Human Evolution
Part I
Who are we?
• Homo sapiens is one approximately 230 living
primate species, which together constitute the
order Primates.
• We, as primates, have inherited a set of
anatomical and behavioural features that reflect
our evolutionary history.
• By studying the characteristics of present-day
primates, we are able to look back at stages in
our own evolutionary development.
What is a primate?
• Most primates are tree-dwellers and are found in tropical forest and
woodland habitats.
• As well as living species, primates also include extinct species such
as Homo erectus and various species of Australopithecus and
Paranthropus.
• Living primates include:
– Prosimians — these include lemurs, lorises and tarsiers
– New World monkeys from South and Central America — these include
capuchin monkeys (Cebus spp.) and spider monkeys (Ateles spp.)
– Old World monkeys from Africa and Asia — these include baboons
(Papio spp.) and macaque monkeys (Macaca spp.)
– Apes — these include gibbons (Hylobates spp.) of south-east Asia,
orang-utans (Pongo pygmaeus) of Borneo and Sumatra, gorillas (Gorilla
spp.), chimps (Pan spp.) of Africa and humans (Homo sapiens).
Characteristics of Primates
• No single feature is diagnostic of a
primate but, taken together, the
following features identify a primate.
• Hands and feet of a primate typically
have:
– five digits that can grasp or curl around
objects and primate thumbs or big toes
(sometimes both) are opposable, that is,
they are able to be brought into contact
with the other digits, flat nails on their
digits with the tips of their digits able to
gain information thorough the sense of
touch.
• Primates have an emphasis on vision
and they have:
– large forward-facing eyes that give
stereoscopic (3-D) vision
– colour vision because they have cones
in the retinas of their eyes
– a protective bone at the outer side of the
eye socket
Characteristics of Primates
• Primate skeletons have flexibility adapted to life
in the trees, such as the ability to rotate the arm
in the shoulder socket so that the arm can
extend behind the body.
• Compared with other mammals, primates have
large brains relative to their body sizes — we
primates are more brains than brawn!
• Primates are social mammals and typically live
in groups that, depending on the species, may
be as large as a troop of several hundred
animals or as small as a pair
• Primates have a relatively long gestation period
compared with non-primate mammals. They
typically produce just a single young at each
birth and provide parental care for an extended
period that is longest in the case of human
children. This longer gestation period allows
for the more extensive fetal brain growth of
primates.
Primate Classification
Humans are hominoids
• Among the primates, humans are hominoids or
members of the superfamily Hominoidea.
• Humans share membership of the superfamily
Hominoidea with the lesser apes or gibbons and the
other great apes (chimps, gorillas, orang-utans).
• All the apes are hominoids.
• Anatomical features common to all Hominoids:
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No tail
Semi-erect or fully erect posture
Broad chest, pelvis and shoulders
Relatively long arms and mobile shoulder joints
Larger brain
Humans are hominins
• Modern classification places humans in the taxonomic group known
as tribe Hominini, that is, humans are hominins.
• It is only at this level of classification that humans are separated
from all the other great apes. Based on this classification, members
of the genus Homo (humans) and their extinct erect-walking
ancestors are now strictly termed hominins.
• Anatomical features and habits of hominins (previously called
hominids) are:
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Bipedal – modified feet, thigh bone, pelvis, spine
Large cerebral cortex (forebrain)
Reduced canines (and teeth in general)
Nose and chin are prominent, reduced eye ridges
Highly sensitive skin
Body hair short or very reduced to assist cooling
Complex social behaviour
Terminology:
hominin versus hominid
The most recent definitions are:
• Hominid - the group consisting of all modern and extinct Great Apes (that is,
modern humans, chimpanzees, gorillas and orang-utans plus all their immediate
ancestors).
•
Hominin - the group consisting of modern humans, extinct human species and all
our immediate ancestors (including members of the genera Homo, Australopithecus,
Paranthropus and Ardipithecus).
Previous definitions:
• Current use of the term 'hominid' can be confusing because the definition of this
word has changed over time.
• The term 'hominid' used to have the same meaning that 'hominin' now has. It was
therefore a very useful term to designate the line leading to modern humans and was
used when referring to various members of our human evolutionary tree.
