The Order Primates Why study primates 1 Compare humans to modern primates to see how alike and different we are Many physical characteristics we think of as human are common to primates 2 What are the implications of shared characteristics between humans and other primates which traits are primate in general Do we share traits because our ancient common ancestor had those traits Analogy similar trait due to similar selective forces similar in function produced by convergent evolution do NOT share a common ancestor with that trait Example Bats type of mammal and grasshoppers type of insect Both fly and have wings Homology similar trait inherited from a common ancestor These are the traits of special interest to us if the traits were present in an ancestor pre dating beginnings of humans and are still present today then early humans would have had those traits Linneaus described organisms by classifying them in a taxonomy based on similarities and differences Taxonomy uses hierarchical sets of nested categories from general to more specific KINGDOM PHYLLUM SUBPHYLLUM CLASS ORDER Animalia animal Chordata Vertebrata vertebrates Mammalia mammals Primates primates CLASS Mammalia reproductive strategy of few usually live births extensive postnatal care associated with higher intelligence and greater capacity for learned behavior differentiated teeth different kinds of teeth skeletal structure capable of swift movement ability to maintain constant body temperature ORDER Primates Very generalized order whose essential environmental niche is arboreal Many primate characteristics relate to living in trees but controversy over whether initial evolution of these traits was adaptation to arboreal lifestyle or instead adaptation to insect hunting in low branches Primates can be divided into two suborders One is more primitive arose earlier and one is less primitive evolved more recently Anthropoids are the less primitive primates Prosimians are more primitive In this case primitive means older evolved first Primate physical tendencies best exemplified by Suborder Anthropoidea Grasping pentadactyl hands and feet Some degree of opposability in hands Emphasis on sight over smell Tactile pads and nails Generalized skeleton with retention of clavicle Largest and most complex brain of mammals Grasping pentadactyl hands and feet Pentadactyl five digits Prehensile ability to grasp Flexible hands and feet Opposable thumbs Adds up to manual dexterity Feder Park 2001 108 Photo by F Lanting Minden Pictures Emphasis on sight over smell Abbreviation of snout less emphasis on smelling ability Portion of brain devoted to smell shrank while portion devoted to vision expanded Vision is binocular overlapping field of Vision provides depth Stereoscopic each eye transmits to both sides of brain Turnbaugh et al 1993 137 Emphasis on sight over smell Color vision in most primates Good visual acuity Presence of postorbital bar eye surrounded by bone In other words most primates see what how we see Tactile pads and nails Most primates have fingernails instead of claws These provide support for tactile pads finger pads that are sensitive to touch Generalized skeleton with retention of clavicle Clavicle collarbone allows unusual flexibility of arms and shoulders Other mammals have lost the clavicle for example dogs have no clavicle Largest and most complex brain Ratio of brain size to body size is larger than most mammals Cortex and neocortex expanded in size Resulting in more brain tissue concerned with memory thought and association capabilities Only marine mammals are comparable Feder Park 2001 123 Most primates give single birth A few regularly bear twins Relative to size primates have the longest postnatal dependency of all mammals long period of growth and development great apes and humans are sexually mature only 10 years also relatively long life span associated with emphasis on learning Skeletal maturation has been studied in detail only in humans macaques chimpanzees and capuchins Related Social Characteristics Parental investment Most primates give single birth Long gestation long life span Prolonged infant dependency Resulting in greater dependency on flexible learned behavior Sociality The need for long care of offspring places a selective value on support by a social group Pictures from Turnbaugh et al 1993 Let s look at primates from top to bottom starting with cranial characteristics Skull has two general parts brain case holds brain and organs of sense face jaws teeth chewing muscles associated soft tissue Within the order the relative sizes and shapes of these two vary Muscles of facial expression are highly differentiated and developed Teeth more than any other body part give basic information on primate evolution are the most often preserved bone give a lot of information Primates have upper lower jaw teeth bilaterally symmetrical General four kinds of teeth incisor canines premolars bicuspids and molars The number of teeth for each species can be expressed by a dental formula that gives the count of the four kinds of teeth for half of a jaw Turnbaugh et al 1993 157 Dental formula Primitive mammals have 44 teeth 3 1 4 3 3 1 4 3 In primates the trend is to reduction Many have 32 teeth 2 1 2 3 2 1 2 3 Turnbaugh et al 1993 157 Primates have deciduous and permanent teeth humans have 20 deciduous teeth none are molars Primate molars often premolars have cusps ridges the pattern can help to identify groups A distinctive type of primate molar has five cusps known as the Y 5 cusp pattern It is found only among hominoids apes and humans Feder Park 2001 30 Postcranial characteristics Postcranial below the head Basic skeletal structure is generalized Wide movement flexibility All primates have a clavicle which is a primitive mammalian trait dogs cats horses have lost it Clavicle collar bone Primates have a variety of limb proportions and modes of locomotion Vertical clinging and leaping Brachiation Quadrupedal terrestrial quadruped arboreal quadruped Knuckle walking Bipedal
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