From the documentary, It could be said that the development of children's language are developed by numerous physical features they have. One feature that  hinders their development of language is by having a lower larynx. The lower larynx prevents choking, but stops the space which prevents language development. 2 year old according to research, they learn 10 new words a day.
Children have a certain skill when it comes to learning language and they often get the grammar correct.
Babies lack self awareness
The older the children become, they more they start to use words like "I, you and me " which shows that they can distinguish themselves.
At 2 years old, they can use language to express their needs and wants.
Children are like sponges when it comes to learning, which also develops their learning of language.