• The problem for students and teachers is that a lot of texts still use the old system and
many Internet sites also haven't caught up, even those of many reputable scientific
establishments. So students/teachers will need to be aware that 'hominids' can mean
two different things depending on how up-to-date a reference is with regard to
incorporating these taxonomy/classification changes.
Evolution of primates
• The times of divergence of various primate groups from a common
ancestor have been inferred by comparing the groups in terms of their
structure and shape (morphology) or in terms of the composition of
particular proteins that they share (biochemical analysis) or in terms of
DNA sequences.
• An early divergence about 65 Myr ago produced one line that led to the
primates that are represented today by lemurs, lorises and the aye-aye,
which form a group known as prosimians.
• About 40 Myr ago, another divergence produced two lines, one leading to
the New World monkeys and the second giving rise to the Old World
monkeys and apes.
• The latter line subsequently diverged, perhaps about 31 Myr ago, to
produce the Old World monkey line and the ape line.
• When the morphology and blood protein composition of the various apes
are compared, it may be concluded that the gibbon line diverged, probably
18 Myr ago, and the orang-utan (Asian ape) line, possibly 14 Myr ago.
• Finally, the evolutionary line that led to humans diverged from the line that
was ancestral to the African apes (chimpanzees and gorillas).
Evolution of primates
• When scientists talk about the ‘human’ line diverging
from the African ape line, this does not mean that
humans evolved from chimpanzees or gorillas.
• It means that at some time in the past the ‘human’ line
and the African ape line shared a common ancestor.
• This common ancestor gave rise to two lines that
evolved along different pathways, occupied different
habitats and were subject to different selection pressures.
• The ‘human’ line evolved over millions of years and is
represented today by the human species, while the
‘African ape’ line over the same period evolved and is
represented today by three species — chimpanzees (2)
and gorillas.
When did the ‘human’ line diverge?
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The answer to this question can only be inferred.
Using the ‘molecular clock’ approach in the late 1960s, two American biochemists,
Vincent Sarich and Allan Wilson, estimated that the hominin line diverged from the
African ape line probably about six million years ago.
This view was initially strongly opposed by several palaeoanthropologists who held
the view that the line that finally led to humans diverged from the ape line 30 or
more million years ago.
Later fossil discoveries supported the date of divergence proposed by Sarich and
Wilson as did comparisons of the DNA sequences of the living apes.
The incomplete nature of the fossil record is incomplete and various
palaeoanthropologists put different interpretations on this evidence.
Consequently, there is not universal agreement on the precise evolutionary history of
the human species.
There is agreement that small-brained hominins separated from the line that led to
the gorillas and chimpanzees, and that these hominins gradually became less ape-like
and more human-like as generations of hominins spent more time at ground level
and were subjected to various selection pressures.
Finally, the hominins reached a stage where they were identifiably human and could
be classified as members of genus Homo.
Evolution of primates
Human characteristics
compared to other primates
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Brains became enlarged
High forehead, head held vertically
Reduced neck muscles
Teeth covered with thick enamel, reduced molars, small canines
Shortened forelimbs
Fully opposable thumb
Reduced lower back with S-shaped curvature
Short, wide pelvis for attachment of gluteal muscles for walking
Femoral head angled and strengthened
Leg bones are thickened and longer
Buttress at knee-joint to allow bipedal walking
Foot has an arch with weight-bearing heel and ball
Non-opposable and forward thrusting big toe
Reduction in body hair to increase evaporative cooling
Selection for Bipedalism
• Seeing over the grass may have helped spot predators or locate
carcasses at a distance
• Carrying food away from a kill site or growing site to a position of
safety
• Efficient locomotion: bipedalism provides an energy efficient
method that favours low speed, long distance movement - walking
• Thermoregulation: two major advantages of walking are:
– Smaller surface area presented to sun at midday (60% less)
– Greater air flow across the body when it is lifted higher off the ground
assists cooling
• Carrying offspring while following the large game herds of the
savannah on long seasonal migrations
• Holding tools and weapons was probably a consequence of
bipedalism, rather than a cause
Selection for Nakedness
Retention of head hair
• Hair on the head (and to a lesser extent the shoulders) reflects and
radiates solar radiation (heat) before it reaches the skin
Parasite control
• Reduced body hair improves control of ectoparasites such as fleas,
ticks and lice.
