The evolutionary relationships between Ar. kadabba and other early hominin species are of great interest to paleoanthropologists. A more recent hominin taxon, Ar. ramidus , which is also found in the Middle Awash of Ethiopia, is argued by some researchers to be a direct descendant of Ar. kadabb a because these two species share many features, such as relatively thin tooth enamel and larger canines. Some researchers further suggest that Ar. kadabba represents the earliest species in a single lineage of descent of East African hominin taxa, starting with Ar. kadabba to Ar. ramidus to Au. anamensis and ending with Au. afarensi s. These species are all found in eastern Africa and some morphological trends, such as the reduction in canine size and premolar morphology, support this hypothesis, but the dates of Ar. ramidus and Au. anamensis (see essay on Ar. ramidus) cast some doubt on this explanation.