Just when our ancestors started talking is something that’s still debated. We can’t exactly ask them, after all. But a new study published in Nature Communications suggests that the earliest language may have been born out of the need for butchering tools starting between 1.8 and 2.5 million years ago.

We don’t know when human ancestors uttered the first “hello,” but we do know when they started making tools. Around 2.5 million years ago, hominid ancestors began to craft sharp flakes of volcanic rocks like flint and use them for slaughtering animals.

The new study suggests that these tools were inextricably tied to language, with one spurring the evolution of the other – and both spurring the evolution of modern man.

Led by psychologist Thomas Morgan of the University of California, researchers tried to mimic the process by which hominids would have learned to make these so-called Oldowan tools from each other.  Their hypothesis was that the creation of the tools would be much easier with language.

When you think of language in a broad sense (including gestures and all non-emotional sounds) you realize that “teaching” doesn’t exist without it. If you can't point or say “yes,” or “no,” you're really not teaching someone to do something – you're just doing it in front of them. And how can people learn to make something consistently as a people if no one is teaching the skill?

So 184 students were split into five groups, and each learned how to make the tools in a different way. The first group was just given two rocks and told to produce a sharp flake. Unsurprisingly, their results were poor – you need to strike the core rock just so to make a sharp piece chip off.

In all the other groups, one student was specifically taught how to make the flakes properly, and all other students had to learn how to do it in a chain, one after the other. One group was able to watch their “teacher,” the next group had instructions to show their students the process of making the tools without using gestures or sounds, the next could use gestures, and the final group could talk normally.

Talking helped, of course: The students in the final group were four times as likely to produce useable tools as the students in the first. But gesturing didn’t hurt either, with those students doubling their success over the first group’s. Neither of the “show but don’t tell” groups improved significantly over the one without teaching.

“If someone is trying to learn a skill that has lots of subtlety to it, it helps to engage with a teacher and have them correct you,” Morgan said in a statement. “You learn so much faster when someone is telling you what to do.”

One caveat: It’s worth pointing out that these modern students are very used to talking and very much not used to making stone tools. So they're an imperfect replication of people who had years to figure out tool making – who may very well have done so without pointing and gabbing.

But if language did make early hominids better tool-makers, it would have helped them to survive – leading to more pointing and primitive talking in the next generation, which would in turn lead to even better tools.

Morgan doesn’t think people were talking much during the long reign of Oldowan tools. “They were probably not talking,” Morgan said. “These tools are the only tools they made for 700,000 years. So if people had language, they would have learned faster and developed newer technologies more rapidly.” But some early proto-language skills, like gestures and simple words, would have kept the tool-making alive.