Humans may have invented them, but they are a pretty natural concept. Once you have a system of numbering, one of the first things one does is to see which num

Humans may have invented them, but they are a pretty natural concept. Once you have a system of numbering, one of the first things one does is to see which numbers can be arrived at by simply adding other numbers to themselves a bunch of times. I have a pretty limited knowledge of number theory, so I may be completely off mark, but I don't know that people have yet arrived at a nice fundamental theory that can encapsulate the way that primes arrange themselves along the number line.