Human Evolution
Mader: Biology 8th Ed.
Classification of Modern Humans
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: sapiens
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IB Learning Objective
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Describe the major anatomical features that
define humans as primates.
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Characteristics we share with primates
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Humans retain
pentadactyl limbs
with five digits and
marked mobility of
digits
All primates have
grasping hands with
long fingers and a
separate opposable
thumb
Mader: Biology 8th Ed.
Characteristics we share with primates
Hands/ Grasping
Limbs – with long
fingers and a
separate opposable
thumb
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Mader: Biology 8th Ed.
Characteristics we share with primates
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Mobile arms with shoulder joints that
allow us to move in three planes
We are born to CLIMB!
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Limbs/ Mobile Arms
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The arrangement of bones at shoulder
permits brachiation movement
– the bones of the shoulder girdle allow
weight to be transferred via the arms
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Characteristics we share with primates
Developed upright walk and extensive head
rotation
Our skulls are modified for an upright posture
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Characteristics we share with primates
Unique Eyes
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Forward facing eyes on a flattened face
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Characteristics we share with primates
Developed unique eyes
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The eyes look forward with overlapping visual giving
stereoscopic vision (depth persption
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Stereoscopic Vision
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Stereoscopic vision and resultant depth
perception allows primates to make
accurate judgments about distance and
position of adjoining tree limbs.
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Mader: Biology 8th Ed.
Characteristics we share with primates
Reduction in nose and teeth
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Flattened noses
decrease ability to smell
Reduced in number of teeth
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Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Other Primate Characteristics
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Skull modified for upright posture
Nails instead of claws.
Single births
Expanded, complex brain.
Emphasis on learned behavior.
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Mader: Biology 8th Ed.
The unavoidable conclusion
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Humans evolved from other primate
species.
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That is we share a common ancestor with
other primates, i.e. chimpanzee.
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From Apes to Humanity in 35 million years
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Anthropoids – Apes
– Earliest fossil 35 million years ago in
Africa.
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From Apes to Humanity in 35 million years
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Anthropoids – Apes
– Early anthropods
were agile tree
dwellers
– Important feature
was brachiation of
limbs that allowed
them to swing
between trees
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From Apes to Humanity in 35 million years
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Anthropoids – Apes
– At the time of human and ape evolution
the climate had periods of extreme
environmental change.
– Environmental change was partially due
to movements in the tectonic plates and
thus the continents.
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From Apes to Humanity in 35 million years
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Climate Change
– About 15 million years ago Africa collide
with Eurasia.
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From Apes to Humanity in 35 million years
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Climate Change
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As a consequence, the climate in Africa became drier
and colder.
Rainforest were the apes lived were reduced to isolated
pockets.
Large Savannahs spread over Africa
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From Apes to Humanity in 35 million years
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Climate Change
– Many scientists believe that bipedalism
(ability to walk upright) developed in the
savanna about 5 Mya;
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Discuss the anatomical features that enable
bipedalism in humans.
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arches on feet;
stronger bones in legs / stronger legs;
longer legs;
shorter arms;
non-opposable big toe;
foramen magnum further forward;
knees closer together;
wide pelvis;
lumbar spine curved;
larger muscles on legs;
Evidence of Bipedalism
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fossil footprints found (at Laetoli) 3.6 Mya;
anatomy of hominids suggests bipedality at 4.4
Mya;
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bipedality possibly associated with a change in
habitat and climate
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Advantages of bipedalism
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Advantages of walking upright
– Freed hands up to obtain or carry food
– Hands are free to carry offspring.
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Advantages of bipedalism
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Advantages of walking upright
bipedality provides greater field of view
for foraging / detecting predators;
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More advantages of being bipedal
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Thermoregulation:
– Smaller surface area presented to the sun
at midday (60%)
– Greater air flow across body when it is lift
off the ground
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Trends in Hominid Fossils
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Hominids are members of the family
Hominidae.
– A notable feature of this family is the
ability to walk on two legs, called
bipedalism.
