Intrinsic estimates of fitness affect the causal structure of evolutionary change

Abstract

The causal structure of Darwinian evolution by natural selection is investigated. Its basic scheme is reproduction resulting from a feedback loop driven by internal and external causes. Causation internal to the loop connects genotype, development, phenotype, and fitness, with environmental constraints on the latter preventing runaway reproduction. External causes driving the core loop are environmental change and genetic change (mutation, used broadly as including recombination and other mechanisms). This basic causal structure is complicated by modern additions such as control of mutation rate, niche construction, interactions between evolution and development, and epigenetic effects. In this article it is argued that at least one of these additions, control of mutation rate, produces an additional feedback loop incorporating a continual, targeted modulation of stochasticity, and thereby produces an unusual form of causation. This form of causation entangles deterministic and stochastic causation in such a way that it imposes, in effect, an active, goal-driven role on the organisms in a line of descent. The goal is defined by the factor driving the stochasticity, which must be regarded as an intrinsic estimate made implicitly by the organism of its own fitness. The estimator itself is an evolved property of the organism, and is aligned with the apparent (not real, post hoc) goal-directedness of natural selection.