148 CHAPTER 7 | The First Bipeds
The remarkably complete remains of Ardipithecus ramidus have allowed paleoanthropologists to
begin to reconstruct the biology and lifeways of the early forest dwelling hominins. When the first
“Ardi” remains were discovered in the early 1990s she was placed on a side branch of human
evolution but scientific investigation of this remarkable skeleton has lead paleoanthropologists to
suggest she is a direct ancestor to the human line.
Figure 7.4 The bipedal gait in some regards is really “serial monopedalism” or locomotion one foot
at a time through a series of controlled falls. Note how the body’s weight shifts from one foot to the
other as an individual moves through the swing phase to heel strike and toe off.the other leg is moving forward through the swing phase
of walking.
The most dramatic confirmation of our ancestors’
walking ability comes from Laetoli, Tanzania, where,
3.6 mya, two (perhaps three) individuals walked across
newly fallen volcanic ash. Because it was damp, the ash
took the impressions of their feet, and these were sealed
beneath subsequent ash falls until discovered by chemist
Paul Abell in 1978. Abell was part of a team led by Brit-
ish paleoanthropologist Mary Leakey in search of human
origins at Laetoli (see Anthropologists of Note). The shape
of the footprints and the linear distance between the heel
strikes and toe offs are quite human.
Once bipedalism is established in a fossil speci-
men, paleoanthropologists turn to other features, such
as the skull or teeth, so that they can begin to establish
relationships among the various fossil groups. Often schol-
ars bring different interpretations to the fossil evidence.Ardipithecus
Made famous through the partially complete 4.4-million-
year-old skeleton specimen “Ardi,” the genus Ardipithecus
has dramatically changed what is known about the earli-
est bipeds. The genus is actually divided into two species,
Ardipithecus ramidus and the older Ardipithecus kadabba
dated to between 5.2 and 5.8 mya. The Ardipithecus
remains show that some of the earliest bipeds inhabited
a forested environment much like that of contemporary
chimpanzees, bonobos, and gorillas; these remains were
found in fossil-rich deposits along Ethiopia’s Awash© T. White