GEORGE C. WILLIAMS' ANTAGONISTIC PLEIOTROPY THEORY: A GENETIC TRADE-OFF BETWEEN EARLY VIABILITY AND LATE DEGENERATION

The Antagonistic Pleiotropy Theory (AP), proposed by George C. Williams in 1957, is the most influential evolutionary model explaining the origin of aging as a byproduct of selection for early reproductive success. In contrast to Medawar's theory of mutation accumulation, AP postulates the existence of genes (or alleles) that have multiple effects (pleiotropy), with some effects increasing fitness in early life and others decreasing survival in later life. Because the force of natural selection is greatest early in life, such alleles become fixed in the population despite their negative later effects. This review presents formal models of AP, experimental data in model organisms (Drosophila, C. elegans, mice), molecular examples of pleiotropic genes (e.g., p53, TOR, *IGF-1*, telomerase), and discusses the clinical implications of AP for understanding age-related diseases, including cancer, neurodegeneration, and metabolic syndrome. It is shown that AP not only explains aging but also predicts the existence of evolutionarily fixed "diseases of aging" as a price for early development and reproduction.