According to this definition, it is incorrect to claim 14 distinct species of finches in the Galapagos Islands as they interbreed significantly. Indeed, Grant himself admits that a maximum of 6 separate species and perhaps less than the 14 recognized currently . Darwin’s claim in the Origin was that his natural selection could be responsible not only for variation within a species but for the origin of species or transpeciation from one species to another. The Galapagos finches have no genetic differences among them . Max Planck Institute and Princeton University in 1999 announced that the traditional classification of Galapagos finches was not apparent at the molecular level  and Hau and Wikelski state, "There is no evidence for an absolute genetic barrier between Darwin's finch species. Thus many species can potentially hybridize.”  All evidence points to the fact that they are all the same species.
Much of Grant’s claim emphasized the change in beak size. The average size of the Galapagos finches' beaks increases or decreases according to food resources and that depends greatly of the rainfall. El Niño takes place at irregular intervals every two and 11 years, and at different levels of intensity, also alters the climatic balances. At such times there is excessive rainfall; subsequent years are then generally dry and arid. In years of plentiful rain, ground finches can easily obtain the seeds they need to grow and breed. In years of drought, however, the plants on the islands may produce a limited amount of seeds and the number of finches decrease. The rainfall in 1976 was normal, but fell to one-fifth in 1977. During the drought there was a significant drop in the quantity of seeds and a major reduction in the numbers of ground finches. The population fell 85%. The finches that survived the drought were rather larger than normal and had 5% wider beaks.
In the research on Darwin’s finches the term natural selection has been used as a substitute for Darwinian evolution. However, Darwin clearly proposed that a change sufficient to create a new species was possible. In his day a substantial change in characteristics may have been essential criteria but in the age of Mendelian genetics and DNA splicing a new species must exhibit new DNA and chromosomal structure. This evidence is completely lacking.