Apes only provide food to conspecifics that have previously assisted them

For us humans, it goes without saying that we reward others as an indication of the gratitude we feel towards them. Scientists from the Max Planck Institutes for Evolutionary Anthropology and for Mathematics in the Sciences in Leipzig have now demonstrated that similar social behaviours exist among chimpanzees. In a behavioural experiment, one animal rewarded another with food if the latter had previously come to its assistance. This suggests that some main motivations for human cooperation might have been present in our common ancestor already while supporting findings from game theory.