What is Overall Primate Pattern?
general tendencies expressed by all primates
Derived Traits
specialized traits that are not shared with last common ancestor
example: Derived traits in humans: Bipedalism
Primitive Traits
more closely resembling the LCA of the group; ancestral trait;
-the trait has been around longer
EXAMPLE: knuckle-walking in gorillas and chimps
What do primitive traits not mean?
Less Successful / Less Evolved
What are the 4 complexes that make up the primate pattern?
- Grasping Hands + Feet
- Vision and Olfaction
- Large Complex Brains
- Generalized skeleton and dentition in primates
Grasping Hands + Feet
- 1 out of 4 complexes that makes up the primate pattern
- opposable thumbs not present in all primates
- pentadactyly –> homology shared by species that acquired it by descent from a common ancestor
- nails/claws - most primates have nails than claws
Vision
- 1 out of 4 complexes that makes up the primate pattern
- forward facing eyes
- found on predatory animals
- great reliance on vision (compared to other senses)
- stereoscopic vision (3D, depth, perception)
- reduction of snout
- reduction of olfactory centres of the brain
- reduced reliance on olfaction
Olfaction
- 1 out of 4 complexes that makes up the primate pattern
- reliance on other senses (other than vision)
- a snout that sticks out more
- EXAMPLE: chimps and lemurs
Large Complex Brains
- 1 out of 4 complexes that makes up the primate pattern
- large brains relative to body size (compared to other mammals)
- allometric relationship between body and brain size
What type of relationship is present between brain and body size?
Allometric Relationship
What is Allometry
when two variables increase or decrease at different rates
What is Isometric
if 2 variables increased or decreased in direct proportion to one another in this relationship
What is an allometric relationship with our brain and body size?
- Our brains are larger than what our bodies would predict
- brains in primates have gotten so much bigger
- brain size does not co-vary in direct proportion with body size
Ecological Intelligence Hypothesis
-ecological selection pressures may have influenced the brain size/body ratio
EXAMPLE: testing two different species but in the same habitat
HOWLER VS SPIDER MONKEY
Explain Howler Monkey VS Spider Monkey
- testing two different species that live in the same habitat
- howler monkey: Folivorous, uniform food sources; small brain-to-body weight ratio
-Spider Monkey: Frugivorous, patchy food sources; Large brain-to-body weight ratio
Why do primates have such a large neocortex?
- responsible for cognitive abilities (reasoning and consciousness)
- in primates neocortex makes up 50-80% of the brains total volume
Social Brain Hypothesis
-group size may have influenced “neocortex ratio”
Group size – in particular grooming clique size
Neocortex ratio
size of the neocortex relative to the rest of the brain
What is the importance of the of the relationship between group size and neocortex size?
the hypothesis implies that constraints on a group size arise from the information processing capacity of the primate brain
what mediates the relationship between group size and neocortex size?
- ability to recognize other group members
- ability to remember who has a relationship with whom
- ability to manipulate information about a set of relationships
Machiavellian Intelligence Hypothesis
-neocortex size strongly predicts the degree to which primates engage in tactical deception
Tactical Deception
- acts that appear to deliberately mislead other individuals
- refers to the idea that others are socially manipulated in a way that benefits the user
Generalized Skeleton and Dentition in Primates
- 1 out of 4 complexes of primate patterns
- unspecialized skeleton (particularity in limb structure)
What are the 4 types of teeth arranged from midline to the back of the mouth?
Incisors.Canine.Premolars.Molars
ICPM
