Citation
Developmental basis of limblessness and axial patterning in snakes
TL;DR
Snake body plans evolved through Hox expression changes, not gene changes
This paper demonstrates how snake body plans evolved through changes in Hox gene expression patterns rather than changes to the Hox genes themselves. Snakes retain functional Hox genes but have changed the regulatory logic determining where developmental programs activate.
This is a powerful example of modular evolvability: dramatic phenotypic innovation (limbless body plan with hundreds of vertebrae) achieved by reconfiguring existing modules rather than inventing new ones. The organizational parallel is clear - companies can achieve strategic transformation by reconfiguring existing capabilities rather than building everything anew.
Key Findings from Cohn & Tickle (1999)
- Snake body plans evolved through Hox expression changes, not gene changes
- Trunk identity extends along most of the body axis
- Limb development is suppressed in regions where other tetrapods develop forelimbs
- Snakes retain functional Hox genes - only regulatory logic changed