[Eu/H] and [Ba/Eu] versus [Ba/H]. Upper panel: Expected evolution of [Ba/Eu] as a function of [Ba/H] when the evolution of Ba and Eu are triggered by AGB winds only, starting at [Ba/H] = − 0.78 and [Ba/Eu] = − 0.4. The five solid lines follow the chemical evolution induced by the AGB models of Cristallo et al. (2009) at different metallicities ([Z∕Z_⊙]), which values are indicated close to the upper edges of the model lines. The Fornax sample stars from this work are shown in open circles, together with the individual error bars in [Ba/H]. Lower panel: Black points show the observations of Fornax stars from this work. The solid line traces the locus of the evolution in Eu and Ba induced by the yields of [Z∕Z_⊙ ] = − 2.14 AGBs (Cristallo et al. 2009), starting at [Ba/H] = − 0.78 and [Ba/Eu] = − 0.4. The black open squares are 85 random trials taking into account the mean observational errors, 0.15 dex in [Ba/H] and 0.19 dex in [Eu/H] indicated at the bottom right of the frame. They show the scattering of the single model line induced by the observational uncertainties only.