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Evolution
Year 10
Semester 2
Introduction
1. How old is the universe?
About 15 billion years since Big
Bang.
2. How old is the Earth?
About 4.5 billion years.
3. How long has there been life on the
Earth? About 3.5 - 4 billion years
4. When did the separation of man and
ape from a common unnamed
ancestor occur? Between 5 and 10
million years ago.
Introduction
5. How old is the human species (Homo
sapiens)? 100,000 to 200,000 years old.
6. Evolutionary theory teaches that humans
evolved from monkeys. True or False?
False - humans and modern monkeys had
a common ancestor.
7. Pope John Paul II does not approve of
the theory of evolution. True or False?
False, according to book Voices for
Evolution.
8. Major Protestant Churches have no
problem with the theory of evolution.
True or False? True, according to Voices
for Evolution.
What do you
notice about
living things?
Describe
each of the
environments
in each era.
Common Idea……
• Life, both plants and
animals, have changed over
time to meet the
conditions of the
environments they live in.
Adaptations
• Three main types:
– Physiological: ?
– Structural: ?
– Behavioural: ?
• An adaptation is a characteristic of a
living thing which allows it to survive
in the conditions provided by its
environment.
Evolution
• The modern day theory of evolution
states that all living organisms share
a common origin dating back more
than 4 billion years.
• Over this period, new species have
arisen and others have disappeared.
EVOLUTION
is a process
of change.
Charles Darwin
•
1.
2.
3.
4.
5.
The Theory of Natural Selection
Variation exists within a population of
organisms
All organisms face a daily struggle to
survive
Those organisms with adaptations that
best suit their environment have the
best chance of survival & reproduction
Those organisms survive & reproduce to
pass on their characteristics
Over time, the population changes to be
best suited to their environment.
Jean Baptist Lamarck
•
•
•
Stated that animals have some
structures that they use frequently
& others they do not use.
The ones that are used frequently
are strengthened & passed on.
He also states that animals can
acquire characteristics if they need
them
How Does Evolution Work?
• Evolution
occurs because
of Natural
Selection
Natural Selection
•
•
•
Within a particular species, there is
variation between individuals.
As a result, some individuals are
better adapted to their
environment and are more likely to
survive and reproduce.
These adaptations are then passed
onto the next generation.
SURVIVAL OF THE FITTEST
Artificial Selection
•
For thousands of years, humans
have made use of two very
important facts:
1. There is variation within a species
2. Offspring resemble their parents
•
•
Knowing this, humans have
selectively bred animals and plants
for desired characteristics
This is artificial selection
Genetic Variation
•
Three main sources of genetic
variation:
1. Meiosis
2. Sexual Reproduction
3. Mutations
•
Genetic variation is important to
the process of natural selection.
Remember:
• Chromosomes are made of DNA
& DNA consists of genes. The
genes control the physical
characteristics of an organism. A
change in gene can lead to a
change in characteristic.
An Example …
• The English Peppered Moth
Speciation
• Species: organisms that interbreed to
produce fertile, healthy offspring.
• Over time, the process of natural selection
can cause such changes in characteristics
that it leads to the formation of an entire
new species. This is speciation.
• It is most often caused by geographical
isolation.
Different
characteristics
arise through
genetic drift,
mutation and
environmental
pressures
The
isolated
population
is now
quite
different
Variation of
characteristics
is present in
population
The
breeding
population
becomes
isolated
The
environment
changes
Frequency of
new
characteristics
increases
Those best
suited to the
environment
survive
Favourable
characteristics
are passed on
New Species
=
SPECIATION
Selection
occurs
Types of Evolution
• Divergent Evolution
– one common ancestor evolves into two
species, which continue to evolve and
become less and less alike over time.
Types of Evolution
• Parallel Evolution
– Two related species
arise from a common
ancestor. The two
species then evolve in
much the same way
over time, probably in
response to similar
environmental
selection pressures.
Types of Evolution
• Convergent Evolution
– Occurs when two or more groups that
are not closely related come to
resemble each other more and more as
time passes. This is usually the result of
occupation of similar habitats and the
adoption of similar environmental roles.
Types of Evolution
• Which is which?
Divergent
Convergent
Parallel
Evidence for Evolution
• There is a variety of evidence that
supports evolution.
