Extant Apes
Review
Order: Primates
Prosimians
Lemur Group
Anthropoids
Tarsiers?
Loris Group
Platyrrhines
(NWM)
callitrichids
Catarrhines
(OWM and apes)
atelids cercopithecoids
cebids
cercopithecines
Hominoids
(the apes)
colobines
“lesser apes”
gibbons
“great apes”
Chimp human common ancestor
human bonobo chimp
gorillas
orangutans
Next topic:
Evolution of the apes and humans
Evolution of the ape lineage
Catarrhines
(OWM and apes)
cercopithecoids
Evolution of the human lineage
Chimp human common ancestor
human bonobo Chimp
Hominoids
(the apes)
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Relative dating
Dating Methods
–  recall from archaeology
–  using what is known from material in surrounding strata to infer dates
–  Drawback: strata can shift due to geological processes, plant processes, animal
processes, etc.
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Absolute dating
–  recall from archaeology
–  using molecular clocks to date fossils
–  Drawback: there may not be a good clock for a particular time period or a particular
region
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Genetic comparisons
–  Assuming a constant rate of mutation, we can compare DNA sequences to figure out
how long ago two species (or individuals) shared a common ancestor
–  Drawback: you have to have an organism’s DNA to do it--not easy when working with
fossils because DNA can decay--really challenging with very OLD fossils--millions of
years
–  (*Hagen 260 lab class note)
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Linguistic comparisons (languages evolve and comparing their features can help
us understand when populations diverged; more on this later; drawback: limited to
humans)
Upshot: for extant species, genetic dating can be used; for extinct species (fossils),
relative and absolute methods more common; also, it’s good when data from
multiple dating methods corroborate
Ape trends
•  How are apes different from OWM (the
rest of the catarrhines)?
•  Teeth: OWM molars have 4 cusps; apes
have 5
•  Locomotor: apes brachiate whereas
most OWMs walk on all 4s on branches
using tails to help balance
•  Suspensory adaptations:
–  Shoulder blades (scapulae) on back
instead of side (makes for more flexible
shoulder joints)
–  Short trunks
–  Broad chests (left-to-right) that are flat
front-to-back
–  Long arms
–  No tails
Evolution of the apes
(the Hominoids)
•  Recall: there are a few hundred extant primate species
•  How many extant primates are apes?
•  8 genera (“genuses”) of hominoids
–  Lesser apes: about 13 species in 4 genera
–  Great apes: 4 genera
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Pongo (2 orangutan species)
Pan (2 chimp species--common chimp and bonobos)
Gorilla (2 gorilla species, though has been contested)
Homo (humans)
•  Apes don’t comprise a very large fraction of the extant
primates (but monkeys do)
•  Apes evolved in the Miocene epoch
Miocene apes
(Miocene hominoids)
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~23-5mya
Early Miocene: warm, wet climate
Late Miocene: colder, drier climate
Early Miocene fossils in Africa from animals that had ape-like cranial
features (e.g., teeth) but monkey-like locomotion
Middle Miocene (~15-10mya): many hominoid fossils found throughout
Africa, Europe, and Asia; lots of variation in cranial anatomy, but clear
evidence that they were brachiators
Early-middle Miocene: according to the fossil finds, there were a LOT of
apes in the world, and far fewer monkeys
Researchers really cannot infer from which Miocene apes the extant
apes descended (with the possible exception of the orangutan)
Late Miocene (~10-5mya) and into the Pliocene (5mya to 1.8 mya):
many apes went extinct and were replaced by monkeys; this is the
same pattern we see today: monkeys outnumber apes
Evolution and “Progress”
•  Evolution does not proceed on a slow and
steady path toward a particular goal (like
“humanness”).
•  Boyd and Silk (2006), referring to the ape
lineage: “Despite our tendency to think of
ourselves as the pinnacle of evolution, the
evidence suggests that, taken as a whole, our
lineage was poorly suited to the changing
[climatic] conditions.”
Even though chimps look more similar
to gorillas and orangutans, they’re
actually more closely related to
humans according to current genetic
data.
