IB Biology
Option D
D3 Human Evolution
1
D.3.1 Outline the method for dating rocks and fossils using
radioisotopes, with reference to 14C and 40K.
•
14C
is a naturally occurring isotope of carbon with a half
life of 5730 years.
Decay
Formation
• Constantly being made in the atmosphere when cosmic
rays cause neutrons to fuse with nitrogen nuclei and
“kick out” protons
http://www.youtube.com/watch?v=2io5opwhQMQ Carbon dating – Mr. Andersen
2
D.3.1 Outline the method for dating rocks and fossils using
radioisotopes, with reference to 14C and 40K.
• 14C production is in equilibrium with its decay to 12C
• The 14C is incorporated in carbon dioxide which is then
taken up by plants. In the end all living things have the
same ratio of 14C to 12C
• When an organism dies it no longer takes in 14C. So
over time the ratio of 14C to 12C changes. This is
measurable and can be used to estimate age.
• The limit for accurate determination of age is about
50,000y
3
D.3.1 Outline the method for dating rocks and fossils using
radioisotopes, with reference to 14C and 40K.
• 40K is an isotope with a half life of 1.3 X 109 y
• 40K decays to 40Ar.
• When 40K is released from a volcano in lava all of the
argon gas is driven off. So brand new rocks effectively
have a ratio 40K: 40Ar of 100:0
• Over time the lava may be weathered and eroded and
incorporated into sedimentary rocks.
• The measured ratio of 40K to 40Ar can be used to date
rocks over one million years old with an accuracy of
around 50000 years
4
D.3.1 Outline the method for dating rocks and fossils using
radioisotopes, with reference to 14C and 40K.
When to use which isotope?
•Rocks
- K-40
- For older samples, over 100,000 years old
•Fossils
- C-14/C-13/C-12
- For young samples, from 1000 to 100,000
years old
- Lots C14 recent death; little C14, old!
5
D.3.2 Define half-life.
Half-life = The time it takes for half of a radioactive
isotope to decay
6
D.3.2 Define half-life.
Half-life = The time it takes for half of a radioactive
isotope to decay
What is the half life for each of the isotopes
represented by these curves?
7
D.3.2 Define half-life.
?.??
0.13
0.7
3.42
8
D.3.3 Deduce the approximate age of materials based on a
simple decay curve for a radioisotope.
9
D.3.4 Describe the major anatomical features that define
humans as primates.
human
gibbon
gorilla
Grasping pentadactyl limbs
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html Did Humans Evolve? (PBS)
10
D.3.4 Describe the major anatomical features that define
humans as primates.
Binocular
Vision
11
D.3.4 Describe the major anatomical features that define
Monkey
humans as primates.
Monkey
Reduced
snout
leading to
reduced
olfaction
Squirrel
vs.
Human
Doggie
12
D.3.4 Describe the major anatomical features that define
humans as primates.
Human
Baboon
Gorilla
Moo
Cown
Generalized
Dentition
13
D.3.4 Describe the major anatomical features that define
humans as primates.
Others:
• Forelimbs able to twist
• Clavicle allows wide range of arm movement
(re. the above two points: if you have a gentle and patient pet dog, give it a
rub on the tummy and then move it’s forelegs, they really only move in one
plane)
• Slower reproduction
- long gestation
- usually one offspring at a time
• Larger skull – relative to body size
• Large brain – more complex, more folds
• Better visual acuity – more of the photoreceptors
have their own sensory neurons
• Social dependency
14
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A.
africanus, and Homo including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
15
D.3.5 Outline the trends illustrated by the fossils of:
approximate
dates
Ardipithecus 5.8 mya –
ramidus 4.4 mya
Australopithecus:
A. afarensis 4 mya – 2.5
mya
A. africanus 3 mya - <2.5
mya
distribution
Ethiopia; similar to
chimpanzee
Eastern Africa;
“Lucy”
Southern Africa
16
D.3.5 Outline the trends illustrated by the fossils of:
Homo:
H. habilis 2.4 mya – 1.6 Olduvai Gorge
mya
(Tanzania), Kenya,
Ethiopia, South Africa;
simple stone tools,
fire, cave-dwelling
H. erectus 1.8 mya –
Europe, India, China,
100,000 ya
Indonesia, Africa
H. neandertha- 200,000 –
Europe, Western Asia;
lensis 30,000 ya
larger brain than
modern human! 
