she had been done out of the right to punch you in return. If, however, the other child managed to shout “Punch-backs!” before you could yell out your protective charm, then a retaliatory punch was in order. Money was not a factor here: you couldn’t buy your way out of being punched. What was at issue was the principle of reciprocity: one punch deserved another, and would certainly get it unless an Out clause was inserted with the speed of lightning.
Ontogeny repeats phylogeny, we’re told: the growth of the individual mirrors the developmental history of the species. Those who fail to discern in the Punch-buggy ritual the essential lex talionis form of the almost four-thousand-year-old Code of Hammurabi — reformulated as the Biblical eye-for-an-eye and tooth-for-a-tooth law — are blind indeed. Lex talionis means, roughly, “the law of retribution in kind or suitability.” Under the Punch-buggy rules, punches cancel each other out unless you can whip your magical protection into place first. This kind of protection can be found throughout the world of contracts and legal documents, in clauses that begin with phrases such as “Notwithstanding any of the foregoing.”
We’d all like the right to a free punch, or a free lunch, or a free anything. We all suspect that the likeliness of our getting such a right is scant unless we can jump in there with some serious abracadabra. But how do we know that one punch is likely to incur another? Is it early socialization — the kind you get while squabbling over the Play-Doh at preschool and then saying, “Melanie bit me”— or is it a template hot-wired into the human brain?
LET’S EXAMINE THE case for the latter. In order for a mental construct such as “debt” to exist — you owe me something that will balance the books once it is transferred to me — there are some preconditions. One of them, as I’ve said, is the notion of fairness. Attached to that is the notion of equivalent values: what does it take to make both sides of the mental score sheet or grudge tally or double-entry bookkeeping program we’re all constantly running add up to the same thing? If Johnny has three apples and Suzie has a pencil, is one apple for one pencil an acceptable exchange, or will there be an apple or a pencil remaining to be paid? That all depends on what values Johnny and Suzie place on their respective trading items, which in turn depend on how hungry and/or in need of communication devices they may be. In a trade perceived as fair, each side balances the other, and nothing is thought to be owing.
Even inorganic Nature strives toward balances, otherwise known as static states. As a child, you may have done that elementary experiment in which you put salty water on one side of a permeable membrane and fresh water on the other side and measure how long it takes for the sodium chloride to make its way into the H 2 O until both sides are equally salty. Or, as an adult, you may simply have noticed that if you put your cold feet on your partner’s warm leg, your feet will get warmer while your partner’s leg will get colder. (If you try this at home, please don’t say I told you to do it.)
Many animals are able to tell “bigger than” apart from “smaller than.” Hunting animals have to be able to do this, as it could be fatal to them to literally bite off more than they can chew. Eagles on the Pacific coast can be dragged to a watery grave by salmon that are too heavy for them, since, once having pounced, they can’t unhook their claws unless they’re on a firm surface. If you’ve ever taken small children to the big-cat enclosure at the zoo, you may have noticed that a medium-sized feline such as the cheetah won’t pay much attention to you but will eye the kids with avid speculation, because the youngsters are meal-sized for them and you are not.
The ability to size up an enemy or a prey is a common feature of the animal kingdom, but among the primates, the