The indigenous population of Papua New Guinea is one of the most heterogeneous in the world. Papua New Guinea has several thousand separate communities, most with only a few hundred people. Divided by language, customs, and tradition, some of these communities have engaged in tribal warfare with their neighbors for centuries.

The isolation created by the mountainous terrain is so great that some groups, until recently, were unaware of the existence of neighboring groups only a few kilometers away. The diversity, reflected in a folk saying, "For each village, a different culture," is perhaps best shown in the local languages. Spoken mainly on the island of New Guinea--composed of Papua New Guinea and the Indonesian province of West Papua--about 650 of these languages have been identified; of these, only 350-450 are related. The remainder seem to be totally unrelated either to each other or to the other major groupings. Native languages are spoken by a few hundred to a few thousand, although Enga, used in Enga Province, is spoken by some 130,000 people. Most native languages are extremely complex grammatically.

Melanesian Pidgin serves as the lingua franca. English is spoken by educated people and in Milne Bay Province.

The overall population density is low, although pockets of overpopulation exist. Papua New Guinea's Western Province averages one person per square kilometer (3 per sq. mi.). The Chimbu Province in the New Guinea highlands averages 20 persons per square kilometer (60 per sq. mi.) and has areas containing up to 200 people farming a square kilometer of land. The highlands have 40% of the population.

A considerable urban drift toward Port Moresby and other major centers has occurred in recent years. Between 1978 and 1988, Port Moresby grew nearly 8% per year, Lae 6%, Mount Haven 6.5%, Goroka 4%, and Madang 3%. The trend toward urbanization accelerated in the 1990s, bringing in its wake squatter settlements, unemployment, and attendant social problems.

Almost two-thirds of the population is Christian. Of these, more than 700,000 are Catholic, more than 500,000 Lutheran, and the balance are members of other Protestant denominations. Although the major churches are under indigenous leadership, a large number of missionaries remain in the country. The bulk of the estimated 2,500 Americans resident in Papua New Guinea are missionaries and their families. The non-Christian portion of the indigenous population practices a wide variety of religions that are an integral part of traditional culture, mainly animism (spirit worship) and ancestor cults.

Foreign residents are just over 1% of the population. More than half are Australian; others are from the United Kingdom, New Zealand, the Philippines, and the United States, most of whom are missionaries. Since independence, about 900 foreigners have become naturalized citizens.

The traditional Papua New Guinea social structure includes the following characteristics:

• The practice of subsistence economy;
  
• Recognition of bonds of kinship with obligations extending beyond the immediate family group;
  
• Generally egalitarian relationships with an emphasis on acquired, rather than inherited, status; and
  
• A strong attachment of the people to land.

Most Papua New Guineans still adhere strongly to this traditional social structure, which has its roots in village life.