32-3 Primates and
Human Origins
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32-3 Primates and Human Origins
What Is a Primate?
What Is a Primate?
Primates means “first” in Latin.
Primates share several important adaptations, many
of which are extremely useful for a life spent mainly in
trees.
In general, primates have binocular vision, a welldeveloped cerebrum, relatively long fingers and toes,
and arms that can rotate around their shoulder joints.
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32-3 Primates and Human Origins
What Is a Primate?
Fingers, Toes, and Shoulders
Primates normally have five flexible fingers that can
curl around objects and flexible toes.
Flexible digits enable primates to run along tree limbs
and swing from branch to branch with ease.
Primates’ arms are well adapted to climbing as they
rotate in broad circles around a strong shoulder joint.
In most primates, the thumb and big toe can move
against the other digits, also called an opposable
thumb.
This characteristic allows primates to hold objects in
their hands or feet.
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32-3 Primates and Human Origins
What Is a Primate?
Well-Developed Cerebrum
The large cerebrum, including a well-developed
cerebral cortex, of primates enables them to
display more complex behaviors than many other
mammals.
Many species have social behaviors that include
adoption of orphans and even warfare between
rival primate troops.
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32-3 Primates and Human Origins
What Is a Primate?
Binocular Vision
Many primates have a flat face, so both eyes face
forward with overlapping fields of view. This facial
structure allows for binocular vision.
Binocular vision is the ability to merge visual
images from both eyes, providing depth perception
and a three-dimensional view of the world.
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32-3 Primates and Human Origins
Evolution of Primates
Evolution of Primates
Humans and other primates evolved from a common
ancestor that lived more than 65 million years ago.
The two main groups of primates are prosimians and
anthropoids.
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32-3 Primates and Human Origins
Evolution of Primates
Prosimians
Most prosimians alive today are small, nocturnal
primates with large eyes that are adapted to seeing in
the dark. Many have dog-like snouts.
Living prosimians include bush babies, lemurs,
lorises, and tarsiers.
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32-3 Primates and Human Origins
Evolution of Primates
Anthropoids
Humans, apes, and most monkeys belong to the
anthropoids, which means humanlike primates.
This group split early in its evolutionary history into two
major branches.
These branches separated as drifting continents
moved apart.
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32-3 Primates and Human Origins
Evolution of Primates
One branch of anthropoids is the New World monkeys.
New World monkeys:
•
are found today in Central and South America.
•
include squirrel monkeys and spider monkeys.
•
live almost entirely in trees.
•
have long, flexible arms to swing from branches.
•
have a prehensile tail, which is a tail that can
coil around a branch to serve as a “fifth hand.”
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32-3 Primates and Human Origins
Evolution of Primates
The other group of anthropoids includes Old World
monkeys and great apes.
•
Evolved in Africa and Asia.
•
Old World monkeys live in trees but lack
prehensile tails (langurs and macaques).
•
Great apes, also called hominoids, include
gibbons, orangutans, gorillas, chimpanzees, and
humans.
•
Chimpanzees are humans’ closest relatives
among the great apes, sharing 98% of their DNA.
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32-3 Primates and Human Origins
New World Old World
monkeys monkeys Gibbons
Evolution of Primates
Orangutans
Gorillas ChimpanzeesHumans
Anthropoids
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32-3 Primates and Human Origins
Hominid Evolution
Hominid Evolution
Between 6 and 7 million years ago, the hominoid line
gave rise to hominids.
The hominid family includes modern humans.
As hominids evolved, they began to walk upright and
developed thumbs adapted for grasping.
They also developed large brains.
Hominids displayed a remarkable increase in brain
size, especially in an expanded cerebrum—the
“thinking” area of the brain.
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32-3 Primates and Human Origins
Hominid Evolution
The skull, neck, spinal column, hipbones, and leg
bones of early hominid species changed shape in
ways that enabled later hominid species to walk
upright.
Evolution of this bipedal, or two-foot, locomotion freed
both hands to use tools.
Hominids evolved an opposable thumb that enabled
grasping objects and using tools.
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32-3 Primates and Human Origins
Modern human
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Hominid Evolution
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32-3 Primates and Human Origins
Hominid Evolution
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32-3 Primates and Human Origins
Hominid Evolution
Early Hominids
At present, the hominid fossil record includes these
genera:
•
•
•
•
•
Ardipithecus
Australopithecus
Paranthropus
Kenyanthropus
Homo
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32-3 Primates and Human Origins
Hominid Evolution
There are as many as 20 separate hominid species.
This diverse group of hominid fossils covers roughly 6
million years.
All are relatives of modern humans, but not all are
human ancestors.
Almost a third of all known hominid species have been
discovered in the last 20-25 years.
Questions remain about how fossil hominids are
related to one another and to humans.
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32-3 Primates and Human Origins
Hominid Evolution
Australopithecus
An early hominid species, Australopithecus, lived from
about 4 million to 1 million years ago.
Bipedal apes that spent at least some time in trees
The structure of their teeth suggests a diet rich in fruit.
Some species may have been human ancestors, while
others formed separate branches.
The best known species is Australopithecus
afarensis—based on a female skeleton named Lucy,
who was 1 meter tall.
Members of the Australopithecus species had small
brains, were bipedal, and spent some time in trees. 18 Slide
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32-3 Primates and Human Origins
Hominid Evolution
Paranthropus
The Paranthropus species had huge, grinding back
teeth and grew to the size of well-fed football
linebackers.
Their diets probably included coarse and fibrous plant
foods like those eaten by modern gorillas.
Most paleontologists place Paranthropus on a
separate, dead-end branch of our family tree.
