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Speciation
Speciation in Darwin’s Finches

Speciation in the
Galapagos finches
occurred by founding of
a new population,
geographic isolation,
changes in the new
population’s gene pool,
reproductive isolation,
and ecological
competition.
Founder’s Arrive

Finches from the
mainland of South
America arrive on
the Galapagos
islands.

As finches do not
usually fly over
open water, it is
assumed they were
blown off course by
a storm.
Separation of Populations

As finches do not fly over open water, they
remained on whatever island they landed
on.
Changes in the Gene Pool

Each island of the
Galapagos has its
own unique flora
and fauna (plants
and animals)—the
finches slowly
adapted to their
islands through
natural selection.
Species

A species is a group of organisms that
breed with one another and produce
fertile offspring.

This population will share a common gene
pool.
Reproductive Isolation

When members of two populations cannot
interbreed and produce fertile offspring,
Behavioral Isolation

Occurs when two populations are capable
of interbreeding but have differences in
courtship rituals or other reproductive
strategies.
Geographic Isolation

Two populations are separated by a
geographic barriers such as rivers,
mountains, or bodies of water.
Temporal Isolation

Two or more species reproduce at
different times.
Ecological Competition

All organisms compete for limited
resources.

The finches evolved specialized beaks for
particular foods to limit the competition.
Continued Evolution

The process of isolation, genetic change,
reproductive isolation, most likely repeated
itself over and over again.

As a result, there are 13 different species of
Galapagos finches.
Human Evolution
Primates

The evolutionary history of
primates began about 85
million years ago.


Fossils have been found
primarily in North America,
however they were
widespread throughout
Eurasia and Africa
Notharctus


Discovered in Germany
~ 16.5 million years old
Primates to Humans

Nakalipithecus (Kenya) & Ouranopithecus
Ouranopithecus (Greece)
Last common ancestors between gorillas,
chimpanzees, and humans.
 Between 8-4 mya, chimpanzees and gorillas
split from the line leading to humans.

Becoming Human

Savannah Theory



Proposed by Raymond Dart
Stated that hominids began to
stand on two legs to peer over
savannah grasses to hunt and
hide from predators.
Aquatic Ape Hypothesis


States that early hominids lived
around water and often dove,
waded, and swam.
Accounts for our lack of hair,
subcutaneous fat, and
abundance of sebaceous glands.
Hominids

Homo habilis
2.4 to 1.4 million
years ago (mya)
 Found in Africa
 Possessed small
molars and large
brains
 Was surrounded by
stone and bone
tools
 Nicknamed “Handy
Man”

Hominids

Homo rudolfensis and
Homo georgicus

1.9-1.6 million years
ago

H. rudolfensis


Incomplete skull found in
Kenya. Scientists debate
whether this is another
species, or another H. habilis
H. georgicus


Found in Georgia (near
Russia)
Thought to be an
intermediate form between
H. habilis and H. erectus
Hominids

Homo ergaster and Homo
erectus

H. ergaster



Discovered in Indonesia
1.8-1.25 mya, seen as a subspecies
of H. erectus
H. erectus





1.5-1 mya, found in Africa, Asia, and
Europe
Used elaborate stone tools
First human ancestor to truly walk
upright
May have used fire
Peking Man
Hominids

Homo cepranensis and Homo
antecessor


Both thought to be intermediate
forms between H. erectus and H.
heidelbergensis
H. cepranensis



1.2 mya-500,000 ya
Based on fossils found in Spain and
England
H. antecessor


800,000 ya
Based on a single skull cap found in
Italy
Hominids

Homo heidelbergensis
lived from 800,000 ya to 300,000 ya
 Heidelberg Man

Hominids

Homo rhodesiensis



300,000-125,000 ya—disputed
separation from H.
Heidelbergensis
Rhodesian Man
Gawus Cranium



Discovered in 2006 in Gawis,
Ethiopia
500,000-250,000 ya
Might possibly be an intermediate
species between H. erectus and
H. sapiens
Hominids

Homo neanderthalensis
300,000 ya to 30,000 ya
 Mitochondrial DNA studies
suggest that H.
neanderthalensis is a
separate species from H.
sapiens
 Neanderthals are NOT our
ancestors

Hominids

Homo sapiens




250,000 ya to the present
Direct evidence suggests
we migrated out of Africa
However, this does not
preclude multiregional
speciation
H. sapiens idaltu


Oldest known anatomically
modern human
160,000 years old, found in
Ethiopia
Hominids

Homo floresiensis
100,000-12,000
years old
 Skeleton of a 30
year old woman
found (~18,000 yo)

 One
meter (3 feet)
tall
 Nicknamed “Hobbit”
Hominids

Homo floresiensis

Separate Species or
Homo Sapien?
 At
first scientists thought
that H. florensiensis was a
separate species
 Now, they believe that H.
floresiensis is a H. sapien
that has insular dwarfism
 Modern day people on the
island of Flores are
pygmies