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Evolution Controversies. 19 September 2016. Evolution. Observation: That life changes through time Mechanism: Variation, inheritance, selection; Darwin called this ‘ natural selection ’ or ‘ survival of the fittest ’ Example: Index fossils. In a narrow layer, from a brief time
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Evolution Controversies 19 September 2016
Evolution • Observation: That life changes through time • Mechanism: Variation, inheritance, selection; Darwin called this ‘natural selection’ or ‘survival of the fittest’ • Example: Index fossils. In a narrow layer, from a brief time • Consider ‘pop tops’
Evidence for Evolution • Vestigial organs • Intermediate forms, like archeopteryx • Convergent evolution: different history to same point • Even cars evolve, because customers select most appealing characteristics • But cars are designed, can we argue for ‘intelligent design’?
Archeopteryx is an intermediate form between reptiles and birds
Melanism in British Peppered Moths • Birds are their major predator • They settled on light, lichen-covered trees • In 1848, less than 1% were dark • But industrial revolution pollution killed the lichens, leaving dark trees • In 2000, more than 95% were dark • With pollution laws, now number of light moths increasing • This shows how air pollution drives evolution
Rabbits and Myxomatosis • Rabbits are not native to Australia • In 1859, 12 wild European rabbits introduced • By 1886, spreading at 66 mi/year: Reached both coasts by 1907 • Nothing could stop the plague of rabbits; fencing, hunting, trapping did not work; they ate grass needed for sheep and cattle • Solution: mosquito-borne virus called myxomatosis : 1952 epidemic killed 99.9%
What happened next? • Viruses that were less deadly were selected, because their victims could infect others. The deadly ones killed the host, and left no descendants • Rabbits were also selected for greater resistance • Today, mortality is only 40% • All is explained by evolution of both virus and rabbit
Convergent evolution of Mammals and marsupials
Problems for Evolution • Not: Age of Earth, it is 4.5 billion years old. But… • Low probabilities: like a tornado going through a junk yard, leaving behind a 747; small changes to proteins and they don’t work • Gradualism: Gradual changes not seen in the fossil record: long stability, then sudden jump. Can we make a new species gradually? • Complexity: is it irreducible? Examples: human eye, blood clotting requires 12 chemical factors: one missing means hemophilia
Replies to evolution questions • Low probabilities: Evolution is not random, selection works only on a useful subset; many other possibilities might work as well, remember convergent evolution on Earth • Gradualism: Fossil record is too poorly preserved; speciation takes longer than a human lifetime; but big random events may be needed • Complexity: Intermediate steps are actually useful; existing genes may be put to new uses; gradually improved; life may be like a Rube Goldberg machine, complicated, but it works
Summary • Evolution is more than ‘just a theory’ • It is an established explanation, universally applied; arguments over details • Creationism is not science: an attempt to use scientific arguments to prove the Bible • Intelligent design is not required: Evolution is like a ‘blind watchmaker’ • But problems still: we can’t explain everything yet! Life found elsewhere could provide info