Chu and Ho's recent article in Artificial Life is riddled with errors. In particular, they use a wrong definition of Robert Rosen's mechanism . This renders their “critical assessment” of Rosen's central proof null and void.

In a recent article in Artificial Life , Chu and Ho suggested that Rosen's central result about the simulability of living systems might be flawed. This argument was later declared “null and void” by Louie. In this article the validity of Louie's objections are examined.

Some reflections on Robert Rosen, Chu and Ho, and Louie.

We previously used simulations of gene expression to demonstrate that rapid activation and deactivation rates stabilized outcomes in stochastic systems. We hypothesized that transient single allele inactivation of an autosomal gene during gametogenesis or very early embryogenesis could have a selective advantage if it permits the functional sampling of each allele and precludes committing maternal effort to an embryo with a deleterious mutation. To test this hypothesis, we simulated the evolution of gene expression activation and deactivation rates and imposed two different selective pressures on the populations: (a) late selection against individuals that cannot maintain a threshold level of gene product that occurs after the investment of maternal effort (i.e., after birth); or (b) early selection: in addition to late selection, maintenance of the gene product above a threshold level was necessary for early development prior to commitment of maternal effort. We found that the opportunity to save reproductive effort from early selection caused the evolution of higher deactivation rates and lower activation rates than in the late selection condition. Thus, we predict that in the special case where early selection can save maternal investment in non-viable offspring, gene expression activation rates and deactivation rates might be selected to permit sampling of the product from each allele.

This letter presents a range of complex patterns, some that seem eerily lifelike, that were produced from some simple algorithms. Some observations are offered that suggest the algorithms are modeling some natural processes.