Natural selection. VI. Partitioning the information in fitness and characters by path analysis

TL;DR

This paper introduces a path analysis framework to partition and interpret the causes of phenotypes and fitness in evolutionary selection, linking statistical models with information theory for deeper causal understanding.

Contribution

It presents a novel method combining path analysis and information theory to dissect causal components of phenotypes and fitness in evolutionary models.

Findings

Provides a complete equation for evolutionary change including causal components.

Interprets covariance, variance, and regression in terms of information flow.

Clarifies the causal roles of genetic and social factors in selection.

Abstract

Three steps aid in the analysis of selection. First, describe phenotypes by their component causes. Components include genes, maternal effects, symbionts, and any other predictors of phenotype that are of interest. Second, describe fitness by its component causes, such as an individual's phenotype, its neighbors' phenotypes, resource availability, and so on. Third, put the predictors of phenotype and fitness into an exact equation for evolutionary change, providing a complete expression of selection and other evolutionary processes. The complete expression separates the distinct causal roles of the various hypothesized components of phenotypes and fitness. Traditionally, those components are given by the covariance, variance, and regression terms of evolutionary models. I show how to interpret those statistical expressions with respect to information theory. The resulting interpretation allows one to read the fundamental equations of selection and evolution as sentences that express how various causes lead to the accumulation of information by selection and the decay of information by other evolutionary processes. The interpretation in terms of information leads to a deeper understanding of selection and heritability, and a clearer sense of how to formulate causal hypotheses about evolutionary process. Kin selection appears as a particular type of causal analysis that partitions social effects into meaningful components.