Introduction

In the Tari basin in the Papua New Guinea Highlands, where the Huli-speaking people live, food security has been a major concern for several decades. Population density has reached 400 persons/km² around the administrative center, and soil erosion and environmental degradation have been observed in the surrounding mountainous areas at higher altitudes (Wood 1985). A previous study by the authors of the present article revealed that the ability to cope with climatic perturbation has decreased in mountainous areas over time, whereas intergroup disputes regarding land tenure inhibited the expansion of garden areas in the swamp (Umezaki et al 1999, 2000).

In 1952 the airstrip and an administrative station were constructed in the central part of the Tari basin. Since then, intrabasin disparities in the level of modernization have increased. In the Huli society an individual belongs to several communities and often moves from one community to another during his or her lifetime (Glasse 1968). Migration may thus be one of the important factors that govern the spatial distribution of the population. The Huli people claim that migrations to the central part of the basin have become prevalent since the establishment of the administrative and commercial center in Tari, which has led to overpopulation in the area around the center. They also maintain that the resulting overpopulation prevents the younger generations from having gardens in the villages around the Tari airstrip, and they are now seeking gardens in mountainous areas at higher altitudes. Quantitative investigation of such migration patterns is indispensable to ensure sustainability of the Tari basin in future.

In practice, however, reconstruction of past migration patterns is difficult. Written records for vital statistics before 1980 are not available, and the people do not remember the years in which events occurred. The only available data for the past are the genealogical relationships reported by the people. The present study used genealogical charts to reconstruct past migration patterns and changes in these patterns over time. Medium-term (between 1980 and 1995) and short-term (between 1993 and 1995) migration patterns were also investigated to enhance understanding of migration in the Tari basin.

The study area

Methodology

Data were collected during fieldwork in August 1993–November 1993, September 1994–February 1995, and July 1998–September 1998. Migration patterns were investigated at 3 levels: short term, medium term, and long term.

For the short-term investigation, monthly movements for all households—22 in Heli and 43 in Wenani—were monitored for a period of 18 months, from August 1993 to January 1995.

For the medium-term investigation, a demographic database in the Papua New Guinea Institute of Medical Research that recorded vital events between 1978 and 1997 (Lehmann et al 1997) was consulted to investigate demographic changes, particularly migration to and from Heli and Wenani between 1980 and 1995. In addition, aerial photographs taken in 1978 (Mapmakers color aerial photographs, scale 1:9500, Tari area, runs 10 and 11, November 1978; available at National Mapping Bureau, Port Moresby, Papua New Guinea) were used to identify the houses in Heli or Wenani at the time. The names of people who resided in the houses in 1978 and vital events since then were recorded. The construction of a highway from the provincial capital of Mendi to Tari in 1978—a well-remembered event—helped people to remember who inhabited the area at that time. A database containing demographic and interview data was cross-checked to compile the final list of inhabitants in Heli and Wenani in 1980 and vital events between 1980 and 1995. For comparison, the population in 1995 was defined as all people who had houses in Heli and Wenani in November 1995, except those who did not use their houses for more than 6 months.

Finally, for the long-term investigation of migration, genealogical charts were reconstructed. All married persons under 60 years of age who had gardens in either of the 2 hameiginis in 1995 (including those who did not inhabit them) were identified and categorized as members of generation 3 (hereafter referred to as G3). In cases where there were more than 2 such persons in 1 family, the youngest was defined as G3. The second, full series of genealogical charts involving 2 generations previous to G3 individuals were reconstructed. The ascendants who were grandparents and parents of the members of G3 were categorized as G1 and G2, respectively, whereas children and grandchildren of the members of G3 were categorized as G4 and G5. All siblings of parents and their descendants were recorded and categorized appropriately (from G2 to G5). The individuals listed in our genealogical charts are potential members of each hameigini.

The genealogical charts contain 942 individuals in Wenani and 734 in Heli (Table 1); the individuals whose sex could not be identified (mostly newborn babies who lived outside the Tari basin) numbered 21 in Wenani and 28 in Heli. Of the remaining 921 and 706 individuals in Wenani and Heli, 82.3% and 79.7%, respectively, were alive in 1995, whereas the percentages were lower in the older generations. When an individual's places of birth and death or residence belonged to different zones in Figure 1, he or she was defined as having migrated.

