number of mutations which occurred in their ancestry lines is even. The probability that an even number of mutations has occurred is y(t) = Pr(si = sj T = t) = (2t) k.21 2) 1/4,2) — 1 + 1 - 2 \ 2t-21 ( u 21 ( 142t 1=0 (4.35) In the continuous time limit, making the substitutions r = t/N