Source : Webster's Revised Unabridged Dictionary (1913)

Neo-Darwinism \Ne`o-Dar"win*ism\, n.
   The theory which holds natural selection, as explained by
   Darwin, to be the chief factor in the evolution of plants and
   animals, and denies the inheritance of acquired characters;
   -- esp. opposed to {Neo-Lamarckism}. Weismannism is an
   example of extreme Neo-Darwinism. -- {Ne`o-Dar*win"i*an}, a.
   & n.

Source : WordNet®

Neo-Darwinism
     n : a modern Darwinian theory that explains new species in terms
         of genetic mutations