In the rongorongo script we encounter many anthropomorphic glyphs with an enlarged body and a hole in the belly. Based primarily on structural evidence present in parallel passages, it is argued that hollow-belly glyphs are in fact a compact form of two normal-belly single anthropomorphic glyphs. The scriptural evolution from two single-body glyphs into one double-body glyph was gradual and its various stages can be seen in different rongorongo inscriptions. The presence of these double-body (hollow-belly) glyphs may well be an indicator of the late chronological association of a text. Bearing this in mind, different rongorongo inscriptions can be classified into older and younger forms. Other palaeographic differences can also be employed for similar classifications. The forms of glyphs 099 and 522 also bear evidence for gradual change from more pictorial forms into other, more simplified forms. A reading of the related literature shows more scribal differences in other rongorongo glyphs as well. By combining various scribal differences together with the analysis of hollow-belly and 099/522 glyphs, most of the existing rongorongo inscriptions can be classified into a chronological list of texts based on their apparent palaeographic chronology. Comparing this list to the artifacts of known manufacture date reveals that palaeographic differences were probably developing quite quickly in rongorongo script evolution and that at least half of all known rongorongo artifacts were probably manufactured in the first half of the nineteenth century.