Before Behe wrote Darwin's Black Box Sir Fred Hoyle identified the evolution of the histone H1 protein as problematic for mainstream evolutionary scenarios. Although he did not use the term irreducible complexity the interactive nature of the protein was implicit to his analysis of the evolution of chromatin.
Another Protzoan and Front-Loading nominates a candidate for a front loading process. In this election year we are sometimes painfully reminded that candidates do not reveal detailed plans for processes effecting outcomes promised in stump speeches. This is not unlike the evolution of irreducibly complex systems.
Telic Thoughts commenter Rock had this to say recently:
As Mike pointed out one can remove H1 from a particular metazoan and retain viability for that particular organism. But if presently observed genomic features in complex organisms resulted from a series of steps constituting a process, then one could reasonably argue that there are steps within the process that were essential to maintaining the integrity of the process itself. We may not be able to identify the steps themselves even if general ideas about them are put forth. But since when have detailed pathways to irreducibly complex systems become a sina quo non for METers?
Rock's approach has the advantage of viewing IC on a process level as opposed to a parts perspective. Part x may be dispensible for organism y but the presence of x and some favorable genomic circumstances may be evidence for front loading. FL in turn may explain a histone complex the way loaded dice are able to explain outcomes resistent to standardized dice rolls.