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Embryo Cells Set Patterns for Growth by Pushing and Pulling
Patterns that guide the development of feathers and other features can be set by mechanical forces in the embryo, not just by gradients of chemicals.
Ancient Turing Pattern Builds Feathers, Hair — and Now, Shark Skin
A primordial developmental toolkit shared by all vertebrates, and described by a theory of the mathematician Alan Turing, sets the growth pattern for all types of skin structures.