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In this paper I explore two lines of thought. First, do life-history tactics exist at the intra-specific level? Four arguments are examined: (1) biological constraints violate the assumptions of the Euler-Lotka equation; (2) experimental evidence on mosquito fish indicates that physiological problems can overwhelm the expected coadaptations of life-history traits; (3) the pattern of heritabilities of life-history traits indicates that they have not responded to the same selection forces; (4) authors of review articles perceive tactics more readily at higher taxonomic levels than within species. Tactics may not exist in the expected form. Second, when might optimality models work, and why? (1) Some optimality models contain a hidden genetic component; (2) polygenic traits are not as tightly constrained as few-locus systems; and (3) the evolution of the developmental system should uncouple the phenotype from the constraints of the genetic mechanism. Implicit in these thoughts is a more general point: training in quantitative genetics, development, and physiology is just as necessary for the study of life-history evolution as is training in demography and population genetics. Finally, four new research programs are suggested as extensions and criticisms of the arguments raised here.
Stephen C. Stearns (Wed,) studied this question.