In the 2016 film Arrival, a linguist must figure out how to communicate with enormous seven-limbed aliens, starting with no shared language at all. Her first trembling, breathless attempt to bridge the communicative gap sees her pointing at herself, trying to convey the meaning of the word “human.”

The aliens seem to understand. This sets them apart from every non-human species on our planet: there’s currently no evidence that even our closest primate relatives can figure out what a new communicative signal means just from context. It’s an ability we humans take for granted, but it’s clearly not trivial at all. This ability intrigues evolutionary linguists, who are trying to piece together a picture of how language may have arisen.

A paper in PNAS this week reports a new part of that picture: four- and six-year-old children are capable of communicating with each other even when they can’t rely on language. What’s more, their communication quickly develops some of the core properties that define language. It’s a finding that fits in well with other research on language evolution, and it helps to explain a little bit more about how humans may have developed our wild and wonderful communication system.