The Iatmul are a large ethnic group of about 10,000 people inhabiting some two-dozen politically autonomous villages along the middle Sepik River in Papua New Guinea. The communities are roughly grouped according to dialect of the Iatmul language as well as sociocultural affinities. The Iatmul are best known for their art, men's houses, male initiation, elaborate totemic systems, and a famous ritual called naven, first studied by Gregory Bateson in the 1930s. More recently, Iatmul are known as a location for tourists and adventure travellers, and a prominent role in the 1988 documentary film Cannibal Tours.