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Human Evolution and Ecology - Week 9 Lecture Notes

Topic = Primate Origins, Evolution and Behaviour

Emotional and Social Behaviors in Animals

  • Dolphin Behavior: A recent incident described dolphins protecting a birthing whale from sharks by swimming in circles around her.

    • Fact-Checking Resources: Suggested URLs for verifying the authenticity of such claims about animal behaviors.

Dolphin Group Hunting Behavior

  • Research Area: Communication among bottlenose dolphins during role-specialized group foraging.

  • Study Reference: Research conducted by a collaborative group including Rebecca A. Hamilton and others.

  • Key Findings: - Role specialization in hunting is rare among non-eusocial mammals, with only four candidates identified: lions, mice, chimpanzees, and bottlenose dolphins.

    • Behavior Observed: Bottlenose dolphins exhibit a behavior called "driver-barrier feeding," where one group (driver dolphins) herds fish toward another group (barrier dolphins) to trap and catch them.

    • Acoustic Cues: Research indicates barrier dolphins use the echolocation sounds of the driver dolphin to coordinate their movements.

Understanding Animal Emotions

  • Emotional Insights: Discussion about the emotional capacities of animals, such as empathy in rats, grief in orcas, and social justice in monkeys.

  • Scientific Recognition of Emotions: Emphasis on ongoing research suggesting that various species exhibit complex emotional behaviors.

    • Source: National Geographic's exploration of animal emotions highlighting that nonhuman species share feelings akin to human experiences.

Primate Classification

  • Taxonomic Hierarchy of Primates:

    • Primates: Divided into Prosimians (e.g., lemurs) and Anthropoids (monkeys and apes).

    • Subdivisions: - Prosimians:

    • Strepsirhines: Lemuroidea (Lemuridae), Cheirogalidae (Dwarf lemurs), Daubentoniidae (Aye-ayes)

    • Haplorhines: Platyrrhines (New World Monkeys) and Catarrhines (Old World Monkeys and Apes).

Primate Evolution

  • Early Primate Evolution:

    • Fossil Evidence: Anthropoids are believed to have evolved approximately 50 million years ago, potentially stemming from a distinct lineage.

    • Oligocene Epoch: Identified as the period when old world anthropoids first emerged (34-23 million years ago).

    • New World Monkeys Evolution: Dated to around 30 million years ago with evidence suggesting ancestors may have migrated across landmasses.

Miocene Hominoids

  • Fossil Evidence of Miocene Hominoids:

    • General Characteristics: Miocene hominids show a blend of primitive and ape-like features, with most being unrelated to today's apes.

    • Notable Genera:

    • Proconsul: Lived in Africa between 21-14 million years ago.

    • Sivapithecus: Known from Asia, resembling modern orangutans, lived between 14-7 million years ago.

    • Genetic Evidence:

    • Molecular dating reveals significant evolutionary splits: orangutans (16-12 million years ago), gorillas (8-6 million years ago), and the human-chimpanzee split (6-5 million years ago).

Primate Social Behavior Studies

  • Longitudinal Studies: Jane Goodall pioneered longitudinal studies on primate behavior in Gombe National Park, Kenya, emphasizing the importance of sociality.

  • Understanding Social Systems:

    • Social Systems Dynamics: Patterns depend on factors like group size, composition, social hierarchies, and selection pressures in mating and reproduction.

Philopatry in Social Structures

  • Philopatry Definitions:

    • Definition: The behavior of remaining in or returning to one's birthplace.

    • Female philopatry: Females remain in their natal group post-maturity.

    • Male philopatry: Males typically leave their birthplace. This aspect influences social structure dynamics in species like chimpanzees and baboons.

Female Reproductive Strategies

  • Female Reproductive Behavior:

    • Reproductive Potential vs. Lifestyle: Females invest significantly in offspring care, affecting mating competition dynamics.

    • Dominance Effects: Higher-ranking females have more reproductive success, encouraging hierarchical social structures.

Male Reproductive Strategies

  • Competition Dynamics: Males invest energy in competing for mating opportunities, with dominance hierarchies established through aggressive encounters.

  • Infanticide as a Strategy: Male reproductive strategy including infanticide to increase sexual receptivity among females after taking over a group.

Social Systems and Kin Relationships

  • Grooming in Social Structures: Grooming serves multiple functions in establishing social bonds and reinforcing group cohesion while also bearing costs in terms of time and energy.

  • Kin Bias & Grooming: Grooming habits are often strongest between kin, enhancing survival and cooperative relationships in primate societies.

Types of Primate Societies

  • Classification of Social Systems:

    • Systems Include:

    • Solitary, Monogamous, Polyandrous, and Polygynous group structures. Each system represents different strategies for access to resources and mates.

    • Adaptive Strategies in Group Dynamics: Strategies vary based on resource availability and demographic pressures in various environments.