In pre-colonial times, the Asmat and many other Papuan tribes were headhunters. Since the arrival of the Europeans in the late 19th century, the latter have expended much effort to eradicate this violent tradition. Yet even today, some elders still mourn the „good old days“. One of them make the point in the film by saying that "formerly, the Asmat were headhunters, today, they are... nothing".
Headhunting (in modern eyes) may be immoral and horrible but it was nothing of the sort to many ancient tribal people. It was the ever-present threat from outside raiders that kept a tribe together, united and disciplined. From the tribal leaders’ point of view, headhunting would have had to be invented if it did not already exist and modern morality is irrelevant in this context. Headhunting is an old and very widespread human tradition that might even be older than humanity itself. It does seem that human societies need an outside threat (such as an enemy) to stick together. Food for thought, indeed!