The specific star formation rate (sSFR, in Gyr^-1) as a function of redshift. The various coloured points represent measurements from the literature at M_⋆ ~ 10¹⁰M_⊙; see the references in the legend at the bottom right. Since the slope of the sSFR-M_⋆ relation is approximately zero, the rate at which the sSFR evolves is largely independent of M_⋆. Thus, this is an appropriate comparison, even for galaxies as massive as the radio galaxies studied here. The black stars, triangles, and upside-down triangles represent the radio galaxy detections, lower limits, and upper limits to the sSFR, respectively. The blue shaded region represents the scatter in the observed sSFR values (±0.3 dex). This rendition of the evolution of the sSFR was inspired by a similar plot in Weinmann et al. (2011). See also Lenhert et al. (in prep.).