Final answer:
Ardipithecus ramidus may not be considered a hominin due to its uncertain status as a human ancestor and conflicting locomotion characteristics. Further research is needed to determine its relationship to modern humans.
Step-by-step explanation:
Ardipithecus ramidus may not be considered a hominin due to its uncertain classification as a human ancestor. While Ardipithecus was bipedal based on the forward position of the foramen magnum and other skeletal traits, it also possessed characteristics that suggest quadrupedal locomotion. The status of Ardipithecus as a human ancestor is still uncertain, and further research is needed to determine its evolutionary relationship to modern humans.