Chapter 3 - Primate Evolution

Abstract

The order Primates, containing some 400 extant species, is clearly defined by a set of shared derived features. There is a basal divergence between strepsirrhines (lemurs and lorisiforms) and haplorhines (tarsiers, monkeys, and apes). Primates are typically tree-living inhabitants of low-latitude forests, with grasping hands and feet, flat nails, enhanced tactile sensitivity, and hind-limb domination. Uniquely among mammals, the petrosal bone forms the auditory bulla. Vision is especially important. Enlarged, forward-facing eyes scan a wide binocular field and special brain organization permits refined stereoscopic vision. Despite extensive overlap with other mammals, primates have relatively larger brains on average because fetal brain development is prioritized. Dentitions are relatively unspecialized, but anterior teeth are reduced while molar cusps are low and rounded. Various features contribute to slow reproductive turnover. A patchy fossil record extends back 55million years, but fossils documenting the earliest primates evolution remain elusive. The little-studied colugos (Dermoptera) may be the closest relatives of primates.