Evolution of Humans

evolution for humans. Unit 2. Topic 9.6. 

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Bipedalism

  • Human's head is balanced on its backbone. The Backbone meets the skull through the FORAMEN MAGNUM. 
  • The Foramen magnum is underneath the skull and the head is balanced on the backbone which means that the muscles are small and attached to the skull down. 
  • IN CONTRAST, the gorilla foramen magnum is at the back of it's skull and large stronge muscles are needed to hold it there (doesn't have the support from the backbone) 
  • Also, humans have short, broad hipbones which supports the body at it's origin, showing that they are bipedal. 
  • Gorilla as a long, narrow hipbone. 
  • Human's thigh bone is striaght and the knees are directly underneath the pelvis which allows humans to stand straight for long periods of time. 
  • Gorillas cant straighten their legs. 
  • Human's foot is arched and the big toe is parellel with the others, so the foot is adapted for walking. 
  • Gorilla has a flat foot with an opposable big toe for grasping. 
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Brain

  • When organisms die the soft parts usually decay which means a fossil will not be found with the brain.
  •  But we can estimate the size of the brain by finding the cranial capacity.
  • This is done by tipping sand into the skull and meauring the volume of of sand. 
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Food

  • Thick enamel = teeth adapted to eating hard foods e.g. seeds and nuts. 
  • Microwear (scratches on the teeth) = hard, tough food sources. 
  • Large jaws and bony crests on the skull would have strong jaws with powerful muscles to move them. This means that the animal can eat tough food. 
  • Hominids had smaller canines that apes, and this change meant that jaws could devleop side to side grinding movements, which is useful for chewing. 
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