• Particularly important when early hominins began to use a regular
‘home base’’ as hatching parasite eggs could reinfect them
Thermoregulation
• Shorter, finer hairs (not hair loss) in early hominins has allowed
greater heat loss by radiating from the skin surface
• Well developed sweat glands allow us to lose heat at an astounding
700watss/m2 of skin (a capacity not approached by any other
mammal)
Adaptations for Bipedalism
Position of Foramen Magnum
• Located more centrally under the skull, so that the skull is balanced on the spine
Spine Shape
• Lower back is reduced to produce and ‘S’ shape that has the effect of keeping the
head and torso above the centre of gravity
Pelvis Shape
• Short and broad, for attachment of large, powerful muscles for walking
• Pelvis has become more ‘bowl-shaped’ to provide support for the organs of the torso
Femur
• Longer and angled inwards from the hips so knees nearly touch (the ‘carrying angle’)
– assists the upper body to be positioned over the centre of gravity
Knee joint
• Bottom of the femur (knee joint) has a buttress of bone (called the lateral condyle) –
this stops the sideways deflection of thigh muscles during walking
Shape of Foot
• The anatomy of the foot has changed to become a platform.
• Toes are short, with big toe forward thrusting.
• Inner side of the foot is elevated into an arch to provide a shock absorber effect.
Changes in the Skull Base
• An important diagnostic feature of whether a prospective hominin fossil
skull belonged to a bipedal individual is the position of the foramen
magnum on the base of the skull
• The foramen magnum is the attachment point for the skull and the spine
through which the spinal cord passes to the brain
• An opening at the
rear of the skull
implies a
quadrupedal habit of
locomotion – the head
is held upright by
powerful neck
muscles
• An opening located
more centrally on the
skull, as is found in
modern humans,
indicates a bipedal
habit of locomotion –
the head balances on
the spine, requiring
less powerful neck
muscles
1960s View of Human Evolution
• Belief in linear progression from primitive ape-like ancestor to
modern humans
• According to this model, the fossil record should consistently show
smooth inter-gradations from one species to the next.
• This is not the case!!!
• Fossil record shows few smoother inter-gradations from one species
to the next,
– Species tend to appear
suddenly in the fossil record
– Species linger for varying but
often very extended periods of
time in the fossil record
– Species disappear as suddenly
as they arrived
– Species are replaced by other
species which may or may not
be closely related to them.
Current View of Human Evolution
• A modern view of human evolution
maintains that it has occurred as a
series of adaptive radiations
• The 1st radiation is that of the early
bipedal apes – australopithecines
• The 2nd radiation involved the genus
Paranthropus, a group of species
that exploited low-grade vegetable
food sources (nuts, root tubers and
seeds) resulting in megadonts (very
large teeth).
• The 3rd radiation is genus Homo,
with the habilines and erectines
developing a larger brain,
diversifying and dispersing from
Africa to other parts of the Old
World.
• The last radiation does not involve
any major evolutionary divergence,
but reflects the dispersal of modern
humans worldwide.
Hominin Evolution
• Grouping of genera within the hominins is constantly changing.
• Previously only two or three hominid genera, Australopithecus, Paranthropus, and
Homo, have been previously accepted, with Paranthropus considered a subgenus
of Australopithecus by some authors.
• New discoveries since the mid 1990s have been assigned to as many as four new
genera of the family Hominidae: Ardipithecus, Orrorin, Kenyanthropus, and
Sahelanthropus.
• These specimens are described as having morphological traits that justify
placing them in the family Hominidae while creating a new genus for the
classification of each.
• Regardless of their final classifications, it is important to appreciate that fossil
evidence can not identify any of these as a direct ancestor of Homo sapiens
• There are different schemes for the evolution of modern humans, and while
there is broad agreement on many matters, some different opinions exist, as for
example, how the various robust species are related.
• The gracile A. afarensis (Lucy) and A. africanus are accepted to be in the line that
is ancestral to the human species in the genus Homo.
