The study addresses the relationship between diachronic change and synchronic polysemy based on the use of diminutives in four closely related Southeastern Mande languages. It explores the synchronic patterns of use of cognate diminutive markers deriving from the word 'child', and accounts for differences between the languages in terms of a Radial Category network, which is designed to capture in one representation both mechanisms of diachronic change and mechanisms of regular meaning extension. The study argues that the same approach can be used to account for the ways diminutive markers acquire new meanings and for the ways an old diminutive category disintegrates, when new markers start replacing the old one in some of the core diminutive functions. The invasion and expansion of new markers may result in discontinuous semantic structures that can only be understood when the diachrony is taken into account (in this particular case study, the evidence for historical change comes from a synchronic comparison with closely related languages).