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RESEARCH ARTICLE

Phase 3 is composed of sequential ditch networks that articulate with major drainage channels, and an earlier curvilinear feature has also been included in this phase (Fig. 2D). The earliest ditch networks are rectilinear, similarly aligned, and contain similar fill types. These early ditch networks date to 4350 to 3980 cal yr B.P. and pre-date R ash [dated to 3980 to 3630 cal yr B.P. (tables S1 and S2)]. Late ditch networks are older than 3260 to 2800 cal yr B.P. and the deposition of an overlying tephra, Y ash.

Younger ditches form more complex net- works that exhibit dendritic, rectilinear, and tri- angular arrangements. Major drainage channels articulate with both early and late networks; for example, channel 107 pre-dates the deposition of a diagnostic tephra (R ash) and articulates with two ditches of the early subphase and one ditch of the late subphase (Fig. 2D). The inno- vation of ditching indicates a further refinement

of, and reliance on, wetland cultivation within resource-poor anthropogenic grassland.

Archaeobotanical evidence. There is a variety of evidence for numerous edible plants being present in the Kuk vicinity from the late Pleistocene (table S3). The lack of an intimate association of most plant remains with archae- ological features indicates that the plants grew in the forested landscape. Modifications to the catchment and wetland margin at the end of Pleistocene and early Holocene may have been intended to increase the availability of edible and other useful plants. Many of these plants are still gathered, transplanted, and cultivated from wild forms in the Highlands today (16). Microfossils from two plants with abundant starchtaro (Colocasia esculenta) and banana (Musa spp.)both record their earliest pres- ence in early Holocene contexts. These two crops were potentially the most important food staples in the Highlands before the introduction

1

9000

None

Amorphous palaeosurface

10,220 to 9910

2

6000 to 5500

None

Subcircular paleosurfaces

6950 to 6440

3

4000 to 2500

Earliest

Sinuous runnel

4840 to 4440

Early

Rectilinear ditch networks

4350 to 3980

Table 1. Chronology for archaeological phases 1, 2, and 3 at Kuk Swamp (see tables S1 and S2 for dates and calibrations).

Phase

Golson 1977 (4) (uncal yr B.P.)

Subphase

Wetland remains

New dates (cal yr B.P.)

Mid-late Late

Rectilinear ditch networks Rectilinear ditch networks

None Pre–3260 to 2800

of the sweet potato (Ipomoea batatas) after European exploration of the Pacific.

Starch grains from Colocasia taro are present on the worked edges of three stone tools from phase 1, phase 2, and the intervening gray clay. The size, shape, surface morphology, clus- tering, and co-occurrence of raphides (calcium oxalate crystals) removed from the used edge of a phase 1 flake (K76/S29B) all signify C. es- culenta. C. esculenta has also been documented from a Pleistocene site in Island Melanesia (17) and an early Holocene site in lowland New Guinea (18). C. esculenta is considered to be a lowland crop, and its current range in New Guinea, exceeding 2000 m AMSL, is consid- ered to be a product of anthropogenic selection (19). Its presence and use at Kuk in the early Holocene are suggestive of deliberate move- ment of the plant into the Highlands.

Musaceae, including Musa spp. (banana), phytoliths are present throughout the Holocene stratigraphy at Kuk (Fig. 3). High percentages are evident in disturbed habitats before 6950 to 6440 cal yr B.P., but these are only suggestive of deliberate planting, because bananas are known to exist in wooded and edge habitats from which they colonize disturbed areas. The high percentages of banana phytoliths in grass- land contexts during phase 2 and in the earliest phase 3 feature (dated to 4840 to 4440 cal yr B.P.) are, however, anomalous. First, grasses produce abundant phytoliths, whereas bananas produce relatively few phytoliths in their leaves, bracts, seeds, and pseudostems. Thus,

Fig. 3. Selected pollen and phytolith data from the Kuk Swamp samples (n 38). Ages are based on radiocarbon dating of strati- graphic features associated with phases 1, 2, and 3 and intervening stratigraphy (that is, gray clay). Samples are arranged in order of oldest (sample 1, right-hand side of the diagram) to youngest (sample 38, left-hand side). The lower half of the diagram depicts pollen and

spore summary curves (for ferns, herbs, and trees and shrubs) and charcoal density (as area of pollen slide). The upper half of the diagram shows Poaceae (as percentage of total sum of pollen and spores) and Musaceae phytoliths (as percentage of total phytolith sum), with the presence of diagnostic seed phytoliths assigned to Eumusa, Ensete sp., and Musa ingens depicted as symbols.

www.sciencemag.org SCIENCE VOL 301 11 JULY 2003

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