Anthro Lecture 2-12 - Anthro Lecture 2/12 I The missing...

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Anthro Lecture 2/12 I. The missing data influences accuracy of phylogenetic reconstructions a. Likely to make errors in phylogenetic reconstructions i. Start with diversity of extinct species 1. Suppose known fossils are randomly drawn from extinct species 2. Wrong ii. The missing data can mislead us about phylogeny 1. Draw phylogenetic tree from known fossils 2. Falsely simplifies actual phylogenetic relationships b. Likely to underestimate the age of fossil species i. Imagine an extinct species with known origin and extinction ates ii. Some will become fossils, most will just disintegrate iii. Millions of years later, a few will be found iv. Not likely to find very earliest or very latest fossils, by chance c. Likely to underestimate lifespan of fossil species II. What do we know? a. In general, hominids became more like humans over time, particularly with regard to brain size b. We know a lot about what fossil hominids were doing in the world i. Locomotor patterns (skeleton) ii. Diet (teeth) iii. Habitat (site characteristics) (paleoecology) iv. Social organization (dimorphism) v. Cognitive abilities (artifacts/brain size) c. Think about adaptive shifts in hominid lineage i. E.g. from quadrapedal to bipedal
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ii. Small-toothed to large-toothed and back again iii. Very sexually dimorphic, to slightly dimorphic iv. Slowing life history v. Small brain to larger brain III. Darwin a. As Darwin saw the problem: Just looking at the characters of living species that are detectable in the fossil record: What are the major ape/human differences (What had to change for an ape to evolve into a human?)? b. Differences i. Bipedialsm: great apes are quadrupeds, humans are bipeds ii. Reduction of the canine teeth; loss of diastema, 2 nd cusp on lower front premolar iii. Brain expansion: human brain is triple the size of a chimp’s iv. Reliance on technology (?); shaped stone stools 1. Not really detectable in the fossil record, but in the archaeological record IV.Primates in the Ancient World a. Primates enter the scene, 65 mya i. Over the last 200 my, the earth rearranged itself ii. Continental drift is important part of human history because it changed global climates iii. Temperatures have declined steeply from the Eocene to the present. Huge fluctuations in the last 5 mya.
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