The single most important advantage we have over the great moral philosophers of the past is our understanding of evolution and its application to ethics. Although the philosophers I have mentioned were able to free themselves from the myth of the divine origin of morality and to explain morality in naturalistic terms, they lacked a proper understanding of how our norms may have arisen by natural selection with the gene as the basic unit for the transmission of inherited characteristics between generations. Without this knowledge, they could observe our feelings and attitudes but not explain them adequately.
-- Peter Singer, Ethics & Intuitions