Evolution is about mutation, right?

Funny thing, there's 3 billion nucleotide-pair locations in human genome. There are 7.5 billion that biologically classify as humans though, each with couple dozen new mutations. So each survivable mutation is already carried by number of people, even if mutations stopped overnight. But that doesn't mean there are people with three arms or superpowers walking around (Or maybe there are, hm...); that needs a complex series of mutations, which is generally called evolution.