Ardipithecus is an early humanlike creature known from fossils found in northern Ethiopia. The fossils are about 4.4 million to 5.8 million years old. Scientists recognize two species (kinds) of Ardipithecus: Ardipithecus ramidus and Ardipithecus kadabba. Ardipithecus is a type of hominin. In scientific classification, hominins are the group that includes human beings and early humanlike ancestors. Scientists think that hominins evolved (developed over time) from an apelike common ancestor, shared with modern African apes, between 10 million and 7 million years ago. Ardipithecus lived soon after this evolutionary split.
The first fossils of Ardipithecus were discovered in 1992. After years of preparation and study, scientists in 2009 described these and other fossils that had been excavated, including a partially complete Ardipithecus skeleton with skull. Certain features of the teeth suggest that Ardipithecus is possibly an ancestor to the australopithecines. The australopithecines are a group of humanlike creatures that appeared in Africa about 4 million years ago. Most notably, Ardipithecus has small canine teeth, which are only slightly larger in males than in females. The fossils also indicate that these creatures were in the early stages of developing bipedalism (movement by walking upright on two legs). But they still retained apelike features, including a big toe adapted for grasping. Ardipithecus probably lived in a woodland environment. The anatomy suggests that Ardipithecus moved about on four limbs in the trees but also walked upright on the ground.
Ardipithecus is thought to resemble the last common ancestor between human beings and the African apes. However, the fossils show a mix of physical characteristics. Some features appear more humanlike, while others are more apelike or even monkeylike. This combination suggests that the last common ancestor of African apes and hominins did not exactly resemble living African apes or human beings. Both African apes and human beings thus evolved considerably over the past several million years to reach their present forms.
See also Human being (Prehuman ancestors); Prehistoric people (The earliest hominins).
