Human Adaptation and Plant Use in Highland New Guinea 49,000 to 44,000 Years Ago

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Science  01 Oct 2010:
Vol. 330, Issue 6000, pp. 78-81
DOI: 10.1126/science.1193130


After their emergence by 200,000 years before the present in Africa, modern humans colonized the globe, reaching Australia and New Guinea by 40,000 to 50,000 years ago. Understanding how humans lived and adapted to the range of environments in these areas has been difficult because well-preserved settlements are scarce. Data from the New Guinea Highlands (at an elevation of ~2000 meters) demonstrate the exploitation of the endemic nut Pandanus and yams in archaeological sites dated to 49,000 to 36,000 years ago, which are among the oldest human sites in this region. The sites also contain stone tools thought to be used to remove trees, which suggests that the early inhabitants cleared forest patches to promote the growth of useful plants.

Sahul, the single Pleistocene continent linking New Guinea, Australia, and Tasmania, is thought to have been colonized by humans some time after 50,000 years ago (1). Reaching Sahul required crossing water from Southeast Asia. Most early sites in New Guinea have been found along the coastal margins (Fig. 1, inset; fig S1; and table S2). An exception first documented in the 1960s is an open site [Papua New Guinea (PNG) National Museum site code AER] in the Ivane Valley of the New Guinea Highlands, where excavations at the Kosipe Mission recovered stone artefacts including waisted tools dated then to 26,870 ± 590 14C years before the present (radiocarbon lab no. ANU-191) (calibrated to 30,350 to 32,580 years ago) (2). Kosipe Mission is located at ~2000 m above sea level, on the spur of a hill overlooking a large swamp (Fig. 1). Further excavations in 2005 (3) extended known occupation there to 41,000 to 38,000 years ago (table S1). A carbonized kernel of a pandanus nut was recovered in the 36,000- to 34,000-year-old levels.

Fig. 1

Map of the Ivane valley with archaeological sites. Seven new late Pleistocene occupation sites were identified. Five are situated on spurs above the valley floor, ranging in altitude from 2020 to 1940 m: Joe’s Garden, South Kov, Airport Mound, Kerapa, and Vilakuav. Two sites were located on the western valley floor: Piari’s Ditch and Nineve.

Subsequent fieldwork in 2007 and 2008 has identified late Pleistocene to Holocene occupation at seven additional locations across the Ivane Valley, with the earliest site dating to between 49,000 and 43,000 calibrated years before the present (table S1). Here we describe the evidence for early occupation of these sites and the subsistence strategies employed by these early colonists.

Sediments in the Ivane valley are dominated by a series of volcanic tephras that are probably derived from Mount Lamington some 140 km to the southeast. All eight highland sites have a basic set of five identified layers: a dark brown topsoil (layer 1), a brown-orange clay (layer 2); a black-brown soil (layers 3a and 3b), and a gray soil (layer 4). These occupation layers overlay culturally sterile orange clay (layer 5). Layer 3 is separated into two distinct units (a and b) at Vilakuav (2), representing separate ash falls. We subsequently identified these two layers (3a and 3b) in most sites. At Vilakuav, Joe’s Garden, and Kosipe Mission, they are separated by a thin band of charcoal (fig. S2). Accelerator mass spectrometry dates were derived from charcoal collected in situ. We use the calibrated dates (4) in our discussion. All dates from Joe’s Garden, Vilakuav, South Kov, and Airport Mound are presented here for the first time.

The earliest dates for occupation of the valley are at Vilakuav, between 49,000 and 43,000 years ago; and three sites (Vilakuav, South Kov, and Airport Mound) contain artefacts that yield calibrated 14C dates earlier than 42,500 years ago, at 95.4% confidence levels. Occupation at the Kosipe Mission site is dated to 41,400 to 38,000 years ago, again at a 95.4% confidence level. Layer 3b shows occupation from 38,500 to 30,000 years ago, and layer 3a dates from 30,000 to 26,000 years ago. Layer 2 dates to the Holocene (table S1).

