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Unique characteristics of the Human Species

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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Unique characteristics of the Human Species

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  1. Unique characteristics of the Human Species

  2. 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

  3. 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

  4. 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)

  5. 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%)

  6. 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

  7. 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

  8. 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.

  9. 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

  10. Evolution of hominins

  11. 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

  12. 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)

  13. 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

  14. 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)

  15. 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.

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