Today's talk (it has been a seminar-filled week) was by John Moustakas (Arizona), who gave us unparalleled evidence for evolution in the mass–metallicity relation. Good, hard evidence for evolution is not easy to find. Unfortunately, he can not yet show direct evidence for non-closed-box evolution (as I am always on about), such as merging or accretion or outflows.
John has put a lot of time into taking integrated spectra of a large variety of galaxies in the local Universe; he showed very nice relationships between line strengths, chemical abundances, and dust. His sample of low-redshift galaxies provides a great baseline for high-redshift studies; oddly the low-redshift part is often the hardest to get (and to get right).