  We use the Galaxy and Mass Assembly (GAMA) and the Deep Extragalactic Visible
Legacy Survey (DEVILS) observational data sets to calculate the cosmic star
formation rate (SFR) and active galactic nuclei (AGN) bolometric luminosity
history (CSFH/CAGNH) over the last 12.5 billion years. SFRs and AGN bolometric
luminosities were derived using the spectral energy distribution fitting code
ProSpect, which includes an AGN prescription to self consistently model the
contribution from both AGN and stellar emission to the observed rest-frame
ultra-violet to far-infrared photometry. We find that both the CSFH and CAGNH
evolve similarly, rising in the early Universe up to a peak at look-back time
$\approx 10$~Gyr ($z \approx 2$), before declining toward the present day. The
key result of this work is that we find the ratio of CAGNH to CSFH has been
flat ($\approx 10^{42.5}\mathrm{erg \, s^{-1}M_{\odot}^{-1}yr}$) for $11$~Gyr
up to the present day, indicating that star formation and AGN activity have
been coeval over this time period. We find that the stellar masses of the
galaxies that contribute most to the CSFH and CAGNH are similar, implying a
common cause, which is likely gas inflow. The depletion of the gas supply
suppresses cosmic star formation and AGN activity equivalently to ensure that
they have experienced similar declines over the last 10 Gyr. These results are
an important milestone for reconciling the role of star formation and AGN
activity in the life cycle of galaxies.
