T H E
E V O L U T I O
N O F M A N
Australopithecus afarensis
Australopithecus afarensis is one of the longest-lived and best-known early
human species—paleoanthropologists have uncovered remains from more than
300 individuals! Found between 3.85 and 2.95 million years ago in Eastern Africa
(Ethiopia, Kenya, Tanzania), this species survived for more than 900,000 years,
which is over four times as long as our own species has been around.
Homo habilis
This species, one of the earliest members of the genus Homo, has a slightly larger
braincase and smaller face and teeth than in Australopithecus or older hominin species. But it
still retains some ape-like features, including long arms and a moderately-prognathic face.
Its name, which means ‘handy man’, was given in 1964 because this species was
thought to represent the first maker of stone tools. Currently, the oldest stone tools are dated
slightly older than the oldest evidence of the genus Homo.
Homo erectus
Early African Homo erectus fossils (sometimes called Homo ergaster) are the oldest
known early humans to have possessed modern human-like body proportions
with relatively elongated legs and shorter arms compared to the size of the torso. These
features are considered adaptations to a life lived on the ground, indicating the loss of
earlier tree-climbing adaptations, with the ability to walk and possibly run long
distances. Compared with earlier fossil humans, note the expanded braincase relative to
the size of the face.
Homo erectus
The most complete fossil individual of this species is known as the ‘Turkana Boy’ – a
well-preserved skeleton (though minus almost all the hand and foot bones), dated around
1.6 million years old. Microscopic study of the teeth indicates that he grew up at a
growth rate similar to that of a great ape. There is fossil evidence that this species cared
for old and weak individuals. The appearance of Homo erectus in the fossil record is
often associated with the earliest handaxes, the first major innovation in stone tool
technology.
Homo neanderthalensis
Neanderthals (the ‘th’ pronounced as ‘t’) are our closest extinct human relative. Some
defining features of their skulls include the large middle part of the face, angled cheek
bones, and a huge nose for humidifying and warming cold, dry air. Their bodies were
shorter and stockier than ours, another adaptation to living in cold environments. But
their brains were just as large as ours and often larger - proportional to their brawnier
bodies.
Neanderthals made and used a diverse set of sophisticated tools, controlled
fire, lived in shelters, made and wore clothing, were skilled hunters of large
animals and also ate plant foods, and occasionally made symbolic or
ornamental objects. There is evidence that Neanderthals deliberately buried
their dead and occasionally even marked their graves with offerings, such as
flowers. No other primates, and no earlier human species, had ever practiced
this sophisticated and symbolic behavior.
Homo sapiens
The species that you and all other living human beings on this planet belong
to is Homo sapiens. During a time of dramatic climate change 300,000 years
ago, Homo sapiens evolved in Africa. Like other early humans that were
living at this time, they gathered and hunted food, and evolved behaviors
that helped them respond to the challenges of survival in unstable
environments.
Anatomically, modern humans can generally be characterized by the lighter build of their
skeletons compared to earlier humans. Modern humans have very large brains, which vary
in size from population to population and between males and females, but the average size
is approximately 1300 cubic centimeters. Housing this big brain involved the
reorganization of the skull into what is thought of as "modern" -- a thin-walled, high vaulted
skull with a flat and near vertical forehead. Modern human faces also show much less (if
any) of the heavy brow ridges and prognathism of other early humans. Our jaws are also
less heavily developed, with smaller teeth.