• As more fossil evidence is discovered, some of these differences will be resolved.
Sahelanthropus
Estimated age: 6 to 7 millon years old
Brain size: 350cc
Height: unknown
Physique: unknown as no bones below cranium and lower jaws discovered yet so no
predictions can be made
Skull Shape:
• tall face, a thick brow ridge (probably a male feature), and a long and narrow
braincase
Teeth and Jaws:
• Dental arch is U-shaped with cheek teeth (molars, premolars) smaller than
Australopithecine ones
• Dental enamel is thicker than Chimpanzee but thinner than Australopithecine.
• Canines don't project far above the other teeth as in Apes
Geographical Distribution: Western Central Africa
Other Information:
• Some scientists have pointed out the foramen magnum of Toumai is positioned
towards the back of the skull as in apes, indicating that the skull was held forward
and not balanced on top of an erect body – an argument against bipedalism.
• Debate still about whether Toumai is a hominin, a fossil from before the point at
which hominins separated from chimps, or even an early gorilla.
Orrorin tugenensis
Estimated age: 6 millon years old
Brain size: unknown
Height: unknown
Physique:
• Femur suggest bipedalism
• About the size of a female chimpanzee (limb bones are about 1.5 times larger than
those of Lucy)
• Adapted to both bipedality and tree climbing
Skull Shape: unknown
Teeth and Jaws:
• teeth of O. tugenensis, suggest this species could even be more closely related to Homo
sapiens than the many Australopithecus species it predates.
• Like our molars, the molars of O. tugenensis were small compared to any of the
australopithecine teeth. Their teeth also had very thick enamel like ours.
Geographical Distribution: Eastern Africa
Other Information:
• Claimed that australopithecines are an extinct offshoot.
• Fragmentary nature of the remains (fragmentary arm and thigh bones, lower jaws,
and teeth) means some scientists have been skeptical of these claims so far
Kenyanthropus
Estimated age: 3.5 to 3.2 millon years old
Brain size: 400-500cc
Height: unknown
Physique:
• broad flat face.
Skull Shape:
Teeth and Jaws: small teeth
Geographical Distribution: Kenya
Other Information:
• The name Kenyanthropus platyops means
"Flat faced man of Kenya".
• mostly complete cranium which came
in two pieces: a skullcase which was
heavily distorted, and a face which was
much better preserved.
•
Ardipithecus ramidus
Estimated age: 4.4 million years old
Brain size: unknown
Height: 1.2m
Physique:
• Possibly bipedal
• Other fossils recovered with ramidus suggest it was a
forest dweller
Skull Shape: foramen magnum more forward than apes
Teeth and Jaws:
• Smaller narrow molars; thinner jaw
Geographical Distribution: Eastern Africa
Ardipithecus ramidus
Other information of interest
• Remains have been discovered to as far back as 5.8 million years.
• Most remains are skull fragments.
• Teeth are intermediate between those of earlier apes and A. afarensis,
but one baby tooth is very primitive, resembling a chimpanzee tooth
more than any other known hominid tooth.
• More recently, a number of fragmentary fossils discovered between
1997 and 2001, and dating from 5.2 to 5.8 million years old, have
been assigned first to a new subspecies, Ardipithecus ramidus kadabba
(Haile-Selassie 2001), and then later as a new species, Ardipithecus
kadabba (Haile-Selassie et al. 2004).
• One of these fossils is a toe bone belonging to a bipedal creature, but
is a few hundred thousand years younger than the rest of the fossils
and so its identification with kadabba is not as firm as the other
fossils.
