154 CHAPTER 7 | The First Bipeds
1.6 meters (3½–5 feet) and 29 and 45 kilograms (64–100
pounds), respectively.^2
If paleoanthropologists are correct in assuming that
larger fossil specimens were males and smaller specimens
females, males were about 1½ times the size of females.
In this respect, they were somewhat like the Miocene
African apes, with sexual dimorphism greater than one
sees in a modern chimpanzee but less than one sees in
gorillas and orangutans. Male canine teeth, too, are signif-
icantly larger than canine teeth of females, though canine
size is reduced compared to that of chimps (Figure 7.6).
Nearly 40 percent complete, the Lucy specimen has pro-
vided invaluable information about the shape of the pelvis
and torso of early human ancestors. The physical appear-
ance of A. afarensis was unusual by human standards: They
may be described as looking like an ape from the waist
up and like a human from the waist down (Figure 7.7). InLucy consists of bones from almost all parts of a single
3.2-million-year-old skeleton discovered in 1974 in the
Afar Triangle of Ethiopia (hence the name afarensis).
Standing only 3½ feet tall, this adult female was named
after the Beatles song “Lucy in the Sky with Diamonds,”
which the paleoanthropologists listened to as they cel-
ebrated her discovery. The Afar region is also famous
for the “First Family,” a collection of bones from at least
thirteen individuals, ranging in age from infancy to
adulthood, who died together as a result of some single
calamity.
At least sixty individuals from A. afarensis (once the
name of a genus has been established, it can be abbrevi-
ated with the first letter followed by the complete spe-
cies name) have been removed from fossil localities in
Ethiopia and Tanzania. Specimens from Ethiopia’s Afar
region are securely dated by potassium argon to between
2.9 and 3.9 mya. Material from Laetoli, in Tanzania, is
securely dated to 3.6 mya. Altogether, A. afarensis ap-
pears to be a sexually dimorphic bipedal species with es-
timates of body size and weight ranging between 1.1 and
Figure 7.7 Trunk skel-
etons of modern human,
A. afarensis, and chimpan-
zee, compared. In its pel-
vis, the australopithecine
resembles the modern
human, but its rib cage
shows the pyramidal con-
figuration of the ape.
Figure 7.6 Sexual
dimorphism in canine
teeth.
(^2) McHenry, H. M. (1992). Body size and proportions in early homi nids.
American Journal of Physical Anthropology 87, 407.