences between the apes.
The scientists found only two interspecies differences between the apes; specifically, social causality and physical causality. Bonobos outperformed chimpanzees in following the experimenter's gaze and determining what the experimenter intended to do, while chimpanzees outperformed bonobos in using a stick to retrieve an out-of-reach reward.
Age only came into play when interspecies differences were found. Age was not a factor in the overall interspecies differences trend.
Younger apes outperformed those who were older in social causality, while older apes outperformed those who were younger in physical causality. Furthermore, female apes outperformed males in communicative cognition when the effect of age was controlled.
Overall evaluation.
The scientist's obervations in this research closely match observations made in the wild. This research therefore adds to evidence that differences in bonobo and chimpanzee cognition are significantly driven by ecological and social influences.
An analysis of the chimpanzee and bonobo genomes will help scientists unravel any genetic underpinnings of their specific cognitive differences. Such research will facilitate investigations aimed at understanding the genetic determinants of human cognitive evolution.
NOTE: The scientists' research was funded by the European Research Commission and the National Science Foundation.
for more information:
Herrmann, E., Hare, B., Call, J., & Tomasello, M. (2010). Differences in the Cognitive Skills of Bonobos and Chimpanzees PLoS ONE, 5 (8) DOI: 10.1371/journal.pone.0012438