Primate Evolution 65 5 mya

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Primate Evolution(65 - 5 mya)
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Fossil Records
High-tech help means we can understand more about
species, even their diet patterns

• Fossils
• Actual bones that have turned to stone, or
  something as simple as an impression of an insect
• Learning From Fossils
• Teeth can be examined using cat scans and
  computer enhanced modeling
• Animals vary in dentition - the number, size, and
  location of teeth
• Gives relative size of animal

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Geologic Ages
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Dating Fossils

• Absolute Dating
• C14
• Thermoluminescence
• Electron Spin
• Potassium-Argon
• Uranium
• Relative Dating
• Stratigraphy
• Type/Indicator Fossils

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Homologies and Analogies

• Homologies
• Similarities that organisms share because of
  common ancestry are called homologies.
• The presence of homologies is the principal
  factor in determining how organisms are assigned
  to taxonomic categories.
• Analogies
• Analogies are similarities between species that
  are the result of similar adaptation to similar
  selective pressures--analogies are not the result
  of common ancestry.
• The process which leads to analogies is called
  convergent evolution.

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Emergence of Primates

• First primates
• Plesiadapiforms or adapids and omomyids?
• Environment - Cretaceous to Palaeocene
• Continental drift (Pangea Laurasia
  Gondwanaland)
• Success of primates
• Arboreal theory
• Visual predation hypothesis (Cartmill 1972, 1992)

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Continents at the end of the Meszoic
Here are the placement of the continents at the
end of the Cenozoic and beginning of the
Mesozoic, about 65 m.y.a.
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Early Cenozoic Primates

• The earliest primates date to the first part of
  the Cenozoic (65-54 m.y.a.).
• The Eocene (54-38 m.y.a.) was the epoch of
  prosimians with at least 60 different genera in
  two families.
• The omomyid family lived in North America,
  Europe, and Asia and may be ancestral to all
  anthropoids.
• The adapid family was ancestral to the
  lemur-loris line.

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Omomyid
An artists reconstruction of Shoshonius, a
member of the Eocene omomyid family.
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Anthropoids

• Anthropoids branched off from the prosimians
  during the Eocene.
• Anthropoid eyes are rotated more forward compared
  to prosimians.
• Anthropoids have a fully enclosed bony eye
  socket.
• Anthropoids have a dry nose separate from the
  upper lip.
• Anthropoids have molar cusps.

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Early Anthropoids

• Undisputed remains of early anthropoids date from
  34 million years ago Fayum area southwest of
  Cairo, Egypt
• Found remains from different types of
  anthropoids, including
• Parapithecids (monkey-like)
• Propliopithecids (ape-like) - some believe that
  the common ancestor for both Old and New World
  monkeys belonged to this group
• Best known of group - Aegyptopithecus which is
  believed to be after the fashion of the howler
  monkey

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Miocene Anthropoids

• Miocene Period 24 to 5.2 million years ago
• First hominid appeared in Africa where remains
  have been found dating 5 million years old
• Early Miocene Period
• Proconsul found in sites in East Africa
• Middle Miocene
• Kenyapithecus 16 to 10 million years ago with
  molars resembling modern hominoids
• Late Miocene Apes
• Movement to Europe and Asia due to warmer weather
  conditions migration from Africa
• Two main groups
• Sivapithecus - link to orangutans
• Dryopithecus

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Proconsul
A skull of Proconsul africanus from the Kenya
National Museum.
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Kenyapithecus
Fossil jaw bones from Equatorius, probably
ancestral to Kenyapithecus africanus and K.
wickeri.
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Sivapithecus

• Sivapithecus belongs to the ramapithecid genera
  along with Gigantopithecus.
• Sivapithecus is now believed to be ancestral to
  the modern orangutan.

A Sivapithecus skull.
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Gigantopithecus

• Gigantopithecus is the largest primate that ever
  lived, some standing over 10 feet tall and
  weighing 600 pounds.
• Since it died out around 250,000 years ago, it
  coexisted with Homo erectus.
• Some people believe it is still alive today as
  the yeti and bigfoot.

A reconstruction of Gigantopithecus by Russel
Ciochon and Bill Muns.
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Dryopithecus

• Dryopithecus lived in Europe during the middle
  and late Miocene.
• This group probably includes the common ancestor
  of the lesser apes (gibbons and siamangs) and the
  great apes.
• Dryopithecus has the Y-5 arrangement of molar
  cusps typical of Dryopithecus and of hominoids.

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Oreopithecus

• Oreopithecus bambolii lived between 9-7 m.y.a and
  spent much of its time standing upright and
  shuffling short distances.
• Its big toe splayed out 90 degrees from the other
  toes.
• Oreo is Greek for mountain

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Early Hominids
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Chronology of Hominid Evolution

• The Pleistocene (2 m.y.a. to 10,000 B.P.) is the
  epoch of human life.
• Lower Pleistocene (2 to 1 m.y.a.)
  Australopithecus and early Homo
• Middle Pleistocene (1 m.y.a. to 130,000 B.P.)
  Homo erectus and archaic Homo sapiens
• Upper Pleistocene (130,000 to 10,000 B.P.)
  modern Homo sapiens

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The Varied Australopithecines

• There are two major hominid genera
  Australopithecus and Homo.
• However, in 1992 Berhane Asfaw and Tim D. White
  discovered substantial remains considered to be
  from hominids ancestral to the australopithecines
  these remains have been called Ardipithecus
  ramidus (thus establishing a third hominid genus)
  and dated a 4.4 m.y.a.
• A more recent (1995, by Maeve Leakey and Alan
  Walker) discovery has been named Australopithecus
  anamensis and been dated at 4.2 m.y.a.

