The Ape’s Reflection? 363In the Miocene, apes were more diverse and successful than the monkeys and occa-
sionally were found in Europe as well as their African homeland. By the middle Miocene,
primitive members of the orangutan lineage (Sivapithecus) are known from deposits dated at
12 million years old in Pakistan, giving us some of the first ape fossils that belong to modern
lineages. Unfortunately, we have lots of fossil apes but no clear-cut fossils of the chimpan-
zee or gorilla clan just yet, probably because both of these apes have always lived in forests
where there is scant chance of fossilization. Most of the fossil apes declined and died out by
the end of the Miocene, and Old World monkeys came to dominate the primate adaptive
zones ever since then.
The oldest specimen that can be truly described as a member of our own family was
discovered and described only a few years ago. Nicknamed “Toumai” by its discoverers, its
formal scientific name is Sahelanthropus tchadensis. The best specimen is a nearly complete
skull (fig. 15.5A) from rocks about 6–7 million years in age from the sub-Saharan Sahel
region of Chad (Brunet et al. 2002). Although the skull is very chimp-like with its small size,
small brain, and large brow ridges, it had remarkably human-like features, with a flattened
face, reduced canine teeth, enlarged cheek teeth with heavy crown wear, and an upright
posture at the very beginning of human evolution. Just slightly younger is Ororrin tugenen-
sis, from the upper Miocene Lukeino Formation in the Tugen Hills in Kenya, dated between
5.72 and 5.88 million years ago. Ororrin is known mainly from fragmentary remains, but the
teeth have the thick enamel typical of early hominins, and the thigh bones and shin bones
clearly show that it walked upright. Slightly younger still are the remains of Ardipithecus
ramidus kadabba, found in Ethiopian rocks dated between 5.2 and 5.8 million years ago.
These consist of a number of fragmentary fossils, but the foot bones show that hominins
used the “toe off” manner of upright walking as early as 5.2 million years ago. Thus our
human lineage was well established by the latest Miocene and fully upright in posture,
even though our brains were still small and primitive and our body size not much different
than that of contemporary apes.
The Pliocene saw an even greater diversity of hominins (fig. 15.3), with a number of
archaic species overlapping in time with the radiation of more advanced hominins. Archaic
relicts of the Miocene included Ardipithecus ramidus ramidus, found in Ethiopia in 1992 from
rocks 4.4 million years in age, which had human-like reduced canine teeth and a U-shaped
lower jaw (instead of the V-shaped lower jaw of the apes). Nearly complete skeletal mate-
rial of this species has now been discovered and reported by Tim White and his colleagues,
making it the oldest known fossil hominin skeleton. Rocks in Kenya about 3.5 million years
in age yield primitive forms like Kenyapithecus platyops. By 4.2 million years ago, however,
the first members of the advanced genus Australopithecus, the most diverse member of our
family in the Pliocene, are also found. The oldest of these fossils is Australopithecus anamensis
from rocks near Lake Turkana in Kenya ranging from 3.9 to 4.2 million years in age. These
creatures were fully bipedal, as shown not only by their bones but also by hominin track-
ways near Laetoli, Tanzania. The most famous of these early australopithecines is A. afarensis
(from rocks 3.0–3.4 million years ago near Hadar, Ethiopia), better known as “Lucy” by its
discoverers Don Johanson and Tim White (figs. 15.2 and 15.6A). When it was discovered
in the 1970s, Australopithecus afarensis was the first early hominin to clearly show a bipedal
posture (based on the knee joint and pelvic bones) but was not as upright as later hominins.
These were still small creatures (about 1 meter or 3 feet tall) with small brains, and very ape-
like in having large canine teeth and a large overhung jaw.