Human evolution
Primates
Kingdom: Animalia
Phylum: Chordata
Class: Mammals
Order: Primates
Suborder: Anthropoidea
Superfamily: Hominoidea
Family: Hominidae
Genus: Homo
Species: sapiens
Human
classification
Phylum Chordata
Sub phylum Vertebrata
Animals with a dorsal nerve cord
surrounded by bony vertebrae.
Class Mammalia
Mammals suckle their young on milk
secreted from mammary glands.
The have hair and sweat glands
 They are homeothermic
They have a four chambered heart and a
diaphragm
 They have an external ear (pinna)
More features of mammals
They have four different kinds of teeth –
incisors, canines, premolars and molars
They are highly intelligent because they
have a larger forebrain than other animals
Three groups of mammals
Monotremes – lay eggs
Marsupials – carry their babies in
pouch for a large part of their
development
a
Placental mammals – nourish their young in
a uterus via a placenta
Hominoidea - Superfamily
(family)
Hylobatidae (family)
Gibbons
Hominins, hominids and
hominoids
• Hominoids – humans, great apes (chimps
and gorillas) and lesser apes (gibbons)
• Hominids- humans and great apes
• Hominins - humans and ancestral species
Order Primates
The features of primates are largely related to
their arboreal (tree living) way of life.
Brain size
• Large and more complex than other mammals.
Collar bone
• Is well developed and the arms have a wide
range of movement.
Posture
• More upright, particularly in the upper
body. Associated with sitting, standing and
in some cases walking.
Reproduction
Usually have only one baby
at a time – this baby is born
well developed after a
relatively long gestation
period.
The mammary glands are
pectoral (on the chest) so the
mothers suckle their young
in a sitting position.
Limb joints
Bones of the lower limbs (radius and ulna,
tibia and fibula) are not fused.
Primitive skeleton – has undergone less
evolutionary change than other animal
groups.
Hands and feet
Hands and feet have five digits
Grasping hands, (not claws) with nails both fore and hind limbs
Tips of the fingers have ridges which make
them more sensitive most have opposable
thumb
Plantigrade foot posture – whole foot is in
contact with the ground
Teeth shape and dental arrangement
• Dental pattern seen in most primates,
particularly in the molars. Unspecialised
teeth mean primates can adopt a flexible
omnivorous diet.
Face shape and snout
Reduced snout.
Olfactory (smell) regions of brain are reduced.
Smell is less important in the life of a treeliving animal than vision.
Vision
Forward facing eyes which allow binocular
vision – makes it easier to judge distance
Colour vision and ability to see detail.
Social organisation
Live in social groups where the individuals
gain protection from predators, food is
shared, rearing of young can be shared and
individuals can learn from each other.
Page 328 –
fill in
Main
Menu
APE FEATURES
Features of apes:
• No tail
• Rib cage is flattened
• Molars have 5 cusps (monkeys have 4)
• Locomotion is brachiating, knuckle-walking, or bipedalism.
• Posture partly (or fully) erect… leaving the hands free
The Y5 molar pattern
Trends in human biological
evolution
A trend refers to a change over a
period of time
We will look at 3 trends in
human biological evolution:
• 1) Trends in changes linked to skull and
endocranial features;
• 2) Trends in changes linked to bipedalism
• 3) Trends in changes to the manipulability
of the hand.
Differences between ape and
human skulls
329 Biozone
Pages 343 and 344
Skull and endocranial changes
Apes
H. sapiens
Reason for change
Smaller cranial capacity
(~450cc)
Bigger cranium (~1450cc)
Increased brain development
Sagittal crest
Large zygomatic arch
Large jaw
Teeth bigger
Brow ridge
No Sagittal crest
Small zygomatic arch
Small jaw
Teeth smaller
No brow ridge
More refined diet, no need for really strong chewing
muscles, muscle attachment points, or teeth
Nuchal crest
No Nuchal crest
Head vertical on spine – less muscle attachment needed.
