In ‘The Language Instinct,’ it's explained why Chomskian mental grammar is likely to be universal, despite isolated counter-examples: pidgin dialects have crappy grammar and are bad at recursion, but children who begin by learning a pidgin from adults, soon develop it into a creole with full-fledged grammar that has all expected features. This happens even when the children speak no other language, e.g. deaf children who learned pieces of a sign language from hearing adults.