  Following extensive numerical experiments, it has been suggested that the
evolution of competing computer programs in artificial life simulations shows
signs of being a self-organized critical process. The primary evidence for this
claim comes from the distribution of the lifetimes of species in the
simulations, which appears to follow a power law. We argue that, for a number
of reasons, it is unlikely that the system is in fact at a critical point and
suggest an alternative explanation for the power-law lifetime distribution.
