ANTH 120 1st Edition Lecture 13 Outline of Last Lecture 1. The Geological Framework for EvolutionOutline of Current Lecture 2. The Geological Framework for Evolution: Dating Methods and FossilsCurrent LectureThe Geological Framework for Evolution: Dating Methods and FossilsContinuation of Dating MethodsRadiocarbon Dating  type: absolute dating, carbon-14, organic material, 75 kya- Plants and animals pick up 12C and 14C in the atmosphere-14C decays to 14N  after animals die carbon turns into nitrogen 14- Measure ratio 14C to 12C- Half-life is ~5,730 years *** test question ***- Up to 50/75 Ka- If it’s organic use Carbon14o Charcoal, bone, basketryo Dating Deposits  for very old artifacts you have to date around an archaeological siteRadiopotassium  potassium (k)-40 Argon (Ar)-40, Volcanic rock, >100kya- Potassium/ Argon dating, measures the rate of decay of potassium decaying into argon- It’s very common, specifically in east Africa- Looks at decay in Volcanic rock and dating the area around the artifact- The half-life is about 1.3 billion years- Useful to date things 100,000 years to earth origins - After 1.3 billion years the half life changesAccumulation of Radiation: TL & ESRo Measures amount of trapped electrons that accumulate in defects within chrystallince substances since depositsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Electron Spin Resonance  concentrations of radioisotopes, used on bones and teeth, <1 mya- Measures Uranium electrons trapped in calcite crystals- Radioactive Isotope Concentrations- Useful for calcite structures- Tooth enamel and coral- Can extract measurements from bones- Bone embedded in calcite structures inside of caves- Good for dating things up to 1 million yearsThermoluminescence (TL) trapped energy, sediments, stone, ceramics, < 800 kya- Electrons accumulate in defects of mineral’s crystalline structure- Material that has been superheated (volcanic, meteorite craters, pottery hearths, burned flint) will reset the clock to zero- Heated to release electrons- Sediments, stone, and ceramics are what this method is best used to date- Up to 800 kaThe Past: Evidence for the Present1. What are fossils?2. What do fossils tell us about the past?Principle of Faunal Succession  fossils succeed each other vertically in a specific, reliable order1. William Smith (1769-1839) a. You can correlate animals based upon what kind of fossils are found in different stratasb. Stratum contain a specific collection of fossils2. Fossils are physical evidence for life that no longer exists3. We are mostly interested in fossils that have bone in them5 Important Functions of Bone1. Supporta. Internal organs, brain, soft tissue2. Movementa. Being able to move around and interact with environment3. Protectiona. Sternum, rib cage, etc4. Blood Formationa. Stores blood stem cells5. Mineral Storage: calcium and phosphate repositoryBone (osseous) TISSUE Composition of bone matrix1. Inorganic Saltsa. Hydroxyapatite: crystals of calcium and phosphate (hardness)2. Organic Mixturea. Collagenous fibers and mixture of protein i. Strength and resilienceDuring the process of fossilization - Loss of organic component- Partial or full chemical conversion to stone- Usually this process happens in sedimentary rock- Limestone cavesTypes of Fossils1. Body Fossil  mineralized bones and teetha. Rare for most of human prehistoryb. No soft tissue except in rare of recent casesc. Ardipithecus a fossil 2. Trace Fossils  foot prints, impressions, feeding marks…a. Example: imprints left by dinosaursb. Fossil burrows, dinosaur skin imprintsc. Archaeological traces  anything material culturei. Increasingly common after 2.5 million years ago1. Stone, flaked-stone artifacts2. Butchered animal remains Context is very important when dealing with fossils and geological contextProvenience: EXACT location  “In situ” = in place1. In sit Surface finds, record where you find it in place2. In situ intrusive finds  human caused3. In situ intrusive naturalIInformation Contained in Body Fossils1. Body size and general appearance2. Age at death (forensic)  “Taung Baby” Australopithecus africanus 3.2-2.2 mya in South Africa: Lots of baby teeth3. Sex  comparing male and female pelvises a. Female = wider because of birthingb. Comparing primate skulls4. Health, disease  what was going on in this population when they died5. Fragmentary DNA sequences (if organics survive) 6. Demographics and Population Variation (if samples are large)7. Adaptationa. Cognitioni. Looking at brainsb. Manipulative Capabilitiesi. How are they using their fingers and toesc. Posture and Locomotioni. How is this species walkingd. Mating systemi.e. Diet (tooth morphology and chemistry)i. Two Basic Types of Vertebrate Dentitions1. Homodonts fish and reptiles2. Heterodonts  Multiple types of teeth, mammalsa. Incisors  bit off morsels of foodb. Canines  bite-off food morsel, threat displayc. Pre-Molars  masticate foodd. Molars  masticate food3. Number of each type of tooth is expressed using a dental formulaTooth Function- Herbivore  Complex in folding of enamel into dentine forming a grating surface- Carnivore  blade like cusps for shearing- Omnivores  low rounded cusps to break down many types of foodWhy are fossils so scarce?- Taphonomy: The process of Fossilization, all of the processes that can happen from the time of death until someone finds ito Deatho Decay or consumption of soft tissueso Bone Destruction (carnivores, weathering)o Burial (in sediment traps)o Chemical dissolution or mineralization?o Exposure of fossiliferous deposito Post-exposure destructiono Paleontological survey of fossiliferous deposito Fossil Collectiono Fossil analysis and