I'm reading The Tribal Imagination: Civilization and the Savage Mind by veteran anthropologist Robin Fox. He started out as a structuralist in the tradition of Levi-Strauss, then absorbed a more Darwinian approach. His 1967 book Kinship and Marriage is in the structuralist mode: it sketches out every conceivable kinship arrangement, and then cites examples for as many as exist in the real world. People love making up complicated rules.
He's got a chapter on rhythm and rhyme in poetry. Rhythm appears to be older and more universal, while rhyme didn't enter mainstream Western poetry until medieval times, perhaps from Arabic and Irish influences. I did not know that.
An amateur poet himself, Fox has a digression in which he denounces free verse that I liked for the unexpected direction it went:
A generation arose after the rebellious sixties that decided the only way to deal with rules you don't like is to abandon the. Thus you are rule-free and hence happy.
You are never rule-free. If you abandon one set of rules, then you must invent another with the same ratio of arbitrary content to noise, because the essences of rules is redundancy; they enable you to predict the world and live forward in time, which is what the neocortex is for in the first place. We do not respond like lower animals to immediate emotional demands; we mediate them with rules; our neocortex controls our limbic brain. And like rhyming, it is all about anticipation and predictability.
In poetry and music, we like it when we can predict what comes next, but we also like it when it surprises us. It's all good. In general, human beings have liked poetry and music a lot. (Obviously, some poetry or music is better than others at combining interesting and powerful patterns of satisfaction and surprise: the fourth movement of Beethoven's Fifth Symphony is better than, say, 99 Bottles of Beer on the Wall. But, people will sing even 99 Bottles of Beer on the Wall for quite some time if they don't have anything else to do.)
... Rule creation is an "appetitive" activity for us. One might even say (metaphorically) that we have an instinct to make rules ... In some sense it does not matter what the rules are as long as we have some; which exact rules we have will be determined by adaptation and history and no little accident. ...
Think of the great defining drama, the Orestia, the Hamlet, of the post-sixties generation: it was Seinfeld. Seinfield was to the post-sixties people what Siegfried was to the Third Reich. And it was about rules. Every episode dealt with the search for rules in a generation that had dispensed with them. What are the rules for dumping a girlfriend; for the copyright on children's namess; ... for double-dipping; for putting people on your speed-dial list; ... for "regifting" unwanted Christmas presents; for calling after ten at night ...
I made a similar point in an early Taki column: Larry David: Alice in Blunderland. Seinfeld wasn't a show about nothing, it was a show about rules.