The development of new taxa from the ancestral taxon, within the same geographic range; it is geographically possible for interbreeding to occur between the potential new taxa, but for some reason this does not happen. Because of the difficulty of envisaging what the reasons might be, until recently few authorities accepted the reality of sympatric evolution, except for certain special kinds of organism; but recent studies have shown that chromosomal mutation can set up a partial barrier to interbreeding, sufficient to permit sympatric speciation.