Stephen Jay Gould famously consider the following analogy. Evolution is like a videotape which if replayed over and over would have a different ending every time. In effect, the evolution of living things is sensitive to initial conditions. If a system starts in slightly different initial conditions, the future states will depart even further.
John Beatty develops this thesis into an argument against there being biological laws. He writes,
The thesis that I will defend, most briefly put, is this: all distinc- tively biological generalizations describe evolutionarily contingent states of nature – moreover, ”highly” contingent states of nature in a sense that I will explain. This means that there are no laws of biology. For, whatever ”laws” are, they are supposed to be more than just contingently true.
This is the evolutionary contingency thesis. Why does Beatty deny there are biological laws? Does this mean there are no laws that govern biological systems?