Our radiocarbon ages are some of the oldest dates for any Sahul site (table S2), excluding several contentious 20-year-old claims in Australia (1). Together with indirectly dated artefacts from Bobongara on the Huon Peninsula, the oldest occupational layers at the highland sites of Vilakuav, Airport Mound, and South Kov are older than any other known sites in New Guinea or Island Melanesia.

All highland sites lack evidence of any occupation during the Last Glacial Maximum (LGM). The mean temperature of the coldest month at Kosipe at the LGM has been estimated to have been between 6.3° to 9.2°C colder than today (5, 6). The climates before the LGM would also have been cooler than those today. Layers 4 and 3b from the Ivane Valley correspond to marine isotope stage (MIS) 3, whereas layer 3a corresponds with the shift to much colder conditions from MIS 3 to MIS 2 (7). Other palynological evidence from the Ivane Valley (6) also indicates that the tree line was lower during the deposition of layers 4 and 3 and that the vegetation zones were compressed downward during the earliest occupation, which is consistent with a colder climate.

Stone artefacts were recovered from the earliest levels (layer 4) of Kosipe Mission, Airstrip Mound, South Kov, and Vilakuav (Fig. 2). Artefacts are made from a diverse range of raw materials, including basalt, schist, baked siliceous metasediment, dolerite, metabasalt, and quartz. Of these, baked siliceous sediment is the only rock type not found in the Ivane Valley. Samples of this rock were obtained along the Kosipe-Woitape track above Woitape, ~20 km distant. It is valuable for making tools because it flakes easily yet is hard.

Fig. 2

Ivane Valley late Pleistocene stone tools. (A and B) Airstrip Mound (PNG National Museum site code AAXD) from layer 4. (C) Joe’s Garden (AAXC) from layer 3b. (D and E) South Kov (AAXEs) from layer 4. Scale bars are in centimeters.

Two waisted stone artefacts made from schist and metabasalt were found from layer 4 at South Kov and one from layer 4 at Airstrip Mound (Fig. 2 and fig. S3). This distinctive artefact type was also found in layer 3a at South Kov and in layer 3b at Joe’s Garden (Fig. 2 and fig. S4) and Vilakuav, but disappears before the LGM. Frequently referred to as waisted axes, they also occur in several other Pleistocene highland and lowland sites of the New Guinea mainland. Waisted axes have been seen as implements used to modify forest environments by opening up patches to sunlight to promote the growth of food and other useful plants (8). In the Ivane Valley, other Pleistocene stone artefacts include flaked artefacts, tool blanks, axe-like bifacially flaked implements, and flaking debris. An expanded range of stone artefacts occurs in the Holocene layers at all other sites except for Airstrip Mound.

Onsite stone artefact manufacture at all sites is indicated by the presence of cores and manufacturing debris and the use of local raw materials. River cobble cortex on both igneous and metamorphic artefacts suggests that local waterways were the primary source of raw material. The stone assemblage is consistent with finds from Bobongara, the only other mainland late Pleistocene assemblage older than 35,000 years. At this site, waisted artefacts were recovered below tephra 2 which dates to 38,000 ± 600 years by thermoluminescence (TL) dating (9), although the excavators argue for an estimate of 40,000 years or more, based on high moisture levels affecting the TL readings.

Abundant starch grains were extracted from several of the stone artefacts from layer 3a at Joe’s Garden and layer 4 at the South Kov site (table S2). Several of these were consistent with starch from yams, specifically Dioscorea species. The size and morphology of the tuber-like starch grains (figs. S5 and S6) from the Joe’s Garden samples were consistent with Dioscorea alata (Fig. 3) comparative reference material. The sample sizes of the yam starch grains from both South Kov artefacts were smaller (n = 7 and n = 8 grains), although two starch grains exceeded 40 μm in size. The shape and surface features of these starches are unlike that of D. bulbifera but broadly similar to those of D. alata (fig. S6C) and/or D. pentaphylla (fig. S6D). There is no clear sculpting of the hilum end of the grain in fig. S6C or S6D, as seen in most grains from D. pentaphylla. However, this feature is not present in all D. pentaphylla grains, and therefore we cannot exclude a contribution from this species.

