Primates Overview Primates include humans, apes, monkeys, and prosimians. Many of them may be familiar, but they also include less familiar animals such as lemurs, which are an ancient, relatively primitive group. World's Most Endangered Primates List This list of highly endangered primate species is selected and published by scientific specialists. The purpose of the list is to attract the attention of the public and to stimulate national governments to do more. Species are selected for the list based on two primary reasons: extremely small population sizes and very rapid drops in numbers. The most endangered South American primates are cotton-top tamarin variegated spider monkey yellow-tailed woolly monke