Weak A-Life approaches, on the other hand, don’t presume the ontological equivalence of structurally similar circuits and cells. Instead, proponents suggest the more modest goal of developing a deeper understanding of life as we know it by exploring the effects of various parameters in simulations, effectively placing life in a broader context of possible biology (Langton 1989, 1995). For example, in the Terra program, software was pitted against other software for processing power (Ray 1993). Unexpected by the researchers at the time, software parasitism evolved: software would co-opt the reproductive processing of other software. Policing mechanisms also evolved, leading to an arms race between free-riders and the software trying to stop them.