This is the title of a review by Parr et al. (Current Opinion in Neurobiology, vol. 15, pp 716-720, Dec. 2005), whose abstract I include here, with a main point of this post being to show pictures of the similar facial muscle groups used by humans and chimpanzees in emotional communication.
Credit: Current Opinions in Neurobiology.
"The social brain hypothesis proposes that large neocortex size in Homonoids evolved to cope with the increasing demands of complex group living and greater numbers of interindividual relationships. Group living requires that individuals communicate effectively about environmental and internal events. Recent data have highlighted the complexity of chimpanzee communication, including graded facial expressions and referential vocalizations. Among Hominoids, elaborate facial communication is accompanied by specializations in brain areas controlling facial movement. Finally, the evolution of empathy, or emotional awareness, might have a neural basis in specialized cells in the neocortex, that is, spindle cells that have been associated with self-conscious emotions, and mirror neurons that have recently been shown to activate in response to communicative facial gestures."