Abstract: How can advances in information theory help us understand the increasing complexity of human societies over time? One of the most basic questions of human history is why human societies have grown radically in scale and complexity over ~300,000 years: why did a species of hunter-gatherers living in small bands, numbering a few million individuals scattered around the globe, with relatively little functional specialization, consuming a few thousand kilocalories per capita per day, become the most ecologically dominant species in the history of the planet – numbering eight billion, living in megacities up to 20 million, dependent on extreme functional specialization (e.g. “professor of complex systems science”), consuming hundreds of thousands of kilocalories per capita per day? Social evolutionary models that address big questions like this one have been out of favor in mainstream historical studies for generations. Proponents of “big history” as well as others who do champion evolutionary models have tended to address the question by explaining human growth in terms of energy – i.e., increases in the extraction and control of free energy that have allowed human societies to expand. But that is at best a proximate and partial answer. Where do increases in the control of free energy come from? Could trying to define and measure increases in information about the external environment help to unify the study of human history in the same fundamental terms that we understand the physical universe and biological evolution? In particular, what new insights into these issues are provided by recent advances in complex systems science and non-equilibrium statistical physics?