Six-month-old emir is sitting in his car seat and repeatedly saying "na-na-na-na." what is emir doing?

This is an example of babbling. Infants begin to learn the process of speech through these pseudo-words. They will repeat a small catalog of these sounds, which are common to almost every language in the world, for the first months of their lives, until they have perfected the movements needed and have the cognitive levels present to begin to use actual understood speech.

They have more resistances against possible life ending threats so they are able to reproduce safely to increase food supply.