That's a very silly argument which evolutionists often make. It is like saying to a person that has won the lottery that because he won the lottery there was a one in one chance of his winning. No, there was a one in 100,000,000 or so chances of his winning before it happened. Unless evolutionists can show that there was a necessity to man descending from bacteria by some sort of materialistic way then the argument of probability is perfectly justified against evolution. Since evolution admits and postulates that the transformations of species are due to random chance, this refutation is not open for evolutionists even if such a necessity were to be found.
Poor analogy. A better analogy is if the lottery winner had no memory of life before the drawing, and all the non-winners were shot. Therefore, he can truly say, 'I exist, therfore there is 100% probability I won the lottery.' We know we exist. Therefore any a priori calculation of the odds of our not existing involves counting scenarios that simply did not, and could not have happened, without some exterior alteration of reality. In other words, a violation of physical laws. And we can't count the odds a posteriori, because we aren't aware of any set of other universes in which we don't exist.