What underlies the ability to deal with numbers and where did it come from? It has been hypothesized that our ability to accurately represent the number of objects in a set (numerousness), and to carry out numerical comparisons and arithmetic, developed from an evolutionarily conserved system for approximating numerical magnitude. Non-symbolic number cognition based on an approximate sense of magnitude has been documented in a variety of species. However, we know little about its origins (i.e., to what extent experience would shape it) and of its neural and molecular bases.