Ardipithecus ramidus (4.4 million years ago)*
*Because fossil evidence for Ardipithecus ramidus is
scant, a range of dates for when this species lived is not available.
Ardipithecus ramidus was discovered in December
1992. Although not nearly as old as Orrorin tugenensis, Ar.
ramidus is much more widely accepted by the scientific community as
a hominid than is O. tugenensis, and thus is considered by some to
be the oldest-known hominid.
A partial skeleton and indirect evidence from
skeletal fragments indicate that Ar. ramidus may have walked upright.
Although considered to be one of the most primitive hominids, Ar.
ramidus shares some novel characteristics with much later hominids,
namely aspects of its teeth. The molars of Ar. ramidus are smaller
than are those of any of the Australopithecus species.
Other fossils found with Ar. ramidus suggest that
it may have been a woodland forest dweller. This may modify current theories
about why hominids became bipedal in the first place. Walking upright has
typically been linked to movement onto the savanna.
(Note: This species has not yet been fully described because
some of the specimens have been difficult to extract from the surrounding rock.)
-> Go to Australopithecus anamensis