One of the unsolved 'paradoxes' in prehistoric archaeology is that of the gap between the considerable advances in human biological and cultural evolution during the Lower Palaeolithic period, and the over one million years of 'stagnation' of the Acheulean handaxe. Most of the research on this topic has focused on innovation - why it was delayed or failed to take place - while overlooking the fact that innovation had occurred in many other fields during the same period. We suggest that practical, social, and adaptive mechanisms were in force in certain areas of human behaviour and led to enhanced innovation, while conservatism was preferred in handaxe technology and use. In this study we emphasise the dependency of Acheulean groups on calories obtained from large mammals, and especially megafauna, as well as the central role of handaxes in processing large carcasses. It is our contention that the handaxe's role in Acheulean adaptation was pivotal and it thus became fixed in human society, probably through the psychological bias towards majority imitation, which subsequently became a social norm or tradition. In brief, we suggest that the technological persistence of the Acheulean handaxe played an adaptive role that was based on a preferred cultural conservatism and led to the successful survival of Lower Palaeolithic populations over hundreds of thousands of years in the Old World.