Chewing is important in order to digest plant matter. A snake cannot chew. All its teeth are pointy, and it lacks the muscles to chew. It probably also lacks some things in its stomach that it would need. read more
Humans are omnivores, so we have considerable flexibility in what we see as food. We are hardwired in the sense that certain food items for other animals (wood, grass, dung) are not seen as such by us, but fruits, meat, vegetables, etc are. read more