H. sapiens 140,000 –
Africa, Europe, Asia;
70,000 ya
cave paintings; tool
technology/weapons
17
THE HOMINIDS
http://humanorigins.si.edu/resources/multimedia/videos
What does it mean to be human? (Smithsonian National Museum of Natural History)
18
Australopithecus afarensis
•
•
•
•
•
•
•
3.9 – 2.9 Mya
Climate changing. Antarctic ice cap advance 5 Mya
Distribution: Ethiopia, Kenya, Tanzania
Cranial capacity: 380 – 450 cm3
Height: 1.07m
Bipedal (footprints 3.6 Mya old) /climber
U-shaped dental arcade but reduced
canines
• Arboreal / terrestrial herbivore
© 2008 Paul Billiet ODWS
19
Australopithecus africanus
(Southern Ape of Africa)
•
•
•
•
•
3 – 2.25 Mya
Cooling of climate reduced rainfall
Further advance of Antarctic ice
Development of scrubland and savannah
Forest cover retreats
© 2008 Paul Billiet ODWS
20
Australopithecus africanus
(Southern Ape of Africa)
• Distribution: Southern and Eastern Africa
• Cranial capacity: 500 cm3
(Chimp = 400cm3)
• Bipedal
• 20 – 35 kg
• Rounder skull
• Parabolic dental arcade
• Longevity: 40 years maximum
• Scavenger of bone marrow/
brain cases
• Used simple tools
© 2008 Paul Billiet ODWS
21
Homo habilis - the handy man
• 2.6 -1.4 Mya
• E. Africa
• Scavenging significant part
of the diet
• Cranial capacity: 600 – 800 cm3
• Height: 1.20 – 1.35m
• Simple fashioned tools – choppers
© 2008 Paul Billiet ODWS
22
Homo erectus – the upright man
•
•
•
•
1.8 to 0.5 Mya
0.9 Mya beginning of the Pleistocene ice age
Oscillations between cold and warm periods
Spread out of Africa (1.6Mya) throughout the
old world
• Scavenging to hunting
• Use of a home base
© 2008 Paul Billiet ODWS
23
Homo erectus – the upright man
• Cranial capacity: 850 – 1100 cm3
(H. sapiens = 1350 cm3)
• Use of fire
• Height 1.55 to 1.8m
• Extended childhood
• 1st molar at 4.6 years old
(H. sapiens = 5.9y)
• Greater longevity
 52 years
• Speech? (Brain says: yes; spine says: no)
• Improved tools: Hand axes
© 2008 Paul Billiet ODWS
24
Homo neanderthalensis
(our distant cousins?!)
• 250 000 to 28 000 years ago
• Europe, Middle East, into Central Asia
• Evolved from H. erectus populations perhaps via
H. heidelbergensis, then became extinct
• Adapted to the ice-age conditions of temperate
zone
• Large nose may have warmed
cold air
• The enigma of its
extinction is not
explained
© 2008 Paul Billiet ODWS
25
http://www.youtube.com/watch?v=P-fyqQSKpGY&feature=player_embedded Meanderthal
Homo neanderthalensis
(our distant cousins?!)
• Cranial capacity: 1400 cm3
(H. sapiens = 1350 cm3)
• Brow ridge, long low skull
• Height: 1.67m
• Stocky build
• Improved sophisticated tools
• Sometimes buried their dead
• Made simple jewelry
© 2008 Paul Billiet ODWS
26
Homo sapiens – Modern Human
• From 150 000 years ago to present
• Originating in Southern Africa then went
worldwide
• Reached Europe about 50 000 years ago
• Cooling of the climate during the last glacial
period from about 50 000a led to their
predominance over other species (e.g. H.
neanderthalensis)
• Omnivore
• Alters environment
• Domestication of species,
farming
© 2008 Paul Billiet ODWS
27
Homo sapiens – Modern Human
• Cranial capacity: 1350 cm3
(range 1000 to 2000 cm3)
• 20% of the body’s energy consumption for 5% of
body mass
• Speech
• Art
• Extensive tool kit including new materials
(bone, ivory, antler)
• Symbolic thought
• 1st molar tooth 5.9 years old
• Longevity 66 years
© 2008 Paul Billiet ODWS
28
Ardipithecus
ramidus
Homo habilis
Australopithecus Australopithecus
africanus
afarensis
Homo erectus
Homo
neanderthalensis
**Skulls not
to scale
29
Homo sapiens
Gorilla
Neanderthal
Australopithecine
Homo erectus
Modern human
30
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A.
africanus, and Homo including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
From the previous two slides you can see:
•enlargement of the brain case
•shortening of the face
•loss of brow ridges
You can’t really see it but the hole in the bottom of the
skull where the spinal cord exits the brain (foramen
magnum) is further forward in modern humans. This
distributes the weight of the head over the spine so
that modern humans do not need huge necks muscles.
