Eastern chimpanzees (Pan troglodytes schweinfurthii) grooming each other
Chimps and bonobos signal ‘hello’ and ‘goodbye’ to one another when entering and exiting social encounters. Until now, this behaviour hasn’t been documented outside of the human species. “Our findings show that two species of great apes habitually go through the same process and stages as humans when establishing, executing and terminating joint actions” of hi and bye, wrote researchers in a study of the primates.