system
Given the following post, respond as if you're commenting on Reddit:
human
Why do babies shove everything they get their hands on into their mouths?

Even in modern times, a lot of babies choke or get poisoned by sticking the wrong thing into their mouth.  Wouldn't this have happened a whole lot more when we were nomadic hunter-gatherers?  

You would think the babies that didn't do this would have had a higher survival rate, and eventually the habit would have been weeded out.
gpt
Highest number of nerve endings per unit area is on the lips and tongue.

Babies do not have fine motor control or developed tactile senses in their hands, whereas their sense of smell and taste is excellent (being one of the first to develop), and they have the best tactile ability located on their lips and tongue.

Therefore their mouth is both how they taste and feel things.