• This includes:
–
–
–
–
–
Fossil evidence
Comparative anatomy
Comparative embryology
Biogeography
DNA evidence
Evidence for Evolution
Fossil Evidence:
• Evidence for many species that existed in
the past can be seen from fossilised
remains of plants & animals that were once
trapped during the process of rock
formation.
• The rock strata & the fossils in them, can
be dated & arranged in sequence to show
how life on Earth evolved over time.
• Fossils also provided evidence about
locations of continents & oceans, & the
changing environments of the past.
Most recent
sediments
Recent fossils are
found in recent
sediments
Numerous extinct species
Fossil types differ in each
sedimentary rock layer
New fossil types mark
changes in environment
Oldest
sediments
Only primitive fossils are
found in older sediments
Evidence for Evolution
Comparative Anatomy:
• Involves looking at the structure of limbs
in birds, reptiles, amphibians & mammals.
• All show similar structures suggesting
common ancestry (known as homologous
structures).
Evidence for Evolution
Comparative Embryology
• Involves comparing the embryonic
forms of different organisms.
• Closely related organisms go through
similar stages in their embryonic
development, often showing
similarities among structures that
become so altered later in
development that their common
origin would not be seen in the adult
form.
Evidence for Evolution
Biogeography
• Study of geographic distribution of a
species using present – day
observations & the fossil record.
• The distribution & evolution of a
species can be affected by
geographic boundaries such as
mountains, lakes, oceans & deserts.
Evidence for Evolution
DNA Hybridisation
• Most powerful piece of evidence: an
organisms genetic code.
• Fossil evidence suggests that the earliest
forms of life were bacteria, so it seems
likely that bacteria developed the code
shared by all living things.
• The degree to which two species differ in
their genetic sequences can be measured
by DNA hybridisation.
DNA Hybridisation
Steps:
• Double – stranded DNA from each species is
heated causing the strands to separate
• The single – strands of DNA are ‘cut’ into smaller
segments using enzymes
• The segments from two species are mixed and
allowed to cool together in a petri dish – any
complementary bases of the two species will bond
and rewind to form a double – helix
• The degree to which there is there is a match
between the two strands demonstrates the
genetic similarity between the two species
Extract human DNA
Extract chimpanzee DNA
Unzip the DNA using
heat (both human and
chimpanzee DNA
unwinds at 86°C)
Mix strands to
form a hybrid
Some of the opposing bases in
the DNA sequence do not
match
Human Evolution
Primate Classification
Prosimians
New World
Monkeys
Old World
Monkeys
Apes
Hominids
Hominids
Anatomical features and habits:
Bipedal with modified feet, thigh bone, pelvis,
and spine
Large cerebral cortex (forebrain)
Reduced canines (and teeth in general)
Prominent nose and chin, reduced eye ridges
Body hair short or very reduced to assist
cooling
Highly sensitive skin
Complex social behaviour
Examples:
Australopithecus
Paranthropus
Homo
Ardipithecus
Paranthropus boisei
Homo neanderthalensis
Homo sapiens
Orrorin tugenensis
O. tugenensis, or ‘Millennium
man’ was discovered in late
2000.
A new hominin from Kenya, it is
claimed to be the oldest
hominin yet described.
Thirteen pieces, consisting of
teeth, fragments of the arm,
thigh bone, and a finger, from
at least five different
individuals have been found.
The size and morphology of the
teeth are intermediate
between those of a chimpanzee
and those of a human.
Other Name “Millennium Man”
Known Date
6.0 million years ago
Brain Size
? cc
Height
?m
Physique
Possibly bipedal, and a
forest dweller. Little else
known.
Skull Shape
?
Teeth and
Jaws
?
Geographical
Kenya, Eastern Africa
Distribution
Ardipithecus ramidus
Discovered in 1994, this species
was originally thought to be an
early hominin, with limited
evidence of bipedalism.
Two subspecies have been
identified:
A. ramidus ramidus (4.4 my old)
A. ramidus kadabba (5.8 my old)
This species is regarded by some
researchers as ‘simply an ape
with some unusual
characteristics’.
Some individuals may have been
1.2 m tall.
Other fossils found with this
hominin indicate that it may have
been a forest dweller.