Fig. 3

Box plots of the maximum dimensions of starch grains through the hilum in micrometers. The box includes 50% of the population, and the horizontal line represents the median value. The tuber grains presented from each archaeological preparation are only a small portion of the total counts from each artefact. The K-JG-I3 sample matches entirely with the D. alata sample. For the K-SKR-AI4 sample, the variation in grain length indicates that it is likely to represent more than one type of yam. The third artefact, K-SKR-AA3, comprises only seven grains, and these overlap with all samples except the D. esculenta sample.

Charred Pandanus nutshells were identified in Kosipe Mission layer 3, layers 3 and 4 from Joe’s Garden, and all layers from South Kov and Vilakuav. All specimens, including fragments, were from single-seeded species of highland Pandanus in the section Karuka (10), which contain nutritious seeds. Morphometric analysis confirmed that complete specimens from South Kov layers 3 and 4 were not from the economically important Pandanus brosimos or P. julianettii, being most similar to an unclassified foraged wild species known as Taip (see supporting online material). A human source for the archaeological remains is indicated by (i) a close repeated association with charcoal, bone fragments, and tools and (ii) the absence of rodent/cuscus gnaw marks on the seeds. The absence of nuts from some sites and layers may indicate variability in activity areas across the landscape. Pandanus was absent at the Airport Mound site and in samples from the swamp sections taken for palynological analysis (6).

The preservation of food plant species in open sites of this age is remarkable, and the analysis confirms that Pandanus and yams were used for subsistence in this valley from the time that the earliest colonists arrived. Although Pandanus would have grown abundantly in the local environment, yams would have been found at lower altitudes, indicating that gathering territories included lower altitudinal zones beyond the Ivane Valley. The gathering of food plants was accompanied by hunting of small animals. Burnt highly fragmented bone was recovered from the lowest levels at Vilakuav (1.1 g from layer 4 and 0.3 g from layer 3b), although it has been impossible to identify the species hunted. The acidic soil ensures that only the highly fragmented burnt bone survives. Although we have little evidence for the nature of hunted animals in the Ivane Valley diet, the range of potential high-altitude game in New Guinea is wide and well documented from later Highlands sites farther to the west (11).

The nature of human impact on the local environment is difficult to assess. In the Ivane Valley, Hope (6) noted an increase in microscopic charcoal between 41,000 and 38,000 calibrated years before the present, soon after the Kosipe Zone-2 stage (KOS-2) (at 42,000 years ago). Hope argued that the early humans burned the wet montane vegetation. The activities of people were probably a contributing factor to the physical changes to the Ivane basin. The base of layer 4 is indicative of the presence of a swampy lake (Hope’s KOS-4 phase), which slowly developed into a peat swamp that extended to the south by the time of occupation in layer 3b (6). A human presence, increased fire, and changes in the lake hydrology are likely to be related.

Our data show that people occupied a New Guinea valley at 2000 m above sea level soon after their arrival in Sahul (1). As the climate cooled, the optimal growing conditions for yams would have occurred at lower altitudes. This may indicate that Pandanus was the most important staple at this time and help explain the late Pleistocene abandonment of the highland sites. Foraging into this high-altitude environment would guarantee a high return in plant fat and protein to complement local animal foods, the starch-rich yams from lower altitudes, and those foods not preserved in the archaeological record.

Supporting Online Material

SOM Text

Figs. S1 to S9

Tables S1 to S3


References and Notes

  1. This research was supported by the Marsden Fund Council from government funding administered by the Royal Society of New Zealand. We thank G. Hope for introducing us to the Ivane Valley and companionship in the field; the communities of the Ivane Valley for their support; and the National Research Institute of PNG and the National Museum and Art Gallery of PNG for their support and affiliation. The authors acknowledge the facilities as well as scientific and technical assistance from the staff at the Australian Microscopy and Microanalysis Research Facility and the Australian Centre for Microscopy and Microanalysis at the University of Sydney. We thank L. O’Neill and M. Hennessey for the illustrations and J. Allen and M. Weisler for providing comments on a draft of the paper. J.F. thanks R. Torrence for access to the Australian Museum PNG starch reference collection. R.F. is indebted to the Australian Museum and the University of Sydney for facilitating the import of quarantined material and access to laboratory space.

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