The evolution of altruism and reciprocity has been explained mainly from ultimate perspectives. However, in order to understand from a proximate perspective how humans evolved to be such cooperative animals, comparative studies with our evolutionary relatives are essential. Here we review several recent experimental studies on chimpanzees’ altruism and reciprocity. These studies have generated some conflicting results. By examining the differences in the results and experimental paradigms, two characteristics of prosociality in chimpanzees emerged: chimpanzees are more likely to behave altruistically (...) and/or reciprocally upon a recipient’s request, than without request, and chimpanzees also show a tendency to regard others and help in contexts not involving food. Supposing that these two characteristics of altruism, recipient-initiated altruism and non-food altruism, were present in the common ancestor of chimpanzees and humans, it is possible that increased social cognitive abilities, capacity for language, necessity for food sharing, and enriched material culture favored in humans the unique evolution of cooperation, characterized by voluntary altruism and frequent food donation. (shrink)

The present study assesses imitative ability in chimpanzees and human children. A direct comparison of these two species was conducted in an object-manipulation task. The subjects were required to copy the model stack by stacking colored blocks in the same order as the model. Four juvenile/adolescent chimpanzees failed to copy the model stack even after a long training-period. Two adult chimpanzees eventually learned to copy the model stack of two blocks. However, they failed to copy the model of three blocks, (...) and analysis of their stacking patterns revealed that they only focused on the color of the top block in the model. Human children started to copy the model of two blocks when they were two years of age and gradually increased the number of successfully copied blocks. The results from both chimpanzees and humans are discussed in terms of the social intelligence involved in object manipulation. (shrink)

The present study assesses imitative ability in chimpanzees and human children. A direct comparison of these two species was conducted in an object-manipulation task. The subjects were required to copy the model stack by stacking colored blocks in the same order as the model. Four juvenile/adolescent chimpanzees failed to copy the model stack even after a long training-period. Two adult chimpanzees eventually learned to copy the model stack of two blocks. However, they failed to copy the model of three blocks, (...) and analysis of their stacking patterns revealed that they only focused on the color of the top block in the model. Human children started to copy the model of two blocks when they were two years of age and gradually increased the number of successfully copied blocks. The results from both chimpanzees and humans are discussed in terms of the social intelligence involved in object manipulation. (shrink)