Human Evolution

• Phylogeny theories:

  • Early evolutionary theory suggested orthogenesis, that large-scale evolutionary trends are goal-oriented towards increasing overall biological complexity.
  • Modern evolutionary theory suggests branching phylogeny, that evolution is driven by species filling niches with speciation occurring sporadically.
• The Homo genus

  • Enlargement of the brain
  • Reduction of canine teeth
  • Development of tool manufacture
  • Perfection of terrestrial bipedality
  • Shift from arboreal to terrestrial habitat
• Hominid interbreeding between modern humans (Homo sapiens), Neanderthals, and Denisovans occurred multiple times, with archaic DNA found across the modern human genome

  • neanderthal DNA represents 1-4% of the modern genome in Eurasian-based populations
  • Denisovans DNA represents 4-6% of the modern genome of Melanesian-based populations (Hypoxia pathway gene - selection of survival at high altitudes)
• Sahelanthropus tchadensis

  • (6-7 mya)
  • First signs of bipedal locomotion with reduced canine teeth
  • potential being the last common ancestor between humans and chimpanzees
• Ardipithecus ramidus

  • (3.5-4.5 mya)
  • Evidence of bipedality (walking on both legs) and arboreality(life in the trees)
  • large grasping toe
  • 3ft 10 in - 4ft 1 in
• Australopithecus anamensis

  • (4-3 mya)
  • condyles of the tibia (shin) is human-like
  • elbow joints have increased flexibility
  • forearms are still long/ape-like for increased climbing strength/dexterity
• Australopithecus afarensis

  • (2-3.5 mya)
  • Lucy
  • reduced canine size
  • human-like foot elements
  • arms are long with weight bearing shoulders for arboreal life
  • human like fingers
• Homo habilis

  • (1.5-2.5 mya)
  • Earliest recorded use of stone tools
  • brain size 500-900cc
  • restricted foot/ankle rotation for increased stability
• Homo erectus

  • (0.1-1.8 mya)
  • first hominid species to leave the African continent
  • average brain size 1000cc
  • human-like shoulders allowing for throwing
  • limb configuration and proportion the same as modern-day humans
  • 4ft 9 in - 6ft 1 in
• fossils of human evolution

  • sahelanthropus tchadensis
  • Ardipithecus ramidus
  • Australopithecus
  • Australopithecus afarensis
  • Homo habilis
  • Homo erectus
• how many bones are in the human skeleton?

  • 206 bones in an adult
  • fused from 300 in babies
• What is the role of the human skeleton?

  • Provides structure and support
  • points for muscle attachment
  • Aids locomotion
  • Protects vital internal organs
  • metabolic store for calcium, phosphorus and carbonates
• Bones

  Living tissues with blood flow of 200-400 ml/min, total in adults
• what is the name for Comparing Primate Skeletons

  Bipedalism
• Human Skeleton VS Chimpanzee

  • Human:

  1. Foramen Magnum (skull to spinal cord) at the base of the scull for balance
  2. Vertebral column 'S' shaped for centre of gravity
  3. Pelvis is modified for bipedal (standing on both legs/ upright) stance
  4. Limbs and body - Flattened hand bones, Longer legs and modified knee for balance
  5. arched foot for weight-bearing

  • Chimpanzee:

  1. Foramen Magnum at the back of the scull
  2. straightened vertebral column supporting the weight of the torso
  3. Pelvis accommodates quadrupedal stance
  4. Limbs and body - curved hand bones, longer arms and grasping feet
• What is the function of anteriorly positioned and horizontal foramen magnum

  • reflects vertical positioning of the spine
• What is the function of an 'S' shaped spine

  • helps efficiently transfer the weight of the upright trunk to hip joint
• What is the function of the short, curved and wide iliac blades?

  • Supports the upright trunk
• Function of the wide sacrum

  • reflects increased loading on pelvis due to upright trunk
• What is the function of the large acetabulum

  • Increased loading through hip joint
• What is the function of the thick inferior neck of femur

  • Increased loading through hip joint
• what is the function of femur angles in medially from hip to knee?

  • places lower leg closer to midline of the body, helps balance when walking on two legs
• What is the function of a relatively long and robust ankle region?

  • increased efficiency of foot leverage during walking
• How has the skull changed?

  • Apes have a gap called the diastema between the upper incisors and canines, accommodating for the enlarged lower canines
  • Foramen magnum is at the back of the apes skull and at the base of a humans skull
  • changes allowing for speech:

  1. drop in the larynx
  2. formation of the pharynx and change in the shape of the tounge
  3. position of the hypoid bond allowing speech to develop by supporting the tongue and larynx in speech
• Foramen magnum

  The opening in the skull that the spinal cord passes through
• Speech in humans

  • Lungs
  • vocal folds
  • moveable tongue
  • trachea
  • hyoid bone (not connected to any other bone) - humans lack the "bulla" found in chimpanzees which connects the laryngeal air sacs
  • humans missing air sacs allows longer, louder calls at boarder frequencies
• Why can humans speak but non-human primates can't?

  
  

  • increased brain size
  • Neuron number/density has gradually developed along the homo lineage
• Ancient human diseases

  • Bacterial pathogens
  • HSV
  • Malaria
  • Mitochondrial pathogenic DNA
  • Retroviruses
  • Tumors
• What is the function of an arched foot

  • shock absorption during walking and running
• what is the function of a fully adducted big toe?

  • efficient weight transfer during toe-off phase of gait cycle
• migration of early humans

  • Africa (1.9 mya)
  • Asia & Europe(200,000 years ago)
  • Australia (50,000-35,000 years ago)
  • North America (30,000 years ago)
  • South America (12,500 years ago)