Results

Figure 2 shows household movements during the 18-month period between 1993 and 1995. Of the 22 households in Heli, 8 had only 1 house (referred to here as a “unilocal household”), whereas 14 had 1 house in Heli and another outside (designated as a “multilocal household”). During the period between August 1993 and January 1995, 13 of the 14 multilocal households actually moved from the house in Heli to other houses and vice versa. Five households had 5–12 months of back-and-forth periods, during which they used the houses and gardens in Heli and another hameigini simultaneously. In Wenani, by contrast, all households were unilocal. But 6 households visited and remained in the houses of relatives in the other hameiginis for several months. They did so to escape from troubles such as disputes over land tenure, suspicion of stealing garden crops or domesticated animals, or quarrels with neighbors. The people reported that the number of such troubles increased as the population density increased; in 1995, rights to cultivation of 63% of the swamp area (potentially arable land) were disputed (Umezaki et al 2000).

Table 2 shows the demographic change in Heli and Wenani between 1980 and 1995. Population increased in both communities: from 57 to 81 in Heli and from 103 to 154 in Wenani; the annual rates of population increase were 2.1% and 2.5%, respectively. Of the increases between 1980 and 1995, 24 in Heli and 51 in Wenani, 46% and 80%, respectively, were due to natural increase. In other words, 54% of the population increase in Heli and 20% in Wenani can be explained by migrations from other communities. Total movements (the sum of in-migrations and out-migrations) were 89 in Heli and 92 in Wenani, despite the fact that the population of Wenani was almost double that of Heli. Migrations were more frequent in Heli than in Wenani. Of the total population in Heli (81) and Wenani (154) in 1995, only 13% of those in the former and 35% of those in the latter also were present in 1980. In summary, the demographic data between 1980 and 1995 indicate that (1) the population increased rapidly in both communities, and (2) frequent migrations are the most important determinant of population size, especially in Heli.

Table 3 shows the places of birth, residence, and death for all the individuals listed in the genealogical charts. For the Wenani people these places were mostly limited to 3 zones in the Tari basin (C, E, and F), especially zone E, where 74% of the Wenani people were born, 64% lived, and 77% died; few individuals used zones A, B, and D during their lifetimes. Of 768 individuals in Wenani whose places of residence were known, 129 lived outside the Tari basin (mostly Port Moresby, Mendi, and Mount Hagen), implying that the proportion of urban migrants was 16.8% in Wenani. Similarly, the Heli people mostly used the 3 zones (A, B, and C) during their lifetimes. Of the 583 individuals in Heli, 72 lived outside the Tari basin.

For the Heli, marriage with neighboring groups (eg, the Duna in the Southern Highland province and the Ipili in Enga province) has been common (Biersack 1995). Thus, the individuals who stayed outside the Tari basin included both urban migrants and those who married in adjacent areas. The proportion of urban migrants was lower in Heli than in Wenani.

In Table 4, intra-Tari basin migration patterns for the Wenani and Heli people are examined by generation. In Heli, 132 individuals moved across a zone (19% of the total population), whereas 87 (9% of the total) did so in Wenani. The percentage of migrants in the total population was higher in older generations than in the younger generations (in Heli, G1 + G2, 25%; G3, 21%; G4 + G5, 12%; in Wenani, G1 + G2, 15%; G3, 14%; G4 + G5, 5%). This simply reflects the fact that the individuals in the younger generations have not yet moved because they are too young. Also, because the genealogical charts included individuals at various stages in life from newborn babies to the dead, the movements in older generations were defined according to the place of birth and the residence in old age, whereas in younger generations they tended to be defined by comparison between the places of birth and residence at a younger age.

Yet, it is also true that on average, movements among older generations occurred many years before the study, compared with the movements among the younger generations. Thus, the direction of the movements of the older generations tended to reflect migration decisions made in the past, whereas those of the younger generations are related to recent decisions. Table 4 shows that in either hameigini, movement from remote to central parts of the Tari basin exceeded that in the opposite direction for individuals in the older generations, and migrations from the central to the remote parts of the basin tended to predominate among the younger generations. The balance (“toward center” movements minus “toward remote areas” movements) was 7 for G1 + G2, 28 for G3, and −9 for G4 + G5 in Heli, and 4 for G1 + G2, 19 for G3, and −10 for G4 + G5 in Wenani.

