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2. Early hominine evolution

2. Early hominine evolution - 1 Early Material a Primate...

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1. Early Material a. Primate Characteristics i. five fingers ii. grasping hands and feet iii. opposable thumbs iv. tendency for upright posture v. specialized shoulder vi. emphasis on vision, de-emphasis on olfaction b. Evolutionary Forces i. Mutation: DNA and Chromosomes random mistakes in DNA replication, only mistakes made during meiosis are heritable ii. Natural selection: Individual organisms descent with modification. need a population, a heritable variation and differential reproduction. iii. Gene flow and genetic drift: Populations gene flow: movement of genes between population (ex: immigration, migration) genetic isolation: physical (like mountains or islands) or cultural barriers -allopatric isolation genetic drift: evolutionary change produced by random factors. the smaller the population, the more some individuals contribute a large share of the genes *a “rare” gene can be passed to a large number of descendents * alleles can disappear Ex: Founder effect: the establishment of a new population by only a few founders (ex: Amish and polydactyl (a symptom of Ellis von Orewald)) 2. Early hominine evolution ape/human divergence ~ 7-5 mya according to the molecular clock (the amount of genetic difference) a. Derived Traits of Hominids and the Mosaic evolution i. bipedalism earliest 6 mya ii. large brain (develops slowly) starts at 6 mya i. jump at 2 mya iii. Slower life history iv. Material Culture (Language?) stone tools at 2.5 mya v. Dental Change first at 5-6 mya i. reversal at 2 mya b. Late Miocene/Pliocene environment i. Late Miocene 1. 23-5mya 2. Earth’s climate cooled 3. Formation of Polar ice caps and glaciers 4. Rainfall decreased was more seasonal 5. Forests Shrunk 6. More woodlands and Savannahs ii. Pliocene 1. Retreating Forests 2. Increasing grasslands diversification of many grazers
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c. bipedalism—skeletal adaptations and theories a. structural change of spine pelvis, legs, and feet ii. Spine 1. Human a. “S” shaped b. Center of Gravity over pelvis 2. Ape a. Slightly curved spine, “lumbar” spine b. Center of Gravity over trunk iii. Theories 1. Climate Driven: with the shift to a savannah environment, those that developed bipedalism survived 2. Tool use: bipedalism freed arms for the use of tools especially for hunting 3. Relief from heat stress: less of the body area is exposed to the sun 4. Provisioning mates: bipedalism enabled the transport of food to mates and offspring 5. Energy Efficiency: humans walked farther and two legs was more efficient than knuckle walking. d.
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2. Early hominine evolution - 1 Early Material a Primate...

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