The first teeth were outside the mouth. Paleontologists (people who study fossils) have presented evidence that the first teeth were specialized scales, appearing on shark-like fish around 400 million years ago. These pointy scales were positioned around the lips, where it’s thought they would convey an advantage to the fish in capturing and holding on to prey. The adaptation proved to be a very useful one, refined over millennia, and co-opted by zillions of animals, including us.
Everyone smiles in the same language. Savvy world travelers are aware that certain gestures and behaviors that mean one thing in one culture may mean something very different in another society. (The “thumbs up” gesture, for example, is considered obscene in Thailand and some areas of the Middle East.) A smile, on the other face, is generally recognized as being interpreted the same way (as a sign of pleasure and warm greeting) in every culture. It appears to be one of the few truly innate behaviors we have as human beings. Even babies smile and respond to smiles in their first year of life.
Your appendix, little toe and wisdom teeth have something in common, besides being part of (most) people’s anatomy. All three are often considered “vestigial,” serving little or no purpose in modern human beings. Wisdom teeth are thought to be an evolutionary holdover from when human diets included much more food that was tough or hard. This third set of molars usually doesn’t erupt until a person’s late teens or early twenties (when they’re optimistically considered to be gaining wisdom).