Here is the killer question: Is evolution ergodic? Like statistical mechanics, evolution links the random microscopic world (gene mutations) with the macroscopic world (the shape and function of living things). If evolution is ergodic — that is, if the trajectory of the evolution of a species behaved in its “phase space” of possibilities the way molecules in a coffee cup do — then we might be able to predict evolutionary outcomes. We could know in advance what evolution would lead to. We even might be able to tell that, in principle if not in practice, circumstances on exoplanet XB4-27A will lead to humanoid looking creatures (but with pointy ears of course).

So, is evolution ergodic? Will it explore all its crazy hyperdimensional phase space? For many researchers, the answer is an emphatic no. Stuart Kauffman, for example, makes the absence of ergodicity in evolution the central point of a lot of his work on life. For Kauffman, the most important aspect of evolution is its path dependence, its history. Run the history of the Earth over again and you would get something different. As Kauffman puts it:

“Even more profoundly, the evolution of life in our biosphere is profoundly ‘non-ergodic’ and historical. The universe will not create all possible life forms. Non-ergodicity gives us history.”