Figure 5.

Tree that requires the minimal number of amino acid changes at the five critical sites under the constraint of the species phylogeny in Fig. 1. Substitutions along branches are indicated as the ancestral amino acid followed by its position on the complete coding sequence and then followed by the new amino acid. Two equally parsimonious pathways are shown; one pathway is above branches (italics) and one is below branches. A shorter tree (11 steps instead of 12 steps) is obtained if the marmoset and tamarin P556 alleles have a recent origin and was derived from the P562 allele, as indicated by the arrow. However, this alternative tree is less likely (see Results).