At least they have not happened yet. Simple human shortcomings got in the way. Personalities Therapists identify three basic qualities of the human personality assertiveness, passiveness, and aggressiveness. Apparently everyone has all these qualities built into their personality, but some of us lean more heavily one way or another. Assertive individuals are quietly confident, they express themselves in non-threatening ways, and they respect themselves and others.
Passive individuals fear disagreements and keep their troubled feelings bottled up.
They're so careful not to infringe on others that they suppress their own rights and needs. Aggressive individuals are demanding, they explode when criticized, and they're unwilling or unable to compromise. They try to get their own needs met, even if it means squashing others. In an organization, assertive people can help keep the group on an even keel, passive people can take the wind out of the sails, and aggressive people create storms that can shake and weaken the group. Apparently some of these qualities of the human ego are entwined with the physical body.