Genus: Australopithecus
Body form:
Period:
Distribution:
Brain Size:
Height:
Body Form:
Skull:
Skull Crests:
Teeth:
Weight:
Locomotion:
Tool Use:
‘Gracile’
5 to 2.3 million years ago
Eastern & Southern Africa
400-500cc
1.0-1.3m
smaller and less robust
more rounded and vertical
little evidence of crests
large front and rear teeth, molars flat like humans
27kg
bipedal
no evidence
Species identified:
• A. anamensis, A. afarensis, A. africanus, A. garhi
Australopithecus anamensis
Estimated age: 4.2 to 3.9 million year old
Brain size: unknown
Height: unknown
Physique:
• Partial leg bones strongly suggest bipedalism
• Humerus extremely humanlike
Skull Shape: primitive features in the skull, possiblly apelike
Teeth and Jaws:
• Very similar to those of older fossil apes, but canines vertical
• Teeth have thicker tooth enamel like in humans
Geographical Distribution: Eastern Africa
Other Information:
• Although the skull and skeletal bones are thought to be from the
same species, this is not confirmed
Australopithecus afarensis
Estimated age: 3.9 to 2 million years ago
Brain size: 375-550cc
Height: 1.07-1.52cm
Physique:
• Light build
• Some apelike features: relatively long arms, curved fingers/toes,
sexual dimorphism (females smaller than males)
Skull Shape: apelike face, low forehead, bony brow ridge, flat nose,
no chin
Teeth and Jaws:
• Human-like teeth, canines smaller than apes but larger and more
pointed than humans
• Jaw shape is halfway between that of an ape and a human
• Large back teeth
Geographical Distribution: Eastern Africa
Australopithecus afarensis
Other Information:
• Adapted to walking rather than
running
• Bones show that they were physically
very strong
• Curved fingers and hands suggested
by most scientists to be evidence that
afarensis was still partially adapted to
climbing in trees (some scientists
thing this is not true – curved fingers
were evolutionary ‘baggage’)
• Famous fossil “Lucy” was found in
Ethiopia in 1974. She is very
complete
Australopithecus africanus
Estimated age: 3 to 2 million years ago
Brain size: 420-500cc (larger than chimps despite similar body size)
Height: 1.1-14m
Physique:
• Light build
• Probably long arms
• More human features, probably less sexual dimorphism
Skull Shape:
• Brow ridges less prominent
• Higher forehead and shorter face
Teeth and Jaws:
• Teeth and jaws much larger than in human, but far more similar to human
teeth than those of apes
• Shape of jaw full parabolic like humans
• Canine teeth further reduced compared to afarensis
Geographical Distribution: Southern Africa
Australopithecus garhi
Estimated age: ~2.5 million years old
Brain size: 450cc
Height: unknown
Physique:
• Humanlike ratio of humerus and femur but apelike ratio of lower and upper arm
Skull Shape:
• sagittal crest for anchoring large temporal (chewing) muscles
Teeth and Jaws:
• Extremely large teeth, especially at rear when compared to other australopithecine
species
• rectangular or slightly diverging dental arcade (i.e. more apelike)
• Some primitive features as seen in A. afarensis but not in A. africanus
Geographical Distribution: Ethiopia
Other Information:
• Not definite that skeletal remains of arms and legs belong to same species as partial
skull that is identified as garhi
• Along with other species mentioned are known as gracile australopithecines, because
of their relatively lighter build, especially in the skull and teeth. (Gracile means
"slender", and in paleoanthropology is used as an antonym to "robust".) Despite this,
they were still more robust than modern humans.
Genus: Paranthropus
Body form:
Period:
Distribution:
Brain Size:
Height:
Body Form:
Skull:
Skull Crests:
Teeth:
Weight:
Locomotion:
Tool Use:
‘Robust’
2.5 to 1.3 million years ago
Eastern & Southern Africa
500-530cc
1.4-1.5m
larger, more heavily built
flatter, tear-drop shaped
nuchal and sagittal crests
smaller front, large rear teeth
45kg
bipedal
minimal evidence
Species identified:
• P. aethiopicus, P. robustus, P. boisei
Paranthropus aethiopicus
Estimated age: 2.3 to 2.6 million years old
Brain size: 410cc
Height: unknown
Physique:
• unknown
Skull Shape:
• Hind portions are very primitive, most resembling A. arafensis
• Massive (broad face)
• Largest sagittal crest in any known hominin
Teeth and Jaws:
• Large teeth
Geographical Distribution: Ethiopia
Other Information:
• Known primarily from one major specimen – the Black Skull, it may be an
ancestor or P. robustus and P. boisei but has a baffling mixture of primitive
and advanced traits
Paranthropus robustus
Estimated age: 2.2 to 1.5 million years
Brain size: 530cc
Height: 1.1-1.3m
Physique:
• Body similar to A. africanus
• Heavy build
• Relatively long arms
• Moderate sexual dimorphism
Skull Shape:
• Long, broad, flat face
• Crest on top of skull
• Moderate facial buttressing
Teeth and Jaws:
• Very thick jaws
• Small incisors and canines, large molar like pre-molars and very large molars
Geographical Distribution: Southern Africa
Other Information:
• Massive grinding teeth in a large lower jaw and presence of sagittal crests suggests its diet would
have been mostly coarse, tough food that needed a lot of chewing.
