Lecture 18: Hominines
The “great apes” are a “family” within the “order” of primates. They are
large, intelligent, tailless primates. The family includes chimpanzees, gorillas,
orangutans, gibbons, and humans as well as many extinct species. The great
apes evolved in Africa about 18 million years ago, though some eventually
migrated to other parts of Eurasia. Only in recent decades have we begun
to realize how complex their social lives are, through the pioneering work
of researchers such as Jane Goodall (1932–) and Dian Fossey (1932–1985),
who studied the great apes in their own
environments. The striking similarities
between us and the great apes persuaded
Darwin that we were closely related.The “hominines” (or “hominids”) are a
“subfamily” of apes that walked upright.
They evolved 7 million years ago. This
date is based on comparisons of the genetic material of modern great apes,
because we have few fossils from this era. Genetic evidence suggests that the
human line split from the chimp line about 7 million years ago, and from the
gorilla line about 8–10 million years ago. The hominines diverged rapidly in
a new “radiation” that may have included 20 or 30 distinct species. However,
today, we are the only survivors of this diverse group of great apes. In recent
decades many hominine fossils have turned up, and these show that the ¿ rst
hominines were characterized not by large brains, but by bipedalism—the
ability to walk on two legs.Why bipedalism? We have no conclusive answers. The creation of the
African Rift Valley beginning 15 million years ago raised mountains that
left much of East Africa in a rain shadow and reduced forest cover. French
researcher Yves Coppens suggested that bipedal species would have found
it easier to travel through the resulting grasslands and to see dangers and
opportunities as they did so. Unfortunately, the recent discovery of hominine
species in forested environments has undermined this promising idea.In what follows, we will focus on just three major groups of hominines. The
“australopithecines” were a large and varied group of hominines that lived
from about 4 million to about 1 million years ago. They include Lucy, whose
remains are described in the next lecture. Australopithecines were bipedal,In short, we are eukaryotic,
multi-celled mammals
from the order of primates.