Previously, theories on speech evolution have focused on vowels. But the noise is a consonant-like sound, suggesting that human ancestors may have combined similar noises to make early syllables and words.

Serge Wich, a professor at Liverpool John Moores University and the co-author of the study published in Nature Human Behaviour, told BBC Radio 4’s Today programme that the noises contain an “enormous” amount of information, from the gender of the orangutan to what kind of context it is made in.

The orangutans have also learnt to sometimes put leaves in or in front of their mouths to change the noise.

Prof Wich explained that the finding was interesting because researchers had previously assumed that that amount of information would not be available in a consonant.