[Macromutation and evolution: the fixation of Goldschmidt's macromutations as species and genus traits. Hairlessness...

A brief survey of the development of concepts on the role of macromutations in evolution is given. Contrary to Iu. A. Filipchenko (1926, 1927), who introduced the "micro- and macromutation" terms and believed that regularities of macroevolution could not be reduced to microevolutionary processes, the majority of "synthetists" explained any form of evolution by changes in allele frequencies. From the studies of Drosophila homoeotic mutants R. Goldschmidt (1940) developed the concept of "hopeful monsters" and their role in macroevolution. However, the homoeotic mutants are of drastically reduced viability, which allows the gradualists to reject Goldschmidt's ideas. The distribution of hairlessness mutations (hairless, nude etc.) with the monogenic pattern of inheritance in mammals was studied. Hairless mutants are known in Peromyscus, Mus musculus, Rattus rattus, R. norvegicus, Canis familiaris, Ovis aries. Hairlessness as norm is found in 53 among contemporaneous 1037 mammalian genera. Part of these cases (hairlessness in all Cetacea and Sirenia) may be explained in terms of both macromutations and obligatory gradualism. There is no doubt as to the macromutational origin of hairlessness in the bat Cheiromeles and the rodent Heterocephalus (Bathyergidae); the genera systematically and ecologically close to these have normal pelage. It is quite possible that hairlessness of walrus (Odobenus) has the same origin. The appearance and fixation of single Goldschmidt's macromutation cannot yet be considered as a macroevolutionary process, though the possibility of fixation of a macromutation in nature as a species and genus character contradicts strongly the concept of obligatory gradualism of evolution.