Here's why:
* Brain size: Australopithecus had significantly smaller brains than modern humans, which are essential for complex language processing.
* Vocal anatomy: While some evidence suggests they may have had the ability to produce some sounds, their vocal anatomy wasn't as developed as modern humans. They likely lacked the necessary structures for complex speech.
* Lack of symbolic communication: There's no archaeological evidence suggesting they used symbolic communication, which is a cornerstone of language development.
While Australopithecus may have used some form of rudimentary communication, it's highly unlikely they possessed anything comparable to human language.
It's important to remember that our understanding of their communication abilities is constantly evolving as new research emerges.