There are around 7,000 human languages that we know of worldwide, and while they're all unique, they're also more similar than you might have realized – particularly when it comes to the grammar, or the way that sentences can be formed and used.
That might be because of certain genetic tendencies, scientists have theorized, or perhaps it's down to the cognitive capacities that all human beings share, like the passage of time that enables us to develop past and future tenses.
A new study proposes a different reason behind this shared grammar: the way that we talk about language itself.
"We propose that in the evolution of language, talking about language was a way of forming some of the first complex language structures and that from these structures new types of grammar could develop," says linguist Stef Spronck, from the University of Helsinki in Finland.
In many languages, reported (or indirect) speech – so sentences indirectly communicating what someone has said, rather than someone actually saying it – can give rise to new meanings that fit with certain grammatical categories.
For instance, "He said, 'I will go'" can also mean "he might go" or "he is about to go" in certain languages. Those additional interpretations aren't exactly reported speech, but they're derived from it.
This extension of meaning, found in certain languages where reported speech is used, can be matched with grammatical constructions like aspect (how something extends over time), modality (discussing possible situations), and topic (what is being talked about), the researchers contend.
So it seems our collective understanding of grammar may have emerged out of the way we talk about other people. Using a sample of 100 languages, the researchers found that reported speech is found on all major continents, occurring independently of language families or areas of contact.
"Humans talk about other people's thoughts and statements all the time, from the moment we first learn to speak," says Spronck.
"It determines our cultures, the way we see the world, and who we trust. A phenomenon that is so fundamental to human existence likely leaves its trace on languages and our study shows that this goes far beyond simple sentences of reported speech."
The researchers suggest that reported speech is an important source for certain core parts of grammar, as well as the meaning of some verbs. It would, in fact, have been one of the first examples of complex language: talking about language.
At the same time, researchers admit that the new hypothesis is at least partly speculative: Tracing language development back thousands of years is no easy task, particularly as human beings were talking for a long time before they learned to write and record anything.
Still, the idea is an interesting one for those fascinated by the evolution of language – and it's something to think about the next time you report on what someone else has said. Next, the researchers want to look for a stronger link between reported speech patterns and categories of grammar.
"Our hypothesis is not meant to replace traditional cognitive explanations of grammar, but provides a new story for the emergence of grammatical categories, particularly those that are traditionally more difficult to explain," says Spronck.
The research has been published in Frontiers in Communication.