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Lesson Overview 26.3 Primate Evolution The Oldest Hominine? Sahelanthropus had a brain about the size of a modern chimp, but its short, broad face was more like that ... – PowerPoint PPT presentation

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Title: Lesson Overview


1
Lesson Overview
  • 26.3 Primate Evolution

2
THINK ABOUT IT
  • Primates means first in Latin. But what are
    primates first in?
  • When primates appeared, there was little to
    distinguish them from other mammals. As primates
    evolved, however, several characteristics became
    distinctive.

3
What Is a Primate?
  • What characteristics do all primates share?

4
What Is a Primate?
  • What characteristics do all primates share?
  • In general, a primate is a mammal that has
    relatively long fingers and toes with nails
    instead of claws, arms that can rotate around
    shoulder joints, a strong clavicle, binocular
    vision, and a well-developed cerebrum.

5
What Is a Primate?
  • Primates share several adaptations for a life
    spent in trees.
  • In general, a primate is a mammal that has
    relatively long fingers and toes with nails
    instead of claws, arms that can rotate around
    shoulder joints, a strong clavicle, binocular
    vision, and a well-developed cerebrum.
  • You can see most of these characteristics in a
    lemur.

6
Fingers, Toes, and Shoulders
  • Primates typically have five flexible fingers
    and toes on each hand or foot that can grip
    objects firmly and precisely, enabling many
    primates to run along tree limbs and swing from
    branches with ease.

7
Fingers, Toes, and Shoulders
  • Most primates have thumbs and big toes that can
    move against the other digits, allowing them to
    hold objects firmly in their hands or feet.

8
Fingers, Toes, and Shoulders
  • Primates arms can rotate in broad circles
    around a strong shoulder joint attached to a
    strong clavicle, or collar bone, making them well
    suited for climbing.

9
Binocular Vision
  • Many primates have forward-facing eyes, giving
    them excellent binocular vision.
  • Binocular vision is the ability to combine
    visual images from both eyes, providing depth
    perception and a three-dimensional view of the
    world.
  • This comes in handy for judging the locations of
    tree branches, from which many primates, like
    this lemur, swing.

10
Well-Developed Cerebrum
  • In primates, the thinking part of the
    brainthe cerebrumis large and intricate, which
    enables more-complex behaviors than are found in
    many other mammals.
  • For example, many primate species create
    elaborate social systems that include extended
    families, adoption of orphans, and even warfare
    between rival troops.

11
Evolution of Primates
  • What are the major evolutionary groups of
    primates?

12
Evolution of Primates
  • What are the major evolutionary groups of
    primates?
  • Primates in one of these groups look very
    little like typical monkeys. This group contains
    the lemurs and lorises. The other group includes
    tarsiers and the anthropoids, the group that
    includes monkeys, great apes, and humans.

13
Evolution of Primates
  • Humans and other primates evolved from a common
    ancestor that lived more than 65 million years
    ago.

14
Evolution of Primates
  • Early in their history, primates split into two
    groups.

15
Evolution of Primates
  • Primates in one of these groups look very little
    like typical monkeys. This group contains the
    lemurs and lorises.

16
Evolution of Primates
  • The other group includes tarsiers and the
    anthropoids

17
Lemurs and Lorises
  • Lemurs and lorises are small, nocturnal primates
    with large eyes adapted to seeing in the dark.
    Many have long snouts.
  • Living members include the bush babies of
    Africa, the lemurs of Madagascar, and the lorises
    of Asia.

18
Tarsiers and Anthropoids
  • Anthropoids, or humanlike primates, include
    monkeys, great apes, and humans.

19
Tarsiers and Anthropoids
  • Anthropoids split into two groups around 45
    million years ago, as the continents on which
    they lived moved apart.

20
New World Monkeys
  • The New World monkeys are found in Central and
    South America.
  • Members of this group live almost entirely in
    trees. They have long, flexible arms that enable
    them to swing from branches.
  • New World monkeys also have a long, prehensile
    tail that can coil tightly enough around a branch
    to serve as a fifth hand.

21
Old World Monkeys and Great Apes
  • The other anthropoid branch, which evolved in
    Africa and Asia, includes the Old World monkeys
    and great apes.
  • Old World monkeys spend time in trees but lack
    prehensile tails.

