On Our Own Two Feet

On Our Own Two Feet
By: Stephen Whitt
Odyssey: Adventures in Science

We are the only animals that can walk on two feet. We are able to balance our whole bodies on two feet. Two things that we know for sure is that walking upright is very old because our ancestors have walked and also before we became humans we were still developing the brain. Chimpanzee's are not our ancestor! But they were related to our ancestors 6 million years ago. If you compare a human's skull to a chimps you could see that the human has a flater face and the chimp's face sticks out in the front. The human brain is much larger than a chimpanzee's. The skull of Australopithecus aferensis is the same type of skull as Lucy's. They lived around 3 million years ago halfway between human and chimps. A.aferensis skull looks more like a chimpanzee's. But their brain case is not as large as a chimpanzee's. In the back of a chimp's head there is a hole called foreman magnum, this allows the spinal cord to connect with the brain. The chimp also walks on fours, the spine angles up slightly but not straight up or down and angled back. Humans also have it but ours does not angle back, ours goes horizontal. Our hole for our spinal cord is at the bottom of the skull, ours is like this because we walk on two legs. A.aferensis theirs is horizontal like us! and at the bottom of the skull like us. This shows that they walked on two legs also. There are many different theories to why humans stood up and walked. C.Owen Lovejoy a scientist from Kent Sate University in Kent Ohio, has also got a theory. His theory is that hominids stood up and walked because it was easier when they were carry things like food. Another theory is that we stood up to cross hot savannas to reach forests. And the forests actually started to shrink because the temperatures went up. And the last theory is we stood and walked to cross rivers and streams. Today we still do not know for sure how we started to walk but walking has made a big difference in the world for humans.