Reducible complexity. In contrast to Behe's claims, many proteins can be deleted or mutated and the flagellum still works, even though sometimes at reduced efficiency. In fact, the composition of flagella is surprisingly diverse across bacteria with many proteins only found in some species but not others. Hence the flagellar apparatus is clearly very flexible in evolutionary terms and perfectly able to lose or gain protein components. Further studies have shown that, contrary to claims of "irreducible complexity", flagella and related protein transport mechanisms show evidence of evolution through Darwinian processes, providing case studies in how complex systems can evolve from simpler components. Multiple processes were involved in the evolution of the flagellum, including horizontal gene transfer.