22
Old World Monkeys and Great Apes
  • Great apes, also called hominoids, include
    gibbons, orangutans, gorillas, chimpanzees, and
    humans.
  • Recent DNA analyses confirm that, among the
    great apes, chimpanzees are humans closest
    relatives.

23
Hominine Evolution
  • What adaptations enabled later hominine species
    to walk upright?

24
Hominine Evolution
  • What adaptations enabled later hominine species
    to walk upright?
  • The skull, neck, spinal column, hip bones, and
    leg bones of early hominine species changed shape
    in ways that enabled later species to walk
    upright.

25
Hominine Evolution
  • Between 6 and 7 million years ago, the lineage
    that led to humans split from the lineage that
    led to chimpanzees.
  • The hominoids in the lineage that led to humans
    are called hominines and include modern humans
    and all other species more closely related to us
    than to chimpanzees.

26
Hominine Evolution
  • Hominines evolved the ability to walk upright,
    grasping thumbs, and large brains.
  • The skull, neck, spinal column, hip bones, and
    leg bones of early hominine species changed shape
    in ways that enabled later species to walk
    upright.

27
Hominine Evolution
  • This figure shows some ways in which the
    skeletons of modern humans differ from those of
    hominoids such as gorillas.

28
Hominine Evolution
  • The evolution of bipedal, or two-footed,
    locomotion was very important, because it freed
    both hands to use tools.
  • The hominine hand evolved an opposable thumb
    that could touch the tips of the fingers,
    enabling the grasping of objects and the use of
    tools.

29
Hominine Evolution
  • Hominines evolved much larger brains.
  • Most of the difference in brain size results
    from an expanded cerebrum, which is, as you
    recall, the thinking part of the brain.

30
New Findings and New Questions
  • The study of human ancestors is exciting and
    constantly changing.
  • Recent discoveries in Africa have doubled the
    number of known hominine species and the length
    of the known hominine fossil record.
  • These data have enhanced the picture of our
    species past, but questions still remain as to
    how fossil hominines are related to one
    anotherand to humans.

31
Relatives Versus Ancestors
  • The hominine fossil record includes seven
    generaSahelanthropus, Orrorin, Ardipithecus,
    Australopithecus, Paranthropus, Kenyanthropus,
    and Homoand at least 20 species.
  • All these species are relatives of modern
    humans, but not all of them are human ancestors.

32
Relatives Versus Ancestors
33
The Oldest Hominine?
  • In 2002, paleontologists in Africa discovered a
    fossil skull roughly 7 million years old. This
    fossil, called Sahelanthropus, is a million years
    older than any known hominine.

34
The Oldest Hominine?
  • Sahelanthropus had a brain about the size of a
    modern chimp, but its short, broad face was more
    like that of a human.
  • Scientists are still debating whether this
    fossil represents a hominine.

35
Australopithecus
  • Hominines of the genus Australopithecus lived
    from about 4 million to about 1.5 million years
    ago. Australopithecus afarensis fossils are
    shown.
  • These hominines were bipedal apes, but their
    skeletons suggest that they probably spent some
    time in trees.
  • The structure of their teeth suggests a diet
    rich in fruit.

36
Australopithecus
  • Australopithecus afarensis fossils indicate the
    species had small brains. Excavations have found
    fossilized humanlike footprints that were
    probably made by members of A. afarensis about
    3.6 million years ago. Such finds show that
    homines walked bipedally before large brains
    evolved.

37
Australopithecus
  • Other A. afarensis fossils indicate that males
    were much larger than females.

38
Lucy
  • The best-known A. afarensis specimen is a
    partial skeleton of an adult female discovered in
    1974, nicknamed Lucy.
  • Lucy stood about 1 meter tall and lived about
    3.2 million years ago.

39
The Dikika Baby
  • In 2006, an Ethiopian researcher announced the
    discovery of some 3.3 million-year-old fossils of
    a very young A. afarensis female, nicknamed the
    Dikika Baby.
  • The skeleton included a nearly full skull and
    jaws, torso, spinal column, limbs, and left foot.
  • Leg bones confirmed that the Dikika Baby walked
    bipedally, while her arm and shoulder bones
    suggest that she would have been a better climber
    than modern humans.

40
Paranthropus
  • The more-recent Paranthropus species had huge,
    grinding back teeth, and their diets probably
    included coarse and fibrous plant foods like
    those eaten by modern gorillas.

41
  • Paleontologists place Paranthropus on a
    separate, dead-end branch of our family tree.

