Living Primates: Traits and Reproduction

• Focus of Lectures 14 & L15, held on February 10th and 12th of 2025, is on the living primates.

Shared Traits in Mammals

• Mammals share traits such as giving live birth, producing mother's milk, having a long period of dependence, and learning through play.
• Mammals are chordates with fur or hair and milk glands.

Primate Physical Traits

• Primates possess a unique combination of physical traits.
• Arboreal adaptations: designed for tree living.
• Prehensile hands and feet and an opposable thumb.
• Flexible arm movement: allows for better motion in trees.
• Specific upper and lower limb bones for climbing and grasping.
• Omnivorous diet with specialized teeth
• Forward-facing eyes for stereoscopic and color vision
• Primates have a larger brain size compared to other mammals.

Primate Reproduction

• Primates typically have one to few offspring at a time.
• Primate infants are born helpless and require extensive care.
• Primates take a relatively long time to reach sexual maturity.
• These reproductive traits reflect a trade-off between quantity and quality of offspring.

Dependency and Play

• Primates exhibit a long period of dependency on their parents.
• Mother-infant bond is crucial for primate development.
• Physical and social skills are developed through play.
• Learning, imitation, independent learning, and deliberate teaching are key aspects of primate development.
• Length of dependency years varies among species of primates.

Social Communication

• Primates use referential communication: sounds associated with objects or events.
• Primates also engage in symbolic communication, where meaning is arbitrary and without a direct referent.
• Primate communication is typically a closed system.

Primate Classification

• Clade approach- derived vs. ancestral traits.

Strepsirrhini Traits

• These primates are mammal-like with longer snouts, a rhinarium, and a strong sense of smell (olfactory).
• They have mobile ears and primate traits such as grasping hands and stereoscopic vision.

Strepsirrhini Characteristics

• Strepsirrhines include lemurs, lorises, and galagos.
• Females frequently dominate social groups.
• They are generally not sexually dimorphic.
• Diet: vegetarian or insectivorous
• Mode of locomotion: quadrupedal, vertical clinging, and leaping

Haplorrhini Characteristics

• Includes humans, apes, and monkeys.
• They have a rounded braincase.
• These possess better vision and lack a rhinarium (dry nose).
• They have reduced and non-mobile ears.
• Relatively small and flat faces
• More fully formed placenta and highly dexterous hands.

Tarsiers Characteristics

• Nocturnal and arboreal creatures
• Diet: insectivores
• Tarsiers are haplorrhines.
• They have eyes in bony orbits and lack a tapetum lucidum (no eye shine at night).
• These primates are vertical clinger leapers like lemurs.

Platyrrhines

• New World Monkeys
• Three premolars
• Prehensile tails
• Arboreal lifestyle
• Dentition is 2.1.3.3/2.1.3.3.
• Examples: Marmosets, tamarins, and Cebids (e.g. capuchin)

Catarrhines and Cercopithecoids

• The Arboreal Colobine Monkeys; Complex stomach
• Arboreal Monkeys & The Terrestrial Baboons share: 2.1.2.3/2.1.2.3 Dentition, variable sizes, male dominance, and a few offspring.
• Terrestrial Baboons, are sexually dimorphic and exist in female troops.

Hominoids

• Apes and Humans share the categories: Hylobates, Pongids, Hominins
• Hominoids have larger brains, greater flexibility, and longer limbs.
• A short, broad trunk and lack of tail are also characteristics.

Hominoid Dentition

• Flat and rounded teeth and Y-5 pattern
• Canine diastema

Hominoids: Hylobates

• Hylobates locomotion: Brachiators
• Small body size and weight
• Frugivores diet
• Live in small family units
• Little sexual dimorphism

Pongids: Orangutans

• Arboreal
• Frugivores Diet
• Sexually dimorphic
• Socially solitary
• The orangutan diet and predation habits are of interest.

Pongids: Gorillas

• Locomotion: Quadrupedal and knuckle-walkers
• Eat and sleep in trees
• Dominant male-protector in groups
• Flexible group membership

Pongids: Bonobos and Chimpanzees

• Bonobos & Chimpanzees Quadrupedal and bipedal
• Diet: Frugivore, with some meat
• Highly social animals; live in large groups
• Chimpanzees Groups: Stable; female centered groups
• Bonobo Groups: Fluid groups

Primate Adaptations

• Small body size adaptations include being nocturnal, arboreal, and frugivorous.
• Fast movement in trees, high energy needs from fruit sugars, and easier mobility in the night
• Large body size adaptations are being diurnal, terrestrial, and vegetarian.
• Slow-moving terrestrial lifestyle, poor CHO vegetation leading to large guts, being active during the day; protection in large groups
• Increase in brain size relative to body size.
• Larger brains in response to frugivorous diets and the need to remember where and when fruit is produced.
• Safety in numbers- group size is variable: smaller number of primates when feeding at night and a larger number when feeding in the day.

Hominins: Homo sapiens

• Bipedal
• Dish-shaped pelvis
• Straight lower limbs
• Feet are not prehensile, used for solely walking
• Hands are dexterous
• Incisors, canines, and no large teeth or claws
• They have a large complex brain comprised of a cerebral cortex that is responsible for thinking and spoken language.
• Lowered larynx
• Reflect omnivorous diet
• Incisors and canines share similarity and have no spaces between them

Hominins Exhibit Culture

• Learn through culture, using tools like greater apes
• Chimpanzees - termite sticks
• Planning and tool usage; Cracking seeds open with two rocks

Models of Hominin Behavior

• Homologous vs Analogous traits; Traits: common ancestor or independently derived in two primates
• Living primate behavior used as a model
• **Limitations: Ethnographic Analogy a Non-Western traditional societies
• All cultural groups have their own qualities and are not always reflective of a universal pattern.