Chapter 11 Primates and Human Evolution

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Chapter 11Primates and Human Evolution
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Primate Characters

• Grasping hands and feet with thumb and big toe
  often opposable
• Sensitive pads on fingertips and nails instead of
  claws
• A mobile shoulder joint, especially in humans
• Large braincase and a postorbital bar
• Flattened face with eyes rotated forward for
  stereoscopic vision
• Usually have one offspring at a time
• Females have only two mammary glands

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Anthropoid Origins

• Anthropoid (human-like)primates were thought
  tohave originated in Africa.
• Recent finds from the early Eocene of China and
  Thailand (above) have challenged this view
  because they are older.
• Anthropoids are distinct in having rounded
  nostrils (not slit-like as in prosimians),
  usually large canines, molar-like premolars, and
  broad square molars.

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Miocene Apes

• Proconsul is the best-known early ape, early
  Miocene of Kenya.
• Proconsul is designed for diverse locomotion
  styles (quadrupedal running, standing upright,
  swinging from branches) and could probably swing
  a stick for defense.

Proconsul
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Hominoid Relationships
Hominidae great apes Hylobatidae lesser apes
Pongidae (ape family) has been eliminated as a
paraphyletic group, and Hominidae (human family)
has been expanded to include most apes. Note in
the right diagram that no common ancestors are
known!
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Classification of Apes and Humans

• Superfamily Hominoidea
• Family Hylobatidae gibbons
• Smaller tree-climbing apes
• Family Hominidae
• Subfamily Ponginae Orang-utans
• Slow climbers and brachiators
• Subfamily Homininae
• Terrestrial quadrupeds chimps and gorillas
• Infrafamily Hominini Terrestrial bipeds
  humans
• Monophyletic group of humans and their closest
  relatives

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Apes

• Apes arose in the Miocene of Africaas grasslands
  developed there,have short 5-cusp molars
• Early-middle Miocene Dryomorphs
• Large canines, Africa to Eurasia
• Middle-late Miocene Ramapithecines
• Small canines, very diverse, Africa to Asia
• Pliocene poor fossil record leaves many
  questions about hominid relationships, including
  the origins of living groups of apes

Baboon
Chimp
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Apes

• It was long believed that Ramapithecus was the
  first human and that the human/ape split occurred
  15 M.Y. ago. DNA and protein similarities,
  however, suggested a mere 5 M.Y. ago split, with
  man, chimp, and gorilla being equally similar.
  Discovery of more skeletal material suggested
  that Ramapithecus is an orang-utan.
• Gorillas and chimps have no definite fossil
  record, so tracing their ancestry is difficult.

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Late Miocene Apes
Sivapithecus (Ramapithecus) of China region
Modern human
Chimp
Lower jaw of Gigantopithe-cus (late Miocene of
India and Pleistocene of China)
Jaw and molars of Sivapithecus showing Y and
cusp pattern
Hand of Dryopithecus
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Humans and Upright Posture
Grasping hand
Gorilla
Loss of opposable toe in foot
Foot flat with straight toes for plantigrade
walking
Walking on knuckles
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Modifications for Bipedalism

• Skull with ventral foramen magnum
• Backbone develops an S-curve
• Pelvis short with bowl-shaped ilium to support
  abdominal organs
• Hip joint faces downward and sideways
• Long, slender leg bones
• Knee forms a straight hinge for standing
• Foot a flat platform with non-opposable toes

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Reasons for Bipedalism

• Ability to stand tall for a better view
• Freeing up the hands to use tools
• Faster or more efficient locomotion
• One theory is that forest-dwelling apes became
  restricted to west Africa where they gave rise to
  chimps and gorillas, while humans arose as an
  adaption to the open grasslands in east Africa.

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Brain First Theory

• The early popular theory was that the big brain
  was required for tool use, so it came before
  bipedalism.
• This was confirmed by a skull at Piltdown,
  England, with a large braincase but primitive
  jaws (a).
• Piltdown man turned out to be a hoax (a human
  cranium planted with an orang-utan jaw).
• Australopithicus found in Africa (b) disproved
  the brain first theory with its small brain and
  bipedalism.

