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irrespective of human biological evolution. Moreover, it occurs at a rate that is probably many orders of magnitude faster than biological evolution and is subject to selective influences that are probably quite alien from any that affect human brains or bodies. Darwin recognized this analogical process, although he did not comment on its implications for human brain evolution.

“A struggle for life is constantly going on amongst the words and grammatical forms in each language. The better, the shorter, the easier forms are constantly gaining the upper hand, and they owe their success to their own inherent virtue” (Darwin, 1871a, p. 91).

The environment that is the source of selection affecting the reproduction and selective elimination of language features is human cognitive limitation and communicative requirements. For this reason, a given language should reflect selection favoring learnability, early acquisition, and ease of use concerning which features are retained or lost over the course of its historical change. In this respect it is an oversimplification to expect that all of the universal design features of language require a biological evolutionary account. So as brains have adapted to the special demands of language processing over hundreds of thousands of years, languages have been adapting to the limitations of those brains at the same time, and a hundred times faster (Deacon, 1997). This means that brain functions selected for the special cognitive, perception, and production demands of language will reflect only the most persistent and invariant demands of this highly variable linguistic niche. This is another reason to expect that the synergistic constellation of human brain adaptations to language will not include specific grammatical content, and to suspect that much of the rich functional organization of any language is subject to influences on this extragenomic form of evolution. In other words, the differential reproduction of language structures through history will be dependent on the fidelity and fecundity of their transmission. Not only will this process be subject to selection with respect to semiotic and pragmatic demands of symbolic communication, it will also favor structures that are more easily acquired by immature brains undergoing activity-dependent intraselection of neural circuitry. Indeed, just as evolvability is aided by evolution-like processes involved in ontogenesis, we should expect that the social evolution of language should itself exhibit analogous processes due to redundancy, degeneracy, and functional interdependency.

Language is too complex and systematic, and our capacity to acquire it is too facile, to be adequately explained by cultural use and general learning alone. But the process of evolution is too convoluted and adventitious to have produced this complex phenomenon by lucky mutation or the genetic internalization of language behavior. These metaphors are more suited to the analysis of a designed artifact. The robusticity of the language



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