Misleading Title
This Register article is badly titled and their use of the term 'missing link' is extremely misleading. 'Missing link' in evolutionary terms suggests some species that shares a common ancestor with humans and monkeys, of which there are already plenty.
The original research article that reports these findings does not use the term nor does it claim that these monkeys are ancestors of humans. It is merely describing a behaviour in these primates that may explain how human language evolved.