Human weaknesses!
To me the only real weakness in the human race is the one that allows us to chose, because I don't think we are sufficiently evolved as yet to make the right choices. Most of us make choices we ultimately regret.
Who we befriend, who we hang out with. What we do on a daily basis. How we make statements which are specifically designed to hurt people rather than help them. Who we marry. How we raise our children etc. etc. etc.
The list of human errors is endless. Would YOU give these people the choices they have? Do you REALLY believe they have the right to make those choices when they affect every other person in the human race? Personally I don't!