One might curiously ask, ‘Why on earth have you continued to conduct research for so long?’ The best possible answer I could muster would be: ‘Because every single thing about the chimpanzee fascinates me.’ Their behaviour is so rich in variety that no matter how many years I watch them, I never grow bored.

To truly get to know their behaviour inside and out, 45 years of research is hardly enough; prolonged observation is necessary. One of the merits of long-term research is that we can acquire heaps of demographic data. It is now clear that an individual chimpanzee’s life span is over 50 years, but the span of my research has just reached 45 years, thus making it difficult to come up with comprehensive answers. Much more research is required, because the population we are studying is so small: finding answers without data that cover large numbers of individuals takes years of research.