query chomsky single mutation page 43 1977 paper language origin theories duane rumbaugh book _ language learning chimpanzee _ gordon hewes asserts chomsky explicitly attributed human language faculty single genetic mutation ancestors gives source chomsky 1967 exasperatingly neither work work chomsky listed bibliography obvious work might citing anyone point places chomsky writings indeed anyone else writings suggestion explicitly made able find chomsky repeated suggestions language faculty might arisen byproduct developments hence something subject natural selection quite thing larry trask cogs university sussex brighton bn1 9qh england larryt cogs susx ac uk