Protein engineers turned evolutionists.

When generating novel tailor-made proteins, protein engineers routinely apply the principles of 'Darwinian' evolution. However, laboratory evolution of proteins also has the potential to test evolutionary theories and reproduce evolutionary scenarios, thus reconstructing putative protein intermediates and providing a glimpse of 'protein fossils'. This commentary describes research at the interface of applied and fundamental molecular evolution, and provides a personal view of how synergy between fundamental and applied experiments indicates novel and more efficient ways of generating new proteins in the laboratory.