A parsimonious view of the parsimony principle in ecology and evolution

Submitted by editor on 20 November 2018.
The curve-fitting problem. The choice of the most plausible hypothesis is based on an arbitrary balance between goodness-of-fit and simplicity criteria. The red curve is the simplest, indicating a linear relationship between the two variables, but also the worst-fit. The dashed line is the most complex, but also the best-fit. The blue line is just one of the infinite possible balances between the best-fit and simplest hypotheses​.

By Marco Túlio Coelho, José Alexandre F. Diniz-Filho and Thiago F. Rangel

The trade-off between simplicity and complexity of theories, hypotheses and models are usually evaluated under the lens of the Parsimony Principle (Ockham's Razor). However, there is no empirical evidence to link simplicity with plausibility. Paradoxically, ecologists and evolutionary biologists tend to invoke the parsimony to judge even mechanistic models designed to understand highly complex natural phenomena. In this study, Marco Túlio P. Coelho, José Alexandre F. Diniz-Filho and Thiago F. Rangel, at Universidade Federal de Goiás (Brazil), discuss Parsimony as a philosophical principle inherited from the early days of modern science. They conclude that invoking the Parsimony Principle in ecology and evolution is particularly important in model-building programs designed to probe nature, in which models are viewed primarily as an operational tool to make predictions and in which data play a prominent role in deciding the structure of the model. However, they also conclude that theoretical advances in ecology and evolutionary biology may be derailed if the parsimony principle is mistakenly used to judge explanatory mechanistic models that are designed as vehicles for theoretical exploration to understand complex natural phenomena.