Step-by-step explanation:
1. The researchers had preconceived ideas about what life would be like in New Guinea, and their ideas were wrong.
A. "There was no unified, hierarchic society.... There was no common tongue, but rather a multiplicity of several languages."
2. People in the highlands were sheltered from the outside world by the difficulty of travel.
A. "The populations of the highland valleys were splintered into thousands of tiny, isolated enclaves, ..."
B. "... it was the presence of these enemies that determined the pattern of life and made freedom of movement, and therefore, wide-ranging travel, impossible..."
3. People in the highlands were isolated from the outside world by a restriction on information.
A. "But by this time information about the origin of the goods was lost...."
B. "... a multiplicity of separate languages.... effectively prevented any free flow of information from the outside
in, and the inside out."