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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’?
Vestigial whale bones
Archeopteryx is an intermediate form between reptiles and birds
The pot top is an index fossil!
Black peppered moth evolved in response to pollution
Melanism in British Peppered Moths
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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?
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
Evolution of the Corvette
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