Division of Labor and Geometry

In the German Ideology, Marx-Engels assert that "Division of Labor only becomes truly such from the moment when a division of material and mental labor appears. From this moment onwards, consciousness can really flatter itself that it is something other than consciousness of an existing practice, that it really represents something without representing something real."  However, a significant gap in this account, which is sheerly speculative, is suggested by the word 'geometry'.  For, the term analyzes as 'the measurement of the earth', thereby suggesting that prior to becoming a purely mental object, Geometry is a practical enterprise, e. g. involving the measurement of land for agrarian purposes, in which case it is both mental and material.  Accordingly, Marx-Engels skip a stage in the purported genesis of Division of Labor--that constituted by a distinction between the organization of material Labor, and its execution.