Foramen magnum on
angle/back of skull
Foramen magnum central/bottom
of skull
Vertical spine with skull on top
No Broca’s and Wernicke’s
areas
Broca’s and Wernicke’s areas
present
Used for language
Less folding of cerebral cortex
Cortex much more folded
Related to memory, attention, language, awareness,
thought, etc… developed as social structure allows more
time, and hands free to carry out abstract tasks
Cerebellum less developed
Cerebellum more developed
Needed for balance, as well as coordination and tool use
Brain size
• The human brain is
much larger at 1400
cm3 compared to
450cm3 in apes.
Brain development
• The cerebral cortex is
much larger in humans
allowing for higher order
thinking, speech and
language.
• The cerebellum allows for
hand eye co-ordination
and fine motor skills.
• These are both larger and
more developed than apes.
cerebellum
2. In modern humans 2 areas of the brain
(cerebral cortex) have become highly
developed:
a) Broca’s area – this is concerned with speech.
It controls the muscles of the jaw, lips,
tongue, soft palate and vocal chords during
speech.
a) Wernicke’s area – this is concerned with
language of comprehension and the ability to
listen.
Page 342
• Look at chimp, human and gorilla skull.
Using notes, see if can identify parts.
Brow ridge
• Area of support for large jaw muscles and
jaw bone. It is thought that when chewing
occurs some stresses can be minimised with
the help of the brow ridge
Pelvic inlet
This is the large space in the
pelvis.
This is much larger in
humans compared to apes
and other hominins
This is due to larger brain
size of young needed a larger
opening during birth
Direct comparison between
human and ape skulls
• Read page 263 and 264. Make a table
comparing the skull anatomy of humans and
apes. Also do ‘teeth’ on page 265.
Trends in skeletal changes linked
to bipedalism
• http://www.youtube.com/watch?v=l0tAQcpLILQ
&feature=video_response
• http://www.youtube.com/watch?v=IHi3xYS3cOs
• http://www.youtube.com/watch?v=ubEi-dyVDyo
• http://www.youtube.com/watch?v=qPag2gVcRe8
Why did bipedalism evolve ?
Mammals thought to have originated in the Permian
age (225-280 million years ago), branching from
primitive reptiles.
Survival during time of dinosaurs indicates
intelligence and development of keen senses.
Once dinosaurs disappeared, mammals flourished.
• At end of Cretaceous period (63 million years ago)
the two supercontinents, Laurasia and
Gondwanaland, started breaking up and moving
apart.
• In the Palaeocene and Eocene, land masses started
to look like they do now. Earliest primates
evolved.
• Shifting continents caused great changes in
climate. North America and Europe became
cooler and plants changed from sub-tropical
vegetation to tougher trees and grasses.
Changing
climate and
bipedalism
Page 360
Advantages of bipedal walking copy
1) See better over greater distances – advantageous
to see predators or prey.
2) Easy harvesting of fruit from small trees
3) Hands free to carry food, tools etc.
4) Can carry babies. – necessary when no longer
hairy.
• http://www.youtube.com/watch?v=NAFwd4CkMM
5) Heat stress in savannas is greater compared with
shade of forest. Bipedalism aids in cooling by:
a) reducing amount of sunlight that falls on body –
falls on head and shoulders only;
b) increasing exposure to wind and breezes, helping
with sweat evaporation. Breezes are faster 2m off
the ground than 1m.
6) Standing upright makes wielding a stick or
throwing a stone easier, to fend off attackers.
7) Dominance, standing up is more menacing to a
would-be attacker.
8) Walking on 2 legs is more energy efficient
than walking on 4 legs. BUT running on 4
legs is more efficient than running on 2.
Disadvantages of bipedalism copy
• S-shaped spine and bowl-shaped pelvis
makes humans prone to backache;
• Birth of large headed baby painful;
• Human child takes about a year to walk,
crawls first. Four-legged mammals often
walking within a few hours of birth.
Adaptations for
bipedalism (use
for 362 Lucy)
Do page 361 and 362
a) The spine
Page 362 biozone
b) The
pelvis and
legs
• Pelvis - Humans transmit weight to
legs; broader and shorter for greater
upper body stability. Apes is
narrower and longer; tipped forward.
