By sequencing extensive regions of the beta-globin gene cluster from capuchin monkey (New World monkey) and tarsier (prosimian) we confirmed that capuchin monkey and tarsier have two and one gamma-globin gene(s), respectively. These findings indicate that the ancestral anthropoid gamma-globin gene duplicated after anthropoids diverged from tarsier, but before they diverged into platyrrhines (New World monkeys) and catarrhines (Old World monkeys, apes, and human). The capuchin monkey gamma 1-globin gene promoter region accumulated many nucleotide substitutions, including a T to C substitution in the proximal CCAAT element. This adverse mutation, along with the previous finding that the gamma 1 locus in spider monkey is a pseudogene, suggests that in platyrrhines the gamma 2-globin gene may be the primary fetal beta-like globin gene. The aligned gamma gene sequences contain several conserved sequence elements (phylogenetic footprint) of 6 bp or longer in the 5' flanking region, but none in the 3' flanking region. Gene conversions frequently occurred in the 5' flanking and transcribed regions of the duplicated genes of anthropoids but rarely in the 3' flanking sequences. However, an absence of conversions within the capuchin and spider monkeys promoter regions suggests that in platyrrhines selection acted against conversions as they could decrease (or inactivate) gamma 2 expression.