Can Galactic chemical evolution explain the oxygen isotopic variations
  in the Solar System?
  A number of objects in primitive meteorites have oxygen isotopic compositions
that place them on a distinct, mass-independent fractionation line with a slope
of one on a three-isotope plot. The most popular model for describing how this
fractionation arose assumes that CO self-shielding produced 16O-rich CO and
16O-poor H2O, where the H2O subsequently combined with interstellar dust to
form relatively 16O-poor solids within the Solar Nebula. Another model for
creating the different reservoirs of 16O-rich gas and 16O-poor solids suggests
that these reservoirs were produced by Galactic chemical evolution (GCE) if the
Solar System dust component was somewhat younger than the gas component and
both components were lying on the line of slope one in the O three-isotope
plot. We argue that GCE is not the cause of mass-independent fractionation of
the oxygen isotopes in the Solar System. The GCE scenario is in contradiction
with observations of the 18O/17O ratios in nearby molecular clouds and young
stellar objects. It is very unlikely for GCE to produce a line of slope one
when considering the effect of incomplete mixing of stellar ejecta in the
interstellar medium. Furthermore, the assumption that the Solar System dust was
younger than the gas requires unusual timescales or the existence of an
important stardust component that is not theoretically expected to occur nor
has been identified to date.
