Bones W5
February 7 , 2017
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Primates
-Nails and sensory pads (not claws)
-Super sensitive, finer sense of touch than other mammals
-Grasping ability
-Opposable thumb/Big toe
-Enhanced vision
-Optic convergence—Binocular vision
-Reduced nasal region
-Higher ration of brain size to body size than any other terrestrial mammal
-Increased brain complexity
-Slow life history
-Most primates have a single offspring at a time
-Relatively slow development
Primate Behavior
-Social
-Adult males often have long-term presence in group
-Greater dependency on CHECK ONLINE FOR SLIDES
Why do primates share these particular traits?
-They had a common ancestor that was adapted to a particular way of life
Phylogeny Again
-One species can diverge into two or more descendants.
-These are branching events
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Arboreal (living in the trees) Hypothesis—Adaptions to an arboreal life style
-Grasping hands to get to the end of branches and top of trees
-Good eyesight is important for living in trees
-Big brains are important to judge distance and how to move from branch to branch, whether a branch could
break under your weight, having a sense of dimension
Are there any problems with these arboreal adaption hypotheses?
-There are tons of other species that live in the trees that don’t have these Arboreal features
Visual Predation Hypothesis
-Features allowed primates to prey on insects at the end of fine branches of trees
Slight Problem
-The most ‘primitive’ primates depend on fruit and other plant matter! (not insects)
Angiosperm Hypothesis
-Features were the result of exploiting fruits on small branches
-Angiosperm are flowering plants (with fruit)
-They evolved in the late Cretaceous (-90 MA)
-They expanded across the world in the Paleocene (65 MA) and this was followed by the first appearance of
Primates
This hypothesis fits best with primate traits because…
-It required sophisticated vision to spot colorful flowers and fruit from a distance
-Thumbs to hold on to terminal branches
-A reduced sense of smell that works up close
-Big brain to tell whether fruit is ripe or not, etc.
Primates likely originated from an ancestor that…
-Was small and arboreal
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