– Homo sapiens is only surviving member
of the Hominidae family, but in the past
several species co-existed,
 example Homo neaderthalensis.
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IB Learning Objectives
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Outline the trends illustrated by the fossils of
Ardipithecus ramidus, Australopithecus
including afarensis and A. africanus.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Trends in Hominid Fossils
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Many hominid fossils have bee found, dated
and assigned to species.
These fossils show the following
evolutionary trends
– Increasing adaptation to bipedalism
– Increasing brain size relative to body
size
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Location of hominid fossils
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Hominids genus/ species fossil location
– Ardipithecus – Ethiopia
– Australopithecus and Homo Habilis –
Southern or Eastern Africa
– Homo Erectus – Eastern Africa & Asia
– Homo neanderthalensis found in
Western Asia & Europe
– Homo sapiens many parts of the World.
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Ardipithecus ramidus
Ardipithecus ramidus
– 4.4 Million years ago
– Only fragments of skulls
and other bones have
been found
– They show intermediate
characteristics between
chimpanzees &
Australopithecus
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Ardipithecus ramidus
Ardipithecus ramidus
characteristics
– Teeth
1.
Small number of
larger molars like a
chimps
2.
Incisors slightly
smaller than those of
a chimp
3.
Canines blunt &
projecting less that
those of a chimp
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Ardipithecus ramidus
Ardipithecus ramidus
characteristics
– Skull & Bipedalism
 Foraman magnum
(hole through which
the spinal cord enters
the skull) further
forward than in chimps
suggesting partially
Bipedalism
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Australopithecines
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It is possible that one of the
australopithecines that evolved
and diversified in Africa 4 mya
is a direct ancestor of humans.
– Southern Africa
 Australopithecus
africanus
– Eastern Africa
 Australopithecus
afarensis
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Australopithecines – Southern Apes
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Existed 5 to 1.5 mya
Lucy – Australipithecus afarensis - 3 mya
– Lucy walked upright ( bipedalism)
– Evidence to support the above idea
footsteps in volcanic ash – known as the
Laetoli Ash.
– The Laetoli Ash was dated using the
radioactive method….
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Mader: Biology 8th Ed.
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Laetoli Ash.
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Australopithecus afarensis
Australopithecus
afarensis
1.4- 2.5 million years ago.
2.Tall lower jaw
3.Fairly large molars
4.Projecting face.
5.Brain size 380- 430 cc
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Autralopithecus africanus
Autralopithecus africanus
1.3-2.5 million years ago
2.Tall thick lower jaw
3.Large molars
4.Projecting face
5.Bony strut
6. Brain Size 435 – 530 cc
Mader: Biology 8th Ed.
Outline the trends illustrated by the fossils of
Australopithecus afarensis. (3 points)
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A. afarensis had traits that indicated bipedality such as a
non opposable big toe, a broad pelvis , a more vertical
posture and a skull on top of vertebrae;
A. afarensis also had short legs indicating bipedality;
A. afarensis curved finger bones; which indicated it was
still arboreal (living in trees);
A. afarensis had conical thorax; indicating vegetarian diet;
A. afarensis dentition (teeth) more like a chimp than
modern humans for example they had larger canines and
parallel molars;
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Homo habilis
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Homo habilis –
– 2.4 to 1.5 mya
– Different from
Australopithecines
by having light
cranial bones and
enhanced cranial
capacity.
– First hominids to
use tools
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Homo habilis –
1.Flatter face
2.Large molars
3.Bigger brain size
relative to body size
4. Brain Size was 600cc
Mader: Biology 8th Ed.
Explain why the approximate date and
distribution of H. habilis are uncertain.(3 pts)
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Homo habilis existed about 2 (±0.5) million years ago in
(sub-Saharan) Africa;
Dates have high uncertainty because:
fossils lacking or not in good form;
soft parts do not fossilize;
interbreeding of between H. habilis and other hominid
species species may have lead to a mixture of traits and
thus miss identification by scientist;
H. habilis might have migrated to other areas ;
Scientists have different views about when and where H.
habilis lived;
Fossil dating method not totally accurate;
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Homo erectus
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Homo erectus –
– 1.7 t0 1.8 mya
– First hominid to migrate to
other places and use fire
– Large body and brain.
