In this essay I argue that many nonhuman animal beings are conscious and have some sense of self. Rather than ask whether they are conscious, I adopt an evolutionary perspective and ask why consciousness and a sense of self evolved---what are they good for? Comparative studies of animal cognition, ethological investigations that explore what it is like to be a certain animal, are useful for answering this question. Charles Darwin argued that the differences in cognitive abilities and emotions among animals (...) are differences in degree rather than differences in kind, and his view cautions against the unyielding claim that humans, and perhaps other great apes and cetaceans, are the only species in which a sense of self-awareness has evolved. I conclude that there are degrees of consciousness and self among animals and that it is likely that no animal has the same highly developed sense of self as that displayed by most humans. Many animals have a sense of “body-ness‘ or “mine-ness‘ but not a sense of “I-ness.‘ Darwin’s ideas about evolutionary continuity, together with empirical data (“science sense‘) and common sense, will help us learn more about consciousness and self in animals. Answers to challenging questions about animal self-awareness have wide-ranging significance, because they are often used as the litmus test for determining and defending the sorts of treatments to which animals can be morally subjected. (shrink)