No, environment and upbringing are the leading causes.
If a child grows up in a loving home with compassion and looking out for those smaller than himself he will learn to be a caring individual.
If however, he grows up with fear, ridicule and abuse he is more likely to be a bully.
A father who places high importance of fighting and physical dominance sometimes teaches his child to be a bully without realizing it. If he teaches compassion along with this lesson the outcome is more positive.
A parent who pokes fun at others, points out flaws or looks down on any weakness can also raise a child who will pick on those that are seen as inferior.