Hard and soft bounds in the evolution of Ubuntu packages. A lesson for species body masses?

Open-source software is a complex system; its development depends on the self-coordinated action of a large number of agents. This study follows the size of the building blocks, called "packages", of the Ubuntu Linux operating system over its entire history. The analysis reveals a multiplicative diffusion process, constrained by size-dependent bounds, driving the dynamics of the package-size distribution. A formalization of this into a quantitative model is able to match the data without relying on any adjustable parameters, and generates definite predictions. Finally, we formulate the hypothesis that a similar non-stationary mechanism could be shaping the distribution of mammal body sizes.