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Piltdown Man

• Discovered 1912 near Piltdown, East Sussex,
  England
• Exposed as a fraud in 1953
• Parts of human skull and orang-utan jaw etched
  with acid and buried at an excavation site.

Why was the hoax so readily accepted by Englands
experts?
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Piltdown Man
Most human fossils hadbeen found in
Africa. There were racistviews about
Africa. It was a relief to findevidence of
humanevolution in Europe. Though the skull
wasfrom a modern human,Piltdown was
consideredintermediate in brain sizebetween
Homo erectusand Neanderthal Man!
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Neoteny is the evolutionary process where
juvenile traits are retained into adulthood.
Adult Chimp
Adult Human
Juvenile Chimp
Juvenile Chimp
Juvenile Human
Human evolution may be a case of neoteny.
Enlargement of the human brain could have been
accomplished by retaining the juvenile
proportions of an ape. This could also explain
the loss of hair in humans. But it fails to
explain our large legs.
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Early Human Fossils

• Orrorin teeth, jaw fragments,broken limb bones
  that suggestbipedalism, 6 M.Y. old
• Sahelanthropus distortedcranium (at right)
  with foramenmagnum that suggests bipedalism, 6
  M.Y. old
• Ardipithecus teeth, skull fragments, and limb
  bones from several individuals with somewhat
  large canines, thin tooth enamel, and clear
  evidence of bipedalism, 5.8 to 4.4 M.Y. old
• Praeanthropus Lucy (most of skeleton found in
  1974) and other bones and teeth, 4.1 to 2.9 M.Y.
  old

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Praeanthropus walked fully upright
Early hominids had the distinct human pelvis for
upright walking. Fossil trackways also
demonstrate full bipedality.
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Evolution of Human Characters
Chimp Ardipithecus Praeanthropus
Palate of Lucy
Ape
Legs
Modern human Fingers
Skeleton of Lucy (Praeanthropus), the most
complete early hominid skeleton
Ape Praeanthropus Modern human
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Australopiths

• All previously included in genus Australopithecus
• Praeanthropus small primitive forms such as
  Lucy (P. afarensis) with strong sexual dimorphism
• Australopithecus advanced gracile
  australo-piths that probably gave rise to Homo
• Paranthropus robustaustralopiths with broad
  facesand massive jaws (at right)
• The last two have smallcanines and no diastema

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Human Timeline
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Later Australopiths

• Australopithecus africanus (gracile,3.0-2.3 M.Y.
  ago)
• Paranthropus robustus (robust, 1.9-1.6 M.Y. ago)
• Paranthropus boisei (robust, 2.4-1.3 M.Y. old)

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Human Relationships
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Hominid Species
Hominid species Age Brain size Height Praeant
hropus afarensis 4.0-3.0 M.Y. 380-450 cc 1.2
m Australopithecus africanus 3.0-2.3 M.Y. 380-450
cc 1.4 m Paranthropus robustus 1.9-1.6
M.Y. 380-450 cc 1.5 m Paranthropus boisei 2.2-1.2
M.Y. 380-450 cc 1.5 m Homo habilis 2.0-1.6
M.Y. 630-700 cc 1.3 m Homo erectus 1.6-0.3
M.Y. 800-1300 cc 1.7 m Homo sapiens 0.1-0.0
M.Y. 1000-2000 cc 1.8 m - Neanderthal Man
(replaced Homo erectus, large brow ridges,
elaborate burials) - Cro-Magnon Man (replaced
Neanderthal 40,000 yr, made cave art in
France/Spain) - Modern Man (developed from
earlier forms, domesticated plants and animals)
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Early Species of Homo

• Homo habilis (handy man)was discovered in
  OlduvaiGorge, Kenya, in the 1960sby Louis
  Leakey and has amuch larger brain than
  theaustralopiths.
• Homo rudolfensis is a possiblesecond species
  from Kenyawith a larger brain but other more
  primitive features (skull above).
• Without the enlarged brain both would better be
  classified as australopiths. Both are 2.4-1.5 M.Y
  old.

