Primate traits: Dependency, play, and communication

Shared Traits in Mammals

• Live young, produce mother's milk, have a long period of dependence, and learn through play.

Primate Physical Traits

• Possess a unique combination of traits
• Arboreal adaptations for tree-dwelling
• Prehensile hands and feet, including an opposable thumb
• Flexible arm movement
• Have specific upper and lower limb bones

Shared Physical Traits

• Have an omnivorous diet, with specialized teeth
• Forward-facing eyes allow for stereoscopic, color vision
• Larger brains

Reproduction

• Typically have one to few offspring
• Infants are born helpless
• Take a relatively long time to reach sexual maturity

Dependency and Play

• Exhibit long dependency periods
• Have a strong mother-infant bond
• Develop physical and social skills through play
• Learning occurs through imitation, independent exploration, and deliberate teaching.

Social Features: Communication

• Use referential communication, where sounds are associated with objects or events
• *Semantic communication is a feature
• Symbolic communication involves arbitrary meanings
• Primate communication operates as a closed system

Primate Classification

• Clades are approached to classify primates
• Derived and ancestral traits are compared in classification
• Refer to Etting 2023 Chapter 5 for discussion of traits.

Strepsirrhini Traits

• Mammal-like characteristics such as longer snouts, a rhinarium, olfactory emphasis, and mobile ears
• Grasping hands and stereoscopic vision are also primate traits

Strepsirrhini Examples

• Strepsirrhines include lemurs, lorises, and galagos
• Females typically dominate social groups
• Not sexually dimorphic
• Diet consists of vegetarian food and insects
• Quadrupeds that use vertical clinging and leaping

Haplorrhini Traits

• Have a rounded braincase
• Rely on better vision and lack a rhinarium (have a dry nose)
• Have reduced, non-mobile ears
• Have relatively small, flat faces
• More fully formed placenta
• Highly dexterous hands

Tarsiers Traits

• Nocturnal and arboreal
• Insectivores
• Haplorrhines
• Have eyes set in bony orbits, lacking a tapetum lucidum (no eyeshine at night)
• Are vertical clinger-leapers, similar to lemurs.

Platyrrhines Traits

• New World Monkeys, defined by three premolars
• Some have a prehensile tail
• Arboreal lifestyle
• Dentition of 2.1.3.3/2.1.3.3
• This group includes marmosets, tamarins, and cebids such as capuchins

Catarrhines Traits

• Includes cercopithecoids
• Arboreal colobine monkeys
• Terrestrial baboons
• 2.1.2.3 dental formula in both upper and lower jaws
• Variable group size
• Male-dominated social structures
• Have few offspring
• Female troops
• Exhibit sexual dimorphism

Hominoids - Apes and Humans

• Includes Hylobates, Pongids, and Hominins
• Larger brains and greater flexibility
• Have longer limbs
• Possess a short, broad trunk and lack a tail

Hominoid Dentition

• Teeth are flat and rounded
• Have a Y-5 pattern
• Canine diastema

Hominoids - Hylobates

• Are brachiators
• Small body size and weight
• Prefer frugivores diets
• Live in small family units
• Display little sexual dimorphism

Pongids - Orangutans

• Arboreal
• Frugivores
• Display sexual dimorphism
• Socially solitary
• Unknown Diet and possible Predation?

Pongids - Gorillas

• Quadrupedal and are knuckle walkers
• Tend to eat and sleep in trees
• Tend to have a dominant male as a protector
• Flexible membership

Pongids - Bonobos and Chimpanzees

• Bonobos live in stable, female-centered groups
• Chimpanzees live in fluid groups
• Both are Quadrupedal and bipedal
• Frugivore based Diet, with some meat
• Highly social, in large groups

Primate Adaptations: Body Size and Lifestyle

• Small body size primates tend to be Nocturnal, Arboreal, and Frugivore
• fast moving in trees, low weight
• Fruit sugars provide high energy
• Easier to move around at night
• Larger body size primates is Diurnal, Terrestrial, and Vegetarian
• Slow moving because of where primates live, large body primates are easier to view
• Vegetation is very poor so primates have large guts for digestive purposes
• Active during day, and live in large groups for protection

General Primate Adaptations

• Exhibit an increased brain size relative to body size.
• Frugivores tend to have larger brains
• They remember when to collect the fruit, where the fruit is located
• Experience variable group size depending on the location
• Use Safety precautions
• Have smaller numbers when feeding at night
• Have larger number when feeling in the day

Hominins - Homo Sapiens

• Capable of bipedalism
• Have a dish-shaped pelvis
• Straight lower limbs
• Feet are not prehensile
• Hands are dexterous
• No large teeth or claws

Defining Traits of Homo sapiens

• Large, complex brain with a large cerebral cortex which helps thinking and helps with spoken language and have lowered larynx
• Capable of Dentition
• Reflect an omnivorous diet
• Similar incisors and canines which lack spaces between teeth

Hominins - Learning and Tool Use

• Learn through culture
• Use tools (Greater apes)?
• Chimpanzees use termite sticks
• Demonstrate planning and make tools
• Able to Crack seeds open with two rocks

Models for Understanding Hominin Behavior

• Considers homologous vs. analogous traits
• Uses the behavior of living primates as a model
• Employs ethnographic analogy, but recognizes its limitations
• All cultural groups have qualities, and this is not always reflective of the universal pattern