My first inkling of cultural primatology came in January, 1975, when Caroline Tutin and I went to the Mahale Mountains of western Tanzania. At that point, I had 15 months of field experience studying the wild chimpanzees of Gombe and thought I knew the species. On the first day out at Kasoje, this was proven wrong. We saw the chimpanzees of K-group doing the grooming hand-clasp, something neither we nor anyone else had ever seen at Gombe, in thousands of hours of observation (see Figure 1.1). We were dumbfounded by its elegant symmetry. However, upon returning to camp, when we mentioned the discovery to our host, Professor Junichiro Itani, he was unimpressed. Did not all chimpanzees do this?

At that point, I realised that there was no such creature as The Chimpanzee, if by that was meant behavioural uniformity across the species Pan troglodytes. Instead, there was behavioural diversity across chimpanzees, apparently at the level of populations. So, how to explain this variation? This book describes my attempts to answer that question, and many other related ones, over the last 25 years.

As an ethologist, I knew about within-species variation in animal behaviour. One of my fellow postgraduate students at Oxford, Michael Norton-Griffiths, had done elegant cross-fostering experiments on oystercatchers, showing that parental foraging and foodprocessing techniques were passed on from parent to offspring (Norton-Griffiths, 1967).