As it currently stands, human beings as a whole are psychologically and biologically incapable of peace. Not only are we inherently violent and competitive due to eons of evolution that has favored savage ruthlessness over all else, we are all separate from each other in the sense that we are unable to emphasize with our fellow human beings. All we are to each other are locked boxes with thoughts and feelings no one but themselves can experience or comprehend. Because humans can't TRULY understand what other human beings are feeling on a national or global scale, history is filled with countless examples of entire groups being oppressed, enslaved, and/or murdered simply because they were weak or different compared to their oppressors. We may have progressed to the 21st century, but our brains are still stuck in the Stone Age or even earlier. Our survival as a species therefore demands that our brains be updated to be more conducive to cooperation and understanding rather than our current tendency for competitive and egocentric behavior that serves to fulfill base desires at the expense of fellow human beings' well-being.
Short of Human Instrumentality or extinction, a good step towards ensuring worldwide peace would be through genetic engineering and/or cybernetics. By making human beings emotionally linked to each other (either through superdeveloped mirror neurons or wireless brain-to-brain interfaces implanted at birth), we would no longer be able to even consider harming another human being for the sake of food, shelter, money, or power. By tearing down the barriers of the ego that contribute to man’s inhumanity to man, woman, and child, we can cast aside our xenophobic and selfish nature and all work towards the betterment of humanity as a whole. Hopefully, there’s at least one scientist in the world who’s working on making the dream of Human 2.0 a reality.
No. Human nature is not something that people can simply change when they see a trait that is undesirable. Even an attempt to change human nature would fail; simply due to the human nature of those trying to implement the change. Basic human natures like envy and greed will always be something to personally battle. Science will not be able to change it in a lab.
In my opinion the only people that should be attempting to change human nature are the individuals who believe that there is something missing from their personal or spiritual beings that is detrimental to them becoming all that they believe that they should be. For society to dictate over individuals and their human nature is wrong.