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 eμ. 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 formulaN 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).

PopulationModelμ (× 10−9) 5 Ma 7 MaNecurrent (× 105)Generations
GlobalExponential4.916.72 ± 0.51160,000 ± 29,000
6.884.79 ± 0.36110,000 ± 20,000
South AmericaConstant4.91 0.55 ± 0.14110,000 ± 38,000
6.880.39 ± 0.10 77,000 ± 27,000
AsiaConstant4.911.16 ± 0.36  94,000 ± 35,000
6.880.83 ± 0.28 68,000 ± 25,000
AfricaStepwise4.911.49 (1.06–2.17) 30,000 (6,000–42,000)
6.881.06 (0.76–1.55)21,000 (4,000–29,000)
Papua New GuineaStepwise4.910.53 (0.30–1.05) 38,000 (0–61,000)   
6.880.38 (0.22–0.75)27,000 (0–43,000)