There's not a solution to over population. There is no need for there to be a first to volunteer people are getting killed, dieing from any number of things like cancer, heart attacks, murder you name it. People are dieing every second the clock ticks.
Hitler and Staling had factories to kill the Jews as fast as they could haul them in by the train loads. The atomic bombs dropped on Japan. You throw in all of the other mass destruction that has killed humans and nothing has ever slowed down global population.
The only thing that will is when the population reaches a point that the world's resources can't support the people living on it anymore. And even then the people who survive will continue to live once the numbers get back in check.