soilguy also posted:
If you DO have some knowledge of biology, why would you ask how mutations can add up? How could they NOT add up?

This has been explained several times on these threads.

lets start with the odds. The human has 3.2 billion base pairs. What are the odds of another RANDOM beneficial mutation occurring in a base pair in such a fashion that it adds to the last beneficial mutation and then is added to the gene pool?