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CHAPTER 5
PRIMATE EVOLUTION
CHAPTER OUTLINE
I. The Fossil Record
A. Preservation
1. The fossil record is not a representative sample of all species that have lived on earth.
2. Some species and body parts preserve better than others.
3. Taphonomy is the study of the processes that affect the remains of dead animals.
B. Finding fossils
1. Fossils are more likely to be found in areas with little vegetation and lots of erosion.
2. Due to issues regarding the preservation and discovery of fossils, the fossil record of
early primates is “limited and spotty”.
II. Dating the Past
A. Fundamental Concepts
1. Paleontology is the study of ancient life through the fossil record.
2. Anthropology and paleontology both are interested in establishing a chronology for
primate and human evolution.
3. Much dating depends upon stratigraphy, which is the study of the sequence of
geographical layers.
B. Relative Dating
1. Relative dating uses the natural layers or strata to establish a relative chronology –
material from this layer is older than the material from that layer.
2. Association with known fossils is the most common method of fossil dating.
3. Fluorine dating is another relative dating technique, and was used to expose the
Piltdown Man hoax.
C. Absolute Dating
1. Whereas relative dating techniques allow you to say only what is older or younger,
absolute dating techniques produce dates in years so differences in age can be
quantified.
2. Radiometric techniques are based on known rates of radioactive decay in elements
found in or around fossils.
3. Examples are: 14C and potassium argon (K/A) dating (both of which are radiometric
techniques), thermoluminescence (TL), and electron spin resonance (ESR) (see table
5.1).
III. Early Primates
A. Arboreal theory
1. Primates became primates by adapting to life in trees.
2. Enhanced sight (depth perception)
3. Grasping hands and feet
B. Visual predation hypothesis (Cartmill 1972, 1992)
1. Binocular vision, grasping hands and feet, and reduced claws developed because they
facilitated the capture of insects.
2. Early primates first adapted to life in the bushy forest undergrowth and low tree
branches.
C. Early Cenozoic Primates
1. The earliest primates date to the first part of the Cenozoic (65-54 m.y.a.).
2. The Eocene (54-38 m.y.a.) was the epoch of prosimians with at least 60 different
genera in two families.
a. The omomyid family lived in North America, Europe, and Asia and may be
ancestral to all anthropoids.
b. The adapid family was ancestral to the lemur-loris line.
3. Anthropoids branched off from the prosimians during the Eocene.
a. Anthropoid eyes are rotated more forward compared to prosimians.
b. Anthropoids have a fully enclosed bony eye socket.
c. Anthropoids have a dry nose separate from the upper lip.
d. Anthropoids have molar cusps.
D. Oligocene Anthropoids
1. During the Oligocene (38-23 m.y.a.), anthropoids were the most numerous primates.
2. The parapithecid family may be ancestral to the New World monkeys.
3. The propliopithecid family may be ancestral to Old World monkeys, apes, and
humans.
IV. Miocene Hominoids
A. The earliest hominoid fossils date to the Miocene epoch (23-5 m.y.a.).
B. Proconsul
1. Proconsul was the most abundant anthropoid in the early Miocene.
2. Its teeth have similarities with modern apes, but below the neck the skeleton is more
monkey-like.
3. Their teeth suggest that they ate fruits and leaves.
4. Proconsul probably contained the last common ancestor shared by Old World
monkeys and the apes.
5. Proconsul was replaced by monkeys in the late Miocene.
a. Monkeys probably were superior at eating leaves.
b. Monkey molars developed lophs, which enhanced their ability to chew leaves.
6. Traits
a. Primitive traits are those passed on unchanged from an ancestor.
b. Derived traits are those that develop in a particular taxon after a split from a
common ancestor.
C. Afropithecus and Kenyapithecus
1. Afropithecus is a large slow moving Miocene hominoid with large projecting front
teeth from northern Kenya (18-16 m.y.a.)
2. Recent research suggests that the two species of Kenyapithecus should be reclassified
as Equatorius.
3. 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.
D. Sivapithecus
1. Sivapithecus belongs to the ramapithecid genera along with Gigantopithecus.
2. Sivapithecus is now believed to be ancestral to the modern orangutan.
E. Gigantopithecus
1. Gigantopithecus is the largest primate that ever lived, some standing over 10 feet tall
and weighing 1,200 pounds.
2. Since it died out around 400,000 years ago, it coexisted with Homo erectus.
3. Some people believe it is still alive today as the yeti and Bigfoot.
F. Dryopithecus
1. Dryopithecus lived in Europe during the middle and late Miocene.
2. This group probably includes the common ancestor of the lesser apes (gibbons and
siamangs) and the great apes.
3. Dryopithecus has the Y-5 arrangement of molar cusps typical of Dryopithecus and of
hominoids.
G. Oreopithecus
1. Oreopithecus bambolii lived between 9-7 m.y.a and spent much of its time standing
upright and shuffling short distances.
2. Its big toe splayed out 90 degrees from the other toes.
V. A Missing Link?
A. Kottak refers to the last ancestral population held commonly by humans, gorillas, and
chimpanzees as Hogopans (after the genus names of these three).
B. The lines of the orangutans, gibbons and siamangs having 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.
C. 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).
VI. Beyond the Classroom: Maceration of a Canadian Lynx
A. Barbara Hewitt studied how the condition of a lynx’s bones reflected its former health.
B. After preparing the skeleton, Hewitt was able to identify pathologies in the animal’s
bones.