Each species belongs to a group or taxon of organisms proceeding from the very general to the very specific. The only objective taxon is the species. Other taxa are defined by shared phenotypic traits. Taxonomic classification is based on homologies. It is the basis for classifying primates.
Phylogenetic relationships help explain why species evolved certain adaptations.
Phylogenetic relationships allow us to compare related species to understand the function of traits. Hominoids divide in the late Miocene. Hominids appeared about 4.5 -4.0 mya.