Shared Traits of Primates
Professor Janaki Natalie Parikh
profjnp@gmail.com
Primate Derived Traits
• 1. Stereoscopic vision: overlapping field of vision from
both eyes due to placement, what type of image?
• 3-D image, depth perception
• Since primates rely most heavily upon sense of vision,
we have skeletal protection surrounding the eyes
Primate Derived Traits
cont’d
2. reduced prognathism: reduced snout
3. Prehensile hands, feet & (sometimes) tail:
• What is prehensility?
• Grasping ability
4. reduction of claws to fingernails
5. increased complexity of cerebral cortex
• Results in:
• -increased intelligence
Primate derived traits
•
(Results in cont’d)
(increased complex. of cerebral cortex offshots cont’d)
-increased play behavior
-extended gestation, meaning?
-REALLY long pregnancies relative to sz. of newborn,
comparison w/ blue whale (9 ½ mos. vs. ~12mos.)
To support this longer pregnancy, it would require?
-increased development of the placenta
6. decreased litter size: (typically singletons)
Evolutionary reproductive strategies
• K-selection: organism has FEW offspring, but
tremendous parental investment (environ. near
carrying capacity)
• r-selection: organism invests energy into production of
MANY offpsring, ltl or no parental investment
• Humans (& primates in gen. utilize which of these?)
• K-selection
(w/ the following poss. exception…)
• R-selecting organisms?
K-selection
r-selection
Primate derived traits cont’d
7. altricial young: what can our newborns do?
• Not much! They’re rather helpless & have a long
period of infant dependancy
8. live in complex social groups: not simply a “bonus” ,
social interaction is actually crucial for our young to
survive & thrive
•
Selection theories (derived traits)
• 1. Arboreal hypothesis (splat hypoth.) : arbor means?
• Tree. Suggests that primate derived traits provided an
advantage to adapting to & living in the trees.
• Sounds plausible. Prob’s/Criticisms?
• Tree squirrels: well adapted to the trees, but don’t
have the derived features of primates
• 2. Visual Predation hypothesis: focuses on what
earliest primates were doing in the trees…hunting
Shared ancestral traits
(not used as basis of taxonom. classification)
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1. pentadactyly: penta means?
Five. presence of 5 digits on hands & feet
2. generalized dentition: we’re heterodonts, meaning?
Many different kinds of teeth in our mouths, how many?
Primates have 4. As opposed to sharks (homodonts)
Those 4 are called?
Incisors.
Ancestral traits cont’d
• Incisors: Canines: Premolars: Molars.
• Dental formula: how many of ea. kind per quadrant
• 2:1:2:3. Full set in humans = 32 (once “wisdom” teeth
have come in)
• 3. clavicle: commonly referred to as?
• Collarbone. Maintains distance btwn
the scapula (shoulder blade) & sternum
Socio-ecology of primates: diet & size
• Primates are homeotherms: narrow range of internal
body temp. comfort, (slight change considered?)
• As organism gets bigger, it’s ratio of surface area to
volume decreases…(implications in plain English)
• Larger animals: produce more body heat
• Smaller animals: more surface area, thus body heat
escapes quickly, have prob’s keeping warm
• Has implications in terms of relative quantity of food
• Who eats more (relatively speaking?)
• Smaller animals eat more in order to pwr their
metabolisms, which generate heat to keep warm.
They eat less in absolute terms, but more in relation to
size (may consume its own weight in food in a day!)
• Smaller animals also require foods that are higher in
calories, while larger animals can’t process the calories
•
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