Can't we live in peace and harmony

Man should be free to move, allowed to believe in whatever he feels right (of course as long as he does not cause injury or harm to others)and able to discover and innovate to improve the livelihood of mankind.

We have gone through numerous wars in history, wars to uphold religion, wars to expand territories, wars to gain wealth and resources, wars to show power and greed. These were the past which led to greatest destruction such as Pearl Harbour, Hiroshima and Nagasaki incidents. But man being man never learns from History. though we have a history tv channel to remind us what happen in the past. Till today wars are still going on in some parts of the world. The oldest and longest being the Palestinian issues, between Muslims and Jews.

My simple question is why can't we live in peace and harmony s brothers and sisters. Like i said in my previous entry that we are from the same species (human beings). Although we are different in skin color, speak different languages, believe in different religion, like different living environment (temperature, urban or rural), think differently (philosophy of life) and eat different food but we are the same human beings having the same red color blood, yellow color brains and we all die when the time comes. Nobody lives forever ( although some say you live forever through your thoughts, writings and creations).

While your on a short journey in this world, why don't we spend quality lifetime helping each other, never repeating past mistakes and for the betterment of mankind.
We always claim we are the greatest creation of God and we are special with thinking power and ability to control the earth and the planets. Sad to say we are the lowest ranked species because with all great minds given we can't live in peace and harmony.