Price Equation

Definition

Mathematically derived formula of evolutionary change (Price 1970). Due to population geneticist George Price in 1970, this equation expresses the between-generation change in a trait mean value in the following way :

$$ \Delta {\text{z}} = {\text{Cov}}{{{\left( {{{\text{w}}_{\text{i}}},{{\text{z}}_{\text{i}}}} \right)}} \left/ {\text{w}} \right.} + {\text{E }}{{{\left( {{{\text{w}}_{\text{i}}} \Delta {{\text{z}}_{\text{i}}}} \right)}} \left/ {\text{w}} \right.} $$

where z (resp. w) is the mean trait value (resp. fitness), w_i is the fitness of individuals i and z_i their value of the trait, and Δz_i the change of this value between individual and offspring. The equation decomposes evolutionary change between the action of natural selection (as covariance between fitnesses and traits) and the transmission biases (Gardner 2008; Frank 1995).

The Price equation is derived mathematically; hence, it is an a priori statement and does not rely on specificities of biology. It can be...