" Thus three conclusions emerge from the eye story: (1) it is easier to inherit a ‘vision acquisition device’ than a full-blown hard-wired visual analyser; (2) the visual analyser, once ‘set up’, is refractory to radical restructuring—hence the existence of a critical period in its development in cats; (3) the eye seems to have evolved in steps from a light-sensitive, innervated cell to our complex organ by common evolutionary mechanisms. Something similar may have been taking place in evolution of the language organ, and may be occurring during individual development. An argument, put forward forcefully by Noam Chomsky and his followers, refers to the ‘poverty of stimulus’. Most permutations of word order and grammatical items in a sentence leads to incomprehensible gibberish. There is no way that children could learn without some internal ‘guide’ which sentence is grammatical and which is not, only on the basis of heard examples. To make matters worse, many parents do not correct their children’s grammatical mistakes (they seem to be much more worried about the utterance of four-letter words). Recent investigations clearly confirm that children’s ‘instinctive’ understanding of grammatical intricacies, between the ages 2 and 4, is far better than one would expect from a conventional learning mechanism. Thus there seems to be a ‘language acquisition device’ (LAD) in the brain, which must be triggered by linguistic input so that its working ultimately leads to proper language. It is the LAD, and not a fully developed linguistic processor, which seems to be innate. "

― John Maynard Smith , The Origins of Life: From the Birth of Life to the Origin of Language