Furthermore, since evolutionary change comes in response to behavioral interactions, industrial engineers may begin to create robots that evolve their hardware as the conditions on the battlefield change. There are some significant hurdles to this, such as being able to quickly and automatically manufacture robots. Rapid prototyping via 3-D printing holds promise, but parts still need to be assembled by someone, and printers must be capable of working with a wide range of materials. This manufacturing bottleneck will initially constrain the battlefield evolution of robots to designs that are structurally simple. Some of the slack can be picked up by the co-evolution of the robots’ software programs, but, as we’ve seen, the neural control system is only part of what creates intelligent behavior. Since combining the evolution of brains and bodies will permit rapid and innovative behavioral adaptation during battle, it’s highly likely that defense programs will soon be putting evolution to work in designing their robotic weapons systems.