Human Origins

Primates

Humans are mammals. More specifically we are classified in the order of mammals called primates. Primates are distinguished from other mammals for the following reasons:

their eyes face forward -- the sockets are in the front of the skull. This allows them to see objects stereoscopically --in 3D
highly developed brains
flexible shoulders and rotating fore arms create a great range of movement. Many primates are arboreal (living in trees)
most primates have hands with long slender fingers and an opposable thumb.

These anatomical features allow primates to live in trees, even swing from tree to tree. The dexterity built into the primate hand allows it to make simple tools and manipulate objects in its environment like no other animal.

Humans have the same general features as all other primates.

Biochemical studies have reinforced the anatomical evidence. For instance there is virtually no difference in the amino acid sequence in the hemoglobin of humans and chimpanzees. Chimps can donate their blood to us and only Chimps and humans may be infected with the HIV virus.

Humans are grouped together with the so called great apes found on the African continent. This very select group includes the:

Gibbon
Orangutan
Gorilla
Chimpanzee (two distinct varieties)
Humans

Africa holds the secret to human evolution. Fossils already indicate that over the last 5 million years the number of great ape species was much greater than it is today.

Human Ancestors

Humans and human ancestors are distinguished from the other great apes by the ability to walk upright, supporting the entire weight of the body on just two legs. Organisms with this ability are bipedal. This anatomical adjustment requires several recognizable changes in bone structure from other apes including:

unique hip joint and pelvic girdle
specialization of foot bones
unique angle for the connection between skull and vertebral column

Any primate that is bipedal and has some or all of the anatomical features described above is considered a hominid.

Humans (Homo sapiens) most certainly evolved from a group of hominids living in Africa from 3 to 5 million years ago. One possible lineage is outlined below.

Australopithecus (sp) -- Southern Ape -- 3.9 - 3 million yrs. old

Major Find: Lucy; a nearly complete skeleton (Donald Johanson)
Bipedal -- could walk upright -- footprints found
Small brain comparable to chimp -- 500 cc
Tool making unknown
Found only in Africa

Homo habilis -- handy man -- 2.4 - 1.5 million yrs. old

Found by Louis and Mary Leakey
Bipedal -- taller than Australopithecus (average 5 feet) females obviously smaller than males. Large variation in skeleton may indicate more than one species
Small brain 650 cc. Internal cast of brain similar to modern humans, may have had speech
First Hominid known to make and use tools -- reason for name
Restricted to Africa

Homo erectus -- upright man -- 1.8 million to 300,000 yrs. old

Found -- Java man -- Eugene Dubois
Bipedal -- as tall or taller than Homo habilis (skeletal features variable)
Brain larger still; about 750 - 1225 cc (cubic centimeters)
Used well crafted stone tools and probably used fire
Fossils found throughout Africa, Asia, and Europe

Neanderthal -- Homo sapiens -- 230,000 - 30,000 yrs. old

Found in the Neander Valley Europe
Bipedal -- 5.5 feet tall (possibly shorter than some Homo erectus
Brain as large or larger than modern humans -- average 1450 cc. Skull retains brow ridges - extensive sinus folds for cold conditions
Used well make stone tools, formidible hunters
Lived in groups probably with oral traditions -- buried their dead

Cro-Magnon -- Homo sapiens -- 120,000 yrs. old to present

Found in Europe, Asia, Australia, (Africa)
Fully human in stature, skeletal features become less robust (heavy, thick etc.)
Brain size averages 1350 cc
Used exquisite stone tools
Culture included fantastic cave art, stone sculpture

For an excellent review of many of the hominid fossils visit the following sites

Under Construction

	Australopithecus (sp) -- Southern Ape -- 3.9 - 3 million yrs. old Major Find: Lucy; a nearly complete skeleton (Donald Johanson) Bipedal -- could walk upright -- footprints found Small brain comparable to chimp -- 500 cc Tool making unknown Found only in Africa
	Homo habilis -- handy man -- 2.4 - 1.5 million yrs. old Found by Louis and Mary Leakey Bipedal -- taller than Australopithecus (average 5 feet) females obviously smaller than males. Large variation in skeleton may indicate more than one species Small brain 650 cc. Internal cast of brain similar to modern humans, may have had speech First Hominid known to make and use tools -- reason for name Restricted to Africa
	Homo erectus -- upright man -- 1.8 million to 300,000 yrs. old Found -- Java man -- Eugene Dubois Bipedal -- as tall or taller than Homo habilis (skeletal features variable) Brain larger still; about 750 - 1225 cc (cubic centimeters) Used well crafted stone tools and probably used fire Fossils found throughout Africa, Asia, and Europe
	Neanderthal -- Homo sapiens -- 230,000 - 30,000 yrs. old Found in the Neander Valley Europe Bipedal -- 5.5 feet tall (possibly shorter than some Homo erectus Brain as large or larger than modern humans -- average 1450 cc. Skull retains brow ridges - extensive sinus folds for cold conditions Used well make stone tools, formidible hunters Lived in groups probably with oral traditions -- buried their dead
	Cro-Magnon -- Homo sapiens -- 120,000 yrs. old to present Found in Europe, Asia, Australia, (Africa) Fully human in stature, skeletal features become less robust (heavy, thick etc.) Brain size averages 1350 cc Used exquisite stone tools Culture included fantastic cave art, stone sculpture