A study of ancient and modern Near Eastern religious canons reveals the mutation, selection, and vertical transmission of fitness-enhancing textual units, defined as theistic memes. The earliest recorded theistic memes dealt with human fear of death and defined man’s earliest relationship to god. Theistic memes that could theoretically affect fitness through selection and incorporation into religious canons included those dictating beliefs about (a) self-awareness in an unknown world, (b) strategies and behaviors toward others and within the nuclear family, and (c) appropriate sexual behaviors within marriage. Prohibition of aberrant sexual practices such as incest, adultery, homosexuality, bestiality, castration, and religious prostitution would have further maximized fitness. A remarkable mutation of the ancient Near Eastern theistic meme of child sacrifice is documented in the Old Testament in the story of Abraham and Isaac.