  It is predicted that the spectrum of radio emission from the whole sky should
show a dip arising from the action of the light from the first stars on the
hydrogen atoms in the surrounding gas, which causes the 21-cm line to appear in
absorption against the cosmic microwave background. Bowman et al. 2018
identified a broad flat-bottomed absorption profile centred at 78 MHz, which
could be this feature, although the depth of the profile is much larger than
expected. We have examined the modelling process they used and find that their
data implies unphysical parameters for the foreground emission and also that
their solution is not unique in the sense that we found other simple
formulations for the signal that are different in shape but that also fit their
data. We argue that this calls into question the interpretation of these data
as an unambiguous detection of the cosmological 21-cm absorption signature.
