1) Different individuals have different characteristics

2) these differences result in varying abilities to reproduce under local circumstances

3) Some of these differences are inherited

4) Those inherited differences that result in highly successful reproduction rates are the ones that will be present at higher percentages in the new generation.

Evolution is common sense but they have very close common ancestors. Now, think about evolution on a family, tribe, society level. Some individuals preserve there species line by being protectors or servants. (ex: ants, bees, certain species of birds) further ex: if a son helps raise 20 of his siblings but does not reproduce himself, then, the DNA from his parents will still be transferred in great abundance even if he doesn’t reproduce at all. Sometimes behavioral evolution is harder to explain in only simple definitions. Think about it.