Hair is unique to mammals. Keratin associated proteins (KRTAPs) are one of the major components of hair and play essential roles in the formation of rigid and resistant hair shafts. The important aspect of hair evolution is the considerable reduction in hair cover in adult humans during their recent history (after humans-African apes split) but, humans actually have a similar density of hair follicles to that seen in apes. Evolutionary patterns that potentially account for morphological characteristics suggest the genetic basis for variation in phenotypes. Under this circumstance, the present paper attempted to understand the variation of primate hair with regard to cross sectional character of ultrastructure on the basis of Scanning Electron Microscopy (SEM). To achieve the purpose hair strands (125 each) from adult male non-human primates Papio hamadryas [representing Catarrhine (OWM)] and Cebus albifrons [representing Platyrrhine (NWM)] was taken for SEM using standard technique. Examination on ultrastructure revealed significantly (p<0.05) higher values for major axis, minor axis, cross section area and hair index in accordance with higher phylogenetic position among the primates. Furthermore, the present study also found more flattened elliptical pattern in Cebus comparison to Papio on the basis of in terms of hair index.