Cultural Evolution and Language Mavenry, Or Why Making Fun of People Who Mix Metaphors Is Not a Waste Of Time

Turn on CNBC during a crisis, and you'll hear people mixing stale metaphors at ferocious speed. "The bubble in tech stocks has jumped the shark, someone should stick a fork in it, unfortunately it will take time to unwind, so there'll be some pretty rough sledding for a while, but we can't just kick the can down the road again." Here a soap bubble becomes Fonsie on a motorcycle, who becomes something barbecued, which becomes a recalcitrant coil of some kind, then suddenly we're in a toboggan race, and then it's an empty can, all in one sentence made entirely of clichés.

I like to make fun of people who say this sort of thing. But am I just being a snob? Is the persnickety language maven a misunderstood hero, protecting civilization from a slow descent into Babel? Or is he simply a nuisance?

I would have thought, until recently, that when I mock a mixed metaphor or a stale idiom I'm pretty much just being a snob. But that might be wrong. It now seems as if the maven may be doing something useful after all.

What could that possibly be?

The discovery that I may actually be accomplishing something with my language snobbery is a serendipitous result of our ongoing effort to find a workable theory of cultural evolution. (A word or an idiom is something we learn from other people, not something we each have to invent for ourselves, so language is a kind of culture.) Ever since Richard Dawkins first suggested, in The Selfish Gene, that culture must evolve, we've been wondering exactly what it is that allows humans to have such a complex, useful, constantly evolving culture and language. Why can't chimpanzees do it? What do we have that they lack, why is human culture unique? The single biggest difference between humans and chimpanzees is probably the sheer number of things we humans learn from others. But why exactly does this difference exist? Is it because we're simply more inventive than they are? Or is it just because we're better at learning things from others? Or is some other, less obvious human ability the really crucial one?

In the last decade, some of the most intriguing attempts to answer these questions have come from people associated in one way or another with Stockholm University's Centre for the Study of Cultural Evolution, set up to help scientists from many different fields work together to try to invent this new science. One of my favorite contributions from this group comes from Magnus Enquist, an ethologist at Stockholm University, and Stefano Ghirlanda, currently a professor of psychology at Brooklyn College, in a paper published in 2007 in the Journal of Theoretical Biology.

We humans really are more inventive than chimpanzees, and we really are better at learning from others, but Enquist and Ghirlanda's model shows that another, less obviously useful human faculty matters more than we might expect. The model (a pair of simple differential equations very similar to the ones used in population genetics) seems to show that, if you want to have an elaborate, human kind of culture, it's also necessary to make good choices about what not to learn from others, and what to discourage.

Why? Not all culture is adaptive. There are also things you might learn, by imitating others, that would make you or your children worse off.

These maladaptive memes come in two different flavors. Some of them were maladaptive from the start. "Learning" that Ebola is caused by witchcraft may kill you. Thinking that heroin is cool, wanting to be exactly like Janis Joplin, is also just a bad idea. Other ways of doing things that you might learn from others are obsolete or garbled, the result of mistakes and inertia. Elaborate mastodon hunting skills aren't really all that useful anymore. Even when they were, your teacher might only have learned an imperfect version of the craft before his own teacher died in a hunt. His way of hunting could be very unsafe.

So there are two distinct sources of maladaptive culture. People may simply have bad ideas, or else items that once were useful might outlive their usefulness, or become garbled in transmission. If the learner wasn't capable of exercising a human kind of critical judgment, however, these bad habits and bad ideas could only disappear in one way - through sheer luck, by just accidentally failing to be passed on.

Useful items, on the other hand, can only come from a single source - someone having a good idea - but can be lost in two distinct ways, either by simply failing to be passed on, or else by becoming obsolete or garbled.

Garbling destroys good ideas, but it's a second source of bad ones. Things seldom spontaneously become un-garbled, or less obsolete, without deliberate human intervention, simply because there are always more ways of doing something wrong, of failing to safely catch a mastodon or cook a perfect turkey, than there are of doing it right. So there's a one-directional flow from the pool of adaptive behaviors, via garbling or obsolescence, to the pool of maladaptive behaviors. That means, in the absence of a human kind of critical judgment, that useless or harmful cultural behaviors are likely to accumulate more rapidly than adaptive ones.

