In order to examine the development of lexical numbers (LN), the linguistic rules which allow for expression of high quantities and complex numerical operations, Overmann examines LN's association with grammatical number (GN), an expression of quantity based on the distinction between singular and multiple entities. LN and GN generally occur together, but LN is also found in a significant number of societies lacking GN, indicating that the two are both independent and related. A subsequent analysis of geographic distribution of LNs and GN indicates that LN may emerge prior to GN as a result of the interaction of numerosity (the ability to perceive different quantities) with tactile engagement with material structures (e.g. tools, the hand) which may subsequently lead to the development of GN. Overmann examines the theoretical implications of and explanations for these findings, and discusses how the present study contributes to the knowledge of linguistic frameworks.