Explanations in evolutionary theory

Abstract

The theory of biological evolution is defined in many ways, leading to considerable confusion in its application and testing against objective empirical observations. Evolutionary change is usually defined as genetic which would exclude both cultural and template evolution; hence the qualifying adjective genetic should not be included in the definition of biological evolution. Darwin's theory, always described by him in the singular, is actually a bundle of five independent theories about evolution as advocated by Mayr. Furthermore only one of these theories, that of common descent, is historical, and the other four - evolution as such, gradualism, processes of phyletic evolution and of speciation, and causes of evolution - are nomological. Hence not all evolutionary theory is historical. Biological comparisons can be divided into horizontal and vertical ones and valid conclusions from one type of comparisons cannot be automatically extrapolated to the other. All phyletic evolutionary change, no matter how extensive it may be, never crosses species taxa boundaries; hence it is not possible to distinguish 'trans-specific evolution' (= evolution beyond or above the level of the species) from evolution within the species level. Macroevolution does not differ from microevolution except in the scale of the overall change; no special causes or processes of macroevolution exist. © 2007 The Author Journal compilation 2007 Blackwell Verlag.