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Earliest Homo (Africa)

• Homo habilis and Homo rudolfensis represent one
  or two species of early Homo from Kenya.
• Homo probably evolved from the Australopithecus
  africanus.
• The primary feature is a large increase in
  cranial size over Australopithecus.
• Homo coexisted with robust Australopithecus for
  about a million years.

Homo habilis
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Homo erectus Exiting Africa
Prior to 2 mil-lion years ago humans were
restricted to eastern Africa.

• The earliest Homo erectus (or H. ergaster) (a)
  dates to 1.9 M.Y. ago and has a brain size of 830
  cm3 but retains heavy jaws and brow and lacks a
  chin.
• More specialized Homo erectus material is found
  throughout Eurasia dating 1.9-0.5 M.Y. ago along
  with Acheulean hand axes (b-d).

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Evolution of Homo
Peking Man(Homo erectus) Common in Africa and
Asia
Neanderthal Man (Homo sapiens neanderthalensis) Co
mmon in Africa and Europe
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Stone Tools
Neanderthal (Homo sapiens) Homo erectus Homo
habilis
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Neanderthal Man

• Neanderthal Man (a, c) is an archaic form of Homo
  sapiens that branched off half a million years
  ago and lived till 30,000 years ago.
• Compared to modern man (b) they had a similar
  brain size but differences in head shape.
  Invading Cro Magnon man may have killed them.

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Modern Man

• Found in Africa and Israel dating back
  100,000-120,000 years ago (skull above)
• Spread into Europe 40,000 years ago (Cro-Magnon
  Man), but no evidence they mixed with
  Neanderthals, and to Australia at the same time
• DNA evidence shows that the latest common
  ancestor of all living humans lived about 200,000
  years ago in Africa (Mitochondrial Eve).

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Dispersal of Modern Humans
The Americas were the last continents to be
colonized, with the oldest well-documented site
in Chile! The Ice-Age Bering Land Bridge is the
obvious route, but theres debate whether they
tra-veled inland (big game hunters) or along the
coast (fishermen).
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Humans arrived in the Americas about 14,000 years
ago.

• The old theory is that humans traveled between
  the ice sheets of Canada in what is called the
  ice-free corridor.
• An newer theory is that they came down the
  Pacific Coast by boat (supported by Dr. Heatons
  Alaska research).

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LGM Ice Cover
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Cast of human mandible in On Your Knees Cave
(9,800 yr B.P.)
By Erik Hill, Anchorage Daily News
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Archaeological Excavation at On Your Knees Cave
Many bifaces, microblades, bone tools, and
cultural charcoal beds were found inside and
outside the cave.
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Common mammals from On Your Knees Cave
Middle Wisconsin 50,000-24,000 yr B.P. Brown bear Black bear Arctic fox River otter Harbor seal Stellers sea lion Caribou Saiga (or goat) Long-tailed vole Hoary marmot gt Heather vole gt Brown lemming gt Last Glacial Maximum 24,000-13,000 yr. B.P. Arctic fox Red fox Ringed seal Harbor seal Stellers sea lion Maybe Brown bear Black bear Otter/Mink Caribou Postglacial 13,000 yr B.P.-present Brown bear Black bear Arctic fox Red fox River otter Stellers sea lion Caribou Black-tailed deer Long-tailed vole Human Bold indicates index species
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The Northwest Coast

• The coast had more exposed land area during the
  Last Glacial Maximum than previously thought.
• The period of maximum ice cover was very brief.
• The coast provided an easy means of
  transportation
• The coast had a more moderated climate then the
  interior.
• The coast had a rich supply of seafood.
• Making a living along the coast required similar
  culture at all latitudes, whereas traversing the
  interior requires diverse adaptations.
• This could explain the rapid colonization of
  North and South America.