According to Eric Lenneberg, the capacity to learn a language is certainly innate and restricted in time.
Lenneberg proposed that there is a critical period of first language acquisition; if a child doesn't learn a language before the onset of puberty, between the ages of two and puberty, the child will never master the language at all.
I found this claim to be fascinating because if in fact Lenneberg's theory were right, then Genie, an adolescent who experience a degree of social isolation and experiential deprivation, confined to a small bedroom from the age of 20 months to roughly 13 years, would never be able to speak properly. If, on the other hand, she did learn to produce grammatically correct sentences, then Lenneberg would be proven wrong.
When Genie was found she did not have the abilities to speak because during isolation she suffered from language deprivation- nobody spoke to her.
Research shows that her experience does imply that over a certain age, any child who has not learned a language will have great difficulty in acquiring one. However, due to Genie's resilient spirit, she kept on advancing regardless of her past deprivation- Genie is living proof of human resiliency; she fought to recover from her hardships, despite all deprivations and abnormalities, and managed to stay alive. Consequently, this suggests that Lenneberg's hypothesis is strongly supported but not proven.