This is oddly poignant to me. I just (literally a few hours ago) submitted my PhD thesis on (broadly) the biophysics of emergent phenomena. People don't usually read theses cover to cover, with good reason, but I included one short paragraph in the preface to be the true "take home" message:<p><i>We wish to understand mechanism through the elucidation of design principles, yet evolution does not select for principles, it selects for fitness, an epistatic and emergent property. If similar outcomes can be achieved in different but equivalently fit ways, then given the stochastic nature of evolution this is almost guaranteed to happen. We have specific examples where every statement in the preceding paragraph is true [ed: a collection of proposed mechanisms]. We do not need one person to be right or wrong; our nascent understanding of complex biological systems is that the space of information-processing solutions is astronomical. Think of the diversity observed in structural biology - the repertoire of tertiary structures is enormous. There are countless examples of nearly identical functions being performed by proteins with radically different structure.<p>This divergence, this variety in structure and function, is what makes evolution robust. It is an inherent bet-hedging mechanism woven into the fabric of statistical physics. On the contrary, the desire to categories and abstract complexity into distinct groups is an inherently human endeavour. Much as we may wish and as convenient as it would be, Nature does not have a plan.</i>