I watched a scientific experiment with fruit flies once, where a few breeders were placed in a secure and clean environment with plenty of food and clean air. They multiplied until there was a huge overpopulation problem. They continued to get enough food, clean water and clean air. But in some way the population began to decline drastically until it was tiny again.

With pollution, global warming, diseases and viruses, and violence, I suspect the human race has reached that threshold and will be depopulating over the next few centuries. Killer drones will be one of the tools to help in the depopulation.

And to carry the author's thoughts further, wait until these drones are built and controlled by other autonomous machines. Pretty much the future world of The Terminator series.