Evolutionary Thought Before Darwin

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Evolutionary Thought Before Darwin

• Species created as they appear today
• Adaptations conferred by Designer
• Earth and living things unchanging
• Affirmed special status of humans highest link
  in the chain, to whom dominion over the rest of
  nature had been granted

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Charles Robert Darwin (1809-1882)

• Son of an English physician
• Studied medicine at Edinburgh but could not
  stomach 19th century surgery
• Began a career in the clergy
• 1831 - received invitation to serve
  as naturalist on the H.M.S. Beagle
• 5 year journey around South America
• - most notable Galapogos Islands

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Charles Darwin
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Darwin and Alfred Wallace

• Mid-1800s Darwin and Wallace independently came
  up with natural selection
• Ultimately lead to publication in 1859 of
• On the Origin of Species by Means of Natural
  Selection by Darwin

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• if variations useful to any organic being ever
  occur, assuredly individuals thus characterised
  will have the best chance of being preserved in
  the struggle for life and from the strong
  principle of inheritance, these will tend to
  produce offspring similarly characterised. This
  principle of preservation, or survival of the
  fittest, I have called natural selection.

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Darwins Ideas

• Populations possess an enormous reproductive
  potential but population sizes remain constant.
• Resources are limited and individuals must
  compete for survival.
• There is variation among individuals of a species
  and this is inherited.
• Only the most fit individuals survive because
  individuals with traits best ADAPTED for survival
  will out compete other individuals for resources.
• The best adapted will leave more offspring.

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Galapogos Finches
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• Evolutionary success defined by survival and
  reproduction

Success of particular variants is NOT
absolute, but dependent on prevailing
environmental conditions!!
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Evidence of Evolution

• Organisms have genetic variation
• Fossil record
• Comparative anatomy - similar structures in
  different organisms
• Vestigial structures
• DNA comparison
• Embryo development

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Fossil Record
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Horse Evolution
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Comparative Anatomy
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Vesitigal Structures

• If organisms are not descended from common
  ancestors then why the presence of vestigial
  structures?
• For example
• - appendix
• - tailbones
• - wisdom teeth
• - pelvic girdle

Snake Whale
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Comparative Biochemistry
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Yeast (Fungi)
of amino acids different from human
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Embryo Development
Fish
Human
Lizard
Chicken
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Direct Observations
Biston betularia (peppered moth)
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Direct Observations
Results show that in areas of high pollution
more dark-colored moths recovered low
pollution more light-colored moths recovered