"If humans and chimpanzees are over 98% identical base-for-base, how do you make sense of the fact that chimpanzees have 10% more DNA than humans? That they have more alpha-hemoglobin genes and more Rh bloodgroup genes, and fewer Alu repeats, in their genome than humans? Or that the tips of their chromosomes contain DNA not present at the tips of human chromosomes? Obviously there is a lot more to genomics than just nucleotide substitution. But the percentage comparison renders that fact invisible, and thus obscures some of the most interesting genetic questions."
"Our DNA is about 75% similar to that of a nematode, which is basically a small soil-dwelling worm. No-one would suggest a nematode is 75% human? Another good example is that during the sixties, American doctors tried to use chimpanzee organs for transplants in humans, but in all cases the organs were totally unsuitable. ... An interesting footnote that shows how complex this issue really is, ... humans differed from most other animals, including chimpanzees, in a small but possibly vital way. In most animals, the surface of every cell, except brain cells, carry glycoproteins that contain one particular member of a family of sugar molecules called sialic acid. In humans, a genetic mutation means this sugar is not present in any cell in the body. Proteins and membrane lipids that have sialic acid take part in many processes. They help cells stick to one another. They may also play a part in disease susceptibility. This might be a reason why Chimpanzees seem far less suspeceptible for infectious diseases like malaria and cholera. ... This might be one factor in those chimp to human transplants in which organs were rejected."