The mouth has connections to one of the oldest parts of the brain, the so-called caudate nucleus. This area is much older than us humans. We have it in common with virtually all animals that have spines, such as lampreys. Since we were genetically separated from these fish over 500 million years ago, we can conclude that these parts of the brain are more than half a billion years old. source: doi.org/10.1113/jphysiol.2012.246660