The Evolution of the Life Cycle: An Integration of Competing Theories

Ronald Lee, University of California, Berkeley

Hamilton's classic mathematical theory of the evolution of the life cycle derived its results by differentiating the stable population equation of mathematical demography, considering only direct effects and ignoring costs and tradeoffs. Another approach finds the optimally shaped life cycle subject to assumed bio-engineering constraints, emphasizing the costs and tradeoffs. In a third approach, genetic theories stress either the accumulation of deleterious mutations affecting different ages, or antagonistic pleiotropy, which occurs when a gene has a beneficial effect at one age but an adverse effect at another age. In a fourth approach, I recently added production, consumption, intergenerational transfers, and density dependence to the Hamilton theory. Here, I will integrate these four approaches in a single analysis, show how they are interrelated, and derive new results.