How can we detect when language emerged?

Views differ radically as to how deep the roots of language lie in human phylogeny, largely because prior to the development of writing systems, this striking human attribute has to be inferred from indirect proxies preserved in the material record. Here I argue that the most appropriate such archaeological proxies encode the modern human symbolic cognitive system from which language emerges. Throughout the 2.5 million years or more for which an archaeological record has existed, change has been both sporadic and rare-until symbolic objects and behaviors begin to appear, well within the tenure of our highly apomorphic species Homo sapiens. I propose that the biology underwriting our unusual cognitive and linguistic systems was acquired in the major developmental reorganization that gave rise to our anatomically distinctive species around 200,000 years ago in Africa. However, the material record indicates that this new potential lay fallow for around 100,000 years, following which it was released by what was necessarily a behavioral stimulus. By far the best candidate for that stimulus is the spontaneous invention of language, which is plausibly underwritten by a relatively simple mental algorithm, and could readily have spurred symbolic cognitive processes in a feedback process. None of this means that earlier hominid vocal communication systems were not complex, or that extinct hominid species were not highly intelligent. But it does emphasize the qualitative distinctiveness of both modern symbolic cognition and language.