1
Overview
This chapter introduces students to the study of the fossil record
using geological techniques. Then it discusses the earliest primate
species which lived during the Eocene and Miocene.
Primate Evolution
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Chronology
• The history of vertebrate life on earth is divided into three eras:
Paleozoic; Mesozoic; and Cenozoic.
– Each era is divided into periods.
– Each period is divided into epochs.
• Anthropologists are concerned with the Cenozoic era, which includes
two periods: Tertiary and Quaternary.
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Chronology (cont.)
– The Tertiary period has five epochs: Paleocene; Eocene; Oligocene;
Miocene; and Pliocene.
– A wide range of small mammals, some possibly ancestral to primates,
appeared during the Paleocene.
– Prosimian-like fossils abound in strata dating to the Eocene.
– The first anthropoid fossils date to the late Eocene and the early
Oligocene.
– Hominoids became widespread during the Miocene.
– Hominids first appeared during the late Miocene or early Pliocene.
– The Quaternary period has two epochs: Pleistocene and Holocene.
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Early Primates
• Arboreal theory
– Primates became primates by adapting to life in trees.
– Enhanced sight (depth perception)
– Grasping hands and feet
• Visual predation hypothesis (Cartmill 1972, 1992)
– Binocular vision, grasping hands and feet, and reduced claws developed
because they facilitated the capture of insects.
– Early primates first adapted to life in the bushy forest undergrowth and
low tree branches.
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Early Cenozoic Primates
• The earliest primates date to the first part of the Cenozoic (65-54
m.y.a.).
• The Eocene (54-38 m.y.a.) was the epoch of prosimians with at least
60 different genera in two families.
– The omomyid family lived in North America, Europe, and Asia and may
be ancestral to all anthropoids.
– The adapid family was ancestral to the lemur-loris line.
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Anthropoids
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Anthropoids branched off from the prosimians during the Eocene.
Anthropoid eyes are rotated more forward compared to prosimians.
Anthropoids have a fully enclosed bony eye socket.
Anthropoids have a dry nose separate from the upper lip.
Anthropoids have molar cusps.
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Oligocene Anthropoids
• During the Oligocene (38-23 m.y.a.), anthropoids were the most
numerous primates.
• The parapithecid family may be ancestral to the New World monkeys.
• The propliopithecid family may be ancestral to Old World monkeys,
apes, and humans.
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Proconsul
• The earliest hominoid fossils date to the Miocene epoch (23-5 m.y.a.).
• Proconsul was the most abundant anthropoid in the early Miocene.
• Its teeth have similarities with modern apes, but below the neck the
skeleton is more monkey-like.
• Their teeth suggest that they ate fruits and leaves.
• Proconsul probably contained the last common ancestor shared by Old
World monkeys and the apes.
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Proconsul (cont.)
• Monkeys replaced Proconsul in the late Miocene.
– Monkeys probably were superior at eating leaves.
– Monkey molars developed lophs, which enhanced their ability to chew
leaves.
• Traits
– Primitive traits are those passed on unchanged from an ancestor.
– Derived traits are those that develop in a particular taxon after a split from
a common ancestor.
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Afropithecus and Kenyapithecus
• Afropithecus is a large, slow-moving Miocene hominoid with large
projecting front teeth from northern Kenya (18-16 m.y.a.)
• Recent research suggests that the two species of Kenyapithecus should
be reclassified as Equatorius.
• Equatorius and Afropithecus are probable stem hominoids, species
somewhere on the evolutionary line near the origins of the modern ape
group that are too primitive to be considered direct ancestors of living
apes and humans.
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Sivapithecus
• Sivapithecus belongs to the ramapithecid genera along with
Gigantopithecus.
• Sivapithecus is now believed to be ancestral to the modern orangutan.
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Gigantopithecus
• Gigantopithecus is the largest primate that ever lived, some standing
over 10 feet tall and weighing 1,200 pounds.
• Since it died out around 400,000 years ago, it coexisted with Homo
erectus.
• Some people believe it is still alive today as the yeti and bigfoot.
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Dryopithecus
• Dryopithecus lived in Europe during the middle and late Miocene.
• This group probably includes the common ancestor of the lesser apes
(gibbons and siamangs) and the great apes.
• Dryopithecus has the Y-5 arrangement of molar cusps typical of
Dryopithecus and of hominoids.
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Oreopithecus
• Oreopithecus bambolii lived between 9-7 m.y.a. and spent much of its
time standing upright and shuffling short distances.
• Its big toe splayed out 90 degrees from the other toes.
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A Missing Link?
• Kottak refers to the last ancestral population held commonly by
humans, gorillas, and chimpanzees as Hogopans (after the genus
names of these three).
• The lines of the orangutans, gibbons, and siamangs split off several
million years earlier. The hominid line almost certainly diverged from
those of chimps and gorillas late in the Miocene epoch, between 7 and
5 m.y.a.
• Hogopans probably split into the three separate lines leading to
gorillas, chimpanzees, and humans no more than 8 m.y.a., with each
group moving into separate niches: equatorial forest-dwelling and
eating bulk vegetation (gorilla), Central African woodland-dwelling
frugivores (chimpanzee), and open grassland (hominids).
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