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Human Evolution
and PREHISTORY
Chapter 5:
MACROEVOLUTION AND THE
EARLY PRIMATES
Link to the Canadian Association for Physical Anthropology
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Chapter Preview
When did the first Primates Appear, and What
Were They Like?
When did the First Monkeys and Apes Appear,
and What Were They Like?
COPYRIGHT © 2008 Nelson Education Ltd. ALL RIGHTS RESERVED.
LINEAR EVOLUTION
A process of non-directional, variational change
 Changes can occur by chance and accumulate over
time because they are advantageous; e.g. elephants
becoming progressively hairier (chapter 3)
 Linear evolution may or may not produce a new
species
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The Nondirectedness of Evolution
“Human brains and bodies did not evolve along
a direct and inevitable ladder, but by a
circuitous and tortuous route carved by
adaptations evolved for different reasons, and
fortunately suited to later needs”
….Stephen J. Gould
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EARLY MAMMALS
By 190 million years ago (mya) true mammals
appear in the fossil record
Today’s diverse forms of mammals (including the
primates) are the products of an adaptive radiation
at the end of the Cretaceous period, around 65 mya
Mass extinction of many reptiles made available
existing ecological niches, and new niches opened up
as climate changed
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RISE OF THE PRIMATES
Adaptive Radiation
The rapid increase in number of related species
following a change in their environment
Ecological Niche
A species’ way of life in a particular
environment, including all other species of
plants and animals in that habitat
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RISE OF THE PRIMATES
By the end of the Cretaceous:
Separation of the continents
New and available ecological
niches
Mild climate supporting new
vegetation, e.g. flowering
plants
Spread of tropical and
subtropical forests
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RISE OF THE PRIMATES
Move to arboreal life
Natural selection favoured flexible decision-making,
depth perception, a strong grip and dexterous fingers
Number of hypotheses to explain primate
specialization, e.g. use of smaller branches for fruit
foraging and insect predation
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Paleocene Primates
 Ancestry of primates is in the insectivore group of mammals
 Earliest known primate fossils are 10 teeth from a site in
Morocco, about 60 million years old, and are very similar to
those of a modern mouse lemur
 These fossils show that primates are going their separate
evolutionary way by 60 mya
 Place of origin is unknown
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Paleocene Primates
Carpolestes simpsoni, 56 mya, Wyoming
 Grasping ability
 Fruit-eating dentition
 Long arms suitable for tree life
All good adaptations for arboreal foraging at
ends of small branches
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Eocene Primates
 55 to 34 mya
 Ancestors of lemurs, tarsiers and other
haplorhines
 Some probably were ancestral to platyrrhines
and catarrhines
 Found in Africa, North America, Europe and
Asia where warm, wet conditions sustained
extensive rainforest
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Eocene Primates
Genus Adapis
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Eocene Primates – Climate change
 Sudden temperature drop in late Eocene,
creating cooler and drier climates
 There was a marked reduction of environments
to which the early primates were adapted, e.g.
they became extinct in North America
 Precursors of monkeys and apes may have
been able to take over some of these niches
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Evolutionary Timeline
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Oligocene Monkeys and Apes
 34-23 mya
 Scarcity of fossils, mainly found in the Fayum Depression,
Egypt (once tropical rainforest)
 Prominence and diversity of haplorhines showing
monkeylike and apelike features, e.g. Aegyptopithecus
 Evidence of ancestors of true monkeys, resembling modernday platyrrhines
 Some of the platyrrines could have found their way to South
America on “rafts” of floating vegetation
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Aegyptopithecus
Oligocene catarrhine
Apelike dentition
Forward eye sockets, as in
modern monkeys and apes
Larger brain than any lemur or
tarsier, past or present
Its teeth suggest that it belongs
in the ancestry of those Miocene
forms that gave rise to both
humans and today’s African
apes
Quadrupedal, monkey-like
locomotion
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Miocene Apes
23-5 mya
Proliferation of apes in forests
throughout the Old World
East Africa is particularly rich in fossils
from early to middle Miocene
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Miocene Apes
Genus Proconsul
(Early Miocene)
Represents an unspecialized tree-dwelling, fruiteating hominoid (the catarrhine superfamily to
which apes and humans belong)
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Miocene Apes
16-5 mya (middle to late Miocene)
Europe, Asia and Africa
Teeth and jaws like Proconsul but more ape-like in
overall appearance
Some species surely were ancestral to later largebodied apes, including the hominids (the primate
family containing African apes and humans)
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ORIGINAL STUDY
Will the Real Human Ancestor Please Stand Up?
The wide variety of Miocene fossils have had many
interpretations and generic and specific names, in an attempt
to find the common ancestor of humans, chimpanzees and
gorillas
Molecular analysis of proteins in the 1970’s indicated a
divergence for living hominoids of 5 mya, no earlier than 7
mya
Fossil remains of the common ancestor have not been found,
but molecular evidence points to Africa as the origin of
humans
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Miocene Apes
Potential hominid ancestors known from teeth,
jaws, and more recently skull and limb bones,
e.g. China, Greece, Hungary, Pakistan, Turkey
Sivapithecus is orangutanlike
Dryopithecus resembles African apes and early
hominines
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Miocene Apes and Human Origins
The ancestry of humans may be among late Miocene apes of
Africa that show some resemblance to Sivapithecus. This is
consistent with:
Dental evidence
molecular evidence that suggests that humans, bonobos,
chimpanzees and gorillas could not have separated from a
common stock more than 8 mya
Forms like Sivapithecus were still on the scene after this split,
and our own human ancestors were going their own separate
evolutionary way by at least 4.4 million, if not 6 million, years
ago.
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Hominoid Adaptations and Late
Miocene Climatic Change
 Climatic shift created mosaic environments, i.e. forest
and open grassland
 Food could be obtained by foraging on the ground as
well as in trees
 Late Miocene fossils typically are found in association
with greater numbers of animals adapted to grassland
 Physical and behavioural changes were needed for
survival on the open ground, e.g. bipedalism
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EARLY APES AND HUMAN
EVOLUTION
The late Miocene apes were much too apelike to be
considered hominines and were optional rather than
obligatory bipeds
However, anatomical and molecular evidence
indicates the separation of apes and humans from
the common evolutionary line some time near the
end of the late Miocene
Some late Miocene fossils do possess traits seen in
humans
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EARLY APES AND HUMAN
EVOLUTION
Some of the Miocene apes evolved into
contemporary apes and remained in the
forests and woodlands continuing to develop
as arboreal apes, and ultimately, for some, a
more terrestrial life
These are the bonobos, chimpanzees, gorillas
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EARLY PRIMATE EVOLUTION:
AN OVERVIEW
 Initial diversification of strepsirhine and some
haplorine forms as they adapted to life in the trees
 Haplorhines diversified into a large variety of
monkeylike apes, from which developed true
monkeys, true apes, and (later) humans
 Apes and monkeys competed in the forests
 Forests continued to shrink and ground-dwelling
niches for primates opened up, particularly for
baboons and humans
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NEXT TIME:
The Earliest Hominines
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