Societal breakdown is inevitable, and so are billions of deaths, as the route toward global-scale mass destructive conflict approaches. Anywhere with an overcrowding of people is done for, and it won’t be long after for the dominoes to fall on surrounding areas, until the world is barren of its leading sapient species once more. When a voice is unheard for too long, it reverts to the basest of instincts, the root language of humanity, and that is a thirst for blood. To lay waste to those who do not listen, filling the streets with corpses and flame to cleanse the world that denied them. It accomplishes everything and nothing. Humans are equal in killing as they are in death.
Humans hold on to ideas for far too long, to the point where it inhibits their evolution. Clearly the argument against religion comes to mind, but more importantly is the fact that humans are trained from birth to obey their superiors. Parents, teachers, pastors, presidents, all of them push back and force humanity back to the cradle that becomes its grave. Laws form the backbone of society, but those laws are created by the superiors, and carry a subtext of maintaining their superiority. Defiance of the law creates a feeling of power, not unlike that which the superiors constantly hold, and thus the reflexive action is to destroy anything that defends the law. This solves nothing, for the root cause runs deeper.
It is this point where it becomes clear that the borders of nations are artifacts from a time long past, where governments are built on fear of the unknown, and build militaries to defend against whatever they deem an enemy. By constantly building that unknown fear and pointing the finger at whoever seems suspicious to any degree, it only strengthens the imaginary borders of a government. Governments are purely constructs of fear, where they counter the base human fears of outside threats and unlimited thought and possibility. Violence is the response from the government, and the people respond in kind. This is where humanity remains and will remain, barring a revelation or effective miracle.
Humanity must evolve or it will die. The people must dismantle the governments that keep them imprisoned, while not falling for the same traps of power and control, or they will be no better and utterly secure extinction for the species. There will be no borders determined from fear, only the walls of homes to protect families from the elements. People would choose the roles they fall into, and the only defense will be against those who simply wish to kill or torment the innocent. There is no foreseeable clean way to do this, as the governments will respond with all possible force to an actual threat to their existence. The most likely successful outcome would have a significant portion of the world population dying, where it would take decades to return to the previous high, if such a thing would even happen. It is when the population drops by such a degree that an interest in children may return, but for the moment, bringing new life into a doomed world is strongly counter-intuitive and simply means the end will come that much faster as there will never be enough for anyone, and thus cannibalism could become a normal occurrence in high density regions while there is a surplus of people, or at least fresh corpses.
If acts that defy all moral grounds must, with no other choice, be committed on the road to global freedom and humanity’s next step, those should be the final atrocities which are never called upon again. Such a result would merge the heroes and monsters of the species, and nothing would be worth celebration. To leave millennia of violence behind would mark a new era of enlightenment for the species. If such an event could be committed simply by all sides agreeing to drop all weapons and dismantle the remaining ones, that would be more of a dream than possible. It is far more likely to result from a final violent push that causes mass destruction, the alleged final world war. Doing so is a gamble in itself, as humanity could very well learn nothing and continue to conflict at less than one percent of its current population until nothing is left. After all, violence is human instinct, and in a neo-primitive world, old instinct would resurface and current instinct may only grow.