• Bones excavated with robustus skeletons indicate that they may have been used as digging tools.
Paranthropus boisei
Estimated age: 2.6 to 1.2 million years ago
Brain size: 410-530cc
Height: 1.2-1.4m
Physique:
• Similar to P. robustus
• Very heavy build
• Relatively long arms
• Marked sexual dimorphism
Skull Shape:
• Long, broad, flat face
• Large crest on top and back of skull
• Facial buttressing
Teeth and Jaws:
• Very thick jaws
• Small incisors and canines, large molar like pre-molars and very large molars
Geographical Distribution: Eastern Africa
Other Information:
• A few experts consider boisei and robustus to be variants of the same species.
Genus: Homo
• The Homo genus is separated from the earlier hominins because of
the emergence of tool use, language, and culture.
• Begins about 2.3 million years ago.
• The characteristics of these species are:
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bigger brain
forehead rises straight up
skull becomes rounder
teeth are reduced
arms are shorter
legs are longer
skeleton becomes more delicate.
• Scientists recognise 8 species at this stage not including
modern humans. We will focus on those about which
most is known.
Homo habilis (small)
Estimated age: 2 to 1.6 million years ago
Brain size: 500-650cc
Height: 1m
Physique:
• Relatively long arms
Skull Shape:
• Small face with developed nose
Teeth and Jaws:
• Smaller, narrow molars
• Thinner jaw
Geographical Distribution: Eastern and possibly Southern Africa
Other Information:
• H. habilis, "handy man", was so called because of evidence of tools found with its
remains.
• The bulge of Broca's area, essential for speech, is visible in one habilis brain cast, and
indicates it was possibly capable of rudimentary speech Sexual dimorphism may
have existed
• Some scientists group this species with Homo habilis (large variant) also known as
Homo rudolfensis to form one species. Other scientists believe variation between the
two is too wide for a single species.
Homo habilis (large)
also known as Homo rudolfensis
Estimated age: 2 to 1.6 million years ago
Brain size: 600-800cc
Height: 1.5m
Physique:
• Robust but ‘human’ skeleton
Skull Shape:
• Larger, flatter face
Teeth and Jaws:
• Large, narrow molars
• Robust jaw
Geographical Distribution: Eastern Africa
Other Information:
• H. habilis, "handy man", was so called because of evidence of tools found with its
remains.
• The bulge of Broca's area, essential for speech, is visible in one habilis brain cast, and
indicates it was possibly capable of rudimentary speech Sexual dimorphism may
have existed
• Some scientists group this species with Homo habilis (small variant) to form one
species. Other scientists believe variation between the two is too wide for a single
species.
Homo erectus
(Homo ergaster for older African forms)
Estimated age: 1.8 to 0.3 million years old
Brain size: 750-1250cc
Height: 1.3-1.5m
Physique:
• Robust but ‘human’ skeleton
Skull Shape:
• Flat, thick skull with sagittal ‘keel’ and large brow ridge
Teeth and Jaws:
• Smaller teeth than H. habilis
• Robust jaw in larger individuals
Geographical Distribution: Africa, Asia, Indonesia and possibly Europe
Other Information:
• Body proportions vary; the “Turkana Boy” is tall and slender (though still
extraordinarily strong), like modern humans from the same area, while the few limb
bones found of “Peking Man” indicate a shorter, sturdier build.
• H. erectus may have been more efficient at walking than modern humans, whose
skeletons have had to adapt to allow for the birth of larger-brained infants
• There is evidence that erectus probably used fire, and their stone tools are more
sophisticated than those of habilis.
