Cenozoic Earth and Life History - The Changing Earth: Exploring Geology and Evolution - page 668

Millions of years ago
3

7 6 5 4 2 1 0

Sahelanthropus tchadensis

Orrorin tugenensis

Ardipithecus ramidus kadabba

Ardipithecus ramidus ramidus

Australopithecus anamensis

Australopithecus afarensis

Australopithecus africanus

Australopithecus boisei

Australopithecus robustus

Homo habilis

Homo erectus

Homo sapiens

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Figure 23.31 The Stratigraphic Record of Hominids The geologic ranges for the commonly
accepted species of hominids (the branch of primates that includes present-day humans and their
extinct ancestors).

ways. Its brain size of 800-1300 cc, although much larger
than that of H. habilis, was still less than the average for
Homo sapiens (1350 cc). The skull of H. erectus was thick
walled, its face was massive, it had prominent brow ridges,
and its teeth were slightly larger than those of present-day
humans. H. erectus was comparable in size to modern hu-
mans, standing between 1.6 and 1.8 m tall and weighing be-
tween 53 and 63 kg.
The archaeological record indicates that H. erectus was
a tool maker. Furthermore, some sites show evidence that its
members used fi re and lived in caves, an advantage for those
living in more northerly climates (Figure 23.36).
Debate still surrounds the transition from Homo erectus
to our own species, Homo sapiens. Paleoanthropologists are
split into two camps. On the one side are those who support
the “out of Africa” view. According to this view, early mod-
ern humans evolved from a single woman in Africa, whose
offspring then migrated from Africa, perhaps as recently as
100,000 years ago, and populated Europe and Asia, driving
the earlier hominid population to extinction.
The alternative explanation, the “multi-regional”
view, maintains that early modern humans did not have an
isolated origin in Africa, but rather they established separate
populations throughout Eurasia. Occasional contact and
interbreeding between these populations enabled our species
to maintain its overall cohesiveness while still preserving the
regional differences in people that we see today. Regardless of
which theory turns out to be correct, our species, H. sapiens,
most certainly evolved from H. erectus.

1.8 million years ago, but also in Europe ( Figure 23.36), India,

China (“Peking Man”), and Indonesia (“Java Man”).
Although H. erectus developed regional variations in
form, the species differed from modern humans in several

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