CREATION BY EVOLUTION
- Evolution: Modification of traits from generation to generation through internal and external factors.
The evolution of living beings or the transmutation of species is conditioned by at least four influences, always present and continually acting on every individual, animal or plant. These moulding factors are heredity, variation, selection, segregation. A species, as properly defined, is a kind of animal or plant which during countless generations has undergone these influences in the open, has thus run the gauntlet of life, and has endured. A sheltered form, watched over in a greenhouse or a breeding pen, is not a genuine species; to become one it must hold its own and survive outside, in the stress of Nature. "The origin of species" therefore concerns the coöperation of tendencies inherent in the organism, these being diverted, modified, or directed by obstacles without.
Inherent tendencies may be summed up as heredity and variation. Heredity is the conservative influence, which unifies groups, limiting divergence; variation is a force creating divergence. Variation results from a complex series of influences, the most obvious and apparently the most important being the biparental factor—that is, sex. External influences, acting on the traits that distinguish species, by serving as obstacles to the even flow of heredity, are selection and isolation. Selection destroys unadapted individuals, and often, through them, the types or species they represent. Isolation, with its consequent segregation, or prevention of mass-breeding, leads to the separation of minor groups from the original stock by barriers, mainly but not wholly geographical. Selection fits all types to their environment; it enforces adaptation on all living beings but does not divide them into species. Segregation is the final moulder
[ 6 ]
