I would say language sets us apart from the animals. Animals have no ability to communicate with each other in any meaningful way and so must act mostly on instinct to survive.
As with animals killing only for food, this premise is also false. The neocortex of dolphins and killer whales (which are, strictly speaking, also dolphins) is more developed than that of a human. Actually, they do communicate in a meaningful way with each other and show patterns of cooperative behaviour which are simply impossible on instinct