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Unique characteristics of the Human Species. Adaptations for Erect Stance: Position of Foramen Magnum (base of skull not back) Double curvature of spine (S-shaped), lumbar vertebrae  wedge shaped Reduction in Jaw size & protrusion

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slide2

Adaptations for Erect Stance:

  • Position of Foramen Magnum (base of skull not back)
  • Double curvature of spine (S-shaped), lumbar vertebrae  wedge shaped
  • Reduction in Jaw size & protrusion
  • Broad, bowl-shaped & short (top to bottom) pelvis (holds abdominal organs)
  • Hip sockets wide apart- femur points in towards knee joint (stability when walking + straight walk)- carrying angle
slide3

Adaptations for Erect Stance: (cont.)

  • Hip joint directly below trunk (straight even weight distribution)
  • Due to carrying angle, knee joint has a stronger ‘hinge’ on the outer part to support weight
  • Non-prehensile feet/non opposable big toe
  • Transverse (only humans) + Longitudinal (front to back) arch in foot (good for striding gait)
  • Longer legs than arms: lower centre of gravity
slide4

Stance & locomotion

  • Support against gravity:
  • Muscle tone (partial contraction of skeletal muscles)
  • Sense/Stretch receptors
  • Postural reflexes maintain balance
  • Striding gait:
  • Walking where hip & knee are fully extended (other apes have bent knees and hips)
  • Foot/ground contact from heel to big toe across transverse arch.
  • Trunk rotates about around pelvis, compensates by swinging arms.
  • Due to carrying angle central axis during walking is kept close. (little/ no swinging hips)
slide5

Brain / Head

  • Relatively large brains (900cm3 to 2200cm3)
  • Ave 1350cm3
  • Apes Ave 400 cm3 - 500 cm3
  • Cerebrum: Largest section of brain (Left & Right hemispheres)
  • Outer portion of Cerebrum: Cerebral Cortex (area of greatest development)
  • Covered by convolutions (increases SA by 50%)
slide6

Brain / Head (cont.)

  • Proportion of Frontal lobe SA increased by 14% (area for higher order functioning – thinking, reasoning, planning, processing) from ape to human
  • Larger proportion of cranium used to house brain
  • Shortened snout
  • No prominent brow ridge
  • More prominent nose
  • Decreased jaw size
  • Decreased teeth size
slide7

Dentition

  • Less prognathism (forward jutting jaw)  smaller teeth
  • Large decrease in size of Canines
  • Minor decrease in size of molars
  • Non interlocking canines, no diastema
  • Dental Arcade (jaw shape): Parabolic, not U-shaped
slide8

Effect of the environment on hominin evolution.

  • Hominin: (tribe) consists of humans and extinct ancestors
  • Likely a woodland/forest environment
  • Early hominis were ape-like (arms/limbs arboreal lifestyle)
  • Between 5-6 million BP temp began to drop, forests shrank and were isolated by areas of grasslands
  • Forests continued to thin and trees spread out  arboreal lifestyle less beneficial, natural selection may have favored hominis which were better at bipedal locomotion.
slide9

Effect of the environment on homininevolution.

  • Advantages of erect stance:
    • Increased range of vision (predators/prey)
    • Increased size deters predators
    • Hands free for other uses (carry food, tools etc)
    • Higher reach (fruit picking etc)
    • Improved body cooling
slide11

Australopithecines

  • Approx 3.6 – 1.4 million BP
  • Home bases, no fire use but tool use appears common. (Oldowan (pebble) tools  choppers, scrapers, flakes, chisels)
  • Tools dated back to 2.5 million BP
  • Likely left Africa (2 million BP) to Egypt  middle East  Asia (?)
  • Evolved to become taller, larger brained & more able hunters
slide12

Early Homo

  • 1.8 – 1.75 million BP (Homo habilis)
  • Walked upright with robust hands
  • May have walked bipedally during day and slept in trees.
  • Larger brain (to provide high energy meat diet would be necessary)
  • Meat diet  animal caught/killed, scavenged (more developed reasoning/cunning) (bones of animals consumed have cut marks  stone (tools) and teeth)
  • Based on modern day hunter-gatherers:
    • Male hunted meat
    • Female gathers fruit/veg
    • Children remained in home base
    • Food sharing between members of social group
  • Increase in spoken communication (bulge in speech producing area in brain/ larynx capable of speech)
slide13

Homo erectus

  • 1.4 million – 250 000 BP
  • Europe / Africa (400 000 BP)
  • Likely modifying environment to suit themselves (environments was less of a selective factor)
  • Use of fire, building of shelters, sophisticated tools (stone and bone)
  • Skillful hunter: planned slaughter of game
    • Slaughter of baboons (Kenya)
      • Required organization, logical thought and communication
    • Fire used to drive elephants into swamp (Spain)
      • Use of fire, stone and bone tools
  • Use of fire: scare predators, warmth, light, hunting, cooking
  • Possibly have a relatively complex spoken language
slide14

Homo neanderthalensis

  • approx 350 000 – 125 000 BP
  • Europe, end of Ice Age
  • More advanced tool making  cutting, gouging, scraping piercing
  • Flake tools allow cloth making
  • Burying of the dead  belief in after life (ceremonial burials)
slide15

Homo sapiens

  • Approx200 000 – 0 BP
  • Environment is no longer a major factor in human evolution as humans adapt environment to themselves rather than adapting themselves.