This may be one reason chimpanzees don't have much of a culture. Enquist and Ghirlanda give a numerical example that makes this point pretty clearly. They assume that cultural innovations come along at some constant rate, and that some fraction of those are actually adaptive. They also assume that adaptive innovations are "corrupted" into maladaptive ones at some rate. The longer it's been around, the more likely it becomes that an innovation has already outlived its usefulness. Given these assumptions, how rapidly should a population of creatures with no ability to think critically about their own culture forget each new cultural innovation? How long is it safe to keep these innovations around, considering their tendency to become maladaptive over time? And what does that imply about the total number of items of culture in circulation?

Even if two thirds of the original innovations are adaptive ones, and only one item in twenty becomes garbled or obsolete in each generation, their model tells us that if the average innovation hangs around for more than about seven generations, cultural learning itself becomes maladaptive. These completely uncritical creatures need to be very forgetful, very bad at learning from others, to safely have any culture at all. If they do manage to forget innovations quickly enough, the total number of cultural behaviors in circulation at any moment will be quite small, as small as it is in actual populations of chimpanzees.

But we humans are smart enough to consciously weed out obsolete or counterproductive or garbled customs, so there's a second way for maladaptive items to be cleaned out of our cultural inheritance. We can avoid and discourage and ridicule and forbid cultural behaviors that seem stupid to us. That, of course, is where the critic comes in. Using the same parameter values as before, Enquist and Ghirlanda added, to their model, a human tendency to weed out some fraction of the stock of maldadaptive cultural behaviors in each generation. If we can weed out just five percent of them, the average lifetime of an innovation can go from less than seven generations to around twenty. If our weeding improves a bit more, we cross a crucial threshold, and gain the ability to safely acquire unlimited amounts of culture. (In their numerical example, this happens as soon as we succeed in weeding out seven and a half percent of the maladaptive items in every generation.) Once we're over this threshold, our clever weeding can even coax optimality out of a flow of new ideas which are mostly bad.

If their simple and intuitive model is actually correct, human evolution has been partly a process of developing the ability to do this sort of "adaptive filtration" in a more and more intelligent way. This would have allowed our ancestors to maintain a more and more elaborate culture and language, until they finally broke out into the regime of unlimited accumulation we inhabit today. The cultural critic is the hero of this story, because it's her willingness to repeatedly reject stale or stupid traditions and conventions that keeps our whole stock of cultural behaviors from slowly deteriorating into a mass of irrelevant nonsense. If we all just let that happen like robots, then cultural learning itself would eventually become maladaptive, and our descendants would have to find some other way of surviving. "Mindless copying will never work," Enquist explains. "The slightest error would quickly spread and make culture useless. That means that ability to judge the value of acquired cultural traits and make corrections must have evolved very early, perhaps even before culture appeared."

In Surfaces and Essences, Douglas Hofstader and Emmanuel Sander argue that analogies are central to our whole way of looking at the world. But not all analogies are equally useful. A fresh, pithy one - using black swans as a metaphor for rare catastrophic events - can be informative, at least at first, because it has to rely on a genuine similarity. There's no cliché to fall back on, the audience has to actually get the point. That makes the fresh metaphor a sort of crystallized insight, which temporarily makes us all a little smarter in a very specific way. But as it becomes conventionalized, and thought is replaced by habit, it can turn into a meaningless noise. If the original thought was a trivial one, a thought about Fonsie jumping a shark, that may happen pretty quickly. That's why stale metaphors are the easiest ones to mix. There are no living ideas still attached to them that could clash with each other, and force us to slow down and actually think about what we're saying.

Of course, some metaphors go stale more quickly than others. Some are eternal. There will always be things that seem dark, or tangled, or fiery, or like wine, or snow, or blood, or the ocean. But we all have to constantly weed out the useless ones, the obscure and uninformative references to Happy Days and Pilgrim's Progress. We must constantly replace them with fresh, interesting analogies, or at least with tried and true classics, to keep our language, the language we think in, from very gradually deteriorating into irrelevance and nonsensicality. We accomplish this weeding by trying to not speak in ways that will seem ridiculous or offensive to the people we would like to impress, and by ridiculing or correcting people who talk in ways we see as trite or confused or unfair. We may politely hold our tongues, most of the time, but the mocking thought is still there, and we should all be grateful for that fact. Without it, we'd be lost.

So even when it's only done for our own amusement, making fun of people who mindlessly jumble together the carcasses of dead metaphors really is performing a public service. Strange as it may seem, living human cultures and living human languages may actually require this kind of maintenance. That sort of weeding and pruning may, in fact, be the only thing that keeps us all from gradually devolving back into chimpanzees. And now, thanks to the people who study cultural evolution, we persnickety language mavens actually have the math to prove it.