Biological Anthropology

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Biological Anthropology

• Review
• Part II

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Part Two

• Format
• 10 Matching
• 20 Multiple Choice
• 4 Short Answer
• Content
• Chapter 5, 6, 7, 8
• Hominid Evolution
• Hominid Classification
• Bipedalism

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Primate Evolution? Hominid Evolution
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The work of Primate Paleontologists and
Paleoanthropologists

• Focus on various questions of primate evolution.
• How did primates emerge?
• What conditions favored them?
• How and why did the early primates diverge?
• Focus on ancestral line leading to humans
• Fossil record is full of diversity as well as
  apparent extinctions
• Most of the primate lineages of the past never
  left any descendants at all

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What challenges do paleontologists face in the
study of primate evolution?

• Reconstruction of primate evolution requires the
  finding of fossil remains
• Fossils are difficult to find (needs to be
  exposed by erosion, strata uplifted, or in
  accessible areas)
• Fossil record incomplete
• Fossils fragmented/ damage
• Rely on anatomical studies of living species to
  make inferences
• Need to use dating techniques to estimate age of
  fossil remains (relies on chemistry, geology, and
  physics)
• Need to study ancient plants and animals,
  geography, and climate to reconstruct environment
  of ancient primates

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When did primates emerge?

• It is generally agreed that the earliest primate
  may have emerged in the late Cretaceous Period/
  Early Paleocene (approximately 55 million years
  ago).

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What was the environment like during the
Cretaceous Period/ Early Paleocene?

• Paleocene Period marked a major geological
  transition from the Cretaceous Period.
• About 75 of all animal and plant life vanished
  by early Paleocene (including dinosaurs)
• Cretaceous Period
• Climate was uniformly damp and mild? but temp
  began to fall
• Seasonal and geographic fluctuations began to
  develop
• Climate became much drier and cooler in many
  areas? vast swamplands disappeared
• Change in climate as a result of CONTINENTAL
  DRIFT

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Continental Drift
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CONTINENTAL DRIFT Movement of continents over
the past 135 million years

• In early Cretaceous there were two super
  continents
• Laurasia North American and Eurasia
• Gondwanaland Africa, South America, India,
  Australia, Antarctica
• By beginning of the Paleocene era
• Gondwanaland broke apart? South America drifting
  west away from Africa, India drifting east,
  Australia and Antarctica drifting south
• Results
• As the continents changed position, they moved
  into locations with different climatic conditions
• The very movement of the continents affected the
  climate

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Climatic Changes resulting from Continental Shift

• Large landmasses affect wind and weather patterns
  differently than smaller landmasses
• Laurasia would have been different from weather
  in other continents
• When continents collide, mountain ranges are
  formed? affect weather pattern
• Clouds drop moisture as they meet a mountain
  range
• Location of continents prevents the movement of
  ocean currents from the tropics to the poles, the
  earths climate becomes colder

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How does this relate to monkeys?

• Continental drift and climate change had profound
  effects on the evolution of primates
• Changes in climate changes in vegetation
• Large trees with fruit and seeds became common
  during the Paleocene Era
• New kinds of plant life opened up sources of food
  and protection for new animal forms
• Changes in climate emergence of new species of
  animals
• New plant life provided an abundant food supply
  for insects
• Primates evolved from mammalian radiations
  (extensive diversifications) ? insectivore order
  of mammals (including modern shrews and moles) ?
  abundance in insects as result of first deciduous
  trees and new vegetation coming with climatic
  changes
• Insectivores were very adaptable? can take
  advantage of variety of habitats (under ground,
  in water, on ground, above ground)
• Above ground adaptation may have been the most
  important

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Arboreal Theory

• Primates evolved from insectivores that took to
  trees
• Favored vision over smell
• Smaller snouts and declining importance of sense
  of smell
• Eyes of early primates would have come to face
  forward
• Vision more useful for animals searching for food
  in the maze of tree branches
• 3-D binocular vision would be favored because an
  animal jumping from branch to branch would be
  more likely to survive if it could accurately
  judge distances
• Tree climbing favor grasping hands and feet, with
  hind limbs becoming more specialized for support
  and propulsion
• Shift in diet from insects to seeds, fruit, and
  leaves might have been important to biological
  changes

