I have maintained an interest in the sphere of human intelligence and language since the later half of the 1980s, however this topic became very important to my research after I concluded that the ability to ask questions was the defining factor for the origins of human intelligence and language. The idea came to me at the end of 1996, very soon after my arrival to Australia, during intensive research at multiple university libraries in Melbourne.
For me the origins of human intelligence and language are closely interrelated, that’s why they are treated together. Articulated speech is a very different and much later phenomenon.
The title of the 2006 book Who Asked the First Question? highlights this topic – the defining moment of the evolution of human intelligence and language. You can read the following text on this subject:"Singing, Questioning, Thinking, Talking, Stuttering"
Roughly the same text, but somewhat shorter and more comprehensive, is in my 2011 book Why Do People Sing? Chapter four: "Singing and Thinking".