Baboons

Modern baboons (Superfamily Cercopithecoidea, Family Cercopithecinae,Tribe Papionini, and Genus Papio) are relatively large Old World monkeys of sub-Saharan Africa. There are five species ofPapio (Hamadryas, Guinea, olive, yellow, and chacma baboons) spread across sub-Saharan Africa (see below for species names and their geographic distribution). It should be noted, however, that the five species are not completely isolated geographically and hybridization does occur. Guinea, olive, yellow, and chacma baboons are generally referred to as the savannah baboons.The hamadryas baboons live in the arid scrublands of Ethiopia. Mandrills(Mandrillus or Papio sphinx), drills (Mandrillus or Papio leucopaeus), mangabeys (Lophocebus and Cercocebus), geladas(Theropithecus), and the macaques (Macaca) are closely related to the baboons.

The baboons are extremely sexually dimorphic; males weigh above 16 kg, and the females are about half the size of the male. Males, especially the hamadryas baboon males, have long hair around their shoulders, giving the appearance of having a cape. Males but not females have large canines adapted for shearing the flesh of their opponents, whether con-specifics or predators. Large unicusp first premolars (the P3), known as sectorial premolars, have a ridge of heavy enamel that runs down the front of the tooth, which is used to sharpen the back side of the upper canine. A gap in the upper tooth row, sectorial P3, and large upper and lower canines are identified as the Canine/P3shearing complex. Baboons have arms and legs of about the same length and are described as terrestrially adapted quadrupeds that walk and run on the ground and on top of tree branches in the same manner. Branch-to-branch leaping, swinging, and jumping are rare in baboons. Like other Old World primates, baboons have stereoscopic color vision. Unlike other primates, however, baboons have a long muzzle.

Source: © iStockphoto/Jakob Mikkelsen.

The cercopithecoids (i.e., the Old World monkeys) diverged from the hominoids (i.e., apes and humans) about 25 million years ago. The fossil record of the cercopithecoids is known from the Early and Middle Miocene with a group of remains recognized as belonging to two African genera named Victoriapithecus and [Page 324]Prohylobates. These two genera preceded the separation of the two extant subfamilies of Old World monkeys, the Colobinae or leaf eaters, and the Cercopithecinae or fruit and insect eaters. During the Miocene, cercopithecine fossils are scarce compared to the more numerous fossil hominoids. The sparse fossil record of the genus Papio dates to about 3 to 4 million years ago and is limited to Africa.

Source: © iStockphoto/Jakob Mikkelsen.

One group of baboons, the kinda baboons (Papio cynocephlus kindae), a subgroup of yellow baboons (Papio cynocephlus), are particularly interesting. They are smaller and have a shorter face than the other savannah baboons. Instead of the dark coat color of other newborn baboons, kinda baboon neonates are born white, and the adult coat color is slightly more golden than other baboons. It might be tempting to view the kinda baboons as the ancestral form of the Papionini, but more fossils are needed to confirm or reject this hypothesis.

The social system of the savannah baboon is a multimale/multifemale troop in which the females remain in their natal troop throughout their lives, and the males emigrate at puberty. The troop forages and sleeps as a single unit, although troops have been observed to permanently divide into smaller troops. Males and females each have a dominance hierarchy; however, males are dominant to females by virtue of their large size. Mating is promiscuous, but females tend to mate with their male friends. Male/female friendships are important to the stability of a troop in that they provide for mutual support and aid, especially during agonistic encounters. Making friends with a female, moreover, can facilitate the entrance of a male into a new troop.

...