Extended Data Fig. 4: Roulette predicts the rate of triallelic SNVs.

Multiple derived alleles could co-occur in the same genomic site. Using Roulette, we predicted the probability of a site containing two derived variants simultaneously (triallelic site) by multiplying the probabilities of each derived allele (this is the correct procedure if derived alleles accumulated independently). In contrast to early studies of multiallelic variants, we do not find deviation from independence.