Homo heidelbergensis
(Archaic Homo sapiens)
Estimated age: 400,000 to 100,000
Brain size: 1100-1400cc
Height: unknown
Physique:
• Robust but ‘human’ skeleton
• Less robust than H. erectus
Skull Shape:
• Higher cranium, face less protruding, skull more rounded
Teeth and Jaws:
• Similar to H. erectus but smaller teeth
Geographical Distribution: Africa, Asia and Europe
Other Information:
• Many still have large brow ridges and receding foreheads and chins.
• No clear dividing line between late erectus and archaic sapiens, and many
fossils between 500,000 and 200,000 years ago are difficult to classify as one
or the other.
Homo neanderthalensis
(The Neanderthals/Neandertals)
Also Homo sapiens neanderthalensis
Estimated age: 150,000 to 30,000 years old (some evidence suggests 230,000)
Brain size: 1200-1750cc
Height: 1.5-1.7m
Physique:
• Robust but ‘human’ skeleton
• Adapted for cold
• Bones are thick and heavy, and show signs of powerful muscle attachments
• Minor anatomical differences from modern humans, the most unusual
being some peculiarities of the shoulder blade, and of the pubic bone in the
pelvis.
Skull Shape:
• Reduced brow ridge, midface projection, long low skull
Teeth and Jaws:
• Similar to H. heidelbergensis except for incisors and smaller teeth
Geographical Distribution: Europe and Western Asia
Homo neanderthalensis
(The Neanderthals/Neandertals)
Other Information:
• Neanderthals would have been extraordinarily strong by
modern standards
• Their skeletons show that they endured brutally hard
lives.
• A large number of tools and weapons have been found,
more advanced than those of Homo erectus.
• Neanderthals were formidable hunters, and are the first
people known to have buried their dead, with the oldest
known burial site being about 100,000 years old.
• Western European Neanderthals usually have a more
robust form, and are sometimes called "classic
Neanderthals". Neanderthals found elsewhere tend to be
less excessively robust.
Homo floresiensis
Estimated age: 38,000 to 18,000 years ago
Brain size: 417cc
Height: 1m
Physique:
• About the size of a three-year old Homo sapiens [modern human] child, but
with a braincase only one-third as large
• Slightly longer arms
Skull Shape:
• Hard, thicker eyebrow ridges than Homo sapiens
• Sharply sloping forehead no chin
• No chin
Teeth and Jaws: no description
Geographical Distribution: Indonesian island of Flores
Controversy:
• Is this a genuine new species or example of Homo sapiens with genetic defect
such as microcephaly (disease with decreased brain size and intellect) or
Laron syndrome (insensitivity to growth hormone)
Homo floresiensis
Other Information:
• Archeological evidence suggests it lived at Liang Bua between at
least 95,000 and 13,000 years ago – this differs from age of fossils
dated so far.
• H. floresiensis used stone tools and fire, and hunted pygmy elephants
(mostly juvenile ones), Komodo dragons, and the giant rats found
on Flores.
• Combined with the fact that Flores remained isolated during the
most recent glacial period, it has been suggested that the species or
its ancestors could have only reached the isolated island by water
transport and this perceived evidence of advanced technology and
cooperation on a modern human level has prompted the discoverers
to hypothesize that H. floresiensis almost certainly had language
• Local geology suggests that a volcanic eruption on Flores was
responsible for the demise of H. floresiensis in the part of the island
under study at approximately 12,000 years ago, along with other
local fauna, including the dwarf elephant Stegodon.
Homo floresiensis
Other Information:
• Significantly overlapped in time with Homo sapiens, who
arrived in the region sometime between 55,000 and
35,000 years ago.
• How they interacted, however--if they ever even met
face to face--remains a mystery.
• This species may have survived longer in other parts of
Flores to become the source of the Ebu Gogo stories told
among the local people.
• The Ebu Gogo are said to have been small, hairy,
language-poor cave dwellers on the scale of H.
floresiensis.
• Widely believed to be present at the time of the arrival of
the first Portuguese ships during the 16th century, these
strange creatures were apparently last spotted as
recently as the late 19th century.