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Weakness of Arboreal Theory

• Tree living not good explanation for many primate
  features
• There are living mammals that dwell in trees but
  seem to do very well w/o primate characteristics
• Tree squirrel? claws rather than nails, lacks
  front facing eyes, smell not reduced, no
  opposable thumb
• Other mammals have primate features but do not
  live in trees
• Cats, hawks, owls, Australian marsupial mammals

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Visual Predation Theory

• Belief that some factor OTHER than moving about
  in trees may account for the emergence of the
  primates
• Proposes that early mammals may have been
  basically insect-eaters which favored 3-D vision
  and other selectively advantageous features for
  hunting insects in the undergrowth of a forest
• 3-D vision would allow predator to gauge preys
  distance accurately
• Grasping feet and hands would allow predator to
  move quietly
• Reduced claws b/c claws make it difficult to
  grasp very slender branches
• Sense of smell reduced, not so much b/c it was no
  longer useful, but b/c the location of the eyes
  at the front of the face allows for less room for
  a snout

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Weakness of Visual Predation Theory

• Not all visual predators have forward facing eyes
  (ex. Mongoose, robins)
• Some primates (actually at least one-i.e.
  Panamanian tamarin) have claws
• Many primate eat more fruits than insects

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Hominid Evolution
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Hominid ClassificationHomo genus to which
modern humans and ancestors belong

• Ardipithecus first bipedal ape
• Combination of ape like features and bipedal
  locomotion
• Australopithecus Afarensis first bipedal hominid
• Lucy
• best represented by fossil record (2 dozen
  individual fossil remains)
• Homo neanderthalenis not in human genus (close
  relatives)
• Homo Habilis early species belonging to our
  genus, 50 of modern human brain capability
• Homo Erectus 1st hominid species to be widely
  distributed in Old World (larger brain than Homo
  Habilis, smaller brain than Homo Sapiens)
• Homo Sapiens all living people belong to this,
  can successfully interbreed

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• Hominid Classification Tree

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What were the physical changes crucial to early
hominid evolution? Which was the most crucial
and why?

• Expansion of brain
• Modification of female pelvis to allow bigger
  brained babies to be born
• Reduction of face, teeth, and jaws
• Increased meat eating
• Extended period of infant/child dependency
• Most crucial bipedal locomotion

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Bipedalism
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Evolution of Methods of Locomotion
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What are the prevalent theories for the evolution
of bipedalism?

• Bipedalism may have been favored by natural
  selection for several reasons.
• Upright walking could have provided improved
  range of vision over tall grasses.
• Easier to see predators and prey
• Bipedalism is more efficient than quadrupled
  locomotion for traveling long distances.
• Bipedalism frees the hands for other tasks
• Carrying food and using tools and weapons
• Bipedalism may allow for better body cooling, as
  more skin is exposed to air and there is more
  opportunity to block the body from direct sun.

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Diagram of CoolingBipedalism may allow for
better body cooling, as more skin is exposed to
air and there is more opportunity to block the
body from direct sun.
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What are the anatomical features of bipedalism?

• Skull
• In both Ancient and Modern apes, the Spine enters
  the skull at the back
• Human spines enters at bottom thru hole foramen
  magnum

• Pelvis
• Ancient and Modern apes have long flat Pelvises
• Humans have bowl shaped
• Hold Organs
• Lower center of gravity for better balance on 2
  legs

• Knee
• Apes are straight from pelvis, Humans slant in.
• Allow straight walking Maintain balance.

• Foot
• Enlarged ankle bones and arches to support
  pressure of walking

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Remember the following

• PELVIS!

• FEET!

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What are the cost or negative affects of
bipedalism?

• Harder to supply the Brain with blood due to
  gravity
• Greater stress on the hips, lower back, knees,
  and feet. (especially for females during
  pregnancy)

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