article_snippet.sent: Dr Esther Clarke, who led the research at the University of Durham, said the findings could also help to provide valuable clues about human speech evolved and perhaps even why humans began using whispers.
article_snippet.sent: The researchers say the study is of direct relevance for the on-going debate about the evolution of human speech.
article_snippet.sent: Researchers say the findings could shed light on the evolution of human speech and why we began whispering .