42
Hominine Relationships
  • A series of hominine adaptive radiations
    produced a number of species whose relationships
    are difficult to determine.
  • As a result, what once looked like a simple
    hominine family tree with a single main trunk
    now looks more like a shrub with multiple trunks.

43
The Road to Modern Humans
  • What is the current scientific thinking about
    the genus Homo?

44
The Road to Modern Humans
  • What is the current scientific thinking about
    the genus Homo?
  • If you look at the Hominine Time Line, you can
    see that many species in our genus existed before
    our species, Homo sapiens, appeared. Furthermore,
    at least three other Homo species existed at the
    same time as early humans.

45
  • Many species in our genus existed before our
    species, Homo sapiens, appeared.

46
  • At least three other Homo species existed at the
    same time as early humans.

47
  • The Genus Homo About 2 million years ago, a
    new group of hominine species appeared.

48
The Genus Homo
  • The fossils of this new group of hominine
    species resemble modern human bones, and so they
    are classified in the genus Homo.
  • One set of fossils was found with tools made of
    stone and bone, so it was named Homo habilis,
    which means handy man in Latin.

49
The Genus Homo
  • The earliest fossils that researchers assign to
    the genus Homo belong to Homo ergaster.

50
The Genus Homo
  • H. ergaster was larger than H. habilis and had a
    bigger brain and downward-facing nostrils that
    resemble those of modern humans.

51
Out of AfricaBut When and Who?
  • Researchers agree that our genus originated in
    Africa and migrated from there to populate the
    world.
  • Some current hypotheses about when hominines
    first left Africa and which species made the trip
    are shown in the figure.

52
The First to Leave
  • Fossil and molecular evidence suggest that some
    hominines left Africa long before Homo sapiens
    evolved and that more than one Homo species made
    the trip in waves.
  • Hominines began migrating out of Africa at least
    1.8 million years ago. Hominine remains from that
    period were found in the Republic of Georgia,
    which is north of Turkey and far from Africa.

53
Homo erectus in Asia
  • According to some researchers, groups of Homo
    erectus traveled across India and through China
    to Southeast Asia.
  • Some of the oldest fossils of H. erectus were
    uncovered on the Indonesian island of Java,
    suggesting that these hominines spread very
    rapidly once they left Africa.

54
The First Homo sapiens
  • There are two main hypotheses of how Homo
    sapiens arose.
  • The multiregional model suggests that, in
    several parts of the world, modern humans evolved
    independently from widely separated populations
    of H. erectus.
  • The out-of-Africa model proposes that modern
    humans evolved in Africa about 200,000 years ago,
    migrated through the Middle East, and replaced
    the descendants of earlier hominine species.

55
The First Homo sapiens
  • Recently, molecular biologists analyzed
    mitochondrial DNA from living humans around the
    world and determined they last shared a common
    African ancestor between 200,000 and 150,000
    years ago.
  • More recent DNA data suggest that a small subset
    of those African ancestors left northeastern
    Africa between 65,000 and 50,000 years ago to
    colonize the world, supporting the out-of-Africa
    hypothesis.

56
Modern Humans
  • The story of modern humans over the past 200,000
    years involves two main species Homo
    neanderthalensis and Homo sapiens.

57
Homo neanderthalensis
  • Neanderthals flourished in Europe and western
    Asia beginning about 200,000 years ago.
  • Evidence suggests that they made stone tools,
    lived in complex social groups, had controlled
    use of fire, were excellent hunters, and
    performed simple burial rituals.
  • Neanderthals survived in parts of Europe until
    about 28,00024,000 years ago.

58
Modern Homo sapiens
  • Anatomically modern Homo sapiens arrived in the
    Middle East from Africa about 100,000 years ago.

59
Modern Homo sapiens
  • By about 50,000 years ago, H. sapiens
    populations, including some now known as
    Cro-Magnons, were using new technology to make
    more sophisticated stone blades and were making
    tools from bones and antlers.
  • They produced spectacular cave paintings and
    buried their dead with elaborate rituals.

60
Modern Homo sapiens
  • Neanderthals and H. sapiens lived side by side
    in the Middle East for about 50,000 years.
  • Later, both groups moved into Europe, where they
    coexisted for several thousand years.
  • For the last 24,000 years, however, Homo sapiens
    has have been Earths only hominine.
  • Why did Neanderthals disappear? Did they
    interbreed with H. sapiens? No one knows for
    sure.
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