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The First Bipeds

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Who were the Australopithecines and what were they like? ... brain suggest a intelligence similar to a modern bonobo, chimpanzee, or gorilla. ... – PowerPoint PPT presentation

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Title: The First Bipeds


1
Chapter 6
  • The First Bipeds

2
Chapter Outline
  • What Is the anatomy of bipedalism and how is it
    preserved in the fossil record?
  • Who were the Australopithecines and what were
    they like?
  • What is the role of bipedalism in human
    evolutionary history?

3
Anatomy of Bipedalism
  • Forward position of the large opening in the base
    of the skull
  • Series of curves in the spinal column
  • Basin-shaped structure of the pelvis
  • Angle of the lower limbs from the hip joint to
    the knees
  • Shape of the foot bones

4
Australopithecus The Earliest Hominine
  • Appeared in Africa 4 million years ago.
  • From the waist down, fully adapted for
    bipedalism.
  • From the waist up, still apelike, with
    intellectual abilities comparable to those of a
    modern-day African ape.

5
Forms of Australopithecus
  • Earliest forms preserve a number of features
    that indicate an apelike ancestor.
  • By 2.5 m.y.a. new form with larger chewing
    apparatus and more massive head, while brain
    size remained stable.

6
Gracile Australopithecus
  • The size of a modern human pygmy.
  • Chewed food like humans.
  • General appearance resembled an apelike human.
  • Size and outward appearance of brain suggest a
    intelligence similar to a modern bonobo,
    chimpanzee, or gorilla.

7
Robust Australopithecus
  • Shared most of the traits of the Gracile
    Australopithecus.
  • Bones were thick with prominent markings where
    muscles attached.
  • Skull was thicker and larger with a slightly
    larger cranial capacity.
  • Skull possessed a simianlike sagittal crest.

8
Species of Australopithecus
  • Gracile Species - Location
  • A. afarensis - Ethiopia and Tanzania
  • A. africanus - South Africa
  • A. anamensis - Kenya

9
Species of Australopithecus
  • Robust Species - Location
  • A. aethiopicus - Kenya
  • A. boisei - Kenya
  • A. gahri - Ethiopia
  • A. robustus - South Africa

10
Bipedalism Drawbacks
  • Makes an animal more visible to predators.
  • Exposes the soft underbelly.
  • Interferes with the ability to change direction
    instantly while running.

11
Bipedalism Drawbacks
  • Quadrupedal chimpanzees and baboons are 30 to 34
    faster than bipeds.
  • Frequent lower back problems, hernias,
    hemorrhoids, and other circulatory problems.
  • Consequences of a serious leg or foot injury
    seriously hinders a biped and they are an easy
    meal for some carnivore.

12
Fossil Sites in South Africa
  • Dirt, bones, and other matter fell down the shaft
    becoming fossilized.
  • In the Pliocene, the earth next to the shafts
    opening provided a shelter for trees that may
    have been used by predators for eating without
    being bothered by scavengers.

13
Reasons for Bipedalism
  • A way to cope with heat stress.
  • Allowed them to gather food and transport it to a
    place of safety for consumption.
  • Mothers were able to carry their infants safely.
  • They could reach food on trees too flimsy to
    climb.
  • Allowed them to travel far without tiring.

14
Reasons for Bipedalism
  • Food and water were easier to spot.
  • More likely to spot predators before they got too
    close for safety.
  • Hands freed from locomotion provided protection
    by allowing them to brandish and throw objects at
    attackers.
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