The facts most scientists agree on
Terminology
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Most scientists agree on the facts, but disagree on how to classify the
different apes (including humans)
–  Some scientists want to classify based on descent only -- these scientists put
humans and chimps in the same group, and gorillas in a different group
–  Other scientists want to classify based on descent plus morphology -- these
scientists put chimps and gorillas in the same group, and humans in a different group
–  No “right” answer.
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Hominoids: all apes, including gibbons; everyone agrees on this term
Hominins: modern humans and their extinct relatives back to the human-chimp
common ancestor which lived roughly 6mya
–  “The hominin fossil record consists of all the fossil taxa that are more closely related
to modern humans than they are to any other living taxon. It is these extinct taxa plus
modern humans that make up the hominin clade; the equivalent clade containing
modern chimpanzees and bonobos…is the panin clade.” (Wood and Lonergan 2008)
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Note: 15 years ago, “hominid” referred to what many now call hominin. The
term changed after it was discovered that chimps are more closely related to
humans than gorillas.
Skip unless Student Questions
–  What people disagree on is how we should create group classifications
based on the facts, i.e., how we should create taxa.
•  One camp’s philosophy is that we should only use the lines of descent and not
group based on morphology; by this, chimps and humans and all their ancestors
back to the common ancestor should be in a group different from gorillas because
they are much more genetically related to each other than either is to gorillas.
•  Other camps think we should group chimps and gorillas and put humans in their
own group based on their morphological traits.
•  Neither is necessarily right or wrong: the solution is to use which grouping
strategy is best suited for exploring a particular scientific problem.
•  DNA tells us descent and time distances, but the genes that are actually building
body parts might just be more similar in chimps and gorillas.
•  Evolution = “descent with modification”
–  The chimp-human lumpers are more descent-oriented
–  The chimp-gorilla lumpers are more modification-oriented
–  This, too, is all a Western construct
Wood and Lonergan 2008
All apes: hominoid
All on the red line: hominin
All on the blue line: panin
The Chimp-human Common Ancestor
Chimp-human common ancestor
Lots of fossils
Very few to no fossils
human
bonobo chimp
Recall late Miocene (10-5mya) climate change: temperatures dropped; this continued into
the Pliocene (5-1.8mya). Tropical forests in Africa shrank and were replaced by drier
woodlands and savannas. Some of the chimp-human predecessors remained in the
shrinking rainforests. Some left the trees and ventured into the woodlands and savannas, all
the while generations and generations of natural selection causing those who left to
differentiate from those who stayed in the rainforests (including those who evolved into
chimps). Fossils don’t preserve well in rainforests, so we have little record of how natural
selection was shaping chimps. Fossils do preserve well in drier climates (woodlands,
savannas), so we have a substantially better record of how natural selection shaped
humans and our extinct hominin relatives from the chimp-human common ancestor.
Conventional wisdom: human-chimp common ancestor lived 6-7mya; more recent genetic
evidence puts the split closer to about 6mya, maybe a few hundred thousand years even
more recently.
Chimp vs. Human
Brains:
Chimp~320-350cc
Humans ~1350cc
Locomotion:
Chimp knuckle walking
Human habitual biped
What evolved in the hominins first:
large brains or bipedalism?
Look to the fossil record!
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An Early Find
•  A nonscientist finds parts of a skull in a local
gravel pit near Sussex. Only the skull was
found.
•  It is somewhat human-like, and somewhat
ape-like.
•  The missing link!!!
•  Took the skull to scientists
•  The skull’s features…
The “Missing Link”?
• Small jaw like an ape
• Small molars like a human
• Large canines like an ape
• Highly vaulted skull like a human (big brain!)
• A mix of human and nonhuman ape characteristics
Fervor over the “Missing Link”
•  Yay! …Proof that Europe was the cradle of
humankind!
•  Moreover, the skull’s large cranial vault suggested
that the European missing link was intelligent!
•  Despite some obvious error in the analyses, the skull
was celebrated for years.
