revise this speculative theory by considering the biological foundations of symbolic representation and their influence on the evolution of the brain. In his memoir Bastard Tongues (2008), he describes himself as a "street linguist" who emphasizes field work, with a "total lack of respect for the respectable", and he outlines his theories for a general audience. In Adam’s Tongue (2009), he makes an argument about the origin of language which relies on niche construction to supply the required evolutionary catalyst. He claims that human language is not on a continuum with animal communication systems (ACSs) but is a qualitatively different communicative system. Animal communication systems are only indexical, restricted to conveying information about immediate circumstances insofar as these impinge upon individual survival, reproduction, and social relations. Human language, on the other hand, is capable of spatial and temporal displacement. Bickerton argues that peculiar features characterizing the ecological niche of early man allowed for this breakthrough from an ACS into language. He cites the fact that around two million years ago our ancestors were finding their way to the top of a scavenging pyramid, accessing the carcasses of megafauna before other predators and holding them off by working in coordinated groups. By imitating an animal, like a mammoth, one member could attempt to communicate information about such food sources. Although such imitative signaling retained an iconic character rather than fully symbolic, they involved an act of displacement in communication since the body could be miles away and discovered hours earlier. Over time, the sounds signifying something like a mammoth would be decontextualized and come to resemble something much more closely resembling a word. Displacement, Bickerton claims, is the hallmark feature of language. In Bickerton's view, these words allowed the formation of concepts rather than mere categories that animals are also capable of. Words began as the anchors for sensory information and memories about a specific animal or object. Once the brain had words it could create concepts which came together as a 'protolanguage'. The protolanguage remained much like a pidgin for a million years or more, eventually it went from the “beads-on-a-string” model of speech to a hierarchical structure through Merge. Bickerton died in March 2018 at the age of 91. Bibliography Payroll, 1959. Adapted into 1961 film of the same title Tropicana, A Novel., 1963 Dynamics Of A Creole System, 1975 Bickerton, Derek, (1984). The language bioprogram hypothesis, in: Behavioral