Verhulst Factor

For VB runs, the birth rate was reduced to B = 3 to avoid extinction caused by overpopulation-driven newborn mortality. Verhulst mortality is random with respect to genotype and cannot distinguish good from bad genomes. The Verhulst factor regulates population through an age-independent survival probability based on population size and carrying capacity. The Verhulst factor is defined as one minus the ratio of the current population to the maximum allowed population. The study also tested an implementation where Verhulst deaths were limited to newborns. Low p can make the model's steady-state behavior depend on a population-control mechanism outside the core recurrence. The combination model may be unstable at low p without adding a Verhulst factor.