Maximum likelihood estimates of demographic parameters.

The best-fitting model was selected by comparing the likelihood of four possible models: Gompertz, Gompertz-Makeham, logistic, and logistic-Makeham. The logistic model provided the best fit of the GRZ and MZM-04/10Plate data (likelihood ratio test, P<0.01), but not for MZM-04/10G and MZM-04/03, for which the simpler Gompertz model was used. The a parameter represents baseline mortality, the b parameter represents demographic rate of aging, and the s parameter is the deceleration of the logistic model. Values in parentheses represent 95% confidence intervals. All simulations were performed using WinModest.