But that is during development. Are you saying that
Drosophila don't need to develop? In that case your argumnet is based surely on the size of the organism and the number of cell divisions needed to create and maintain any specific germ cell population, not necessarily generation time.
Either way these effects aren't the main reason the human per genome rate is higher than that of drosophila. Or do you not agree that a larger genome is likely to have a larger per genome deleterious mutation rate simply because of its size (leaving aside the distibution of functional regions)?
In other words, it doesn't matter if you are right about having a longer generation time being
a source of additional mutation since we already have numerous reasons for expecting humans to have a higher rate than
Drosophila.
Interestingly there are published long term experiment on
Drosophila, ~250 generations, which have seen small experimental lines run to collapse, but small populations will tend to be more susceptible to such effects (
Avila et al., 2006).
TTFN,
WK