  The physical processes driving chemical evolution in the Milky Way can be
probed using the distribution of abundances in low-mass FGK type stars in space
phase at different times. During their final stages of evolution stars
experience nucleosynthesis several times, each at different timescales and
producing different chemical elements, so finding abundance ratios that have
simple variations across cosmic times remains a challenge. Using the sample of
80 solar twins for which ages and abundances of 30 elements were measured with
high precision by Bedell et al 2018, we searched for all possible abundance
ratios combinations that show linear trends with age. We found 55 such ratios,
all combining a neutron-capture element and another one produced by different
nucleosynthesis channels. We recovered the ratios of [Y/Mg], [Ba/Mg] and [Al/Y]
reported previously in the literature, and found that [C/Ba] had the largest
dependency with age with a slope of $0.049 \pm 0.003~\mathrm{dex/Gyr}$,
imposing constraints on the magnitude of time dependency of abundance ratios in
solar twins. Our results suggest using s-process elements, in lieu of Fe, as a
reference for constraining chemical evolution models of the solar
neighbourhood. Our study illustrates hows a large variety of chemical elements
measured from high resolution spectra is key in facing current challenges in
understanding the formation and evolution of our Galaxy.
