KOKO the gorilla knew over 1,000 signs based on American Sign Language, and used them to do everything from asking for food to joking around. Her trainer and long-term companion, Penny Patterson, thought Koko went further still, signing in novel ways and showing complex emotions. According to Ms Patterson, when a cat that Koko loved was killed in an accident, Koko signed: “Cat, cry, have-sorry, Koko-love.” When Koko died last month, some of her obituaries mourned the gorilla who had “mastered American sign language”.

Then came the backlash, from linguists and experts in sign languages. These have complex grammars, equivalent to spoken tongues in expressiveness. Koko’s ability, it was pointed out, fell well short of a fluent human signer. Moreover, Ms Patterson was her interpreter, a role that invited the question of how much she was inferring what Koko “must have meant”, and explaining away random signs. (Koko was particularly fond of “nipple”.) It was hard to be sure: Ms Patterson preferred speaking to journalists over sharing her video and raw data about Koko with fellow researchers.

There is no doubt that animals communicate. Bees can demonstrate the direction and distance of a source of food. Dolphins make noises that function like names. Animals from one region can share sounds that differ from groups in another, leading researchers to talk of animal “dialects”. Then there are the remarkable achievements of Koko and her primate predecessors, including a chimp delightfully named Nim Chimpsky.

Yet there is an important distinction between communication and language. Take the misleading term “body language”. It is sometimes claimed that words convey just 7% of meaning, and that body language and tone of voice do the rest. This wildly overstretches an old study which found that most emotional messaging—as opposed to the propositional kind—comes from tone and body language, especially when a neutral word such as “maybe” was used. But try conveying a fact like “It will rain on Tuesday” with your eyebrows, and the difference becomes clear. Language allows for clear statements, questions and commands.

Or take the debate over whether emoji constitute a language. If anything, emoji are too good at communicating to count. They are blunt and literal. A smiling emoji means a smile. Nearly all words in a human language, by contrast, are arbitrary. A dog does not make a sound like “dog”. Form has no connection to meaning. With a few joking exceptions, emoji are like gesture and tone of voice, in that their form and meaning are inextricable; they are almost impossible to misunderstand because they are universal and obvious. Indeed emoji are so popular because they do in writing what gesture and tone do for speech. But attempts to “translate” novels into emoji are mere amusements. No one without previous knowledge of the plot could possibly understand them.

Nim Chimpsky’s near-namesake, Noam Chomsky, has argued that people have a kind of “universal grammar”, and that all humankind’s languages are mere variations on a theme. Mr Chomsky has changed his mind repeatedly on what constitutes the core of human language, but one obvious candidate is syntax—rules, not just words, which allow the construction of a huge variety of meaningful utterances. This capacity may even be infinite. Any statement in English, for example, can be made longer by adding “He said that…” at the beginning. This property is called recursion: a simple statement (“It’s cold”) is embedded in a more complicated one (“He said that it’s cold”). Human syntax also allows for hypotheticals (“If she hadn’t arrived…”), talking precisely about events distant from the present, and so much more.

Some languages may be missing some of these features. Daniel Everett, a linguist, claims that Pirahã, an Amazonian language, lacks recursion, and that its speakers do not talk about the distant past or future at all. But they still have complex grammar. No language in the world merely strings relevant signs together like emoji, or communicates at the tourist-abroad level of pointing and making exaggerated facial expressions.

That gorillas lack syntax should not blind humans to their magnificence. But the fact that Koko could communicate should not mislead observers into thinking she possessed language. Homo sapiens is an impressive primate too.