Humans have larger gluteus maximus
to hold femur and pelvis in upright
position.
Arms and legs
• Humans Legs are longer than our arms.
This allows us to cover more ground per
step compared to apes.
Human - Gorilla - Chimpanzee - Orangutan - Gibbon
(Note the finger tip level gradation)
c) Feet
Apes and humans
have a plantigrade
feet- their whole foot
is in contact with the
ground
d) Knee
joint
• Read 266 and 267 textbook
Trends in changes in the
manipulative ability of the hand
• Ape fingers are longer
and slightly curved.
Human fingers are
shorter and straight.
• Ape opposable thumb
is short and less
dexterous. Human
opposable thumb is
longer and more
dexterous
Trends in changes in the
manipulative ability of the hand
• The Humans opposable thumb allows for a
precision grip. This is because the thumb
can be in direct contact with the tips of our
fingers. This allows greater control of
objects (tool) and to manipulate even small
objects.
• In apes, the thumb is short and fingers are
long so no precision grip.
Selection
for
nakedness
Hominid evolution- evolution of
humans and pre-humans
A 1960s view of hominid evolution was that
evolution progressed in a linear fashionfrom a primitive ape-like ancestor to
modern humans.
• http://www.youtube.com/watch?v=faRlFsY
mkeY
• http://www.youtube.com/watch?v=Lc6U7_BeGc
BUT Fossil record does not show
gradual changes from one species
to next
Now Human Evolution thought of as a succession
of adaptive radiations.
• First radiation: early bipedal apes
- Australopithecines evolved
Second radiation: - Paranthropines evolved
Third radiation – Genus Homo evolved
Paranthropines
Australopithecines
Main
Menu
HUMAN ORIGIN
6 m.y.a.
5
4
3
Ardipithecus ramedus
Australopithecus anamensis
gracile
Australopithecines
A. afarensis
A. africanus
2
1
0.5
Present
Paranthropus
robustus P. Boisei
The megadonts –
vegetarians. a.k.a.
robust A.s
This represents
one possible
interpretation
of the fossil
data:
Homo habilis
H. rudolfensis
H. ergaster
H. erectus
H. heidelbergensis
H. neanderthalensis
H. florensiensis H. sapiens
Manual pg 344/5/7
Early hominids of Africa
Sahelanthropus tchadensis
(toumai)
• Dated at 6-7 mya
• Found in Chad
• might not be bipedal
• ape-like skull and
dentition
• Lived in a forest
environment
• May be a common
ancestor to humans and
chimpanzees
• http://www.youtube.com/watch?v=RViD7x
iZBjE
Orrorin tugenenesis – found near village
of Tugen, Kenya.
Orrorin tugenenesis claimed to be oldest
hominid described.
Volcanic rock in area dated
to 5-8-6.1 million years
ago.
Teeth intermediate between
those of chimp and human.
Main
Menu
IMPORTANT BIPEDAL FINDS
Important “first” bipedal species finds include:
Australopithecus africanus
- 1942 (2.5 m.y.a) “Tuang boy”
Australopithecus afarensis
- “Lucy”, 1972
- “The first family”, 1975 (3 m.y.a)
- “Laetoli footprints”, 1977 (3.75 m.y.a)
Ardipithecus ramidus
- 1995 (4.4 m.y.a)
Orrorin tugenensis
- 2001 (6 m.y.a! 1.5 my before thought)
Ardipithicus ramidus
•Ramidus means “root” in the afar language (Ethiopian).
•Fossils found about 4.4 million years old in Ethiopia.
• Teeth part way between apes and Austalopithicus afarensis
• Scientists divided as to whether A. ramidus is an ancestor to
chimps or whether an ancestor to australopithicenes.
•Cannot tell if it was bipedal or not.
Key features of Australopithicines
• Australopithecus anamensis, afarensis, and
africanus, and Kenyanthropus platyops are
collectively known as gracile
australopithecines, because of their relatively
light, slender build.
• All the gracile species were still more robust
than modern H. sapiens.