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32-3 Primates and Human Origins
Hominid Evolution
Recent Hominid Discoveries
In 2001, a team lead by Meave Leakey discovered a
skull in Kenya.
• Its ear resembled a chimpanzee’s.
• Its brain was small.
• Its facial features resembled those of Homo
fossils.
• It was put in a new genus, Kenyanthropus, which
lived at the same time as A. afarensis.
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32-3 Primates and Human Origins
Kenyanthropus platyops
Hominid Evolution
Homo erectus
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32-3 Primates and Human Origins
Hominid Evolution
In 2002, paleontologists working in the desert in
north-central Africa discovered another skull.
•
Called Sahelanthropus, it is nearly 7 million
years old.
•
If it is a hominid, it would be a million years
older than any hominid previously known.
•
It had a brain like a modern chimp and a flat
face like a human.
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32-3 Primates and Human Origins
Hominid Evolution
Sahelanthropus tchadensis
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32-3 Primates and Human Origins
Hominid Evolution
Rethinking Early Hominid Evolution
Researchers once thought that human evolution took
place in steps, in which hominid species became
gradually more humanlike.
Hominid evolution did not proceed by the simple,
straight-line transformation of one species into
another.
Rather, a series of complex adaptive radiations
produced a large number of species whose
relationships are difficult to determine.
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32-3 Primates and Human Origins
Millions of years ago
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Hominid Evolution
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32-3 Primates and Human Origins
Hominid Evolution
The hominid fossil record dates back 7 million years,
close to the time that DNA studies suggest for the
split between hominids and the ancestors of modern
chimpanzees.
There are many known fossil hominid species,
several of which display a confusing mix of primative
and modern traits.
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32-3 Primates and Human Origins
The Road to Modern
Humans
The Road to Modern Humans
Paleontologists still do not completely understand the
history and relationships of species within our own
genus.
Other species in the genus Homo existed before
Homo sapiens and at least two other species in the
genus Homo existed at the same time as early
humans.
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32-3 Primates and Human Origins
The Road to Modern
Humans
The Genus Homo
The first fossils in the genus Homo are about 2.5
million years old.
These fossils were found with tools made of stone and
bone, so researchers called the species Homo habilis,
which means “handy man.”
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32-3 Primates and Human Origins
The Road to Modern
Humans
2 million years ago, a larger species called Homo
ergaster appeared.
It had a bigger brain and downward-facing nostrils
that resembled those of modern humans.
At some point, either H. ergaster or a related species
named Homo erectus began migrating out of Africa
through the Middle East.
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32-3 Primates and Human Origins
The Road to Modern
Humans
Out of Africa—But Who and When?
Researchers agree that our genus originated in Africa.
Evidence suggests that hominids left Africa in several
waves, as shown in the following diagram.
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32-3 Primates and Human Origins
The Road to Modern
Humans
It is not certain where and when Homo sapiens arose.
One hypothesis, the multi-regional model, suggests
that modern humans evolved independently in several
parts of the world from widely separated populations
of H. erectus.
Another hypothesis, the out-of-Africa model, proposes
that modern humans evolved in Africa between
200,000–150,000 years ago, migrated out to colonize
the world, and replaced the descendants of earlier
hominid species.
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32-3 Primates and Human Origins
Modern Homo sapiens
Modern Homo sapiens
The story of modern humans over the past 500,000
years involves two main groups.
The earliest of these species is called Homo
neanderthalensis, named after the Neander Valley in
Germany where their remains were first found.
Neanderthals lived in Europe and western Asia
200,000–30,000 years ago.
They made stone tools and lived in organized social
groups.
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32-3 Primates and Human Origins
Modern Homo sapiens
The other group is Homo sapiens—people whose
skeletons look like those of modern humans.
Probably arose in Africa and appeared in the Middle
East around 100,000 years ago.
Neanderthals and Homo sapiens lived side by side in
what is now Israel, Lebanon, Syria, and Turkey for
around 50,000 years, using similar tools and living in
remarkably similar ways.
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32-3 Primates and Human Origins
The Road to Modern Humans
50,000–40,000 years ago some populations of H.
sapiens seem to have changed their way of life:
•
They made more sophisticated stone blades
and elaborately worked tools from bones and
antlers.
•
They produced cave paintings.
•
They buried their dead with elaborate rituals.
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32-3 Primates and Human Origins
The Road to Modern Humans
About 40,000 years ago, one such group known as
Cro-Magnons appeared in Europe.
By 30,000 years ago, Neanderthals had disappeared
from Europe and the Middle East. How and why is
still not known.
Since that time, our species has been Earth’s only
hominid.
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32-3
The ability to merge visual images from both
eyes is called
a. monocular vision.
b. binocular vision.
c. overlapping vision.
d. color vision.
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32-3
Which of the following is true about hominid evolution?
a. The development of a large brain happened before
bipedal locomotion.
b. There is a straight line of descent from the earliest
hominid species to Homo sapiens.
c. The genus Homo appeared before the genus
Australopithecus.
d. Hominid evolution took place as a series of adaptive
radiations that produced a large number of species.
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32-3
The evolution of bipedal locomotion was
important because it
a. increased brain size.
b. made it easier to see.
c. freed both hands to use tools.
d. allowed easier escape from predators.
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32-3
The multi-regional model hypothesizes that
a. Homo sapiens evolved independently in
several parts of the world.
b. Modern humans evolved in Africa, then
migrated to various parts of the world.
c. Neanderthals produced cave drawings.
d. Homo habilis descended from Homo erectus.
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32-3
The oldest known Homo sapiens skeletons are
about
a. 6,000 years old.
b. 100,000 years old.
c. 3 million years old.
d. 30 million years old.
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