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ANTC17 - W4.docx

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University of Toronto Scarborough
Genevieve Dewar

ANTC17 – W4 Human Origins - When we look into human evolution we must start at the beginning and look to the earliest of our ancestors, the earliest members of our Order –Primates. - How do we know which fossils are our ancestors and which are not? - What exactly is a primate? o Opposable thumb o Infant dependency o Stereoscopic vision and vision is the dominant sense (dogs –smell) o Clavicle o Large brain relative to body size - In order to understand the past, we rely on models of associated behavior in the present: o Uniformitarianism  The idea that things behave the way we do today cuz of the they did in the past o Parsimony or Occam’s razor  If there are many explanations, usually the simplest one is the right one. Doesn’t necessarily mean it is right though General definition of Primates - Arboreal mammals (adaptation to live in trees) - Vision-dominated senses (dos focus on smell) - Large complex brain to body size - Complex social organization - Long gestation and infant dependency - Typically one young per pregnancy - Manipulate an arboreal environment through grasping and dexterous hands and feet Group Exercise - Fossils – bones and teeth – how are we going to use these fossils to distinguish them to be primate vs. dogs or cat? *** o Dentition o Crania  Post orbital bar  Primates need bone things to protect their eyeballs because it is the dominant sense, whereas dogs nose is dominant  Eyes forward  Dental formula  Sagittal crest o Post-crania  Nails instead of claws  Opposable thumbs/toes  Clavicles o Another category  Large skull to body Primate anatomy - Grasping foot with divergent Hallux (thumb) - Presence of nail on Hallux and most other digits - Elongation of the heel - Dominance of hindlimb during locomotion - 5 digits on the fore and hind limbs with opposable thumbs and big toes (Hallux) - Tactile pads on end of digits - A complex visual system with stereoscopic vision, high visual acuity, and colour vision - Orbits encircles with bone – bar or fully enclosed sockets - Reduced number of teeth compared to primitive mammals - Trend number of teeth compared to primitive mammals - Trend toward holding the torso upright - Retention of the collar bones - 2 mammary glands We are from Lagomorpha - They share almost identical morphology - They are directly related to functional behavior and loco-motion (how they move around on land) - Be comfortable with different dentition and what they represent - What is the dental formula  2:1:2:3 Functional morphology - Humans have thicker enamel - Enamel – white section outside of tooth. We need to know the size of enamel - Directly related to enamel – we need to know how thick it was - Shape of the teeth o Left dental shape  Unlikely to be on human lineage  Cusps are tall and sharp because they tend to eat things like grass and insects they need to sheer thru them o Right dental shape  Low rounded cusps  Apes, human lineage Dental microwear o How what they eat affects their teeth o A – monkey – deep pits in enamel o B – homo erectus o C – homo hatelus (sp?) o D – they have scratch marks on enamel o We can study their diet depending on their enamel Inferring body size from diet - We can usually associate body size depending on diet. - At the top there is ratio of browsers and grasser *** o Browsers eat trees and bushes – C4 eaters o Grassers eat grass – C3 eaters - Insectivore tends to be very small. - We use modern primates to interpret the past Primate tree - Today we are focusing on the Orange-highlighted period - Adaptive radiation – when new habitat comes up it spreads Strepsirrhini – wet nosed primates - Rhinarium. o Dominated by sense of smell. - The most primitive - Post-orbital bar - Elongated snout - Toothcomb - Nocturnal – large orbits - Losiformes, lemuriformes, chiromyiformes (aye aye) - Not primate-like: grooming toothcomb, incisors are basically horizontal - Some are nocturnal and some are not - Aye aye o From Madagascar o Use long claws to grooming o Long snout o Very primate Haplorrhini – dry nose primates - No rhinarium - Post-orbital plate o Orbit is now bony support being invested in those eyes - We lost some snout - Diurnal – operating during the day - Hands and feet are more generalized - Only specializations are based on locomotion (VLJ)
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