The neurological rewiring of the mammalian brain to activate a broader array of emotions was the critical breakthrough in the development of not only moral systems, but other features often considered unique to humans, such as the capacity to use language and to think abstractly and rationally. Data from African apes and from ethnographies of hunter‐gatherers provide the best clues as to the selection forces operating on the hominid line to produce an increasingly emotional and moral primate, Homo sapiens.