The human and chimpanzee genomes differ by just 1.2% between the coding genes. So Why are we so different?
Professor Svante Paabo, from the Max Planck Institute, Leipzig, Germany, is investigating which genes are present and the manner in which they are expressed. In particular, he believes the key lies in the degree to which they are expressed in each species: http://news.bbc.co.uk/2/hi/science/nature/3594937.stm