This is probably a bit late on in the thread, but re. the 'mutations' thing, well as someone said they are just copying errors of our code, and can be caused by loads of stuff from random chance to radiation exposure.
We can cope with a certain level of radiation screwing up our code (corrupt cells usually get destroyed) but sometimes they don't and the mutation is perpetuated to further generations.
Generally any changes are so small that they are practically unnoticable anyway, but if it aids you some how, e.g. you're slightly more immune to disease, then you are more likely to survive and thus this mutation will be passed on.
Now, the effect will be small, and that carrier might get killed by some other means (e.g. crushed by a falling Sathanas) and all that combined means you won't see any results for thousands of generations.
The most obvious 'benficial' mutation that comes to mind is the one that has allowed groups of people in Africa to become highly resistant to maleria - It is just one gene that is slightly altered, but it was enough to grant this resistance and has perpetuated itself slowly over time.
Of course, there is a bad side to this: If a child is born with one copy of the gene it will be normal, but if the child doesn't have the gene it will be vulnerable to maleria. However, if it gets 2 of these genes it will likely develop sickle-cell anemia.
Humans as a species are AFAIK unique in one thing however: Unlike the rest of nature's children we have access to drugs and med-tech. Because of this, someone with really ****ty code won't necessarily die - We can cure what ails them so to speak, but the problem there is that any faults in there genes will be passed on to offspring.
I reckon this is a lot like why Asian countries have such a greater number of short-sighted people than Western countries - They had access to corrective lenses a lot earlier than the West; Being able to see clearly is a very important trait for a species which relies on sight as it's primary sense, so whereas an English guy might have got crushed by a elephant 'cause he didn't see it, his Chinese counterpart would have seen it thanks to his glasses and lived to pass on his code to the next generation.
Track this down a thousand or so generations and we have the state where we are now.
An interesting thing I have been noticing is that increasing numbers of people need glasses/lenses to see clearly in this age too...
