Early Objections to the Theory

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Early Objections to the Theory

• 1. Prevailing idea of inheritance in 1859
  blending
• If factual, then new phenotypic changes would be
  diminished and lost in a few generations.
• Argument
• A red flowered plant appears in a population of
  white flowered plants.
• Hypothetically, might be advantageous (e.g.,
  pollination)
• red x white ? pink flowered plant
• pink x white ? pale pink
• pale pink x white ? pale, pale pink
• Quickly, all back to white

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• Missing in 1859 the particulate nature of
  transmission genetics.
• Particulate inheritance of discrete entities
  (alleles).
• Mendel experimental results published in
  Proceedings of the Brünn Natural History Society
  in 1866.
• Several editions of Origin post-1859, so
  available to Darwin, but generally unknown.

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• 2. The idea that intermediate structures would
  lack adaptive functionality.
• E.g., eyes (too complex to have advantageous
  intermediates?)

Hypopthetical stages in eye evolution
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Phenotypic variation in eyes of different groups
of mollusks. What it suggests and doesnt suggest.
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Path of light
Squid and octopus
Rods and cones
Convergent evolution Which is the better design?
Mammal
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• 3. An absence of transitional forms?

Transitions between limbed and limbless conditions
Fossils of transitional forms Two paths to
a marine existence
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Transitional forms A dinosaur with tufts
of down-like feathers
Discovered in 1861 Modern feathers and a
dinosaur skeleton. Probably not an ancestor
of modern birds.
B
A.
145-150 mya
C
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A 4-winged dinosaur
B
A
Feathers evolved prior to flight. Feathered
dinosaurs were preadapted for flight.
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3. Persistence of useless (vestigial) structures.
Kiwi
Persistence of rudiments of previously
functional structures
Rubber boa
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A 95 My old transitiona form to legless snakes
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Law of succession modern species most closely
resemble extinct species from the same region.
Extant
Extinct
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• A few examples of molecular evidence for
  evolution.
• Molecular homologies genetic similarities among
  organisms because of shared ancestry.

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Universally shared genetic code
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Differences in the universal genetic code found
in nuclei of some organisms considered
"primitive"
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Molecular Homology A. Peripheral
myelin protein-22 Chromosome 17 A genetic flaw
shared by humans and Chimpanzees What is
most parsimonious explanation for the
shared genetic arrangement?
3 doses
1 dose
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B. Homologous pseudogenes not expressed, not
removed by selection
Originate from processes mRNA Genetic markers
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Relationship between phylogeny and age
of pseudogenes
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• Selective review
• 1. Morphological change in Soapberry bugs.
• What was the natural selector.
• 2. Geospiza fortis.
• What was the selector of beak size?
• Did seed size change?
• What affect did the 1977 drought have on the
  plants of Daphne Major?
• 3. How did the BMP-4 gene produce interspecific
  differences in beak size?