…Found in England ~1908-1912 at the Piltdown gravel pit
Named it Piltdown Man
More fossils (7-4.4mya)…
Sahelanthropus tchadensis
Found fossils 2001-2002 in Chad (about 100 years after
Piltdown man was found)
Sahelanthropus tchadensis Features
•  7-6mya
•  Found in center of Africa rather than East Africa and South Africa
where most research on human evolution has been conducted
•  Large jaw
•  Large browridge
•  Reduced canines
•  Large molars
•  Small brain~roughly the size of today’s chimps at ~335cc; today’s
humans are ~1350cc
•  Only skulls have been found, so we are not yet sure if Sahelanthropus
was bipedal
•  It is an unexpected mix of human and apelike features, and found in
an unexpected area: this is more evidence that hominin evolution did
not follow a simple progression from ape to human--rather, there were
probably many different hominin species that possessed a variety of
different adaptations
More fossils
•  ~4-2mya the hominins increased in number and
spread out in Africa
•  Multiple species lived at the same time
•  Roughly 2 categories; most found in south and east
Africa
–  Australopithecus (6 species) “gracile” type
–  Paranthropus (3 species) “robust” type
Australopithecus
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“southern ape”
Small bodies relative to humans
Clearly bipedal
Teeth, skull, jaw adapted to a generalized diet
Small teeth relative to Paranthopus
Chimp brain is ~335cc
Average Australopithecine brain ~500-700cc
Taung child
(Australopithecus africanus)
-2.5myo
-discovered in S. Africa, 1924: the first
Australopithecine fossil ever found
Raymond Dart, an Australian anatomist living in
S. Africa (local workers in a mining pit brought it
to him)
-foramen magnum location like bipedal
humans, so Dart concluded it was a biped
-brain small like that of an ape
-rejected by scientists because at the time they
believed large brains evolved before bipedalism
(like Piltdown); with no postcranial skeleton,
foramen evidence not strong enough to prove
bipedality
How did they know it was a child? Still had it’s
baby teeth and molars ready to erupt.
Australopithecus africanus
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Subsequent adult A. africanus fossils found
Found in South and East Africa
Lived 2.2-3mya
Postcranial skeletons confirmed bipedality
Sexual dimorphism in canines and body size; males
much larger than females, and male canines much
larger than those of females
–  Males: 4’6 and 90 lbs.
–  Females: 3’9 and 66 lbs.
A. afarensis
•  Very similar to A. africanus except teeth
are a bit different
•  Clearly bipedal, as evidenced by knee
bones and footprints
A. afarensis
In A. afarensis and humans, knee is under the centerline of the
body, making bipedal locomotion more efficient
Laetoli footprints
c. 3.6 MYA
Footprints
made in East
Africa, probably
by A. afarensis,
several bipedal
creatures
walked across
a bed of wet
volcanic ask
about 3.6mya;
footprints were
preserved when
it dried
A. afarensis
Diastema: needed by
animals with large
canines, it is a gap on
opposite jaw for large
canines to sit into
Gracile types:
Australopithecus
Australopithecus africanus 2.5-2.6myo
Australopithecus garhi c. 2.5myo
Robust types: Paranthropus
Paranthropus aethiopicus c. 2.5 MYA
Paranthropus boisei c. 1.8 MYA
Paranthropus robustus c. 1.5-2 MYA
Paranthropus
•  “parallel to man”
•  Similar to Australopithecines from the neck
down (bipedal, short relative to humans)
•  Small brains
•  BUT they had massive molars and premolars,
and jaws adapted to chewing tough plant
materials; their skulls were modified to carry
the enormous muscles necessary to power
the chewing apparatus
Paranthropus
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Exceptionally large teeth, esp. molars
(unlike Australopithecus)
Exceptionally large jaws (unlike
Australopithecus)
Big teeth and big jaws mean:
Large jaw muscle (temporalis muscle) to
move the heavy, powerful jaw; jaw
muscles connect up and around the
sides of the head, and run underneath
the cheekbones to the jaw
Large jaw muscles mean:
–  Large zygomatic arches (cheekbones)
needed to create space for jaw muscle
–  More skull for the large jaw muscles to
connect to: a sagittal crest
–  Test yourself, clench your teeth and feel
