Why Can't We All Just Get Along?
I am always a bit surprised how few of the people who ask that question have thought deeply about the answer. We have known the answer in some detail since Malthus and Darwin, and approximately from time immemorial. To put the tragic answer bluntly: we can't all just get along because resources are finite, and the population increases to exploit any increases in resources, and, finally, because we have evolved to live in a world where those things are true.
We are fabulously lucky to live in an age when we no longer have to continue to reproduce like rabbits, and in many countries, we no longer do. In most countries, we are approaching sustainable reproduction rates. On the other hand, we still do have all those instincts that were developed to deal with the Malthusian world. Also, population will continue to increase for some decades, even if favorable trends in declining fertility continue. Worse news, however, is that ecological damage due to global warming is likely to diminish world food production, possibly by dramatic amounts.
A world where we really can all just get along, or at least stop murdering each other in mass quantities is out there, still lying just beyond our grasp.