  Galactic chemical evolution (GCE), solar analogues or twins, and
peculiarities of the solar composition with respect to the twins are
inextricably related. We examine GCE parameters from the literature and present
newly derived values using a quadratic fit that gives zero for a Solar age
(i.e., 4.6 Gyr). We show how the GCE parameters may be used not only to
"correct" abundances to the solar age, but to predict relative elemental
abundances as a function of age. We address the question of whether the solar
abundances are depleted in refractories and enhanced in volatiles and find that
the answer is sensitive to the selection of a representative standard. The best
quality data sets do not support the notion that the Sun is depleted in
refractories and enhanced in volatiles. A simple model allows us to estimate
the amount of refractory-rich material missing from the Sun or alternately
added to the average solar twin. The model gives between zero and 1.4 earth
masses.
