formed about 0.7 Gyr after the Big Bang, but that the oldest galaxies at $z\sim
0$ formed $\sim 3$ Gyr after the Big Bang. Since the oldest galaxies in the LRG sample are as old as the oldest GCs, we consider this to be an unlikely explanation. Furthermore, not only would this scenario require that [*a*ll]{} local galaxies either formed their stars more recently than galaxies at high redshift or had a recent episodes of recent star formation, but would also require a remarkable fine-tuning for them all to obtain exactly the same age. We therefore conclude that this extreme model for $w(z)$ is unlikely given the data.

Unfortunately, the small number of galaxies in our samples at $z>0.2$ does not allow us to compute $dz/dt$ with enough accuracy to constrain $w(z)$, and therefore this measurement will have to await better data. However, the $z < 0.2$ region is well populated by LRG galaxies (Figure 4) and we can determine $dt/dz$ at $z\sim 0$. This is illustrated in the bottom panel of Figure 4 by the clear shift in the upper envelope of the age histogram between the two redshift ranges $0 < z < 0.04$ and $0.08 <
z 