31
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A.
africanus, and Homo including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
Homo sapiens
Pan troglodytes
(chimpanzee)
32
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A.
africanus, and Homo including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
The jaw has developed from a U into
a V shape. Teeth have generally
reduced in size. (Chimpanzee
provided for comparison)
33
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A.
africanus, and Homo including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
Human hands are adapted for grasping and fine
manipulation. In contrast gorillas have short fingers for
knuckle walking and gibbons have elongated fingers
and reduced thumbs for brachiating.
34
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A.
africanus, and Homo including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
Skeleton, locomotion and posture
• Human knees aligned under the body’s centre of
gravity because femurs are angled inwards.
• Human legs straighten completely when walking.
• Human spine has additional curves to keep
centres of mass of head and trunk aligned for
bipedalism.
• Big toe not opposable in humans,
which allows for an arched foot.
• Ratio legs:arms greater for
humans than other apes
• Human pelvis broader
35
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A.
africanus, and Homo including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
Neoteny, also called juvenilization or pedomorphism, is the
retention, by adults in a species, of traits previously seen
only in juveniles.
D.3.5 Outline the trends illustrated by the fossils of Ardipithecus
ramidus, Australopithecus including A. afarensis and A.
africanus, and Homo including H. habilis, H. erectus, H.
neanderthalensis and H. sapiens.
Some human characteristics thought to be a result of
Neoteny:
• Lactase production
• Lack of body hair
in adults
• Small teeth and reduced
• Epicanthic eye fold
numbers of teeth
• Small nose
• Prolonged growth period
• Longer trunk relative
• Long life span
to arms and legs 37
• Flat face and thin skull bones
37
D.3.6 State that, at various stages in hominid evolution,
several species may have coexisted.
•
•
•
•
Doesn’t necessarily mean they lived together/near each
other...just means fossils present at same time
A. afarensis & A. africanus
~ 3mya
A. africanus & H. habilis
~2mya
H. neanderthalensis, H. erectus, and H. sapiens
~100,000 yrs ago
38
THE CHANGING TREES OF
HUMAN EVOLUTION
© 2008 Paul Billiet ODWS
39
1960
Up the ladder
• The idea that one species
smoothly evolves from one
into another is regarded
today as an
oversimplification
• Unfortunately it is a very
persistent view that
continually resurfaces in
cartoons
© 2008 Paul Billiet ODWS
Homo sapiens
Homo erectus
Australopithecus
Public Domain Images
40
1970
• The 1960s and 1970s
were a fertile period for
fossil hunting in Africa
• The idea developed that
more than one hominid
species existed at the
same time developed
Branching out
A. boisei
Homo sapiens
Homo erectus
A. robustus
Homo habilis
Australopithecus
africanus
Australopithecus afarensis Added
“Lucy”
1974
© 2008 Paul Billiet ODWS
41
1991
Changing status
As more specimens
were found a
clearer idea
developed of the
relationships A. boisei
between them
A. robustus
Homo sapiens
Homo erectus
Homo habilis
A. africanus
Australopithecus afarensis
© 2008 Paul Billiet ODWS
42
2001
From a tree to a bush
Homo sapiens
Homo neanderthalensis
Homo
erectus
H. heidelbergensis
1 Ma
Paranthropus
boisei
H. ergaster
P. robustus
?
2 Ma
Homo
rudolfensis
A. africanus
P. aethiopicus
3 Ma
Homo
habilis
A. garhi
?
?
4 Ma
Australopithecus
afarensis
?
?
Australopithecus anemensis
?
Ardipithecus ramidus
© 2008 Paul Billiet ODWS
43
2003
DEEPER
ROOTS
Gorilla gorilla
Pan trogolodites
Homo sapiens
Homo neanderthalensis
Homo
erectus
H. heidelbergensis
1 Ma
H. ergaster
Paranthropus
robustus
Paranthropus.
boisei
?
