It's a good question, that has fascinated many people for a long time, why is there still movement of the body and the head as well after a beheading? read more
As we now know - they do. Even animals as primitive as insects and squid can feel pain. Certainly all vertebrates can and do feel pain, just as we do. The ability to feel pain evolved VERY VERY early, and we simply inherited it, as all other higher animals have. Pain is a useful thing. read more
Each species shows pain in different ways. Dogs may yelp and we'd notice a behavioural change, but prey species are unlikely to advertise vulnerability to predators. read more