For centuries, philosophers, theologians, and other scholars have attempted to determine what factors motivate people to act ethically. Religion has frequently been cited as a primary force motivating ethical behavior. All religions contain specific ethical principles that believers are expected to follow. People may follow the ethical guidelines of their religion through fear of divine punishment if they transgress or in anticipation of being rewarded for leading a virtuous life.

Recently, however, some scientists have proposed that humans’ sense of ethical behavior evolved through natural selection. They maintain that an individual’s altruistic behavior, such as warning relatives of the approach of dangerous animals, increased the likelihood that these early humans would survive the threat and would live to pass on their altruistic genes to their descendants. According to this theory, humans are “hardwired” for ethical behavior...