Prospective and retrospective tests of evolutionary theories of senescence

Retrospective and prospective methods in the study of the evolution of longevity and senescence are compared. Retrospective studies can provide tests of evolutionary theories of senescence through the interpretation of evolutionary pattern demonstrated by species in nature. Patterns in longevity displayed by African rivulin fishes provide a clear and incisive example of the evolution of longevity and associated life history characters, but such tests are often difficult to find or unclear in the a posteriori interpretation of evolution that they offer. Far more experimentation of the prospective kind has been applied to testing theories of life span. Though prospective tests of evolutionary theory are compromised to a degree by the artificiality of the laboratory environment, experiments performed there are not necessarily invalid. In addition, prospective tests offer the added impetus that theoretical predictions are tested a priori. The use of Drosophila melanogaster as a laboratory model for the study of longevity has provided a number of particularly enlightening recent advances describing the number and distribution of genes controlling longevity, the metabolic pathways by which other characters are physiologically associated with life span, and even the controlling genetic elements affecting those traits. Improvements in longevity shown under programs of selective breeding may be the result of adaptations in the glycolytic pathway altering the ability to utilize the sugar sucrose as a food source.