Hum Hist handout 2

Hum Hist handout 2 - Human History Week 2, lecture 2 Human...

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Human History Week 2, lecture 2 Human evolution 1/14/10 Gould’s lottery 440 million years ago, 25% of all biological families and 65% of species go extinct 4 more mass extinctions follow Stephen Jay Gould suggests mass extinctions make biology a lottery; survivors are not “better” Gould’s conclusion—if we reran the last 500 million years, it’s very unlikely that humans would be here Another way to see things: evolution—and pre-biological development of universe—is full of lotteries, but lotteries are repeated, generating random results, but cumulative effects of lotteries are predictable, skewing complexity rightward Catastrophes shuffle the deck, just as sexual reproduction mixes genes The age of mammals About 100 million years ago small mammals evolve but can’t compete well with dinosaurs—until catastrophe 65 million years ago Dinosaurs unable to adapt; mass extinction followed by mammals proliferating, mutating, filling empty niches Primates evolve across 55-35 million years ago in warming period
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Hum Hist handout 2 - Human History Week 2, lecture 2 Human...

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