Mammalian/Primate Evolutionary
History
I.
II.
III.
More Taxonomic Concepts
Time Scale
Early Primate Evolution
(Paleocene through Oligocene)
IV.
V.
Miocene Fossils
Rate of Evolutionary Change
I. Taxonomic Concepts
A. Structures that are shared through
descent from a common ancestor
are called homologies.
B. Homoplasy is the process by
which similarities can
develop in different
groups
of organisms.
I. Taxonomic Concepts
C. Structures in organisms
that are used for the same
function, but have
developed
independently and are not
the result of common
descent, are called
analogies.
D. Analogies are often the
result of convergent
evolution.
I. Taxonomic Concepts
E. Cladistic Taxonomy (Reminder)
An approach to taxonomy that groups species according
to shared derived characteristics.
– Traits that reflecting the ancestral condition of an
organism are primitive.
– Traits shared by all members of a group, but not
present before the group's appearance, are said to be
shared derived characteristics.
II. Time Scale: Geological Eras
A.
Paleozoic
The first vertebrates appeared 500 mya
B.
Mesozoic
Reptiles were dominant land vertebrates.
Placental mammals appeared 70 mya
C.
Cenozoic
Divided into two periods: Tertiary and Quaternary
and 7 epochs.
II. Time Scale: Cenozoic Epochs
Draw and fill in this chart:
Epoch
Paleocene
Eocene
Oligocene
Miocene
Pliocene
Pleistocene
Holocene
Time
65 mya
55 mya
34 mya
23 mya
5 mya
1.8 mya
0.01 mya
Primates
II. Time Scale: Mammalian
Evolution
The Cenozoic era is known as the Age of Mammals.
 After dinosaurs became extinct, mammals underwent
adaptive radiation, resulting in rapid expansion and
diversification.
 One advantage was the larger neocortex, which
controls higher brain functions, comprised the majority
of brain volume in mammals resulting in greater ability
to learn.

III. Early Primate Evolution
Primate origins began in the placental mammal radiation
65 mya with the plesiadapiformes, represented by
members of the genus Purgatorius.
B. There are very scarce traces of the beginnings of the
primate radiation.
C. The earliest undoubted primates appear in the Eocene
epoch.
D. Most of our knowledge of primate Oligocene evolution
comes from a site in Egypt, the Fayum.
A.
Eocene Forms

Prosimians start here
Omomyidae family is ancestral to tarsiers
Adapidae family is ancestral to lemurs and lorises
Oligocene Forms

Possible roots of anthropoid evolution are illustrated by
different Fayum (a region of Egypt) forms:
Apidium
– Small, primate, that may lie near or before the evolutionary
divergence of Old and New World anthropoids.
Aegyptopithecus
– Largest of the Fayum primates with a small brain, large snout, and
none of the traits of Old World monkeys or the hominoids.
IV. Miocene Fossils
A. Miocene was marked by a spectacular hominoid
radiation and could be called “the golden age of
hominoids” (apes).
B. Hominoids are grouped geographically: African
forms (23-14 mya), European forms (13-11 mya),
and Asian forms (16-7 mya).
C. Miocene hominoid fossils were geographically
widespread, numerous, span between 23 and 6
mya and are poorly understood overall.
IV. More Miocene
D. Proconsul is an important early
Miocene form
 Transitional between early
anthropoids and later hominoids
 Mixture of ape and monkey traits
–
–
–
–
Y-5 Molar
No Tail
Intermembral Index ~1.0
Palmigrade locomotion
V. Rate of Evolution
A.
Punctuated Equilibrium
– Long periods of no change
punctuated by rapid
evolution and speciation
– S. Gould and N. Eldredge
– Explains gaps in record
B.
Phyletic Gradualism
Darwin’s idea of slow
gradual change leading to
eventual speciation