A quotation by Pierre-Simon Laplace
This may or may not be the inspiration for the graffiti seen during an early part of X-men 2. On a large plywood wall surrounding the church in Boston early in the film are scrawled these words:
Nature laughs last
It is both a commentary relevant to the whole evolution/mutation theme of the film and a foreshadowing of sorts. On either level it is a superior little plot device.
* Quoted in I Gordon and S Sorkin, The Armchair Science Reader (New York 1959).