•
•
•
•
•
Bell shaped cranium
Brain size 380-550cm3
Large face, no chin
Bipedal
Jaw and teeth moving from being ape-like
to more human-like.
• May have spent some time still in the forest
as well as in the open savannah.
• Diet probably nuts, fruit and seeds, possibly
scavengers.
• Existed 4.2-2mya.
Australopithecus anamensis
•
•
•
•
At least 4.2-3.9 mya
Found in Kanapoi, Kenya by Meave Leaky.
Though to be ancestor of A. afarensis.
Evidence suggests living in woodland and open
savannah.
• Lower jaw similar to chimps. Leg and ankle
bones similar to A. afarensis, evidence of
bipedalism. Upper arm bone very human-like.
Australopithecus anamensis
Laetoli footprintsabout 3.8 million
years old.
http://www.youtube.com/watch?
v=w1Lu4VggDH0
• Footprints showed big toe, ball of foot and
arch of foot. Real evidence for bipedalism.
• Two individuals walking closely together.
• Fossils footprints thought to be made by
Australopithecus afarensis.
Australopithecus afarensis – the
Southern Ape from Afar
• “Lucy” discovered by Don Johanson and
his team at Hadar, Ethiopia.
• 40% complete skeleton – 47 bones.
• Dated at 3.2 million years old. Other fossils
show A. afarensis around 3.9-2.9 myo.
• Pelvis shape indicated female skeleton.
• Short legs indicated 1.1-1.2m tall.
• Ape-like face, brow ridges, flat nose and no
chin. Rest of body more human-like.
• Bipedal.
• Gracile (light, not heavy build).
• Sexual dimorphism. Males larger than
females. Other scientists think two different
species.
• Brain 375-550cm3.
• Smaller canines.
• Teeth are small and unspecialized, indicating a
mixed, omnivorous diet of mostly soft foods, such
as fruits. The canines, highly developed in existing
ape species, are small and undeveloped, in this
species, much as in human beings.
• Geographic distribution- East Africa.
• In same area (Afar) the “First Family” uncovered.
Fossils of 9 adults and 4 children found.
Australopithecus africanus (southern
ape of Africa)
• Thought to have evolved from A. afarensis.
• The partial skull of a six year old child
found in Taung, Southern Africa.
• Existed between 3 and 2 mya.
• Less ape-like than A. afarensis
• Large molars, smaller canines (more humanlike)
• Foramen magnum at centre of skull - bipedal.
• 1.1-1.4m tall
• Gracile
• Slightly larger brain than A. afarensis ranging
from 420-500cm3.
• Diet – fruit and leaves, probably also dug up
tuber and roots and may have scavenged meat
from dead animals.
Australopithecus garhi
•
•
•
•
Discovered in 1997.
“garhi” means surprise.
Dated at 2.5 mya.
There is much controversy about the
classification
• Cranial capacity at 450 cm3
The genus Paranthropus
• The paranthropines are thought to have evolved
as a side branch (adaptive radiation) from
Australopithecus afarensis.
• They were originally clasified as “robust”
Australopithicines, ie A. aethiopicus, A robustus
and A. boisei. But many scientists think the
differences between this branch and the gracile
Australopithicines are so great that they should
be given there own genus.
Features of paranthropines
• Heavily built, slightly larger that A. africanus.
• Large molars, very heavy jaws, powerful
chewing muscles all specialised for eating a
bulky, low grade vegetarian diet, probably of
roots, shoots and other food.
• Robust skull – large crests for muscle
attachment.
• Existed 2.5-1.1mya
Paranthropus robustus
• Existed 2-1.5 mya
• Brain size: 530cc3
• Massive flat face with brow ridges, no
forehead.
• Bipedal – but long arms and a heavy build.
• Huge grinding molars, very large lower jaw,
relatively small incisors and canines. Diet
probably tough plant food and roots that
require lots of chewing.
• 1.1-1.3m tall
• May have used bones as digging tools
Paranthropus boisei
Paranthropus boisei
•
•
•
•
Existed 2.1-1.1mya
Brain size: about 530cc3
1.1-1.4m tall
Skull – similar to P. robustus but larger face
and larger molars. Diet same as P.
robustus.