– Because of brain size and
shape probably developed
language.
– Brain size 1000cc
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Homo erectus
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Homo erectus –
1. Smaller molars
2. Receding forehead
3. A large brow-ridge
4. Smaller jaw
5. Bigger brain size relative
to body size
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Homo erectus
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Larger brain and flatter face than Homo
habilis.
Much taller than previous hominids.
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Early Humans Had large brains and busy hands
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Homo erectus –
– Fossils have been found all over Europe,
Asia, and Africa.
 Steinheim Germany (0.25 mya)
 Sale, Morocco (0.25 mya)
 Petralona, Greece (0.3 mya)
 Choukoutein, China (Peking Man) (0.5 mya
 Swartkans, South Africa (1 mya)
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Where Homo erectus fossils have been found.
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1.
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Homo neanderthalensis
200,000- 30,000
years ago
Existed at the same
time as Homo
sapiens
Lower forehead
Smaller brow ridge
Smaller molars
Smaller jaw
Brain Size 1600 cc
Mader: Biology 8th Ed.
IB LEARNING OBJECTIVE
State that, at various stages in hominid
evolution, several species may have
coexisted.
– An example of this is H. neanderthalensis
and H. sapiens.
Mader: Biology 8th Ed.
Homo Sapiens
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140,000 years ago
High forehead
Very small jaw
Small molars
Flat face
No brow ridges
High forehead
Brain size 1300 cc
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
IB Learning Objective
•
Outline the trends illustrated by the fossils of
including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
Mader: Biology 8th Ed.
IB LEARNING OBJECTIVE
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Knowledge of approximate dates and
distribution of the named species is
expected
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Ardipithecus ramidus,
Australopithecus afarensis
A. africanus.
H. habilis,
H. erectus,
H. neanderthalensis
H. sapiens.
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The Origin of Modern Humans
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Homo sapiens –
– Arose in Africa about 140,000 ya
– Evidence from Mitochondrial DNA indicate
that today’s population are related to an
African human ancestor.
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More evidence
analysis of Ychromosome suggest
modern humans
–are descendents of
African-inhabiting
ancestors at least
150,000 ya.
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The Origin of Modern Humans
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Homo neanderthalensis–
– Arose in Central and Western Europe
about 250,000 ya
– Went extinct between 45,000 and 32,000ya
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The Origin of Modern Humans
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Homo neanderthalensis–
– Brain size was bigger than modern
humans
– Heavier & more muscular than modern
humans
– Existed at the same time and place as
modern humans.
– Why did they go extinct?
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Homo neanderthalensis
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Human Evolution
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Evolution of the modern human brain
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The brains of early hominids (Australopithecus)
were only slightly larger relative to body size
than modern apes.
The teeth and jaws of early hominids suggest a
mainly vegetarian diet.
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Human Evolution Tutorials/ Animations
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https://www.23andme.com/gen101/prehistor
y/prologue/
http://www.becominghuman.org/
http://www.smithsonianmag.com/ist/?next=/
science-nature/The-Top-Ten-DailyConsequences-of-Having-Evolved.html
Mader: Biology 8th Ed.
IB LEARINING OBJECTIVE
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Discuss the correlation between the change
in diet and increase in brain size during
hominid evolution.
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Evolution of the modern human brain
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About 2.5 million years ago Africa became
cooler and drier.
Savannah and grassland replaced the
forest.
This change in climate is thought to have
prompted the evolution of the first Homo .
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Evolution of the modern human brain
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The Homo population could no longer hide
in tree and there was less vegetation to feed
on.
Homo could make and use tools to hunt
other animals and defend themselves from
predation survived.
This change in diet from a vegetarian based
diet to a meat based diet corresponds to a
rapid change in brain size. WHY?
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Mader: Biology 8th Ed.
Diet and Brain Size
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Brains are metabolically expensive.
