  We re-examined data from the classic Luria-Delbruck fluctuation experiment,
which is often credited with establishing a Darwinian basis for evolution. We
argue that, for the Lamarckian model of evolution to be ruled out by the
experiment, the experiment must favor pure Darwinian evolution over both the
Lamarckian model and a model that allows both Darwinian and Lamarckian
mechanisms. Analysis of the combined model was not performed in the original
1943 paper. The Luria-Delbruck paper also did not consider the possibility of
neither model fitting the experiment. Using Bayesian model selection, we find
that the Luria-Delbruck experiment, indeed, favors the Darwinian evolution over
purely Lamarckian. However, our analysis does not rule out the combined model,
and hence cannot rule out Lamarckian contributions to the evolutionary
dynamics.
