Humans can swarm too. When large crowds gather, the limited communication between people causes them to fall back on simple rules: keep moving in the same direction as everyone else; try not to get too squashed up; don’t get left behind. If there’s a bottleneck or something triggers a panic, the crowd can suddenly become dangerous. In 2005, almost a thousand people died during a stampede in Iraq, when pilgrims marching to the Al-Kadhimiya Mosque in Baghdad became panicked by fears of a suicide bomber.
But the science of swarming can also be useful to humans. The simplicity of the rules that control a swarm makes them ideal for robots and simulations. Airports use swarming behaviours adapted from ant colonies to model the flow of passengers through the terminal and to determine the best departure gate to assign to each flight. Elsewhere hovering drones the size of your hand have already been successfully programmed to fly in formation and navigate around obstacles without a human to steer them. In the future, these could be used for military reconnaissance as well as search and rescue missions.