primates

Tiny parents invest more time in their offspring than any other male.
Most students (aged 18-23) lived with their parents until the age of 18, which is rare in the animal kingdom.
Parental investment in the animal kingdom:
- Mice live with parents for a few days.
- Puppies can be adopted around the eight-week mark (they are weaning and able to survive independently).
- Humans and certain primates devote significant time and resources to their young, often until age 18.

Monkeys can be divided into two categories based on their geographic regions:
- Old World Monkeys: Found in Africa and Asia (everything to the right of the Atlantic Ocean).
- New World Monkeys: Found in the Americas (everything to the left of the Atlantic Ocean).
Important to understand this geographical division for future topics.

Adaptation features of primates, especially in their skeletal structure:
- Chimpanzees and humans have similar skeletal structures but adapted for different environments.
- Both have 26 bones in their feet, but adaptations differ due to arboreal versus terrestrial living.
Terms:
- "Quadromanus": Latin for “four-handed”, referring to the dexterity of primate feet akin to hands.
- Opposable thumbs are unique to some primates providing them an evolutionary advantage in grasping and manipulation.
- "Grasping calyx": opposable big toe aiding arboreal locomotion and gripping tree branches.

Humans possess an S-shaped spine for bipedalism, vital for upright walking and weight distribution.
Quadrupedal primates have a C-shaped spine, suitable for walking on all fours, distributing weight differently than bipeds.

Primates possess mobile joints, essential for maneuvering through trees.
Unlike humans, primates can execute brachiation—swinging from branch to branch—which requires joint adaptability.

Precision grip:
- Ability to touch thumb to each fingertip; crucial for tool use (e.g., holding a pen).
Power grip:
- Enables the use of tools (e.g., holding a hammer securely).
These grips are unique to primates, allowing for complex tasks not possible in other species.

Human fingerprints are classified as dermal ridges—enhancing tactile sensitivity and grip.
Functions of dermal ridges include:
- Improving touch sensitivity.
- Regulating moisture on fingertips to maintain grip in various environmental conditions.

Primates typically have nails, which facilitate movement through trees without risking getting stuck (as claws can).
Nails provide protection and enhance functionality for arboreal adaptation.

Forward-facing eyes enhance depth perception, critical for navigating tree branches.
Color vision enables primates to identify ripe fruits and distinguish between different insects.
Protective adaptations for eyes:
- Post-orbital closure in humans and other apes provides essential protection for the eyes.
- In contrast, bears possess eyes on the side of their heads, relying on smell over vision.

The rhinarium:
- A moist, fleshy area around the nostrils that enhances olfactory capabilities in non-primate mammals (e.g., dogs).
- Primates have reduced or lack a rhinarium, indicating lower reliance on smell.

Dietary plasticity:
- Ability to consume a wide variety of foods (e.g., chocolate is toxic to dogs, but humans can eat it).
Primate dental features reflect dietary needs:
- Incisors, canines, premolars, and molars adapted for various diets.

Every primate has a dental formula, defining the number and types of teeth in a quadrant of their mouth.
Human dental formula:
- 2-1-2-3 (2 incisors, 1 canine, 2 premolars, 3 molars).
New World Monkeys have two possible formulas:
- 2-1-3-3 or 2-1-2-3.
Old World Monkeys consistently have the dental formula of 2-1-2-3.

Incisors:
- Blade-like teeth that shear or cut food. Example: tooth comb in strepsirrhines.
Canines:
- Sharp and pointed teeth used for puncturing; vary between species.
Premolars:
- Large and broad, used for crushing and grinding food.
Molars:
- Large and broad, similarly used for crushing and grinding food.

Frugivores:
- Primarily eat fruits; possess broad molars with low rounded cusps (buddadon molars).
Insectivores:
- Feed on insects; require small molars with sharp cusps for puncturing tough exoskeletons.
Folivores:
- Consume leaves; have specialized premolars and molars adapted for breaking down fibrous plant material.

Primates exhibit a significant evolutionary investment in their offspring relative to their lifespan, highlighting a distinct feature of their social and reproductive strategies.
The nature of this care includes extended interaction and sustenance until offspring are capable of independent survival.