your temporalis muscle--feel the muscle
where it stops, about an inch above your
temple
–  Sagittal crest
“Black Skull” (because it is black; just due to
the process of fossilization with high
manganese content):
Paranthropus aethiopucus
Paranthropus robustus and boisei
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P. robustus: wear marks on molars
indicate hard foods and nuts, but
research on fossil contents also
suggest a significant amount of
meat in the diet
• P. boisei: a super-robust
paranthropus
• P. robustus used to be called Australopithecus robustus and P. boisei used to
be called Australopithecus boisei
To summarize 4-2mya
•  Spread around South and East Africa
•  Small brains (~500-700cc) but somewhat bigger than
today’s chimps
•  Small in stature
•  “gracile” group, “robust” group
•  Sexually dimorphic
•  Clearly bipeda…l
The Evolution of Bipedalism
•  Several theories
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Walking on 2 legs is an efficient form of ground locomotion
Erect posture allowed humans to keep cool
It left the hands free to carry things
Allows for efficient harvesting of fruit from low trees
•  Different lines of evidence for and against these and
other theories
•  But one thing we know for sure:
Bipedalism evolved BEFORE big
brains/intelligence evolved
But wait, what about Piltdown Man???
Piltdown Man: A Hoax
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Skull fragments were of a human--hence the large brain
Jaw of an orangutan--hence the large canines
Molars were filed down to look like the small molars of a human
The signs were obvious, but, consistent with the prevailing notion in
England at the time, people wanted to believe that large brains
evolved prior to other features
They also wanted to believe that Europe was the location of humans
evolving from apes into modern humans
A set-back to science--a total waste of time
Forgery wasn’t discovered until 1953! Though as early as 1915
other scientists had rejected it.
It did wane in acceptance with the finding of the Taung Child
The hoax is still cited by creationists in support of their view that the
theory of evolution cannot address the origins of man. Many cite it
as evidence of the frequent acceptance in the scientific community
of viewpoints with very little data.
Tools
•  Hominins have been making stone tools for at
least 2.5my
•  Earliest found in Ethiopia (2.5myo)
•  East Africa: similar tools from 2.4-1.7mya
•  South Africa: similar tools dating back to
2mya
•  These tools: Oldowan tools (“Oldowan tool
industry”)
Oldowan tools
Oldowan tools
-Several flakes can be
chipped from I core
-It is not clear if the
core was used as a
chopper of if the flakes
were used for cutting
-Experiments in
knapping (stone
toolmaking) have
shown:
-knappers were almost
certainly right-handed
-flakes were best at
processing carcasses,
though cores/choppers may
have been useful in other
activities
Question: Who was making and using them?
Who used Oldowan tools?
•  Members of the genus Homo (next), including H.
ergaster and H. erectus--but these guys also started
using more advanced tools (Acheulean)
•  Probably Australopithecus and Paranthropus
–  We don’t have direct evidence of these early hominin bones
associated with Oldowan tools, but that doesn’t mean they
didn’t use them (no one died and was fossilized with an
Oldowan tool in their hand, but we find the tools at the same
time they were alive, and we find clearly-processed animal
bones with the tools)
–  Also, recall: the chimps of today (and several other primates)
do use tools
Final Group: Genus Homo
(includes us)
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Homo ergaster (African)
Homo erectus (Asian)
Homo heidelbergensis
Homo neanderthalensis (no longer
considered Homo sapiens neanderthalensis)
•  Homo sapiens (us)
The Pleistocene Epoch
•  Miocene: 23-5mya
•  Pliocene: 5-1.8mya
•  Pleistocene: 1.8.mya-12kya (12 thousand
years ago)
•  Recall: world getting colder starting in the
mid-late Miocene
•  Temperatures decline further in Pliocene
•  Sharp drop in temperature at beginning of
Pleistocene, and large fluctuations of
temperatures for the rest of the Pleistocene
•  12kya to present: a warm interglacial phase
H. ergaster
•  Clearly a different
genus from
