Origin of language
Chomsky's single-step theory

According to Noam Chomsky 's single-mutation theory, the emergence of language resembled the formation of a crystal; with digital infinity as the seed crystal in a super-saturated primate brain, on the verge of blossoming into the human mind, by physical law, once evolution added a single small but crucial keystone. Thus, in this theory, language appeared rather suddenly within the history of human evolution. Chomsky, writing with computational linguist and computer scientist Robert C. Berwick, suggests that this scenario is completely compatible with modern biology. They note that "none of the recent accounts of human language evolution seem to have completely grasped the shift from conventional Darwinism to its fully stochastic modern version—specifically, that there are stochastic effects not only due to sampling like directionless drift, but also due to directed stochastic variation in fitness, migration, and heritability—indeed, all the "forces" that affect individual or gene frequencies... All this can affect evolutionary outcomes—outcomes that as far as we can make out are not brought out in recent books on the evolution of language, yet would arise immediately in the case of any new genetic or individual innovation, precisely the kind of scenario likely to be in play when talking about language's emergence."

Citing evolutionary geneticist Svante Pääbo, they concur that a substantial difference must have occurred to differentiate Homo sapiens from Neanderthals to "prompt the relentless spread of our species, who had never crossed open water, up and out of Africa and then on across the entire planet in just a few tens of thousands of years.... What we do not see is any kind of 'gradualism' in new tool technologies or innovations like fire, shelters, or figurative art." Berwick and Chomsky therefore suggest language emerged approximately between 200,000 years ago and 60,000 years ago (between the appearance of the first anatomically modern humans in southern Africa and the last exodus from Africa respectively). "That leaves us with about 130,000 years, or approximately 5,000–6,000 generations of time for evolutionary change. This is not 'overnight in one generation' as some have (incorrectly) inferred—but neither is it on the scale of geological eons. It's time enough—within the ballpark for what Nilsson and Pelger (1994) estimated as the time required for the full evolution of a vertebrate eye from a single cell, even without the invocation of any 'evo-devo' effects."

The single-mutation theory of language evolution has been directly questioned on different grounds. A formal analysis of the probability of such a mutation taking place and going to fixation in the species has concluded that such a scenario is unlikely, with multiple mutations with more moderate fitness effects being more probable. Another criticism has questioned the logic of the argument for single mutation and puts forward that from the formal simplicity of Merge, the capacity Berwick and Chomsky deem the core property of human language that emerged suddenly, one cannot derive the (number of) evolutionary steps that led to it.
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