The Developmental Theory of Feather Evolution

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The Developmental Theory of Feather Evolution

• By Jesse Seale

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• Feathers are complex hierarchal structures with
  multiple interacting parts necessary for function
  (for example interlocking barbules and
  asymmetrical rachis in flight feathers)

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• Because feathers are novel structures we see no
  evidence of their evolutionary history in other
  animals
• Because feathers are so well adapted we see no
  evidence of their evolutionary history in extant
  birds ( all primitive forms are secondarily
  derived)
• Archaeopteryx shows advanced asymmetrical flight
  feathers

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• Since a feathers function relies on its complex
  structure how did it get there?
• What where its primitive forms?
• How can we know this?

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• Developmental evolution seeks to reconstruct
  evolutionary history from observable
  developmental pathways.
• Prum and Brush in 2002 used this theory to
  construct an evolutionary model for feather
  evolution.
• Theory is supported by paleontological evidence
  and morphological evidance.
• Sound criticism of fossil evidence.
• But, it is the most logical theory so far

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Feather Morphogenesis