TT.TTo

By counting the number of derived variants in two samples of size two (one sample of size two from each of the two sub-populations) in a simple split model (see figure), TT estimates all parameters. Specifically, each split time (in generations scaled by the mutation rate) is estimated separately. TT assumes a model with a constant ancestral population size (NA in the figure). TTo alleviates this assumption but requires an appropriate outgroup.