Unit 2 Class Notes - Week 4
Unit 2 Class Notes - Week 4 ANTH260
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This 5 page Class Notes was uploaded by Jessica Shook on Thursday March 12, 2015. The Class Notes belongs to ANTH260 at Washington State University taught by Luke Premo in Fall. Since its upload, it has received 136 views. For similar materials see Physical Anthropology in anthropology, evolution, sphr at Washington State University.
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Date Created: 03/12/15
Dating techniques how old are the fossils o 2 general types of dating techniques 0 Relative Dating place nds in a sequence relative to one another but provide no actual dates or date range Ex stratigraphy n Makes use of the law of superposition older layers are overlain by more recent layers like a cake or the Grand Canyon n Bottom layers usually older Ex quotI m taller than my daughterquot 0 RadiometricAbsolute dating Provides date estimates in years before present BP for geological deposits Ex KAr Potassium Argon ArAr Argon Argon radiocarbon ssiontrack etc Ex stopwatch analogy Radiocarbon dating a C12 stable does not decay same amount whether dead or alive same amount as C14 while alive a C14 decays through time created constantly plants take it through photosynthesis we eat C14 in their bodies even though its decaying amount is the same in all living things still decaying after death but not being replenished 0 Ex organism dying starts stopwatch Goes into C14 and N14 0 C14 halflife the amount of time required for a radioactive isotope to decay to half of its life 0 Scientists measure the amount of C12 and C14 to determine the date of deceased 5720 years x 3 halflives 17190 years old ldon t need to know decays very quickly very hard to measure after a certain amount of years 0 depends on the material that you have available to study and test ash turf and lava from volcanoes can be dated by K40Ar40 radiometric dating methods 0 halflife of K40 125 billion years 0 using both relative and absolute dating techniques what can we say about the age of fossil x 0 using both radiographic and stratigraphic techniques not necessarily testing the bones The Evolution of Early Primates Our goal trace our lineage back in time sometimes wphylogeny 0 General Timeline for early primate evolution 0 Miocene 235 mya hominoid radiation quotplanet of the apesquot Proconsu 2717 mya a First apes appear in East Africa in the late Oligoceneearly Miocene n The small generalized ape exhibits a monkeylike body D But it also shares some derived traits with hominoids o No tail 0 Some details of the thumb and big toe Hominoids originate in Africa early in the Miocene and then later spread into Eurasia n Miocene hominoids in Europe Dryopithecus Spain 95 mya o The teeth are chimplike in size and morphology including thin enamel indicating frugivory o The cranium is apelike o The skeleton is apelike but not adapted to knucklewalking o Locomotion brachiation n Miocene hominoids in Asia Sivapithecus 148 mya 0 Found in India and Pakistan 0 Had big powerful jaws with large molars and thick enamel o Orangutan Pongo ancestor The world became cooler and drier during the latter half of the Miocene As a consequence of climate change selection the fossil record shows a shift in primate species during latter half of the Miocene n fewer ape species more monkey species climate change during the Miocene sets the stage for the appearance of hominins hominoids ourished early in the Miocene but most went extinct leaving only the ancestors of the fat fewer ape species of today what was it about the hominin lineage that allowed us to survive while many other hominoids went extinct in the face of the cooler drier conditions that marked the late Miocene o Oligocene 3423 mya anthropoid radiation Fayum Basin Egypt n The best known early anthropoids come from early Oligocene fossil beds in the Fayum 3633 mya Aegyptopithecus I Found in sediment that dates to 29 mya n Relatively long snout and tiny brain relative to rest ofhead Postorbital closure and binocular vision Apelike dental formula 2123 in mandible Fairly pronounced stout small brain Sexual dimorphism bigger male skull than female 0 Eocene 5434 mya Prosimian radiation Appearance of true primates Prosimian radiation Eocene Prosimian adaptive radiation 2 larger categories Adapids amp Omomyids El sometimes considered the rst true primates grasping hands and feet with nails 0 reduced prognathism Ex lda 47 mya is the worlds best preserved adapid o Paleocene 6554 mya rst possible primates Plesiadapiforms Plesiadapids El Small primatelike animals from the late Paleocene Solitary terrestrial and arboreal quadrupeds Well developed sense of smell most had claws on hands and feet and they did not have binocular vision Ex Carpoestes simposoni 56 mya Nearly complete skeleton discovered in 2002 in Wyoming 0 C Simpsoni had opposable big toe with nail but claws on rest of digits What was it about the hominin lineage that allowed us to survive while many other hominoids went extinct in the face of the cooler drier conditions that marked the late Miocene Origins of Bipedalism How do we discern whether a fossil is from a hominin 0 Look for characteristics of humans not present in any other primates shared derived features 0 The earliest and most universal derived feature of the hominid is bipedal gait our form of which is unique among animals 0 walking on two legs and feet 0 bipedalism leaves its signature on the skeleton from head to toe ln bipeds foramen magnum small hole that spinal chord attaches to skull is located under in the middle rather than at the far rear of the skull Sshaped curvature to spine helps balance cushion torso also makes us prone to lower back problems Bipeds have a broad bowlbasinshaped pelvis rather than a tall narrow pelvis Femur is angled inwards in a biped unlike a quadruped which makes our legs closer to the center of gravity to balance better and keep ourselves upright The bipeds foot I Arches provide extra spring a Short straight toes n Toes in line no divergent big toe
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