Periphery and archaic forms
In many groups the more primitive, more ancestor-like species are living in the periphery of the range of the group. Many authors have regarded this phenomenon as a rule, e.g. MATTHEW, 1915: ”Whatever agencies may be assigned as the cause of evolution of a race, it should be at first most progressive at its point of original dispersal, and it will continue this progress at that point in response to whatever stimulus originally caused it and spread out in successive waves of migration, each wave a stage higher than the previous one. At any one time, therefore, the most advanced stages should be nearest the center of dispersal, the most conservative stages farthest from it.” However, in his recent ”Animal Species and Evolution”, MAYR, 1963, replies to this: ”the zoogeographic phenomenon of the survival of primitive types has nothing to do with infraspecific geographic variation. Indeed, the generalization one can make concerning infraspecific variation is precisely the opposite of that of Matthew: the ”original” phenotype of a species is usually found in the main body or central part of a species range, while the peripheral populations, particularly the peripherally isolated populations, may deviate secondarily in various ways.”
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Hillenius, D. (1964). Periphery and archaic forms. Beaufortia, 11(138), 75–83.