My last essay was on the origins of bipedalism. Having a human bones practical class in the University Museum really helped, and we got to examine real human skulls. I think that's pretty cool, some might say it's creepy. Potato, potaato. One thing I've learnt is the placement of the foramen magnum, the hole which your spinal cord attaches to, on the base of your skull. If it's anterior (forwardly) placed, it's indicative of bipedalism as the angle shows the person would be standing upright. However, if it's posteriorly placed, it is likely to belong to a quadruped. Logical stuff.
The main difference between the walking of human and chimpanzees is that we do it habitually and with a striding gait. Our walking is formed of the 'swing phase', and the 'stance phase'.
We can 'toe off' using our big toe, which is aligned with the rest of our toes, to push off in the stance phase. However, chimps have opposable toes, and can't do this. Their valgus angle of the thigh bone to lower leg bone is also straight. Our is curved, allowed us to shift the weight of a leg to the other side.
This diagram shows the predicted angle of the australopithecine leg, as a sort of midway between chimp and human angles. However, although it used to be assumed that we can from quadrupeds who strode out into the savannah to see over long grasses, this illusion has been disproved from recent fossil finds. The contexts of A. afarensis, for example, show that it dies in a heavily wooded area, and not an open grassy savannah at all! Similarly, research on orang-utans show that bipedalism in an arboreal contexts mostly occurs when trying to maneuver slender, multiple branches. In fact, it appears that our bipedal ancestors may not have been quadrupeds after all. Some evidence suggests that adaptations towards bipedalism, because of whichever selective pressures, such as thermoregulation or for food resource attainment, may have actually evolved more than once. This might explain why some older specimens, such as Orrorin tungensis (6-7 Ma), may like more human like than more younger species like Australopithecines (3.5 Ma).
Being ill, I decided to watch some arch and anth (related-ish) videos... Here's one by Armstrong and Miller on the 'Origin of Teenagers'. It made me feel a little better.