• Prominent nuchal crest (where neck
muscles attach)
• Broad, flat face, large zygomatic arches
(cheekbones)
Paranthropus aethiopicus
• Thought of have lived
2.7 – 2.5 mya
• Small brain 410 cc
• Thought to be the
direct descendant of
A.afarensis because of
its similarities.
• Limited other
information.
What happened to the
Paranthropines?
• Paranthropines co-existed with
Australopithicines and early Homo species.
• They were driven to extinction, probably
by an intense period of cooling and drying
caused by the Ice Age.
• Other species may have been better adapted
to changing environment.
Once We Were Not Alone
There is good fossil evidence that four kinds of hominid
lived about 1.8 mya in what is now part of northern
Kenya.
They foraged in the same area around Lake Turkana.
We have no idea how, or if, these different species
interacted.
P. boisei
Photos courtesy of: SkullsUnlimited.com
H. habilis
H. rudolphensis
H. ergaster
General features of the genus Homo
• Changes in shape of the size of the skull,
jaws and teeth.
• Increase in brain complexity
• Proportional lengthening of legs in relation
to arms and trunk
• Development of speech
• Development of tools
• Gradual development of group living and
culture
Key features of Homo habilis
• First member of the Homo line.
• Existed between 2.4-1.5mya.
• Brain size larger than Australopithicines: 500-800cc3 .
This is still only half of H. sapiens.
• Habilis = handyman. Thought to be the first to make and
use tools. Tools indicate partly carnivorous diet. Teeth
indicate omnivorous. Small jaws with small incisors and
canines and small molars (but larger than H. sapiens).
• Evidence of co-operative hunting and
scavenging for food.
• Height: 1-1.3m.
• Some sexual dimorphism but less than
Australopithicines.
• Skull – rounded human shape but with brow
ridges.
• As H. habilis evolved about 2.5 mya when world’s
weather system undergoing great changes. Bouts
of warming and cooling occurred every few
thousand years. Ocean currents shifted and
realigned, sometimes in less than a decade.
• Resulted in lower temperatures and less rainfall.
Forests in Africa dried up, animal populations
began to crash. Human ancestors, ie all those prior
to H. habilis, lived through many cycles of climate
change but each caused population bottlenecks, so
many relatives eliminated.
• H. habilis thought to have made tools. By
making tools could skin carcasses and crack
open the bones for the marrow. Could also
use tools to break down veges and nuts.
• Australopithicines responded to climate
change by walking upright. The first
members of the Homo line responded to
climate change by developing tools and
eating a more varied diet.
Tools = Oldawan tools
• Reading 274-278 textbook
Key features of Homo ergaster
• Existed 1.9-1.7 mya. Previously classified
as H.erectus.
• Brain 850-1000cc3
• Body shape similar to modern humans
• Higher domed cranium and thinner skull
than H.erectus.
• Small front teeth and smaller molars than
H.habilis – omnivores.
• Thought to have travelled out of Africa to
Asia.
• 1.3-1.85m tall.
• Nose projected more
• May have been capable of speech
• No sexual dimorphism, suggests males
didn’t fight for females.
9 years old and
1.6m tall
Key features of Homo erectus
• Migrated extensively from Africa to Asia and
Europe.
• Developed acheulian tools – cleavers, picks and
handaxes. More advanced tools show H.erectus
could plan with forethought.
• Brain = 750-1250cm3
• Projecting nose. Prominent brow ridges, thicker
skull bones.
Acheulian tools
• 1.3-1.7m tall.
• Similar build to modern humans but sturdier
arms and leg bones
• Used fire. Charred bones and stones have
been found with fossils in may sites,
indicated cooked food.
• May have hunted and trapped animals. Had
a much more diverse diet due to eating
animals. This meant less energy spent
digesting low nutrient containing
vegetation.
• Infants would get higher quality food for
their brains. Therefore brains get bigger,
could think of better ways to get meat and
the cycle continues.
