They're bipeds and rhythm comes the part of the brain responsible for walking and running. It's likely one of the earliest forms of abstract cognition. The jive behavior is similar to a child counting on their fingers or an adult mathematician using notation to remember and reform their thoughts. You probably take your own advanced rhythm cognition for granted. Just don't laugh at the negro. There are still higher minds than yours in this universe who find your mathematical proofs akin to jive, for to them such things are obvious and completely internalized.