As soon as the last human has perished we will have finally achieved world peace.

Until that happens, it is simply not possible.

Humans are aggressive, greedy, jealous creatures and unless those traits are "bred" out of humanity (at which point are we still even human?) there will never be true world peace

Someone will always covet what someone else has, believe they are better able to lead or dictate or be in charge, etc. As long as one individual believes themselves superior to another for any reason such as wealth, IQ, divine right, race, colour of skin, or whatever, world peace is not possible.

Religion will not offer a solution as every religion believes they are the "only" one and has followers that will not abide another religions beliefs existing.

So until or unless we reach a Utopian stage where everyone's every needs, including spiritual, are met simply by asking mankind will never have world peace.

Simply put, we don't want it. We thrive on conflict, we grow, we evolve because of conflict and that will never change until humanity is no longer human.

We must evolve out of our selfish base desires and into something else before this can have any hope of becoming reality.