Scientists are claiming that the whispers of gibbons could be the key to understanding the evolution of human speech.

Scientists have discovered that the apes use sophisticated communications with a range of over 450 unique calls to speak with their fellow gibbons. According to Durham University's Esther Clarke, lead author of the study, the discovery suggests that animals could be talking to one another in a language that is more precise than previously believed.

Clarke's research has shown that gibbons create different kinds of their "hoo" calls, which are low-volume sounds compared to their "song" calls that are more melodic.

The call categories allow gibbons to determine if other gibbons are searching for food and to alert or warn them about dangers such as predators and faraway noises.

Clarke also found that the different categories of "hoo" calls could even be further broken down, which makes the communication of gibbons more specific.

The research found that warnings about lurking birds, for example, are different compared to warnings about leopards and pythons. The warning calls for birds have low frequencies so that the birds will not hear them. Warning calls about leopards and tigers, however, are similar, as they are both big cats.

Clarke revealed that she initially aimed to study the songs that made gibbons so popular. While located in a forest in Thailand, however, she started to notice the unique patterns and variations of gibbon sounds, leading to the discovery that could have implications on the understanding of all animals.

The "hoo" calls of gibbons were initially identified back in the 1940s, but because of the low volumes that make the calls almost indistinguishable to humans, they have gone unanalyzed for so long. The whispering calls of gibbons are also very hard to decipher.

"These animals are extraordinary vocal creatures and give us the rare opportunity to study the evolution of complex vocal communication in a non-human primate," said Clarke, adding that the vocalizations of gibbons could lead to a significant understanding of vocal communication processes. Because they are apes, their own methods of communication could offer the best chance at understanding the evolution of human communication.

The researchers were in the forests of Thailand for four months, coming back with recordings that contained over 450 sounds of "hoo" calls. A computer analysis of the sounds found connections between the calls and the context wherein they were reported to be recorded.

Clarke's research was published in the BMC Evolutionary Biology journal.

Photo: Benjamin Radzun | Flickr