I'm trying to get some real numbers for the probability of evolution occurring by random mutations, but cannot find anything helpful in the literature--- except that a single base-pair genome mutation occurs once in every 10exp-6 DNA replications. So I'm trying to use this meager information to calculate the probability for the evolution of the 2.9 billion base-pair human genome. My approximations for the entire genome produce horrid numbers. To simply the calculations, I'm trying to figure out the evolution probability for a single 900 base-pair gene. Since there are only four possible base-pairs, the problem appears simple. (To keep it simple, I assume that the probability of a new base-pair addition needed to build a gene is the same as that for a mutation.) The sequence of base-pairs is critical. Let's define a "correct" base-pair as one that continues the sequence for a particular gene. When a new base-pair appears, the probability that it will be "correct" is simply 0.25. It looks like the probability for a complete, correctly sequenced gene is then, 0.25exp900, which I calculated as 1.4x10exp-50. This seems unreasonably low. Given that there are about 23,000 functional genes in the human genome, the probability for all of them coming together right is a downright ugly (1.4x10exp-50)exp23000. That number chokes my calculator, might keep a Cray minicomputer busy for a few milliseconds, and seems too tiny to even be worth figuring. I'm only trying for reasonable approximations, but these numbers are absurd. In their face, random mutations cannot have produced a single small gene. (By comparison, there are only 10exp80 atoms in the known universe.) And I've yet to attempt to use the base-pair mutation probability to calculate the number of generations required to produce a human body. Why bother, when the anticipated result looks like we need more generations than the number of microseconds elapsed since the Big Bang? Where have I gone wrong?