Other
Name
Known Date
Brain Size
Height
Physique
Two subspecies:
A. ramidus ramidus
A. ramidus kadabba
4.4 - 5.8 million years
ago
? cc
c. 1.2 m
Possibly bipedal forest
dweller.
Little else known.
Foramen magnum more
Skull Shape forward
than apes.
Teeth and
Jaws
Smaller, narrow molars;
thinner jaw
Geographica
l
Eastern Africa
Distribution
Australopithecus anamensis
•
•
•
•
Anamensis was discovered at
Kanapoi, Kenya in 1994.
Other Name: None
Known Date:
4.2 – 3.9 million years ago
The find consists of
complete upper and lower
jaws, teeth, a piece of skull,
and arm and leg bones.
Brain Size:
? cc
Height:
?m
Anamensis had a mixture of
primitive, ape-like features
and advanced, human-like
features.
Physique:
The teeth and jaws are
similar to older fossil apes,
but the lower leg bones show
evidence of bipedalism and
the upper arm bone is
extremely human-like.
Skull Shape:
Teeth and
Jaws:
Geographical
Distribution:
Partial leg bones strongly suggest
bipedalism; humerus extremely
humanlike
Primitive features in the skull,
possibly apelike
Very similar to those of older
fossil
apes, but canines vertical; teeth
have thicker tooth enamel as in
humans
Eastern Africa
Australopithecus afarensis
Other Name
‘Lucy’, ‘First Family’
Known Date
3.9 – 2.5 million years ago
Brain Size
400 – 500 cc
Height
1.07 – 1.52 m
Physique
Skull Shape
Teeth and Jaws
Geographical
Distribution
Light build. Some apelike
features: relatively long
arms, curved fingers and
toes, sexual dimorphism
Apelike face, low forehead,
bony brow ridge, flat nose,
no chin
Human-like teeth, canines
smaller than apes, larger
than humans.
Jaw shape is half way
between that of an ape and
a human.
Eastern Africa
Photos courtesy of: SkullsUnlimited.com
The Primitive Features of 'Lucy'
This is a reconstructed
skeleton of ‘Lucy’
Australopithecus
afarensis – one of the
earliest known bipedal
hominins.
The skeleton exhibits
features consistent with a
Jaw shape half way
between V-shape of
ape's and U-shape
of human jaw
Chest (thorax)
is funnelshaped
species adapted for
walking bipedally ....
Sexual dimorphism
in the canine teeth
(a primitive trait)
Shoulder joint
that is orientated
towards the head
Relatively long
arms compared
to legs
But it also possesses many
‘primitive’ features
normally associated with
an arboreal existence.
Wrist has
high mobility
Relatively
short legs
Ankle joint is
highly mobile
Finger bones
are curved
Toes are long
and curved
Redrawn from a photograph
by © David L. Brill 1985
Australopithecus afarensis
Small brain
(410cc)
Low forehead
Brow ridge
Large, dishshaped face
Wide midface
Flat nose
Big, ape-like
incisor
Little of the skull is
behind the foramen
magnum
Diastema
(gap)
Large, thickly
enameled molars
A Modern Human Skull
(for comparison)
Canines larger
than in humans
Australopithecus africanus
Other Name
None
Known Date
~3.0 - 2.3 million years ago
Brain Size
Height
400 – 500 cc
1.1 – 1.4 m
Physique
Light build. Probably long
arms, more ‘human’ features,
probably less sexual
dimorphism than A. afarensis
Skull Shape
Brow ridges less prominent;
higher forehead and shorter
face.
Teeth and
Jaws
Geographical
Distribution
Teeth and jaws much larger
than in humans; shape of jaw
fully parabolic as in humans;
canine teeth further reduced.
Southern Africa
Australopithecus africanus
Small brain (450cc)
same size as gorilla's
but organization is
different from an ape's
No sagittal crest
Brow ridge
Low facial angle
A Modern Human Skull
(for comparison)
Very large molars compared with
modern humans (not shown here)
Lower face
protrudes forward
into a snout
(prognathism)
Paranthropus robustus
Other Name
Australopithecus robustus
Known Date
2.2 - 1.5 million years ago
Brain Size
Height
Physique
Skull Shape
Teeth and
Jaws
Geographical
Distribution
530 cc
1.1 - 1.3 m
Heavy build. Relatively long
arms. Moderate sexual
dimorphism.
