Micro- and Macroevolution: A Continuum or Two Distinct Types of Change?

Abstract

How microevolution and macroevolution are related is one of the major unanswered questions in evolutionary biology. The most prevalent view is that microevolution and macroevolution are part of a continuum of one type of change and that macroevolution is the cumulative result of microevolution. Mathematics, however, distinguishes two fundamentally different, singular types of change: change of a vector in its parameters versus its dimensions. This mathematical distinction may help to articulate the concept of evolution by distinction of two fundamentally different types of evolution: the change of the state vector of an organism in 1) its parameters (= ‘first-order evolution’) and 2) its dimensions (= ‘second-order evolution’). This distinction can be operationalized by identifying genes and regulatory elements in the nucleotide code of an organism as dimensions and the level of expression as parameters of its state vector. This operationalization allows us to substitute the phenotype-based analysis of evolution with a genotype-based analysis and draws attention to the molecular mechanisms that change the parameters or the dimensions of the state vector, respectively. We illustrate the distinction between first- and second-order evolution with a simulation of the adaptive dynamics of a population of digital amoebae. Our genotype-based systems approach reveals that micro- and macroevolution are largely similar to first- and second-order evolution respectively, and are not a continuum of change.