ANT101_Lecture 13_2025

Overview of Primate Origins

• Primate evolution is complex and has several key takeaway concepts.

  • Primates are part of the expansion of placental mammals, currently the most common type of mammal.

  • The survival of primates is linked to the extinction of dinosaurs.

Key Concepts in Primate Paleontology

1. Dinosaurs' Extinction

   • The absence of dinosaurs opened ecological niches that allowed for the diversification of placental mammals, including primates.

2. Calculating Divergence Times

   • Divergence estimates can be obtained from:

     • Fossil Records

     • Genetic Data

   • Genetic dating relies on the molecular clock method which involves comparing DNA sequences from different species.

   • The molecular clock assumes a constant mutation rate across lineages.

3. Limitations of Fossil Data

   • Fossils often represent limited anatomical features, mainly teeth, leading to gaps in understanding evolutionary timelines.

   • Comparisons must be made between fossil primates and modern species to glean insight into morphological diversity.

Biological and Morphological Patterns

• Primate Molar Cusp Patterns

  • Monkeys exhibit bilophodont molar patterns.

  • Hominoids have a Y-5 pattern on their lower molars, indicating dietary adaptations.

Evolutionary Origins and Timeline

• Primates evolved over the last 65 million years, with significant milestones:

  • Paleocene and Eocene: Earliest fossils resembling primates.

  • Oligocene: Emergence of anthropoids.

  • Miocene: Appearance of apes.

  • Pliocene: Development of hominins.

Paleocene Epoch

• Plesiadapiforms

  • Early mammalian forms (70-55 mya) with characteristics suggesting a potential link to primates but lacking defining traits of true primates.

  • Structure: small, insectivorous like tree shrews, with dental formulas varying.

Eocene Epoch

• Euprimates: The First True Primates

  • Three forms:

    1. Adapoids: Resemble lemurs and show adaptations for a folivorous diet.

    2. Omomyoids: Resemble tarsiers and have an insectivorous diet.

    3. Anthropoids: Ancestors to modern monkeys, apes, and humans.

Anthropoid Development

• Anthropoids originated around 35-23 million years ago:

  • Radiated during this period with clear anthropoid traits present in fossils primarily found in Egypt.

• Platyrrhine Origins

  • Ancestors are believed to have migrated from North America to South America via land bridges or other dispersal mechanisms.

• Catarrhine Origins

  • Miocene epoch (24-5 mya) characterized by higher primate diversity, often termed the "Planet of the Apes".

Key Miocene Developments

• Debate on Great Ape Evolution

  • Ongoing discussions about whether ancestors of great apes evolved predominantly in Europe or Africa, with evidence favoring an African origin.

  • General fossil representatives include:

    • Pierolapithecus: Early hominids from Spain.

    • Sivapithecus: Ancestral to orangutans, found in Pakistan.

    • Gigantopithecus: A large species from Asia, primarily known from dental remains.

    • Oreopithecus: A specialized primate with adaptations for swampy forest habitats.