Of the three complementary theories of aging, two (mutation accumulation and antagonistic pleiotropy) were formulated over fifty years ago before the introduction of molecular biology, and the third (disposable soma) is over thirty years old. Despite rigorous research in the past fifty years, none have gained substantial experimental support. Here, I review these theories and introduce a new hypothesis called the selfish anti-aging (SAA). Aging happens because natural selection is indifferent to the organism's life beyond reproduction; however, many mammalian species acquired anti-aging genes, which are providing instructions following completion of developmental, ontogeny, program. Such instructor-genes might be responsible for the elongation of lifespans of primates as a byproduct of parental care program. According to the SAA hypothesis, the animal models used in aging research could be divided into three groups, based on the degree of perceived presence and action of instructor-genes in each group. This new hypothesis is grounded in evolutionary theory and describes the unique primate aging process.