The unique environmental need selecting for a communication system capable for displacement in humans or their direct ancestors is not identified, but hypotheses include Bickerton's theory of small groups finding large herbivore carcasses, and needing the assistance from other small groups of humans to defend against other dangerous scavengers (large cats, hyenas) competing for the same source of food. Language development most certainly did not stop there—since otherwise bees or ants would have comparable communication systems to humans—but this is where it is hypothesized to have begun, giving human ancestors the ability to take communication out of the here and now.