BS

ANBH1101 Primates 1 lecture 1 pwp

Primates in Human Biology

Learning Outcomes

  • Understand the significance of studying primates.

  • Describe evolutionary relationships and similarities between humans and other primates.

  • List characteristics that define primates and differentiate them from other mammals.

Recommended Reading

  • Background: Chapter 4

  • Primate Lectures: Chapters 5 & 6, also see Chapter 9 for extensions.

  • Hominin Lectures: Chapters 10-13.

Primates in Society

  • Primates are a specific group within mammals but receive disproportionate attention in both scientific and non-scientific contexts due to:

    • Their anatomical and evolutionary similarities to humans.

Evolutionary Context

  • Linnaeus (1735):

    • Recognized anatomical similarities among monkeys, apes, and humans, categorizing them into the order Primates.

  • Darwin (1871):

    • Commented on humans’ classification and relation to other primates, suggesting that if humans hadn’t classified themselves, they wouldn’t have created a distinct order.

Primate Family Tree

  • Key Relationships:

    • Connection with gorillas, chimpanzees, bonobos, Neandertals, Denisovans, and humans.

    • Significant genomic similarities: 15% of the human genome is closer to gorillas than to chimpanzees or bonobos.

  • Chimpanzees:

    • Historically viewed as the closest living relative, now reassessing previous beliefs with new genomic evidence.

Key Evolutionary Concepts

  • Homology: Similar traits among close relatives due to shared ancestry.

  • Phylogenetic Constraints: Evolutionary history imposes limits on current species' variations.

  • Vestigial Traits: Non-functional traits inherited from ancestors (e.g., reflexes, appendix).

  • Convergence: Similar traits arising in unrelated groups due to similar selective pressures.

Reasons to Study Primates

Reasoning by Homology

  • Closely related species share morphological similarities due to common descent, offering insights into ancestral anatomy and behavior.

Reasoning by Analogy

  • Natural selection leads to convergent evolution among similar environments, showcasing adaptive evolution across species based on ecological pressures.

Notable Themes in Human and Primate Behavior

  • Chimps exhibit lethal intergroup aggression that parallels human warfare. (Jane Goodall)

  • Evidence of chimpanzee cultures and traditions.

  • Noteworthy prosocial behavior seen in bonobos, with instances of cooperative rescue.

Study of Non-Human Primates

  • Duration: Evolutionary study spans 50-60 million years.

  • Clade: Primates radiated from a common ancestor with adaptive radiation across separate geographic areas (4 continents).

  • Mosaic Evolution: Different traits evolve at varying rates and times.

Classification Hierarchy of Primates

  • Kingdom: Animalia

  • Phylum: Chordata

  • Class: Mammalia

  • Order: Primates

  • Suborder: Anthropoidea (monkeys & apes)

  • Infraorder: Catarrhini (Old World monkeys & apes)

  • Superfamily: Cercopithecoidea (Old World monkeys)

  • Family: Cercopithecidae

  • Subfamily: Colobinae (leaf-eating monkeys)

  • Genus: Rhinopithecus (snub-nosed monkeys)

  • Species: bieti (black-and-white snub-nosed monkey)

Primate Characteristics

Derived Traits of Primates

  • Adaptations relevant to an arboreal lifestyle:

    • Prehensile hands and feet

    • Opposable big toes

    • Stereoscopic vision (improved depth perception)

    • Reduced olfactory apparatus

    • Nails instead of claws

    • Unspecialized teeth

    • Relatively larger brain size relative to body

    • Small litter sizes (typically one offspring)

    • Extended childhood dependency

Functionality of Derived Traits

  • Stereoscopic Vision:

    • Enables depth perception through overlapping visual fields from both eyes.

    • Lack of color vision in nocturnal primates.

Comparative Anatomy: Prosimii vs. Anthropoidea

  • Illustrated differences include:

    • Prosimii: Postorbital bar with varied rostrum lengths

    • Anthropoidea: Established postorbital plate and relative anatomical complexity

Evolutionary Development of Sensory Structures

  • Decreasing reliance on olfaction in diurnal primates, leading to reduced snouts and diminished sensory areas in the brain.

Variability in Dental Structures

  • Primates exhibit generalized dentition that provides insights into dietary habits, age, and social structures.

  • Dental Formulas:

    • A distinct formula of 2-1-2-3 in upper and lower jaws for Old World anthropoids distinguishes them from New World primates.

Brain Size and Evolution

  • As body size increased, primate brains have evolved more rapidly, resulting in significant cognitive capabilities.

  • Comparative analysis shows anthropoid primates possess larger brain sizes relative to their body weight than non-primate mammals.

Evolutionary Diversification Themes

  • Diverse locomotor modes among primates:

    • Vertical clinging and leaping

    • Quadrupedalism

    • Brachiation

    • Bipedalism

  • Variations in diet: Insects, fruits, leaves, seeds, meat.

  • Social structures: Preferences for solitary living, monogamous and polygamous pairings.

  • Significant brain development in relation to body size, particularly in hominoids.