Controlling for the effect of generation time.

1Cultural rates = 0; Biological rates = 1;Estimates of fixed effects and covariance parameters for the linear mixed model of interaction between rate, type of rate (biological or cultural rates), and time interval. The analysis controls for generation time by calculating rates as the amount of change per generation time (cultural rates are calculated assuming a generation time of 20 years). The test is performed on the logged (ln) values of rates and time intervals. Number of biological rates = 283, number of cultural rates = 573.