Unit 5
Chapter 16

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 majority live in trees ( arboreal ) include lemurs, monkeys, apes, and humans

 Rounded heads
 Flattened faces
 Opposable thumb
 Binocular vision
 Flexible joints
 Full arm motion
 Some with prehensile tails
 Large brains

 a thumb that can cross the palm to meet the other fingertips
 Adaptation: gripping object

ancestral primates lemurs and ayes-ayes
Tarsiers and anthropoids
Lemur Tarsier

 Large eyes
 Nocturnal
 Habitat: tropical rain forests
 Oldest found fossils: 50-55 MYO

 Larger brains
 More upright posture
 Anthropoids include humans, apes, and monkeys.
 Humans and apes are in a group called hominoids .
 Monkeys are divided into two groups: Old
World and New World.

 Habitat: rainforests of Central and South
America
 Prehensile tail : able to grasp and hold with this fifth limb
Squirrel monkey

 Larger than New World monkeys
 Tails that are prehensile not
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Appear superficially to be like hominoid apes except that apes lack tails.
Habitat: diverse, including African savanna and
Japanese mountains
Mandril

Hominoid apes : orangutans, gibbons, chimpanzees, bonobos, and gorillas
 long, muscled forelimbs
 climbing in trees
 swinging from branches
 knuckle walking
Bonobo knuckle-walking

 May be arboreal but mostly spends time on the ground
 Defined social structure and behaviors
(including grooming)

 Even larger brain capacity than apes
 Upright stature
Note the differences in brain capacity of the skulls: left to right , ape, chimp, human

 Scientists believed that Old World and New
World monkey shared a common anthropoid ancestor.
 From DNA evidence, scientists believe this to be the order of ape evolution: gibbons, orangutans, African apes, gorillas, and chimpanzees.

Comparing DNA of humans and chimps
 Humans and chimps share the greatest sequence of DNA nucleotides.
 This implies that humans and chimps are more likely to share a recent ancestor.
 This does not imply that humans descended from chimps.

 Fossil and DNA evidence indicates that about
5 to 8 million years ago, an ancestral hominoid diverged into two pathways: chimps and humans.
 Changes in food supply and climate favored those hominoids that could forage for food on land rather than in trees.

Characteristics for non-arboreal primates
Bipedalism is a more adapted behavior than knuckle-walking apes.
 Bipedal : using two legs for upright walking
 Upright posture : facilitates primate to see farther
 Bipedal hominoid primates are called hominids and include humans.

How do scientists know that early hominids walked upright?
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The opening in the skull where the spinal cord attaches shows how the head and spine are positioned.
Anthropologist
Raymond Dart discovered an early skull that appeared ape-like but had the spinal attachment position like modern humans.
Notice how the angle of the arrow changes with the human skull as compared to the ape and chimp.

Australopithecus africanus
 The skull that Dart discovered was named
A. africanus .
 Estimated age: 2.5 to
2.8 MYO
 These primates are called australopithecines
(apelike and humanlike).

1974 discovered australopithecine Lucy
Australopithecus afarensis , dated about 2-3 MYO, shows pelvis structures that would indicate bipedalism.

Chimps Early hominid Modern human
Similar brain case size between these two
Shorter and wider pelvic bones indicate bipedalism.

 Fossil records indicate a disappearance about 2.0-2.5 MYA.
 Hominids more like modern humans with larger brain cases may have evolved next.
In 1964, Louis and Mary
Leakey discovered skulls more like modern humans in Tanzania and named this group
Homo .

 “handy man”
 Ancient stone tools found near the fossils of H. habilis
 Estimated age: 1.5-2.5
MYO
Examples of tools that H. habilis may have used

Homo erectus may have evolved from
H. habilis .

 Larger brain than H. habilis
 More human-like face

 Stone hand axe were found near H. erectus fossils, indicating they hunted.
 Hearths with charred bones found in H. erectus caves indicate that they may have used fire.

 About 1 MYA, H. erectus migrated throughout
Africa, Asia, and Europe.
 They became extinct between 130,000 and
300,000 years ago.
 This is about the time that Homo sapiens fossils appear in the fossil record (100,000-
500,000 YA).

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35,000-100,000 YA in
Europe, Asia, and
Middle East
Larger brain cases than
H. erectus
Prominent nose
Thick bones
May be a sister species to modern humans (not direct ancestor)
Lived about the same time as Cro-Magnon

 35,000-40,000 YA
 Same height, skull structure, tooth structure, and brain size as modern humans
 Toolmakers and artists
 Language

Possible appearance of Cro-Magnon

 12,000 years ago, evidence shows that they crossed a land bridge into North
America.
 They built settlements and domesticated animals.
Modern coastline
Ancient coastline
Ice sheets 21,000 yrs ago
Ice sheets 12,000 yrs ago
Possible migration route