The Developmental Theory of Feather Evolution

By Jesse Seale

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

• 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

• Since a feathers function relies on its complex structure how did it get there?

• What where its primitive forms?• How can we know this?

• 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

Feather Morphogenesis