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Macroevolution and the Early Primates

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Over time, macroevolutionary forces produce new species from old ones. ... can separate breeding populations and lead to the appearance of new species. ... – PowerPoint PPT presentation

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Title: Macroevolution and the Early Primates


1
Chapter 5
  • Macroevolution and the Early Primates

2
Chapter Outline
  • What Is Macroevevolution?
  • When and Where Did the First Primates Appear, and
    What Were They Like?
  • When Did the First Monkeys and Apes Appear, and
    What Were They Like?

3
Macroevolution
  • Over time, macroevolutionary forces produce new
    species from old ones.
  • Macroevolution focuses upon the formation of new
    species and on the evolutionary relationships
    between groups of species.
  • Isolating mechanisms can separate breeding
    populations and lead to the appearance of new
    species.

4
Isolating Mechanisms
  • Geographical
  • Anatomical structure
  • Social and cultural concepts

5
Isolating Mechanisms
  • In branching evolution, isolating mechanisms
    separate breeding populations, creating divergent
    subspecies and then divergent species.
  • Geographical, biological, or social isolating
    mechanisms block gene flow between groups,
    contributing to the accumulation of genetic
    mutations in each population.
  • Biological isolating mechanisms include phenomena
    such as the sterility of hybrid offspring.

6
Anagenesis and Convergence
  • Anagenesis
  • When natural selection, over time, favors some
    variants over others.
  • Creates a change in a populations average
    characteristics.
  • Convergence
  • Occurs when two unrelated species come to
    resemble each other owing to functional
    similarities.

7
Primate Evolution
  • Primates arose from a branching of mammalian
    forms that began more than 100 million years
    after the appearance of the first mammals.
  • Most ecological niches that mammals have since
    occupied were
  • preempted by reptiles
  • nonexistent until flowering plants became
    widespread about 65 million years ago.

8
Ancestral Features
  • Features in the Eocene genus Adapis are found in
    prosimians today.
  • Like modern lemurs, it has a postorbital bar, a
    bony ring around the eye orbit.

9
Primate Evolution
  • Geological changes in the orientation and
    position of the earths continents affected the
    global climate.
  • This played a key role in the evolution and
    distribution of the primates.
  • The first primates were arboreal insect eaters
    and the characteristics of all primates developed
    as adaptations to this early way of life.

10
Early Primates
  • The earliest primates developed 60 million years
    ago in the Paleocene epoch.
  • They were small arboreal creatures.
  • Diverse prosimianlike forms were common in the
    Eocene across what is now North America and
    Eurasia.
  • By the late Eocene, 45 million years ago, small
    primates combining prosimian and anthropoid had
    emerged.

11
Primate Evolution
  • By the late Eocene small primates combining
    lemurlike and tarsierlike features with those in
    monkeys and apes developed.
  • In the Miocene epoch, apes proliferated and
    spread over many parts of the Old World.
  • Ancestors of large apes and humans appeared by 16
    m.y.a. and were widespread as recently as 8
    m.y.a.

12
Primate Evolution
  • Details of dentition suggest that hominines arose
    from these earlier apes.
  • Some populations lived in parts of Africa where
    pressures existed to transform a creature just
    like it into a primitive hominine.
  • Other populations remained in the forests,
    developing into todays bonobo, chimpanzee, and
    gorilla.
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