Evolution as a Random Walk on a High-Dimensional Manifold Defined by Physical Law: Implications for Open-Ended Artificial Life

This short article presents a discussion of the underlying conditions under which natural evolution of life occurs and how these natural conditions may be extremely difficult to implement in artificial life (ALife) systems. In particular, the Darwinian concept of adaptation via natural selection may not have a complete or functional macro-level description that could be used to build any evolutionary environment that is defined at the agent-environment interaction level. Here we are specifically addressing open-ended evolution (Ruiz-Mirazo et al., 2004) in artificial systems (Standish, 2003; Nolfi, 2012; Mouret and Doncieux, 2012). One of the goals of ALife is to generate systems capable of sustained evolution of life-like complexity. Such systems, although artificial, could then be considered to produce real life of a kind (Pattee, 1987; Ray, 1993), as opposed to being just simulations of life. For evolutionary computing applications aimed at solving particular problems, a well-defined goal that is separate from survival in and of itself can be formalized into a selection criterion and used to evolve solutions (Oduguwa et al., 2005). However, in the case of open-ended evolution, many researchers now accept that agent-level definitions of fitness are unsuitable to drive differential selection and replication (Lynch, 2007; McShea, 1991; Lehman and Stanley, 2011). This includes even the most unbiased and high-level implicit fitness criteria in which replication is seemingly made to be a direct result of agent interaction with the environment (see for example Yaeger, 1994). Interestingly, concerns about the adequacy of neo-Darwinian and Darwinian theory to fully describe the evolution of life have come from several ALife researchers, often after attempting to implement evolvin