> ...some monkey dialects can be just as sophisticated as human language.
These kinds of throw-away claims are a form of perennial nonsense. Nothing in the article suggests anything close to this being true. He looks at the shades of meaning of three sounds and yet asserts a similar sophistication to human speech.
It's a regular meme in animal articles that this group (monkeys here, other times dolphins or whales) have language skills that rival humans. It's a kind of warm fuzzy feel-good claim asserted regularly despite supporting evidence.