I've just found a web-site that has a bit of information as to why i can't walk straight. I thought someone may be interested. If you want more details, don't ask me.
http://docuwiki.net/index.php?title=Origins_of_Us
Dr Alice Roberts - '... In six million years we have become very different, and what kick-started this can be found in an extraordinary fossil - Sahelanthropus. A single hole where the spine was attached suggests that our ancestors started the journey to being human by standing upright. We take it for granted, but standing up and walking is surprisingly complex - each step involves the co-ordination of over 200 muscles. Charting the major advances from Australopithecus to Homo erectus and beyond, Alice tells the epic story of human evolution through our body today. New research has uncovered clues in our ankles, waists and necks that show how our ancestors were forced to survive on the open plain - by walking and running for their lives. From the neck down we have inherited the body of our ancestor Homo erectus, who lived on the plains of Africa nearly two million years ago.'
Of course it doesn't do me any good really but if I ever get arrested for being 'drunk and disorderly' I can explain a bit.