Tool use is a central topic in research on cognitive evolution and behavioral ecology in non-human animals. Originally thought to be a uniquely human phenomenon, many other species have been observed making and using tools for a variety of purposes, starting with Goodall’s groundbreaking work with chimpanzees in Gombe. Despite the frequent attention and great research interest in animal tool use, and ubiquity of the behavior, we argue here that chewing sticks by dogs should be included as a case of (...) tool use. We discuss alternate possible explanations and then propose several testable predictions regarding this hypothesis. We suggest that tool use may be more common than is often assumed and that many cases of animal tool use may be overlooked. (shrink)

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)