by Xauri'El Zwaan

Created on: February 17, 2009

Bipedalism and brain size are two of humanity's most distinctive adaptations. Among close relatives such as chimpanzees and gorillas which are able to walk bipedally, we stand out as being the most efficient users of bipedal motion. Our bodies have evolved to make it not just easy but necessary for us to stand, walk and run on two legs; we are able to use our hands to manipulate tools and objects, and our arms and torsos enable us to put great strength into motions like swinging and throwing. Our brains, the pride and joy of the human species, are among the most complex of any creature on earth, and we have one of the largest brain-to-body ratios around. Our brains are so big that we have to be born before they can even fully function; many of the abilities that in other animals are instinctual and develop quickly take years for human babies to learn, let alone the computation-intensive capabilities of language, imagination and reasoning. How, when, and why did these peculiar mutations develop? The common thread between these different adaptations is the central story of the human race: the story of constantly increasing intelligence.

The earliest definitely known human ancestors are a race of ape-like bipeds called Australopithecus Afarensis, which lived 3 or 4 million years ago. They were spread over an area of Africa which included both arboreal and savanna environments. Australopithecus had a small brain compared even to today's great ape species, but was definitely bipedal. They may have used primitive tools in the same way that chimpanzees can use rocks to crack nuts and twigs to 'fish' in termite mounds. About 1.5 to 3 million years ago, A. Afarensis started evolving into a number of distinct species. These included Homo Habilis, the most primitive of the Hominids, which had a much larger brain and has been found with the earliest known examples of stone tools. Early hominids also evolved a complicated hand structure with more versatile thumbs, and may have had the ability of speech. There are various theories as to why the Australopithecines evolved into the early Hominids. There would need to be some sort of selective pressure that reinforced the adaptations of more efficient bipedal motion and bigger brains for increased intelligence. These adaptations have drawbacks that still plague us today: a vertical spine is less efficient than a horizontal one and leads to problems such as spinal compression, hernias and balance problems; and a larger brain

• 1
• 2
• Next Page >>