Mammalian and Primate
The Fossil Record
Biological evolution is descent with modification.
This encompasses small-scale evolution
…and large-scale evolution
(changes in gene frequency in a population from one
generation to the next)
(the descent of different species from a common ancestor
over many generations).
Evolution helps us to understand the history of life.
Early Signs of Life
By 3 billion years ago,
large colonies of simple
such as blue-green algae,
were flourishing at the
surface of the oceans and
The most advanced
creatures were sponges,
which are essentially
single and multi-celled
The Birth of Earth
Biological evolution is not simply
a matter of change over time.
Lots of things change
over time: trees lose their
leaves, mountain ranges
rise and erode, but they
aren’t examples of
because they don’t
involve descent through
All life shares a common
The central idea of
is that all life on
Earth shares a
just as you and your
cousins share a
We’re all distant cousins: humans, oak
trees, hummingbirds and whales.
Through the process
of descent with
common ancestor of
life on Earth gave rise
to the fantastic
diversity that we see
documented in the
fossil record and
around us today.
Life has a history and different
species share common ancestors.
The Family Tree
The process of evolution
produces a pattern of
relationships between species.
As lineages evolve and split
and modifications are inherited,
their evolutionary paths
This produces a branching
pattern of evolutionary
By studying inherited characteristics and
other historical evidence, we can reconstruct
evolutionary relationships and represent them
on a “family tree,” called a phylogeny.
that tie all life
When a lineage splits (speciation), it is
represented as branching.
When a speciation event occurs, a single
ancestral lineage gives rise to two or more
Fish With Fingers
before they left
Each lineage has ancestors that are
unique and ancestors that are shared.
A grouping that includes a common ancestor
and all the descendents (living and extinct) of
Trees, Not Ladders
branches on a
tree, not a
and share a recent
that was neither
Principles of Classification
Building a Phylogenetic Tree
To build a tree
data about the
heritable traits of
each organism they
are interested in,
such as physical
structures shared through descent from a
structures used for the same function that
developed independently and are not the result of
the process by which similarities can develop in
different groups of organisms.
An example of
characters is the
four limbs of
Birds, bats, mice,
and crocodiles all
have four limbs sharks and bony
fish do not.
Not all characters are homologies, in
this case the wings are analagies.
Bat wings consist of flaps of skin stretched between
the bones of the fingers and arm.
Bird wings consist of feathers extending all along
This phylogeny illustrates how distant bats
and birds are in an evolutionary sense.
The Linnaean System of
The classic system of classification was
developed by Carolus Linneaus.
In this system every organism is assigned to
a kingdom, phylum, class, order, family,
genus, and species.
This system is not based on evolution.
This system names only clades.
Groups species according to shared derived
Primitive traits reflect
shared traits that
before the group's
Genus and Species
Species is the most precise taxonomic level.
Genus is a group of species more closely
related to each other than to species from
These Happy Face
Spiders all appear
different but can
interbreed so they are
considered the same
Approaches to the Definition
Species are defined by reproductive
Biological Species isolation. Only members of the same
species can interbreed
Key aspect is the ability individuals have to
identify members of their own species for
A species is a group of organisms
exploiting a single niche. Natural selection
separates species from one another.
Tigons and Ligers
If you wanted to squeeze the 3.5 billion years of
the history of life on Earth into a single minute:
Wait about 50 seconds for multi-cellular life to
Wait another 4 seconds for vertebrates to
invade the land
Wait another 4 seconds for flowers to evolve
In the last 0.002 seconds “modern” humans
Complex Multicellular Life
Life began 3.8 billion years ago…
Insects diversified 290 million years ago…
The human and chimpanzee lineages
diverged only five million years ago…
How have scientists figured out the dates of
long-past evolutionary events?
The universe is full of naturally occurring
radioactive elements. Radioactive atoms
are inherently unstable; over time,
radioactive “parent atoms” decay into
stable “daughter atoms.”
This technique relies on the half-life decay of
radioactive elements which allow scientists to
date rocks and materials directly.
The principles of
and its application
in determining the
age of Earth
Fossils can be dated relative
to one another by noting
their positions in layers of
rocks, known as strata.
This techique provides a sequence of events
from which relative dates can be
The Permian - Triassic
million years ago
Some evolutionary changes occur in a
clock-like fashion. When a stretch of
DNA does indeed behave like a
molecular clock, it becomes a powerful
tool for estimating the dates of lineagesplitting events.
This technique allows scientists to use the
amount of genetic divergence between
organisms to extrapolate backwards to
Vast changes have
occurred during the life of
There have been cycles of
mass extinction, bursts of
speciation, and massive
geologic changes – even
the movement of
The Insect World
The first vertebrates appeared 500 mya
Reptiles were dominant land
Placental mammals appeared 70 mya
Divided into two periods: Tertiary and
Quaternary and 7 epochs: Paleocene,
Eocene, Oligocene, Miocene, Pliocene,
Pleistocene and Holocene.
The Cenozoic era is known as the Age of
After dinosaurs became extinct, mammals
underwent adaptive radiation, resulting in
rapid expansion and diversification.
The neocortex, which controls higher brain
functions, comprised the majority of brain
volume, resulting in greater ability to learn.
Creatures of the Skies
Major Mammalian Groups
Primitive, egg laying mammals
Infants complete development in an eternal pouch
Longer gestation allows the central nervous
system to develop more completely
the Key to
The evolution of life has not
been a smooth process.
There have been catastrophic
global events such as ice
ages, immense volcanic
eruptions, and asteroid
The result has been at least
five episodes of mass
extinction and many minor
Early Primate Evolution
Primate origins began in the
placental mammal radiation 65
The earliest undoubted primates
appear in the Eocene epoch.
Most of our knowledge of primate
Oligocene evolution comes from
a site in Egypt, the Fayum.
Fayum Forms: Possible Roots
of Anthropoid Evolution
Small primate that near the
evolutionary divergence of Old
and New World anthropoids.
Largest of the Fayum primates
with a small brain, large snout,
and none of the traits of Old
World monkeys or hominoids.
Miocene Fossil Hominoids
Marked by a spectacular hominoid radiation
and could be called “the golden age of
African forms (23-14 mya)
European forms (13-11 mya)
Asian forms (16-7 mya)
The location of our very own twig:
Humans on the tree of life.
The Language of the
The Human Animal
Early hominid lineage gave rise to
many other (now extinct) hominids.
Who are we - where
are we going?
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