SMILING IS JUST WEIRD

So, I was recently thinking about how strange smiles are. Think about it. You are basically looking at someone and saying, "Want to see my teeth?" Smile right now. It's weird, isn't it? We pose for pictures and make sure the camera takes shots of our teeth. Why get an x-ray at the dentist? We can just check for cavities in the pictures. We walk by perfect strangers and just flash our teeth. It's like saying, "I think I have something in my teeth. Check it out for me." What would life be like if instead we stuck out our tongues in greeting and went, "Ptttt!!!" Just curious...