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Natural Selection Wasn’t As Readily
Accepted As Evolution
• Age of the Earth
• Genetics
– How does variation arise?
– How are traits inherited?
Age of the Earth
• Biblical: Archbishop James Ussher (1664)
– Earth was created at 9 a.m. on Oct. 26,4004 B.C.
• Lord Kelvin(1860’s)
– Based on rate of cooling of the Earth & Sun
– Earth is a maximum of 25-20million yrs. old
Radiometric dating
Earth is approximately 4.5 Billion years old
Oldest fossils are 3.5 Billion years old
Darwin had no knowledge
of genetics
• Without mutation, heritable variation would
run out
• “Blending Inheritance”
1900’s: Mendel’s Work
Rediscovered
• Mutationists (Mendelists):
– William Bateson, Thomas Hunt Morgan
• Biometricians (Darwinists):
– Karl Pearson, Francis Galton
The Modern Synthesis
• R.A. Fisher, Sewall Wright, J.B.S. Haldane
• Gradual evolution results from small genetic changes
that are acted upon by natural selection
• The origin of species and higher taxa
(macroevolution) can be explained in terms of
natural selection acting on individuals, or
microevolution
Darwin’s postulates restated
• As a result of mutation and genetic recombination,
individuals within populations are variable for many
traits
• Individuals pass their alleles on to their offspring intact
• In every generation, some individuals are more
successful at surviving and reproducing than others
• The individuals that survive and reproduce, or who
reproduce the most, are those with the alleles and
allelic combinations that best adapt them to their
environment