Traits and Trends

60mya

primates broke off from Scandentia (tree shrews)

carpolestes

55-60mya, potentially oldest primate, arboreal, small bodied, frugívoros, grasping hands, nails

distinguishing traits of hands and feet

pentadactyly, elongation of fingers and toes, opposable thumb and big toe, nails instead of claws; these traits enhance coordination and tactile sense of hands and feet

elongation of fingers and toes

enhanced mobility, long compared to base of the hand

opposable thumb and big toe

precision grip allows for handling and holding onto small objects

nails instead of claws

protective backing to fingertips that allow for sensitive skin exposure for grasping and feeling objects

homologous

traits similar due to common ancestry; similar structure but may have different function

analogous

traits coevolved to do the same job; similar in function but different in structure

distinguishing primate traits

hands and feet, increased reliance on vision, large brains, lengthening of life history traits

increased reliance on vision

stereoscopic vision, color vision, post-orbital bar/enclosure, reduction in olfaction

stereoscopic vision

forward-facing eyes that allow for accurate depth perception, arboreal hypothesis, visual predation hypothesis

arboreal hypothesis

depth perception evolved to help jump through branches

visual predation hypothesis

most predators have forward-facing eyes to hunt

color vision

most mammals are dichromatic but most primates are trichromatic (except male new world monkeys), may allow for better detection of fruit from foliage and ripe fruit

large brains

large brains and large neocortex relative to body size

lengthening of life history traits

later age at first reproduction (AFR), longer maximum lifespan, lower fertility (reduced litter size)