Long, broad, flat face; crest
on top of skull; moderate
facial buttressing.
Very thick jaws; small incisors
and canines; large molar-like
premolars; very large molars
(megadont).
Southern Africa
Paranthropus robustus
Small brain
(530cc)
Very prominent sagittal
crest for the attachment
of powerful jaw muscles
Heavy brow ridge
Part of the rear
and top of this
skull is missing
Low facial angle
Massive
zygomatic arch
and cheek bones
Little of the skull is behind
the foramen magnum
A Modern Human Skull
(for comparison)
Small incisors
(missing in this
specimen)
Massive molars with thick enamel
are well worn suggesting a tough
vegetarian diet
Homo habilis
Other Name Homo rudolfensis
Homo habilis
2.4 - 1.6 million
years ago
2 - 1.6 million
years ago
600 - 800 cc
500 - 650 cc
c. 1.5 m
1.0 m
Robust but
‘human’ skeleton.
Relatively long
arms
Skull Shape
Larger, flatter
face
Small face with
developed nose
Teeth and
Jaws
Large, narrow
molars; robust
jaw
Smaller, narrow
molars; thinner
jaw
Eastern, and
possibly Southern
Africa
Known Date
Brain Size
Height
Physique
Geographical
Eastern Africa
Distribution
Homo habilis
Bigger brain
(650-680cc)
Large variant
Rounded cranium with no sagittal crest
Bulge in the
Broca's area
of the brain
for speech
production
Brow ridge
Smaller, narrower
face than the
australopithecines
Flat nose
Small variant
Projecting jaw
(prognathism)
More of the skull is behind
the foramen magnum
Jaw is less massive than
in the australopithecines
A Modern Human Skull
(for comparison)
Tooth row displays a
modern curve, with
narrow molars
Homo erectus
Other Name
Homo ergaster for older
African forms
Known Date
1.8 - 0.3 million years ago
Brain Size
Height
Physique
Skull Shape
Teeth and
Jaws
750 - 1250 cc
1.3 - 1.5 m
Robust but ‘human’
skeleton
Flat, thick skull with
sagittal keel
and large brow ridge
Smaller teeth than H.
habilis, robust jaw in
larger individuals
Geographical Africa, Asia, Indonesia,
Distribution and possibly Europe
Homo erectus
Bulge in the Broca's
area of the brain for
speech production
Bigger brain
Earliest: 850cc
Latest: 1100cc
Long, flattened cranium with a
distinctive keel along the top
Bulge in Wernicke's
area of the brain for
speech recognition
More recent
Asian forms
Shelving
forehead
Thick brow
ridge
Flat face
Older
African forms
A Modern Human Skull
(for comparison)
Occipital lobe
(bun-like swelling)
Attachment for strong neck
muscles to stop the head
from sagging forward
Teeth are smaller than
H. habilis, but more
massive than our own
Projecting
jaw
No chin
Homo heidelbergensis
Other Name Homo heidelbergensis
Known Date
Brain Size
Height
Physique
Rhodesia
skull
Atapuerca
skull
Stenheim
skull
400 000 - 100 000 years
ago
1100 - 1400 cc
?m
Robust but ‘human’
skeleton
Skull Shape
Higher cranium, less face
protruding. Many regional
variants with mosaics of
modern and more primitive
features.
Teeth and
Jaws
Similar to H. erectus, but
smaller teeth
Geographical
Africa, Asia, and Europe
Distribution
Homo heidelbergensis
Large brain
(1200 - 1430cc)
Flat, oblong shape
to the cranium
Sloping
forehead
Large brow
ridge
Broad, upright
face
Broad nasal
opening
Occipital 'bun'
for neck muscle
attachment
A Modern Human Skull
(for comparison)
No muzzle (no
prognathism)
Teeth are generally
modern in form
Homo neanderthalensis
Other Name
The Neanderthals;
H. sapiens neanderthalensis
Known Date
150 000 - 28 000 years ago
Brain Size
Height
Physique
Skull Shape
Teeth and
Jaws
Geographical
Distribution
1200 - 1750 cc
1.5 - 1.7 m
Robust but ‘human’ skeleton,
adapted for cold climates
Double-arched brow ridge,
high rounded orbits, midface
projection, weak chin, long
low skull, small mastoid
process,
Similar to Archaic H. sapiens;
except for incisors, smaller
teeth.