Homo sapiens sapiens
(Early anatomically modern humans)
Estimated age: 160,000 to 60,000
Brain size: 1200-1700cc
Height: 1.6-1.85m
Physique:
• Modern skeleton possibly adapted for warmth
Skull Shape:
• Small or no brow ridge, shorter and higher skull
Teeth and Jaws:
• Teeth may be smaller
• Shorter jaws than Neanderthals
• Chin developed
Geographical Distribution: Africa and Western Asia
Homo sapiens sapiens
(Early anatomically modern humans)
Other Information:
• Even within the last 100,000 years, the long-term trends towards smaller molars and
decreased robustness can be discerned.
• The face, jaw and teeth of Mesolithic humans (about 10,000 years ago) are about 10%
more robust than ours.
• Upper Paleolithic humans (about 30,000 years ago) are about 20 to 30% more robust
than the modern condition in Europe and Asia.
• These are considered modern humans, although they are sometimes termed
"primitive".
• Interestingly, some modern humans (aboriginal Australians) have tooth sizes more
typical of archaic sapiens.
• The smallest tooth sizes are found in those areas where food-processing techniques
have been used for the longest time. This is a probable example of natural selection
which has occurred within the last 10,000 years (Brace 1983).
• About 40,000 years ago, with the appearance of the Cro-Magnon culture, tool kits
started becoming markedly more sophisticated, using a wider variety of raw
materials such as bone and antler, and containing new implements for making
clothing, engraving and sculpting.
• Fine artwork, in the form of decorated tools, beads, ivory carvings of humans and
animals, clay figurines, musical instruments, and spectacular cave paintings
appeared over the next 20,000 years.
Origin of modern humans
• Two main competing theories of the origin of modern humans (Homo
sapiens) are the Out-of-Africa or Replacement hypothesis and the Regional
Continuity or Multiregional Hypothesis.
• Each of these hypotheses has contrasting predictions:
• Out-of-Africa Hypothesis
– Modern humans should appear first in Africa and only later in other parts of the
world.
– Transitional forms from ancestral to modern humans should be found only in
Africa.
– Variation in mtDNA should be greater in African populations than in other
populations.
• Regional Continuity Hypothesis
– Modern humans should appear throughout Africa, Asia and Europe during the
same period.
– Transitional forms should be found in Africa, Europe and Asia.
– Variation in mtDNA should be about equal in human populations from all
regions of the Old World.
Origin of modern humans
• Regardless of whether we interpret mtDNA
results and fossil evidence to support the Out-ofAfrica hypothesis or suggest that there may have
been a number of waves of migration and
interbreeding of populations……..
• mtDNA studies, combined with studies of Y
chromosome DNA and other nuclear DNA
sequences, strongly support the conclusion that
small groups of Homo sapiens dispersed from
Africa about 100,000 years ago and that their
genes can be found all over the planet.
What’s so special about mtDNA
• mtDNA is passed down the maternal line, so all modern
humans can trace their evolutionary heritage to a single
woman via changes in mitochondrial DNA.
• This woman, dubbed “Eve” lived about 200,000 years
ago in Africa.
• The descendents of this population of modern humans
dispersed throughout the world.
• The question is:
– Did they displace all other humans (Out-of-Africa Hypothesis)?
or
– did they breed with other human populations (Multiregional
Hypothesis)?
• Important to realise that “Eve” was not the only woman
around at this time – she is the only woman to which we
can trace a continual inheritance of mtDNA ie she must
have had daughters as well as, or instead of sons
The Dispersal of Modern Humans
•
•
•
An African origin is probable, with south eastern Africa being the most likely place
The dispersal was affected at crucial stages by the presence or absence of ‘land
bridges’ formed during the drop in sea levels that occurs with the onset of ice ages
The late development of boats and rafting allowed dispersal into Australia and the
Pacific
Early humans in Australia
• Early humans entered Australia from S.E. Asia.
• Oldest fossil skeleton provides date of 40000
years ago but evidence of fire suggests it may be
100000 years ago
• Migration of humans to Australia was assisted
by the low sea levels of the Pleistocene glacial
periods which exposed land bridges.
• Activities of early Australians, together with
glacial climate change led to changes in the
Australian environment.