The problem and the approach

Most people avoid the subject of Pleistocene world population growth. It has to be said that there are many obstacles to such study and few willing to venture into the distant and extremely hazy regions of early human palaeodemography. Because of innate difficulties in establishing solid parameters for such a study, it is easy to fall into the wide grey area between fact and supposition or be reduced, as some might say, to mere ‘arm waving’. Nevertheless, to venture in is not always a bad thing, if for no other reason than to get the discussion going or hopefully strike a few mental matches. I believe that answers to who we are and where we came from as modern humans are fundamentally bound up with how and where humanity grew during the Pleistocene and the size and rate of that growth. The processes and strength of flow and exchange of genes across the world is the key to the evolution of modern humans and their regional variation. To facilitate gene flow, however, you need populations, and the bigger they are the greater the flow within and from them. Knowing something about long-term world population growth is, therefore, critical to evolutionary processes as well as understanding human biological and cultural evolution, early hominin adaptation and the spread of humanity across the planet: all ingredients of the previous chapter.