WHY WE SHOULD STOP TRYING TO MEASURE THE COST OF REPRODUCTION CORRECTLY

The Cost of Reproduction (CoR) is a basic assumption of most models of life-history evolution. CoR's "correct" measurement, such that strictly genetic correlations between traits related to present versus future reproduction are evaluated, is not a valid test of the explanatory power of life-history models. If the genotype for an optimum effort is prevalent in a population, genetic variation for reproductive effort will be near zero. It follows that genetically based correlations will also be small, and artificial selection experiments will not reveal a genetic CoR. Similarly, no particular relationship between present and future reproductive output results from considering life-history traits to be "adaptively plastic" or using the "comparative approach" at inter-specific or higher taxonomic levels. Life-history theory is difficult to test because its predictions are general and relative rather than specific and quantitative.