Ernst Mayr on MutationPopulations, Species, and Evolution (Cambridge, Mass: Belknap Press, 1984), p. 235.
The occurrence of genetic monstrosities by mutation … is well substantiated, but they are such evident freaks that these monsters can be designated only as ‘hopeless.’ They are so utterly unbalanced that they would not have the slightest chance of escaping elimination through stabilizing selection …. the more drastically a mutation affects the phenotype, the more likely it is to reduce fitness. To believe that such a drastic mutation would produce a viable new type,
capable of occupying a new adaptive zone, is equivalent to believing in miracles …. The finding of a suitable mate for the ‘hopeless monster’ and the establishment of reproductive isolation from the normal members of the parental population seem to me insurmountable difficulties.