5. The Early Hominins.pptx - UNIT 5 The Early Hominins 5.1...

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UNIT 5: The Early Hominins 5.1 Dating and PalaeoEnvironment Reconstructing Techniques
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How old is this? What was it like back then?
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Isotopes Different versions of the same ______… just slightly different _____! Carbon 12, carbon 13, carbon 14 Some are stable, some are not (radioactive)
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Isotopes Radioactive Usually for dating Decay at a steady rate (exponentially) “______” Stable Usually for environmental(and/ or physiological) reconstruction Does not _____ (hence “stable”) Stable isotope analysis
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Radiometric Dating… I 14 C dating (Radiocarbon dating) Measure the ratios of 14 C / 12 C. 14 C is _________, so amount of 14 C will decrease at a steady rate after an organism die (______ = 5730 years). Can estimate how long ago since the organism died…. Up to about 45,000- 50,000 years. Only work on ______ materials.
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Radiometric Dating… II Potassium-argon/ argon-argon dating Measure ratios between K-Ar and 40 Ar / 39 Ar – 40 K decay to 40 Ar. Reliable between the range of 100,000 and 4.3 million years, with a half-life of 1.3 billion years. Only works on ______ or __________ (measuring the time since the igneous rock first formed).
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Radiometric Dating… III U-series dating 238 U, 235 U, 232 Th  214P b, 210 Pb, 206 Pb Reliable between 10,000 to 500,000 years, depending on materials. Need _____________ materials, such as coral, speleothem, some rock, also sometimes shells as well as teeth.
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Combining the strengths of all methods! Use radiocarbon dating to establish min age Use K/Ar dating to establish max age Use U-series dating to narrow down age range
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____________ _ ______ _______________
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Molecular clock DNA accumulates _______ at a fairly constant rate over time. ~ 98% similarity Common ancestor 5-7 mya Australopithecines ~ 4mya Gorilla ~ 8 mya
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Palaeoclimate reconstruction What kind of animals live there? What kind of plants grow there? What was the temperature like? What did they eat?
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_____________ Fish – aquatic environment Tapir – jungle, rainforest Horse - grassland Frog – swampy area
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____________ ____________ Evergreen shrubs and trees ~ tropical rainforest Maple leave ~ temperate Macroscopic remains
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____________ ____________ Microscopic remains Diatoms Phytoliths Pollens
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Stable isotope analysis Stable oxygen isotope analysis ( δ 18 O)
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Stable isotope analysis Stable carbon isotope analysis ( δ 13 C)
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Odontology SEM of occlusal surfaces Dental microwear Pathology - Cavities Calculus / plaque
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Ancient poop!! (_______)
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Age and sex… how can we tell? Age Tooth eruption chart Fusing of bone epiphysis Pubic symphysis
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Age and sex… how can we tell? Sex Sexual dimorphism!
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  • Spring '12
  • Sandgathe
  • Hominina, Olduvai Gorge, Hadar

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