The contingency of biological regularities—and its implications for the existence of biological laws—has long puzzled biologists and philosophers. The best argument for the contingency of biological regularities is John Beatty’s evolutionary contingency thesis, which will be re-analyzed here. First, I argue that in Beatty’s thesis there are two versions of strong contingency used as arguments against biological laws that have gone unnoticed by his commentators. Second, Beatty’s two different versions of strong contingency are analyzed in terms of two different stabilities (...) of regularities. Third, I argue that Beatty and his commentators have focused on the more ineffective trajectory stability version of the argument, whereas the constancy stability version provides a more substantial and applicable argument against the existence of biological laws. Fourth, I develop a counterexample to Beatty’s thesis. Finally, I discuss the possibility of evolution producing repeatable and general non-lawlike regularities and patterns by utilizing the notion of generative entrenchment and by criticizing the thesis of multiple realizability of biological properties. (shrink)