Europe and western Asia.
Homo neanderthalensis
Large brain (1600cc)
Larger than a modern
brain but organized
differently
Low, long cranium
Sloping forehead
Double-arched
brow ridge
Occipital lobe
(bun-like
swelling)
Large prominant
nose and mid-facial
projection
Swept back,
lightly built
cheek bones
Skull widest at the base
(unlike modern skulls which
are widest near the top)
Powerful jaw but
reduced compared
to H. erectus
A Modern Human Skull
(for comparison)
Weak chin
Teeth are smaller
than H. erectus, but
bigger than our own
Homo sapiens
Other Name
Early anatomically modern
humans;
Homo sapiens sapiens
Known Date
195 000 - 60 000 years ago
(for early humans)
Brain Size
Height
1200 - 1700 cc
1.6 - 1.85 m
Physique
Modern skeleton possibly
adapted for warmth
Skull Shape
Small or no brow ridge;
shorter and higher skull
Teeth may be smaller; shorter
jaws
Teeth and Jaws
than Neanderthals; chin
developed
Geographical
Distribution
Africa and western Asia (for
early forms)
Homo sapiens
Large brain
(1400cc)
Convex cranial vault
High, vertical
forehead
Skull widest
high up
No brow ridge,
just a slight
swelling of the
glabella
Vertical
face
Low, rounded
occipital area
Sizable mastoid
process
A Modern Human Skull
(for comparison)
Reduced tooth size
with thinner enamel
No muzzle
(no prognathism)
Sizable jaw with
projecting chin
Human Evolution Timeline
In 2001, the 6-7 my old remains of a
nearly complete skull with gorilla-like
features was unearthed in Chad.
Nicknamed “Toumai” and assigned to a
new genus, Sahelanthropus tchadensis,
scientists debate whether it is human or
the remains of a proto-gorilla.
Photos courtesy of: SkullsUnlimited.com
Human Evolution Timeline
Orrorin tugenensis, or
‘Millennium man’ was
discovered in late 2000 at a
site in Kenya.
It is claimed to be the
oldest hominin yet described.
Photos courtesy of: SkullsUnlimited.com
Human Evolution Timeline
Originally given the name Australopithecus ramidus,
it was reclassified under a new genus,
Ardipithecus.
Two subspecies have been identified:
A. ramidus ramidus (4.4 my old)
A. ramidus kadabba (5.8 my old)
Regarded by some researchers as ‘simply an ape
with some unusual characteristics’.
Human Evolution Timeline
Discovered at Kanapoi, Kenya in
1994, this earliest known species of
the genus Australopithecus had a
mixture of primitive, ape-like features
and advanced, human-like features.
Human Evolution Timeline
Human Evolution Timeline
Discovered in Kenya, a new
genus Kenyapithecus appears
to be an offshoot from the main
evolutionary branches
Photos courtesy of: SkullsUnlimited.com
Human Evolution Timeline
As many as four species from the
genus Australopithecus emerge,
with a wide geographic distribution,
ranging from southern Africa,
through East Africa, to Chad in the
north.
Human Evolution Timeline
A group of species from the genus
Paranthropus emerge in southern and
eastern Africa. Superbly adapted to
exploit low grade vegetarian diet, they
coexist with the emerging genus Homo.
Human Evolution Timeline
From a probable Australopithecine ancestor
emerges the first species of genus Homo.
A small-brained species with fully developed
bipedal locomotion, it has a talent for shaping tools
from stone. This hominin does not venture out of
Africa.
Human Evolution Timeline
What followed was an adaptive radiation of the
genus Homo, leading to increased body height,
brain capacity, complex social behavior, and a
geographic distribution that extended well beyond
Africa.
Human Evolution Timeline
The most recent, and perhaps most perplexing part of this
emerging story, is the discovery in 2003 of what appears to
be a ‘pygmy’ species of human that lived on the
Indonesian island of Flores between 95 000 - 13 000
years ago.