By Victoria Gill Science reporter, BBC News
9 February 2017
Scientists who spent years listening to the communication calls of one of our closest ape relatives say their eavesdropping has shed light on the origin of human language.
Dr Adriano Reis e Lameira from Durham University recorded and analysed almost 5,000 orangutan "kiss squeaks".
He found that the animals combined these purse-lipped, "consonant-like" calls to convey different messages.
This could be a glimpse of how our ancestors formed the earliest words.
The findings are published in the journal Nature Human Behaviour.
"Human language is extraordinarily advanced and complex - we can pretty much transmit any information we want into sound," said Dr Reis e Lameira.
"So we tend to think that maybe words evolved from some rudimentary precursor to transmit more complex messages.
"We were basically using the orangutan vocal behaviour as a time machine - back to a time when our ancestors were using what would become [those precursors] of consonants and vowels."