Know Your Primate: Theropithecus gelada

Order: Primates
Suborder: Haplorrhini
Family: Cercopithecidae
Subfamily: Cercopithecinae
Genus: Theropithecus
Species: Theropithecus gelada
Theropithecus was a widespread and diverse genus during the Pliocene and early Pleistocene. Various species occupied most of Africa and parts of southwestern Asia. Today only a single species occurs in the mountains of central Ethiopia. The gelada is a highly terrestrial primate that resides in a grassland environment (sleeping in cliffs at night).

They primarily feed on grasses, seeds, and roots and because of this they have acquired a number of specializations (more of this below).
Geladas are primarily brown and black, they have long fur, long whiskers (in males), a mane on the shoulders (also in males) and a uniques red patch on their chest (both sexes). The red patch is outlined by white vesicles in females. They weigh anywhere from 25-50 pounds. Like other baboon species they have white eyelids that are revealed by moving the scalp backwards (something macaques also do). They have short, deep muzzles with large (even for baboons) canines. The molars are high-crowned and crenelated. The mandible body is deep. The skull is characterized by postorbital constriction, a large infratemporal fossa, and somewhat prominent postorbital bar. Postcranially, the forearm is relatively elongated, the elbow and wrist are highly flexible, as is the thumb, and the index finger is somewhat shortened. These are all considered to be adaptations to a highly terrestrial, grazing lifestyle. The gelada has played an important role in understanding human evolution and the evolution of bipedalism. This is due to the work of Clifford Jolly, in the early 1970’s, on the “Seed-eater Hypothesis.” Jolly noted that the Australopithecines inhabited dry savanna and adjacent forest areas in East and South Africa and argued that perhaps the gelada would be a better model for human evolution. Jolly buttressed the argument by noting a number of parallelisms in anatomy between the gelada and Pleistocene hominids.
Geladas live in single male/multifemale groups (occasionally one or two more males can attach themselves to the group). Male offspring leave the group and form all male unites with other male geladas until they can acquire females of their own. Larger groupings of up to about 670 individuals can also occur. The main factor keeping the reproductive unit together is the strength of the bond between the females (who may or may not be related since females also move between groups). Males seem to have little control over group movements. Usually the male interacts with a single female. Even more interesting is the fact that females frequently choose the winner in bouts of male competition – so even if a given male wins the combat he can still be ousted from his role by the females…

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