Within the primate sub-clade, three separate clusters of IFITM1, IFITM2, and IFITM3 were observed. The IFITM1 cluster contains the sequences from all analyzed primates, excluding marmoset and orangutan, and is located at the basal position of the primate sub-clade, indicating that IFITM1 separated earlier than other IR-IFITM genes, including IFITM2 and IFITM3, during the primate evolution. The IFITM2 and IFITM3 clusters only contain sequences from three hominids (human, chimpanzee and gorilla), indicating that IFITM2 and IFITM3 originated prior to the separation of these three hominids.