 Darwin’s reinterpretation of the moral sense tradition within his evolutionary framework, however, implied important transformations. The moral sense, for Darwin, was derived by biological descent from animal instinct, and particularly from the social instincts developed by natural selection. From this perspective, Darwin could then argue for a genuine “homology” of ethical foundations holding between humans and animals, with the precursors of human ethical behavior found in the behavior of other animals, particularly those with social organization. Natural and sexual selection then shaped these ethical instincts in ways that favored group survival rather than immediate individual benefit (Descent 1871: vol. 1: 98). Human ethical behavior is therefore grounded in a natural property, and ethical action can occur without moral calculus or rational deliberation. Because he considered ethical action to be grounded on a biologically innate property, Darwin criticized John Stuart Mill’s Utilitarian theory because it relied on acquired habits rather than something present in humans from the beginning (1871: vol. 1: 71n5). The innate moral sense is his explanation for self-sacrifice and other altruistic acts that cannot be attributed to individual self-survival (1871: vol. 1: 86). Humans can be 