Eric Linneberg (1921-1975) was a neurologist and linguist who developed theories on language acquisition and biological capacities for language. He contributed much to the field of cognitive psychology and did research with Noam Chomsky.
Linneberg believed that there was an innate biological capacity for language that only humans have. Evidence for this is that language universally appears at the same age across the entire human species no matter what situational or cultural factors exist. Language is continually present in humans over time and doesn't get 'lost' and not used. More evidence can be seen in that humans develop and learn language in a predictable progression that occurs in stages.