Australopithecus,
Paranthropus
•  Appear 1.8 mya in
Africa (dates and
climate…colder)
Homo ergaster c. 1.75 mya (Africa)
H. Ergaster
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H. ergaster appears 1.8mya and disappears .6mya (600 thousand
years)
Found in East, South, and other parts of Africa
Also found in…Eurasia! And at the same time of the earliest finds in
Africa
Traits like earlier hominins: receding forehead, no chin
Traits like modern humans: smaller, less prognathic face, higher skull,
smaller jaws and teeth, similar body size, similar sexual dimorphism
Other trait: very large brow ridges, horizontal ridge at the back of the
skull (occipital torus) which allows a better biting and tearing action with
the incisors and canines
Biting and tearing what? MEAT. Molars are far smaller (and
proportionately so) than those of the earlier hominins who were
chewing and grinding hard plant foods
Bigger brains than earlier hominins ~800cc
Probably mastered fire
Probably hunted large game
Used Oldowan and Acheulean tools
Acheulean hand axes
Regular, bifaced, teardrop-shaped flaked tooks; can have different
sizes (few inches to 2 feet have been found) and be made of
different materials, but always the same proportions; probably most
used for butchering, with less use for other tasks; 1.6mya to 300kya:
remarkable regularity of the tool industry for over a million years
Acheulian hand axes
H. ergaster
Homo erectus
•  1.8mya-30kya
•  Very similar to H. ergaster but
–  found only in eastern Asia
–  Much larger brow ridges
–  Sagittal keel (a lump rather than
a crest) with unknown function
–  More sloped sides of skull
–  Used Oldowan tools mostly, but
a few Acheulean tools have
been found in eastern Asia, and
stone tools are absent from the
entire region above the latitude
line where bamboo grows
Homo erectus c. 1.6-0.7 MYA (Asia)
H. heidelbergensis
H. heidelbergensis
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Used to be called “archaic Homo sapiens” (just 15 years ago!)
Appearance dates unclear: 800-500kya
First in Africa and Europe, then later in Asia
Name from Heidelberg, Germany, where 1st specimen was found
Used Acheulean and other stone tool industries, and Acheulean
tools were very finely made--better than H. ergaster; also developed
more advanced stone tools
•  Clear evidence of big game hunting, including wooden spears 6 feet
long, some of which had stone flakes attached to the ends
(evidence of hafting)
•  Higher forehead with more rounded skull, large brow ridge, and
bigger brain
Neanderthals
Homo Neanderthalensis
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Only in Europe, 137-30kya
Adapted to cold environment: stalky, huge noses and faces
Large front teeth, many with cut marks
Well-adapted to hunting large game
We clearly did NOT evolve from them; genetic evidence shows they
were a separate branch that had a dead-end (I.e., they went extinct)
We know a lot about them because European paleoanthropologists did
a lot of digging there
First one found in Germany’s Neander valley
LARGE BRAINS, averaging 1520cc--bigger than us, who average
~1350cc (though reflects large body size, and they are about 30%
larger than us)
Probably buried their dead
Had short, brutal lives
Interesting fact: the patterns of injuries we see in Neanderthal bones
match those of human rodeo riders (yes, they did this cool study)
Skeletal
morphology
Neanderthal diet
Neanderthal tools (Mousterian Industry)
Homo sapiens
Homo sapiens…
•  Hominins living in Africa were more similar to modern humans
than Neanderthals
•  Big brains: ~1350cc
•  Appeared in Africa ~190kya
•  Vertical forehead
•  Small face
•  Less robust bodies than earlier hominins
•  Small teeth
•  Chins (function unknown--probably a byproduct of teeth
shrinking so fast over generations)
•  Round on back of head
•  Advanced tools and art
•  We eventually replaced the Neanderthals in Europe
Homo sapiens
Europe c. 25,000-50,000 BP
Homo sapiens
Europe c. 25,000-50,000 BP
Evolution of hominin brain size
The phylogenetic map to Homo
sapiens is still being investigated
Current thinking
More controversial
(need more fossils)
Human dispersal based on genetic evidence:
the Out of Africa Hypothesis (probably right
based on converging lines of evidence)