Discussion

One drawback of our genealogy-based method is that migration is defined on the basis of a comparison of the place of birth and the place of residence or death. Thus, migration is only a snapshot of where people are at the time of survey, and the migration histories of younger people may be incomplete. The finding that migration flows in opposite directions between the older and younger generations can be interpreted in either of 2 ways:

In Huli society, infants, small children, and adolescent females usually live and move with their mother. Thus, the mother makes the decision about migration. Adolescent males leave their mother's house to live in a “men's house” and often wish to move to urbanized areas, preferably Port Moresby. Marriage is the event that most likely triggers migration across environmental zones. In a cognatic descent system, theoretically the number of hameiginis with which an individual affiliates genealogically is 2ⁿ, where n is the number of generations from the individual to the founder of his or her lineage. For example, the Wenani people, whose founder is around 10 generations back from the present, can be members of 2¹⁰ (=1024) hameiginis. In practice, however, most affiliations are not recognized. Those with neighboring hameiginis are the best recognized, and hence people must usually find a spouse in a remote place, that is from a hameigini in different environmental zones. After marriage, a change of residence can take 2 forms: movement within an ecological zone involving multilocal households and cross-ecological zone movement on a semipermanent basis, triggered by tribal fighting, climatic perturbation, and other causes. Moves across the environmental zones were not prevalent among old people.

Here, the point is whether the direction of the migration flows also changed in accordance with stages in an individual's life, thus explaining the findings in Table 4. But our interview surveys suggested that it is the younger generations who prefer to move to urbanized central areas. Also, the motivation to move toward thinly populated mountainous areas, where it existed, was relatively stronger among older people because the demand for land was larger in the postmarital period when compared with the premarital period, and it increased as the number of children increased.

On the other hand, with regard to the possibility of changing migration patterns over time, the following explanations are possible. If the migration patterns of the Wenani and Heli changed over time, migrations to the central parts predominated in the past, whereas flows in the opposite direction have prevailed recently. In the present study, G3 was defined to include married individuals less than 60 years of age in 1995; their birth years are expected to range between 1935 and 1975 (when the marital age is 20 years). Assuming that the intergeneration interval is 25 years, G2 and G1 are expected to have been born between 1905 and 1950, and 1880 and 1925, respectively. Similarly, G4 may have been born after 1960 and G5 after 1985. Although the genealogical category and actual age do not necessarily correlate, it is also true as a general tendency that G1 and G2 individuals spent most of their active years around the time of the initial period of modernization since 1952 (when the Tari township was established). Among G3, G4, and G5, the younger the generation, the higher the population density in the Tari basin and the larger the intrabasin disparities in the extent of modernization because population increase and rural development since 1952 have progressed in a linear fashion. It is plausible that individuals in G1 and G2 tended to move toward the center in search of cash or modernized lifestyles. It is also true that the central part of the basin was overpopulated and the younger generation could not cultivate gardens large enough for survival. The authors' fieldwork in Kikida hameigini (located in the administrative center; see Figure 1) in 1998 revealed that the per capita garden size was less than half that in Wenani or Heli (unpublished data). A gold rush from the end of the 1980s to the beginning of the 1990s may also have induced migrations from the central parts toward the north among the Heli people.

Migration flows from the surrounding areas toward the central parts of the Tari basin have already been pointed out by Wood (1985) and Allen (1995). They suggested that the migrations are taking place in response to degradation of garden soils in the surrounding parts and to greater economic opportunities in the central parts. The migration patterns among the older generations in the present study may be consistent with such statements. Migrations toward remote areas by the younger generations may be a relatively recent phenomenon caused by overpopulation in the central part of the Tari basin.

Intrapopulation migration is one of the key factors in food security in high-density residential areas. Density-dependent migration has been reported in many historical populations (Relethford 1986); migrations from overpopulated areas to thinly populated areas may have sustained food security in the places of origin. In contrast, people often move regardless of the population density of destinations in modernized human populations (Ohtsuka et al 1985). Access to a cash economy, modernized lifestyles, and transportation can be powerful pull factors for migrants (Lee 1966). Migration to overpopulated areas will impair the food security of the destinations; depressed food security is often observed in the neighborhoods of urbanized areas to which many people have moved from rural areas (Joumard 1993). In this respect, intrapopulation migration in the Huli may have diminished food security around the administrative center and some people have responded to this by migrating to thinly populated remote areas. Under the dynamic changes of human–environment relationships in the basin, the Huli's flexible systems of migration and land use may have operated to ensure survival. This example illustrates that indigenous social organization has merits for the sustainability of this mountain region. Further studies with a larger sample size would be needed to reach clearer conclusions about migration patterns in the Tari basin, as well as in other densely populated areas.