Notes on Primate Evolution

Introduction

• Focus on primate evolution from origin to emergence of humans
• Primate adaptations and characteristics
• Evolutionary evidence and factors affecting primate survival

Early Primate Evolution

• Adaptive Radiations: Led to diversification of lemurs, monkeys, and apes over 50 million years
• Environmental Changes: Climate change affecting forest types and primate extinction/adaptation

Diagnosing Primates

• St. George Jackson Mivart's Traits: Nails, clavicles, orbits encircled by bone, opposable thumb/toe
• Modern Diagnosis: Focus on grasping extremities, brain blood supply, petrosal bulla
• Primates identified by descent from common ancestor

Hypotheses on Primate Origins

Arboreal Hypothesis

• Primates evolved traits for life in trees (e.g., grasping extremities)
• Vision adaptation for depth perception

Visual Predation Hypothesis

• Traits evolved for detecting and capturing insect prey
• Forward-facing eyes for vision overlap

Angiosperm-Primate Coevolution Hypothesis

• Primates evolved with angiosperms, adapting to access fruits

Origin of Primates

Paleocene Epoch

• Emergence of plesiadapiforms (archaic primates)
• Plesiadapiform features: Claws instead of nails, unusual anterior teeth

Debate on Plesiadapiforms

• Relationship with true primates debated; new skeletal finds show similarities

Emergence of Modern Primate Groups

Early Eocene

• Appearance of adapoids and omomyoids
• Adapoids: Mainly diurnal, herbivorous
• Omomyoids: Nocturnal, insectivorous/frugivorous

Strepsirrhines and Tarsiers

• Origin of crown strepsirrhines traced back to Afro-Arabia
• Fossil record limited for tarsiers, suggesting early morphological stability

Fossil Findings and Climate Impact

• Eocene warming allowed diverse dispersal
• Cooling and aridity led to extinctions, limiting primates to lower latitudes

Early Anthropoids

Fayum Basin Discoveries

• Key site for early anthropoid fossils
• Fayum anthropoids: Diurnal, fruit-based diet, quadrupedal locomotion

Anthropoid Origins

• Debated origins: Asia or Africa
• Eosimiids and amphipithecids possibly linked to anthropoid emergence

Primates in the Miocene

Ape Diversity

• Initial ape radiations in Africa
• Miocene climate and geography changes allowed dispersal

Eurasian Apes

• Diverse adaptations; some species linked to modern apes

Platyrrhine Dispersal

• South American primates originated from African ancestors
• Debate on dispersal methods (rafting hypothesis)

Modern Ape Origins

Great Apes

• Limited fossil record for non-human great apes
• Insights from molecular clocks and fossil evidence

Review Questions

• Compare hypotheses on primate origins
• Discuss climate impact on primate biogeography

Key Terms

• Definitions of key evolutionary and anatomical terms related to primates

About the Authors

• Jonathan Perry: Focus on primate feeding behavior and anatomy
• Stephanie Canington: Research on lemur jaw morphology

Further Exploration

• Recommended readings and references for in-depth study