WOBBLY COMPLEXITY. “Gould, for example, argues that any recognizable trend can be explained by the “drunkard’s walk” model, where “progress” is due simply to a fixed boundary condition. McShea investigates trends in the evolution of certain types of structural and functional complexity, and finds some evidence of a trend but nothing conclusive. In fact, he concludes that “something may be increasing. But is it complexity?””
http://www.pnas.org/content/97/9/4463.full