When diagrams first appeared in human history, they did not arrive out of the blue. Humanity had an evolutionary history that produced the abilities for spatial cognition that form the foundation of diagrammatic thinking. Of course, it is extremely difficult to follow such a cognitive development in the anthropological and archaeological record. However, evolutionary cognitive archaeologists interpret the emergence of symmetrically shaped hand axes around 500,000 years ago as a sign that many aspects of spatial cognition were developed already. The knapping of such tools required coordination between symmetry sensitive visual cell groups and cell groups for motor activity. Compared to our ancestors and relatives among the apes, this required developments in the processing of visuospatial working memory.