I just noticed this comment:

"I can ask you the same thing, show me physical proof that a snake can't have feelings?"

So here ya go.

http://www.buffalostate.edu/orgs/bcp...cs/triune.html

The brain, devided into its evolutionary milestones as according to triune brain theory. Reptiles only have the first part, conviniently called the "Reptilian Complex", which DOES NOT have any of the parts necessary to feel emotion. Those parts are present in the Limbic brain (i.e. the amygdala), which evolved in mammals. Hope that helps further your understanding of what we know about the brain.