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Proximal On humans: towards the head; more for limbs Distal On humans: towards the feet; more for limbs Lateral On humans: side away from the midline Medial On humans: side towards the midline Posterior a.k.a. Dorsal On humans (from profile): side with your back Anterior a.k.a. Ventral On humans (from profile): face side Superior On humans: towards head; more for the trunk Inferior On humans: towards the feet; more for the trunk Why Study Primates? -Humans are primates -Comparative method -Closest extant relatives -Extremely diverse order -Conservation What makes humans human? Primates are our closest living relatives and provide the standard reference for comparisons with humans Understanding the Evolution of the Human Lineage Primates provide comparative behavioral information to use in reconstructing early human behavior -Morphological similarity -Genetic similarity Homology -Features that result from a common ancestry -Is a feature unique to a group? Can we use it to characterize that group? -Primitive (or ancestral or generalized) traits Homoplasy -Common features that are not the result from a common ancestry -Ex: human forward facing eyes and owl forward facing eyes Convergent Evolution -When distantly related species evolve the same/similar trait as an adaptation to the same ecological pressures Derived Traits -Specialized traits that distinguish species from its last common ancestor Comparative Method: Sexual Dimorphism in Living Primates -Body size and canine size tends to correlate with the degree of male mating competition -If lots of sexual dimorphism, you can conclude you have non-monogamous mating Behavior in Early Humans -How did their environment, diet, habitat, or morphology shape their behavior? Sexual Dimorphism in Early Hominids -Australopithecus afarensis had lots of sexual dimorphism Differences Between Species -Similarities between closely related species-- homology -Any differences represent adaptive responses to specific ecological conditions -Humans share a close relative with bonobos and chimps Knuckle-Walkers -Gorillas, bonobos, & chimps knuckle walk, but humans don't -Did humans just lose it? Then it would be homology and we would look for a knuckle-walking ancestor -If it were homoplasy, then we wouldn't have to look for a knuckle-walking ancestor Transition to Human Behavior -Can be understood studying primates in the present and using these observations to infer behavior in the past -This method depends on the principle of homology and a shared ancestry with apes and monkeys Some Key Behavioral Features Likely to be Found in Early Hominins -We know that chimpanzees & bonobos (Pan) are our closest living relatives --We can analyze behaviors found in both chimpanzees/bonobos and humans to see if they are likely to be found in the common ancestor of chimps and humans -Evidence that chimps possess cultural attributes (socially learned behaviors) --In chimps, there are at least 39 different, locally expressed learned behaviors that cannot be explained ecologically; occurs in bonobos but less documented -A lot of evidence for tool use; in chimps, orangutans, and some monkeys. Not as common in Bonobos, but likely ecological -Something like warefare, once thought to be uniquely human has been well documented in several chimp communities --Male chimps regularly patrol boundaries of their home ranges & have intergroup conflicts; rare, but not absent in Bonobos -Chimpanzees regularly hunt vertebrates (cooperative group hunting) --Most hunting appears to be a cooperative effort & meat sharing is important --Rare, but not absent in Bonobos Tool Use -Manipulating a natural object to achieve a desired goal -Sticks, twigs, blades of grass (none of these would show up in the fossil record) What is a Primate? -Primates are an order of mammals. Class: Mammalia Characteristics of Mammals -Hair -Specialized sweat glands -Live young (vivaparity) -3 Middle ear bones -Heterodonty -Pentadactyly Characteristics of Primates: Morphology 1. Petrosal bulla 2. Complete postorbital bar 3. Grasping hands & feet with opposable hallux (big toe) and/or pallux (thumb) 4. Nails instead of claws on at least some of the digits 5. Primates have larger brains than other mammals (relative to body size) -Increased complexity of brain 6. Decreased importance of olfaction --Less prognathism --Smaller olfactory bulb relative to total brain size 7. Increased importance of vision --Orbital convergence (more forward-facing eyes) --Binocular vision (overlapping visual fields) --Stereoscopic vision (better depth perception) --Post orbital bar, plate or enclosure --Larger & more developed visual cortex 8. Dietary Plasticity: primates eat a highly varied diet -Primates have retained primitive characteristics in their teeth -Dental traits in four functionally distinct tooth types: incisor, canines, premolars, molars -Molars are unspecialized (each one looks pretty much like the next Petrosal Bulla -Auditory bulla made up of the petrosal bone Differences between a claw and a nail -Nails don't grow to a point -Claws have 2 layers -Claws are long and curved Characteristics of Primates: Life Histories -Slow life histories with extended ontogeny (development) -Single offspring per birth (typically) -Longer period of fetal nourishment -Longer infant dependency and parental care -Only 2 mammary glands Primate Biogeography ~230 extant species; mostly tropical nowadays -Japanese macaques can live in snow Linnean Classification -Kingdom: Animalia -Phylum: Chordata --Subphylum: Vertebrata -Class: Mammalia --Subclass: Theria --Infraclass: Eutheria -Order: Primates --Suborder: Anthropoidea --Superfamily: Hominoidea -Family: Hominidae -Genus: Homo -Species: Sapiens Primates -Strepsirhines -Haplorhines *Prosimians and anthropoids (monkeys and apes) classification changed because tarsiers are more closely related to the monkeys and apes, but branched off quite early (DNA checked); dropped the family Pongidae from Hominoidea Cercopithecoidea -Ex: Old world monkeys -Bilophodont molars -Narrow thorax -Tail, but not prehensile Ceboidea [Old Classification] -New world monkeys The Apes: Common Traits -No tail -Large body size -Short, broad trunk -Flexible shoulder joint Hominidae [Old Classification] Old Classification: (paraphyletic) -Humans -Fossil Humans Pongidae Old Classification: (paraphyletic) -Chimpanzees -Gorillas -Orangutans Hylobatidae Old Classification: (paraphyletic) -Gibbons Hominini New Classification: (monophyletic) -Humans -Fossil Humans Homininae New Classification: (monophyletic) -Humans -Fossil Humans -Chimpanzees Paraphyletic -Some, but not all of the descendants of a common ancestor Gorillinae New Classification: (monophyletic) -Gorillas Ponginae New Classification: (monophyletic) -Orangutans Hylobatidae New Classification: (monophyletic) -Gibbons Hominidae [New Classification] New Classification: (monophyletic) -Humans -Fossil Humans -Chimpanzees -Gorillas -Orangutans Haplorhines vs. Strespsirhines -Haplorhines have fully enclosed orbits -Haplorhines have a fused frontal bone -Haplorhines have a fused mandibular symphysis -Strepsirhines tend to have more prognathism Strepsirhines -Tooth comb (in some) -Grooming claw -Pointier cusps on molars -Wet and split nose -Tapetum Lucidum -Relatively smaller brains -More prognathism -Unfused mandible -Orbits with more lateral orientation -Ex: Lemurs & lorises Haplorhines -No tooth comb -No grooming claw -More rounded cusps -Dry nose, continuous upper lip -No tapetum lucidum -Relatively larger brain -Postorbital closure -Orbits with more forward orientation -Fused mandible -Molars with flatter cusps -Reduced prognathism -Nails on all digits -Infraorders: Tarsiiformes, Platyrrhini, Catarrhini Tarsiiformes -Vertical clingers and leapers -Huge eye orbits for nocturnality -Unfused mandible -Grooming claw -Molars with sharp, pointy cusps Platyrrhini -Lateral facing nostrils -Dental formula: 2-1-3-3 -No boy ear tube -Some with prehensile tail Catarrhini -Ex: Old World Monkeys, Apes, and Humans -Forward directed nostrils -Dental formula: 2-1-2-3 -Bony ear tube -Superfamilies: Cercopithecoidea, Hominoidea Hominoidea -Ex: Apes & Humans -Largest relative brain size -Y5 Molar Pattern -Broad Thorax -No Tail