Macaca mulatta (originally Cercopithecus mulatta, Zimmermann 1780a, b) is the extant rhesus macaque, Old World monkey. Derived from a sister to Aegyptopithecus, it is basal to Proconsul.

According to Wikipedia, "Rhesus macaque have the widest geographic ranges of any nonhuman primate, occupying a great diversity of altitudes and a great variety of habitats, from grasslands to arid and forested areas, but also close to human settlements." They live in troops of 20-200 males and females in a ratio of 1:4. Rhesus macaques are unusual in that the youngest females tend to outrank their older sisters. Perhaps because young females are more fit and fertile. Rhesus macaques interact using a variety of facial expressions, vocalizations, body postures, and gestures. Adult male macaques try to maximize their reproductive success by entering into sex with females, both in and outside the breeding period. Females prefer to mate with males that are not familiar to her. Outsider males who are not members of the female's own troop are preferred over higher ranking males."

"Humans and macaques apparently share about 93% of their DNA sequence and shared a common ancestor roughly 25 million years ago."