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.