To some people, Greek bears an uncanny phonetic similarity to Spanish. “We used to have Greek news on the TV, and I’d listen to it and think, ‘Whaaaaa?’ It was like listening to Spanish, but I couldn’t understand most of it,” an internet user noted some years ago.

The perceived commonalities in two foreign languages is not an unheard phenomenon. A new study explains why global languages — and more than 7,000 of them — tend to sound similar. Published in Frontiers in Communication this month, the researchers argue that the way people talk about languages gives grammar a shared identity. This connection may form a piece in the longstanding puzzle of how languages evolve.

“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,” linguist Stef Spronck, from the University of Helsinki in Finland, one of the authors of the study, said. Over time, this tendency also leads to a shared grammar structure.

Despite being unique, 7,000 global languages bear some similarities. These similarities can be in the way we construct grammar, how we form words or sentences. Previous research in this linguistic field mapped two possible reasons: people may be born with certain genetic tendencies that build their grammar, and the shared cognitive abilities of, say, experiencing time help develop past and future tenses in language. What’s lacking in these assumptions is that they partly explain the grammatical similarities and do not attempt to trace the origin of grammar.

The new theory anchors the evolution of language to a linguistic device: the reported speech. A quick grammar lesson would remind people that any sentence that indirectly communicates what someone said is the “reported” part instead of someone saying it. For instance, “he said: ‘I will go.'”

This article you’re reading is reported speech too — where we explain what the researchers said. Reported speech, formed around talking about other people and things, is found on all major continents.

What is it about reported speech that makes it essential in language evolution? The above sentence of “I will go” can give rise to many meanings. In some languages, the intention can be: “He was about to go,” “He might go,” or some other construction. The vast array of meanings derived from reported speech fits within grammatical ideas, giving different communities a shared linguistic basis.

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These are not mere instances of reported sentences. Each conversation about something else carries some meaning clubbed as thought (desires, intentions), attitude (emotional states), cause (reason, purpose), and time (future tense, state of affairs). Any reported speech involves a critical element of meaning; this shared understanding makes some languages sound similar. For instance, “She said ‘I will go'” could be interpreted as “She wants to go.” This non-speech interpretation fits within common grammatical categories, which are used by other global languages too.

In other words, talking about other people is what makes our grammar so similar. “Humans talk about other people’s thoughts and statements all the time, from the moment we first learn to speak,” Spronck said. “It determines our cultures, the way we see the world, and who we trust.”

The research also helps explain specific grammatical categories, the origins of which have proved difficult to explain. “Our hypothesis is not meant to replace traditional cognitive explanations of grammar,” the researchers warned. One of the most popular ones is the Sprachbund effects, which means languages come to share standard features after being spoken in neighboring areas for a very long time. For instance, the Indian subcontinent’s Dravidian and Indo-Aryan languages share several features, such as echo words or subject-verb-object order, not inherited from a common source.

Language is one of the most fertile fields of study. Humans were communicating for long before someone put a writing instrument to a surface. The new theory is one facet of what makes our languages sound so similar despite their eccentricities.

“…saying clauses (reported speech) are an important source for a wide, but also a quite regular range of meanings that constitute core parts of grammar and the meaning of some verbs and thus have played a central role in the constitution of language,” Spronck said.

“A phenomenon that is so fundamental to human existence likely leaves its trace on languages…”