Evil and suffering.

[Mudhammam]

To add to what Alex said, evil (at least as I define it) is merely one of two other categories all intentions and actions of self-aware beings necessarily fall into; the other two are good and neutral. Actions that lead to greater flourishing and progeny of our species, which also includes bettering all of our actual and potential psychological and physiological states, are described by most thinking beings as "good." Rudimentary examples of how this came to be, in the early development of life, might be the simple mechanistic reactions embodied in the Four Fs that virtually all organisms adhere to--flight, fight, feed, or mate. As animals gradually evolved under the environmental pressures that besieged them, their brains developed the ability to communicate thoughts and in turn, contracts between rivaling tribes became necessary for maximizing their quality of life and most importantly, their offspring. At some point we developed empathy for strangers because we gained the ability to reflect on what it's like to actually be them. Morality is ultimately a product of biology, as Alex said, but it's also a product of the evolution of consciousness and culture.