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Evolution of Bipedalism

• Tool use and bipedalism (Darwin/Washburn)
• Energy efficiency and bipedalism (Isbell/Young)
• Radiator theory (Falk)
• Body temperature and bipedalism (Wheeler)
• Habitat variability and bipedalism (Potts)
• Reproduction and bipedalism (Lovejoy)
• Canine reduction and bipedalism (Jolly)

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Skeletons
Comparison of human and chimpanzee skeletons.
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Pelves
A comparison of human and chimpanzee pelves.
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Dentition
Comparison of dentition in ape, human, and A.
afarensis palates.
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Crania Comparison
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The Species of Australopithecus

• Ardipithecus ramidus 4.4 - ? million
  years ago
• A. anamensis 4.2 - 3.9
• A. afarensis 4.2 - 2.5
• A. bahrelghazali 3.5 - 3.0
• A. africanus 3.5 - 2.5
• P. aethiopicus 2.7 - 2.3
• A. garhi 2.5 - ?
• P. boisei 2.3 - 1.3
• P. robustus 2.0 - 1.0

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Phylogenetic Tree
Phylogenetic tree for African apes and hominids.
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Ardipithecus ramidus

• Hominid who walked bipedally 4.4 mya
• Discovered in 1992 by Tim White in Aramis,
  Ethiopia (as yet largely unpublished)
• Distinct enough to be a new species?
• ape-like dentition
• bipedal locomotion
• overall hominid-like skeleton
• small cheek teeth with thin enamel and large
  canines
• arm bones are hominid-like
• foramen magnum indicates bipedalism

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Australopithecines Robust or Gracile?

• Two species of australopithecines robust and
  gracile
• Most palaeoanthropologists classify robust
  species as Paranthropus and gracile species as
  Australopithecus, although both species are
  australopithecines.
• Gracile
• A. anamensis, A. afarensis, A. bahrelghazali, A.
  africanus, A. garhi
• smaller dentition, lighter musculature
• Robust
• P. aethiopicus, P. boisei, P. robustus
• larger teeth, massive jaws, sagittal crest

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Australopithecines
Skulls of Robust (left) and Gracile (right)
Australopithecines.
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Australopithecus anamensis

• 4.2 - 3.9 mya
• average weight - 110 pounds
• primitive bipedalism, possibly climbing
• found primarily in Kenya
• discovered in 1995

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Australopithecus afarensis

• 4.2 mya, with oldest definite specimen placed at
  3.8 mya
• apelike features (long arms, prognathic face,
  toothrow, brain capacity)
• pelvis, leg, feet, and foramen magnum all
  indicate bipedalism

• first discovered by Don Johanson in 1974 and
  called Lucy
• thought to be the missing link until A.
  anamensis was discovered 20 years later

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Australopithecus afarensis
Left Trail of footprints of A. afarensis made
in volcanic ash, discovered by Mary Leakey at
Laetoli. Right Close-up of footprint at
Laetoli
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Australopithecus bahrelghazali

• 3.5 - 3.0 mya
• discovered by Michel Brunet in Bahr el Ghazal,
  Chad in 1995
• assumed bipedalism (few post-cranial remains)

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A. africanus

• 3.5 - 2.5 mya
• 3.8 - 4.5 feet tall, 55-130 lbs
• ape-like tibia, grasping big toes
• wide pelvis, parabolic tooth row
• primitive bipedalism
• first found by Raymond Dart in Taung, South
  Africa in 1925

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Australopithecus garhi

• possibly the direct ancestor of early Homo
• larger molars than afarensis, but not as large as
  Paranthropus
• lacks enlarged brain of early Homo
• toolmaker and butcher
• 2.5 mya

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Paranthropus aethiopicus

• 2.7 to 2.3 mya
• earliest robust australopithecine, but least well
  known
• larger dentition, cheek bones, dish-shaped faces,
  sagittal crests
• resembles afarensis but with increases in dental
  apparatus size
• assumed bipedalism
• first discovered in Omo, Ethiopia, 1967-1974

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The Black Skull - P. aethiopicus
The black skull, dated to 2.5 m.y.a., was
discovered by Alan Walker in 1985 near Lake
Turkana.
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Paranthropus boisei

• 2.3 - 1.3 mya 4.1 - 4.5 feet tall, 75-175 lbs
• discovered by Louis Leakey at Olduvai Gorge in
  Tanzania in 1959
• originally named Zinjanthropus
• dished face, sagittal crest
• parabolic toothrow, wide pelvis
• primitive bipedalism

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Paranthropus robustus

• 2.0 - 1.0 mya 3.6 - 4.3 feet tall 70-175 lbs
• discovered by Robert Broom in 1938 at Kromdraai,
  South Africa, who created the name Paranthropus
• dished face, sagittal crest
• parabolic toothrow, human-like
• big toes, wide pelvis, no diastema
• for canines
• bipedalism (more primitive than
• modern human walking)

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Map of Australopithecine Finds
Map of Australopithecus sites in Africa, with a
focus on the East African rift valley and
limestone caves of South Africa.
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Facts about Australopithecines
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Facts about Australopithecines