Stars from the selection in the [Mg/Fe]-[Fe/H] plane with colour-coding to represent age. Black dots represent C_enh stars and the red contours show the density distribution of these. We note that there are fewer C_enh stars in the low α disk with ages younger than ~4 Gyr. We hypothesize that this is explained by lack of time for the more massive member of an asymmetric binary to evolve to the AGB and WD stages.