One of the most interesting investigations I have recently come across is the decipherment of the hoo sounds produced by gibbons. Gibbons are apes that live mainly in Southeast Asia. They are known for their loud songs but they can produce also a kind of whispers known as “hoo calls”. Hoo calls are difficult to distinguish by the human ear but recently a group of researchers succeeded to record and analyse them by using modern computer technology. The gibbons investigated were groups of lar gibbons in North-eastern Thailand. They were followed during four months from the morning till the evening. The sounds were recorded and the researchers noted the event that elicited the response. Back home they managed to distinguish and analyse the “gibbonish”and to relate the hoo-calls to the events that had elicited them with advanced computer techniques, so that it was no longer gibberish for them.
The results are surprising and important. The researchers could identify more than 450 hoo sounds and connect them with the situations in which they were uttered. In this way they found that – and now I quote from an article in the Science Daily (see below) – “distinct hoo calls are made in response to specific events, such as foraging and encountering neighbours, and that subtle differences even distinguish between different predators when used as a warning.” For instance, the gibbons are able to warn their companions for tigers and leopards with a sound meaning something like “big cat”. They use different other hoos for specified other predators (like snakes and eagles). They can also mobilize other gibbons for going to look for food together. They have hoo calls for meeting together, greetings, delimiting their territory etc.
As the researchers say, this study is very relevant in the debate on the evolution of human speech, seen as an ability to produce context-specific sounds for communicating meanings to other recipients. But if gibbons have a kind of speech – and so it seems – I have a question: Is a gibbon a sort of human being? If we follow Aristotle the answer will be “yes”, for in the Politica (Book One, Part II) he says that man is the only animal whom nature has endowed with the gift of speech. In order to show that a gibbon is a man, let me formulate a syllogism in the sense of Aristotle:
All gibbons are endowed with the gift of speech
Only man is endowed with the gift of speech
So gibbons are men
I think that there are good reasons not to accept the conclusion, but then one of the premises must be false. As it looks now most likely the second premise (minor) is. But does it make a difference whether or not a gibbon is a sort of man? Look around: Sometimes we get the impression that men behave “like animals”. Actually this expression is an insult to the animals. What a mesh we, men, have made of this world. One of the best developed techniques of human behaviour is waging war. We are more and more destroying our own environment in that way that it can lead to the end of human civilization in the long run. And before this will happen probably we’ll have destroyed already the life world of the gibbons, because we’ll have irretrievably damaged their forest habitat. Then not only another precious species will have become extinct but also a unique language will have gone, and with it we’ll have lost a part of our own cultural heritage.