Niklas Luhmann, one of the most important social thinkers at the end of the 20th century, places the evolutionary perspective in the center of his sociological theory. According to Luhmann, evolutionary theory ¿ both biological and social ¿ gets started trying to resolve the paradox of the probability of the improbable. However, Luhmann does not specifically clarify what the paradox involves, what are the ways to solve it, and how the evolution can explain the facts adduced in it. In this article, these flaws are faced up through the systematization of the probabilistic elements that characterize the evolutionary process, taking elements from evolutionary biology and the probability theory. From the four ways of probabilization here described, Luhmann seems to refer indirectly only to three of them. This probabilistic systematization not only allows dealing with the complex social order problem, but also anticipates future investigations of social evolution.