  We investigate the recent Daya Bay results on the changes in the antineutrino
flux and spectrum with the burnup of the reactor fuel. We find that the
discrepancy between current model predictions and the Daya Bay results can be
traced to the original measured $^{235}$U/$^{239}$Pu ratio of the fission beta
spectra that were used as a base for the expected antineutrino fluxes. An
analysis of the antineutrino spectra that is based on a summation over all
fission fragment beta-decays, using nuclear database input, explains all of the
features seen in the Daya Bay evolution data. However, this summation method
still predicts an anomaly. Thus, we conclude that there is currently not enough
information to use the antineutrino flux changes to rule out the possible
existence of sterile neutrinos.
