Wandering drunks and general lawlessness in biology: does diversity and complexity tend to increase in evolutionary systems?

Abstract

Does biology have general laws that apply to all levels of biological organisation, across all evolutionary time? In their book ‘‘Biology’s first law: the tendency for diversity and complexity to increase in evolutionary systems’’ (2010), Daniel McShea and Robert Brandon propose that the most fundamental law of biology is that all levels of biological organisation have an underlying tendency to become more complex and diverse over time. A range of processes, most notably selection, can prevent the expression of this tendency, but they predict that, on average, we should see that lineages tend toward greater diversity and complexity, driven by fundamentally neutral processes. Their hypothesis can be summarised as ‘‘diversity is easy, stasis is hard’’. Here, I consider evidence for this ‘‘zero force evolutionary law’’. It provides a fair description of evolutionary change at the genomic level, but the predictions of the proposed law are not met for broad scale patterns in the evolution of the animal kingdom.