Nobody knows! This is one of the biggest problems in the field of language evolution. Unlike stone tools or skeletons, the language that people use doesn't fossilise, so we can’t study it directly. We have examples of writing from over 6,000 years ago which can help us work out what languages were like relatively recently, but recent research suggests that people have been using languages very much like our own for maybe 500,000 years.

Image: Alexandre Duret-Lutz

In order to get an idea of how languages might have evolved, researchers use model systems. These might include computational models, experiments with real people or the study of languages that have developed very recently such as sign languages or creoles. We can’t know for sure what the first languages would have sounded like, but we can work out how communication systems tend to evolve and develop. 

For example, one series of experiments studied how communication systems develop by using a game like Pictionary: players had to communicate about meanings by drawing. They found that negotiation and feedback during communication was very important for a successful communication system to develop.

Another experiment used a chain of learners who had to learn an artificial language. The first learner had to learn a language with no rules, then teach the next person in the chain whatever they could remember. This second person tried to learn the language and then passed it on to the third person in the chain, just like a game of ‘broken telephone’. In this way, we can simulate the process of passing a language down through the generations, but now it only takes one afternoon rather than thousands of years. What researchers noticed is that the language changed from having a different word for every possible meaning to having smaller words that referred to parts of the meaning that could be put together. That is, a language with rules emerged. 

So, early languages may have had a different word for every meaning and gradually broken them apart to create rules. However, other researchers think that languages started with small words for every meaning and gradually learned to stick them together. Some think that language evolved very suddenly, while others think it evolved slowly. Some think that parts of language evolved in many different places at the same time, and contact between groups brought the ideas together. Some think that early languages would have sounded more like music. There are many suggestions that the first languages were signed languages, and that spoken language developed later.

Researchers in this field have to find creative ways of studying the problem and integrate knowledge from many fields such as linguistics, psychology, biology, neuroscience and anthropology.

 Written by Seán Roberts & Harald Hammarström

Experiments on language evolution:

Communicating with slide whistles (link)
The iterated learning experiments (link)
Blog posts on language evolution experiments (link1, link2)

Further reading:

Galantucci, B. (2005). An Experimental Study of the Emergence of Human Communication Systems. Cognitive Science, 29, 737-767. (link)

Hurford. J. (forthcoming). Origins of language: A slim guide. Oxford University Press.

Johansson. S. (2005), Origins of Language: Constraints on hypotheses. Amsterdam: John Benjamins.

Kirby, S., Cornish, H. & Smith, K. (2008). Cumulative cultural evolution in the laboratory: An experimental approach to the origins of structure in human language. Proceedings of the National Academy of Sciences of the United States of America, 105,10681–10686. (link)