Inquiry into the evolution of some biological system evidently can proceed only as far as its nature is understood. Lacking such understanding, its manifestations are likely to appear to be chaotic, highly variable, and lacking significant general properties; and, accordingly, study of its evolution cannot be seriously undertaken. These truisms hold of the study of the human faculty of language FL just as for other biological systems. As discussed below, FL appears to be a shared human capacity in essentials, with options of variation of a kind to which we return.
After a long lapse, the problem of evolution of language arose in mid-twentieth century when the first efforts were made to construct accounts of FL as a biological object, internal to an individual, with particular internal languages – I-languages in current terminology – as manifestations of FL.