Table 1 Demographic model, current effective population size, and generations since the most recent common ancestor (MRCA) or time since expansion event. Numbers in parentheses are 95% confidence intervals; numbers following ± are standard deviations. We present different measures of variance depending on the methods used to calculate the population mutational parameter θ that in turn depended on the demographic model. *N*
_{e} was calculated from θ = *N*
_{e}μ. We used programs to estimate θ under different models: exponential growth and constant model [FLUCTUATE (22)], stepwise growth [GENIE (23)]. Time to *N*
_{e} < 100 was calculated for the world population using the formula*N*
_{e} =*N*
_{o}
*e*^{-r}
^{t}
. TMRCA was calculated for Asia and South America in GENETREE (28). Time to expansion for Africa and Papua New Guinea was estimated using τ (14).