Brains make up 2% of our body mass, but
respire 20% of our energy budget.
Human brain is 3X the size of apes’.
This means a requirement for human
evolution was a reliable diet of protein and
fat.
Scientists believe that early humans ate a lot
of bone marrow discarded from larger
predators.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
Diet and Brain Size
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The correlation between brain size and diet
are explained in two ways:
1. Eating meat increases the supply of
protein, fat, and energy in the diet,
making it possible for the growth of larger
brains.
2. Catching and killing prey on the savannas
is more difficult that gathering plants, so
natural selection favoured hominids with
larger brains and greater intelligence.
Mader: Biology 8th Ed.
Outline consequences of an increase in brain
size for the Homo lineage.
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large brain size correlates with language;
large brain correlates with improvements in
tool-making;
improved tools allow more nutritious diets for
further brain development;
increased brain size leads to rituals / burying
the dead;
excellent eye-hand coordination;
increased brain size leads to written history /
cave art / symbolic thought;
Large brain size lead to
cultural evolution
Mader: Biology 8th Ed.
IB LEARNING OBJECTIVE
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Distinguish between genetic and cultural
evolution.
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Genetic vs. Cultural Evolution
Genetic Evolution
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Refers to changes in allele frequency in a
population.
Genetic Evolution
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Changes in allele
frequency are due two
main factors:
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Genetic Variation in
phenotypes
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Some phenotypes are
better able to survive
and reproduce than
others
Cultural Evolution
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Refers to the development of customs,
civilization and achievements of people.
Mader: Biology 8th Ed.
Mader: Biology 8th Ed.
IB LEARNING OBJECTIVE
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Discuss the relative importance of genetic
and cultural evolution in the recent evolution
of humans.
Mader: Biology 8th Ed.
Important Developments in cultural
Evolution
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Extension of the Period of parental care
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The Development of Language
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The development of tool technology
Important Developments in cultural
Evolution
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Extension of the Period of parental care
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Delayed onset of puberty
Resulting long childhood, when the next
generation of a population are trained
and schooled as they develop essential
survival skills.
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The Development of
Language
– Structures necessary for
elaborate vocal
communication was
found in early hominids:
 Fossilized braincase
show that areas of the
brain where language
is constructed was
enlarged.
 Positions of Vocal
folds in the neck
 high positioned larynx
Important Developments in cultural
Evolution
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The Development of Language
– Verbal communication advantages:
 Passing on new ideas
 What else can you think of that would
be an advantage of having a language?
Important Developments in cultural
Evolution
The development of tool technology
– About 35000 years ago modern humans
had spectacular advances:
 bones, antlers and stones were
modified to make blades, chisels, drills,
arrowheads, and barbs
Important Developments in cultural
Evolution
The development of tool technology
– Artistic skills developed.
– Drawing dating to 25000 to 10000 years
ago showing contemporary animals in
scientific detail.
Relative importance of genetic and
cultural evolution
Human cultural evolution
– human agricultural and other
technologies has allowed humans to
significantly change their environment.
Relative importance of genetic and
cultural evolution
Human cultural evolution
– Enlarged populations
– Rules & laws succeeded basic customs.
– individuals have acquired rights and
responsibilities
Relative importance of genetic and
cultural evolution
Human cultural evolution
– Occurring at a very fast rate
– Neolithic revolution to industrial
revolution
– Silicon revolution/ information
revolution of today.
Outline the difference between genetic and
cultural evolution (2 Pt).
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genetic evolution occurs through
variation and reproduction / inheritance
of genes;
cultural evolution occurs through
customs / languages, etc. taught /
learned;
Mader: Biology 8th Ed.
Discuss how cultural evolution in humans
depended on increases in brain size. (3 pts)
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large brain size correlates with language; large
brain correlates with improvements in tool-making;
improved tools allow more nutritious diets for
further brain development;
increased brain size leads to rituals / burying the
dead;
excellent eye-hand coordination;
increased brain size leads to written history /
cave art / symbolic thought;
Mader: Biology 8th Ed.