• H. erectus first to have barrel-shaped
ribcage. Makes way for lungs AND means
a smaller gut area.
• Worlds oldest house, found in Japan, dated
0.5mya attributed to H.erectus.
Homo floresiensis
Borneo
Discovered in 2003 on the
Indonesian island of Flores,
nicknamed ‘the hobbit’, these
New Guinea
Sulawesi
Sumatra
hominids lived 95 000 - 13 000
years ago.
Flores
Java
Timor
The dimensions of the skull and
skeleton of H. floresiensis fall well
outside the extremes seen in H.
sapiens.
It is equal to the smallest known
australopithecines, and approaches
that of modern chimpanzees (which
have a brain size of 400cc).
H. floresiensis skull shown next to a
modern human skull to show its size.
Photo courtesy of: SkullsUnlimited.com
Homo floresiensis
Fossils from a number of individuals
include a 30 year old female with a brain
size of 380cc and standing just 1.0m tall.
May have resulted from long-term
isolation, with subsequent endemic
dwarfing, of an ancestral Homo
erectus population (dwarf forms of
large mainland mammal species are
not uncommon on islands).
Astounded scientists by showing
clear signs that (despite their very
small brain size) they used stone
tools and fire, and hunted dwarf
elephants, also found on the island.
H. floresiensis may have been part of
the Asian dispersals of the
descendants of H. ergaster and H.
erectus.
Photo courtesy of: SkullsUnlimited.com
Key features of archaic H.sapiens
= H.heidelbergensis
• Existed 400,000 to 100 000 years ago in
Africa, Asia and Europe.
• 1.5m tall
• Robust but human-like skeleton
• A lot of variation in fossils dated to this
time. May indicate populations responding
to diverse regional selection pressures.
• Brain size: 1100 to 1400cc3.
• More prominent nose
• Changes in voice box position may indicate
speech.
• May have evolved into H.sapiens and/or H.
neanderthalensis.
Key features of Homo
neanderthalensis
• Existed 230,000-28,000 years ago
• Brain size 1200-1750 (larger than modern
humans, but they were also bigger overall)
• 1.5-1.7m tall
• More sloping forehead than H.sapiens.
“Bun” at back of head where strong neck
muscles attached.
• Brow ridges, receding chin.
• Had thicker bones than H. sapiens, for
attachment of large muscles.
• Lived in very cold conditions. Thicker
limbs and stocky shape were adaptations to
the cold and still found in modern human
populations in cold climates.
• Used Mousterian tools – more advanced
than Achaulean tools. Some attached to
handles.
• Buried their dead with things such as food,
flowers, tools or jewellery. Suggests may
have thought about afterlife, or they
mourned their dead.
• Used fire for cooking, warmth and to scare
off predators.
• Sometimes lived in caves and built stone
walls and curtains of skin to keep out wind.
Also made tents and clothes.
• Probably had some form of language as
they had the required throat structure to
allow speech.
• Originally thought H. neanderthalensis
evolved into H. sapiens, but mt DNA
analysis between the two shows large
number of differences. Suggests H. sapiens
originated in Africa, migrated to Europe
where they replaced H. neanderthalensis
with little or no interbreeding.
BUT have found a skeleton with DNA
features of both human and neanderthal
DNA. Suggests may have interbred.
Key features of Homo sapiens
• Cranial volume 1200-1700cm3.
• Earliest H. sapiens fossils from Africa about
160,000 years ago.
• Then spread to Asia, Europe, Australia and
America. Reached Europe about 35,000 years
ago.
• In Europe co-existed with H. neanderthalensis
but then H. neanderthalensis died out about 25,
000 years ago.
• More gracile than neanderthals, probably
because evolved in a hot climate.
• Skull has no brow ridges, a high forehead,
well-developed chin, long nose, small teeth
in a v-shaped jaw.
• With appearance of Cro-Magnon man (35
000 years ago) a cultural revolution was
caused. Cro-Magnon man was artistic,
made more sophisticated tools including
fish hooks, needles and harpoons.
Buried their dead.