APES VS. HOMININ SKELETONS

=Key Skeletal Differences= [image:http://i.imgur.com/sF5K1o6.png?1] '''Chest / Rib Cage''' Humans have a broad chest that is flatter (front to back), placing the centre of gravity back towards the spine, helping us to stand more upright. Apes have a rounder, barrel shaped rib cage. '''Spine (Vertebral Column)''' The human spine has an S shape that keeps the head and the torso above the centre of gravity. It also acts a little like a spring to absorb force or jarring during activity. [image:http://i.imgur.com/sdT3bvg.png?2] '''Pelvis''': Humans have a much broader pelvis giving stability when walking upright as it transfers the weight directly to the legs. Humans have a more ‘bowl shaped’ pelvis to better support the organs above. [image:http://i.imgur.com/w8BCtuL.png?2] '''Femur (thigh bone)''': Bipedal standing increases the weight on each leg, and the area of the '''joint surfaces''' of the femur (upper leg bone) reflects this. This photo shows the femur from a chimp (left) through to that of a modern human (right). The intermediates represent different Hominin species (in chronological order). You should be able to see that the top of the femur increases in size, which reflects the increased weight load on the joint as humans spent more time walking on two legs and grew larger in size. [image:http://i.imgur.com/JC5Tstq.png?3] '''Knee -Valgus angle''' Humans also have a '''larger valgus angle'''; the angle the femur makes at the knee. This means that our thighs slope inward (we are ‘knock-kneed’) bringing our feet in closer to the centre of gravity. This means that we shift less weight when walking, making it more efficient. Apes have a much smaller valgus angle and when they attempt to walk on two legs, they waddle (try walking with your feet at shoulder length apart. Humans also have '''wider femoral condyles''' (the point on which the bone pivots) to prevent sideways movement of the knee. [image:http://i.imgur.com/nOWadfD.png?3] '''Feet''' Apes tend to be flat footed (have plantigrade feet). Human have arched feet, supported by ligaments on the underside of the foot. These prevent the arch from collapsing and act like springs, which are stretched, thus storing energy, when the foot comes down. This helps to catapult the body upwards again. Apes have prehensile (grasping) feet with a sideways facing big toe. Humans have a forward facing big toe to provide extra final thrust when walking. The phalanges (toe bones) are curved in apes to aid grasping. [image:http://i.imgur.com/QpqvrMo.png?1] '''Hands''': As apes developed the habit of brachiating, the thumb became reduced, using the fingers more as hooks. In humans however, the thumb is enlarged. More significantly the first metacarpal (hand bone at base of thumb) is connected to the wrist by a ‘saddle’ joint, which enables the thumb to be brought across the hand so that it can touch the tip of the first or any other finger. Humans are the only ape which can achieve the full thumb tip to finger tip '''precision grip'''. Humans also have an independent muscle / tendon dedicated to flexing the last joint of the thumb (apes cannot flex their thumb independently). Lastly, the bones of the finger tip have an enlarged apical tuft, which increase the surface of the finger tip for grasping fine objects. [image:http://i.imgur.com/I7j3MEYl.png]