Well here's what it is. Natural selection is selfish on the genomic level. We are reminded of this by books like Richard Dawkin's "The Selfish Gene." But beyond genetic frequencies, or what Steven Pinker calls the "ultimate cause" of human behavior, humans are in reality motivated by "proximate causes", like love, which ultimately move along the genes. Some proximate causes can, however, be labeled as "evil." An answer to the question of whether humans are evil really depends on whether humans are motivated by more "evil" proximate causes, like greed, than good.