Transcript Chapter 5, Macroevolution and the Early Primates

Chapter 5
Macroevolution and the
Early Primates
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?

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.

Isolating Mechanisms
Geographical
 Anatomical structure
 Social and cultural concepts

Cladogenesis
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.

Anagenesis and
Convergence
Anagenesis
– When natural selection, over time,
favors some variants over others.
– Creates a change in a population’s
average characteristics.
 Convergence
– Occurs when two unrelated species
come to resemble each other owing
to functional similarities.

Anagenesis
Continental
Drift
Primate Evolution

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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.
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. Note
that the orbit is open behind the ring.
Primate Evolution
Geological changes in the orientation
and position of the earth’s 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.

Early Primates
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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.
Location of Hominid
Fossils
Primate Evolution
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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.
Primate Evolution
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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 today’s bonobo, chimpanzee,
and gorilla.