'Chimps form friendships just like humans'
Chimpanzees share the same instinct as humans to form close friendships based on trust, scientists have found.
A study of chimps at a Kenyan sanctuary had shown a shared trait of "selectively trusting friends in costly situations".
The findings suggest the characteristics of human friendships have a "long evolutionary history and extend to primate social bonds".
In the report, published in Current Biology, scientists identified each chimp's closest "friend" by those who ate together and groomed each other and one of their "non-friends". The researchers then played a game with each chimp, first with their "friend" and later with their "non-friend", in which they were given the option of pulling one of two ropes.
One rope allowed the chimp to eat a food that he or she was not keen on, while the other rope gave their partners access to a more tempting food and the option to share it. The interactions between the 15 chimps showed "much greater trust between friends than non-friends".