2 Ma
Homo
rudolfensis
A. africanus
P. aethiopicus
A. garhi
?
3 Ma
Homo
habilis
Australopithecus
afarensis
4 Ma
?
Australopithecus anemensis
?
?
5 Ma
Ardipithecus
ramidus
?
6 Ma
Orrorin tugensis
?
7 Ma
© 2008 Paul Billiet
ODWS
Sahelanthropus tchadensis
“Toumai”
?
44
D.3.6 State that, at various stages in hominid evolution,
several species may have coexisted.
45
D.3.7 Discuss the incompleteness of the fossil record and the
resulting uncertainties about human evolution.
Reasons for the incompleteness of the fossil record:
•
•
•
•
fossils only form when buried under sediment before
decomposition occurs;
animal bodies are usually eaten by detrivores,
decomposed by bacteria, or broken down chemically
of remains fossilized, most remain buried in sediment/
remain unfound;
Measurements imprecise b/c age differences of
organisms at death (juvenile  adult)
46
D.3.7 Discuss the incompleteness of the fossil record and the
resulting uncertainties about human evolution.
Reasons for the incompleteness of the fossil record:
•
•
•
hominid fossils that have been found may or may not
be representative of hominid history;
hominid fossils that have been found are usually
partial, and the remainder of the organism must be
inferred/ inferences may or may not be correct;
only hard parts of individuals fossilize, leaving many
questions concerning the rest of the individual’s
phenotype;
47
D.3.7 Discuss the incompleteness of the fossil record and the
resulting uncertainties about human evolution.
The large gaps in the human evolution fossil
record are consistent with punctuated
equilibrium
The following four slides show how the gaps
are filled over time with new discoveries. The
graphs plot cranial size against the age of the
fossil.
48
D.3.8 Discuss the correlation between the change in diet and
increase in brain size during hominid evolution.
The benefits of a bigger brain
include:
•More complex tools
•Mastery of fire
• Cooking
• Warmth
• Protection
•Greater behavioral flexibility
(less reliance on instinct and
better able to learn and pass on
knowledge necessary to adapt
to an environment)
49
D.3.8 Discuss the correlation between the change in diet and
increase in brain size during hominid evolution.
The cost of having a big brain:
•Longer gestation period
•Years of development before
young can look after themselves
•Much more brain development
occurs post birth that for any
other animal
50
D.3.8 Discuss the correlation between the change in diet and
increase in brain size during hominid evolution.
In summary:
Big brains are energetically
expensive. The mother must
take in lots of energy not only
during pregnancy, but for a
significant time after.
Hominids needed to increase
their energy uptake.
51
D.3.8 Discuss the correlation between the change in diet and
increase in brain size during hominid evolution.
The solution to this energy crisis was to swap a
diet of these:
52
http://www.flickr.com/photos/heydrienne/22080973/
D.3.8 Discuss the correlation between the change in diet and
increase in brain size during hominid evolution.
For some chunks of this:
The increase in brain
size observed in
hominid fossils has
been closely
correlated with an
increased intake of
meat.
A bigger brain made
hunting and killing
easier
53
D.3.9 Distinguish between genetic and cultural evolution.
Genetic evolution refers to the genetic changes
that have occurred during the evolution of
hominids. e.g. increased brain size, spine shape,
position of knee
Cultural evolution is the changing of ideas held and
actions carried out by societies and the
transmission of these ideas through social learning
from one generation to the next.
e.g. the use of fire, agriculture, tools, weapons,
religion, beliefs
54
D.3.9 Distinguish between genetic and cultural evolution.
• Genetic
 Inherited, parent to child only
 Body morphology (e.g. increased brain size, spine
shape, position of knee)
 # chromosomes
 Biochemicals
• Cultural
 Acquired knowledge, passed on to many in the
group/family, generation to generation (e.g. the use of
fire, agriculture, tools, weapons, religion, beliefs)
 Language
 Customs/rituals
 Art
55
 Technology
D.3.9 Distinguish between genetic and cultural evolution.
Comparison
GENETIC
CULTURAL
The product of natural
selection
The product of learning. the
transmission of acquired
behaviour characteristics
Darwinian
Lamarkian
Innate not modified during
the organism’s life time
Learned during the life time
Passed on through
hereditary information
Passed on to kin (family),
social group, population,
within a generation and
between generations
Slow change
Fast change
56
© 2008 Paul Billiet ODWS