Barbary macaques are yellowish gray to grayish brown with paler underparts and a dark pinkish face (MacDonald 1985).
The Barbary macaque has an extremely short vestigial tail. This tail reduction is a uniquely derived feature of the Barbary macaque and resulted in the popular misnomer of Barbary Ape.
Morphological evidence suggests an early divergence of M. sylvanus from other extant macaques. Barbary macaques lack some morphological specialisations of other macaques (Groves 1989). Adult males have ischial callosities that fuse across the midline, unlike other macaques that have lost this condition (Groves 1989). High-resolution restriction site mapping of the mitochondrial ribosomal genes confirm that Macaca sylvanus is the sister clade to all Asian macaques (Morales and Melnick 1998).
The ancestral macaque stock originated in Africa ca. 7-6 million years ago (Ma) and dispersed into to Eurasia ca. 6–5 Ma (Fooden 2007). Species that are closely related to M. sylvanus have been recorded in the European fossil record dating from the Middle Pliocene to the Middle Pleistocene (Gentili et al 1998). Macaques became extinct in Europe during the Pleistocene. The Gibraltar colony of Barbary macaques was reintroduced, probably in historic times.
The divergence of the Moroccan population and the two main Algerian subpopulations can be dated to approximately 1.6 million years ago, assuming an origin of 5.5 million years ago for the genus Macaca. The distinction between Moroccan and Algerian haplotypes provides a basis for determining of the origin of the Gibraltar macaques. The Gibraltar sample includes both Algerian and Moroccan haplotypes, implying a dual origin of the founding females (Modolo et al 2005).