Palaeoenvironmental Evidence of Island Colonization: A Response

Article excerpt

More on whether evidence of prehistoric environment on the Pacific island of Mangaia does or does not demonstrate an early human presence there.

Kirch & Ellison (1994) argue in the June ANTIQUITY that new palaeoenvironmental research on Mangaia (Cook Islands) seriously challenges the short chronology of East Polynesian pre-history proposed by Spriggs & Anderson (1993). It does not, for reasons shall discuss following clarification of several points.

Spriggs & Anderson (1993) do not hold the view that a standstill of colonization in West Polynesia was followed by resumed colonization eastward driven by explosive population expansion (Kirch & Ellison 1994: 319). We said the opposite, that 'East Polynesian colonists presumably outran the push of population growth' (Spriggs & Anderson 1993: 211, my emphasis), and have argued that case repeatedly. We are not looking for the 'first colonization site' as a 'Holy Grail', nor do we take a negative position with regard to palynological evidence (Kirch & Ellison 1994: 318). Actually, we are both currently engaged in palynological projects concerning Pacific prehistory. Lastly, Kirch & Ellison (1994: 318) say there is now evidence of anthropogenic palaeoenvironmental disturbance dated at 1400 b.p. in New Zealand. However, Striewski et al. (1994: 22) claim only that the determination suggests disturbance by about 1000 b.p.

The Mangaian case

The Mangaian case is based on analysis of three, out of 24, sediment cores. Two cores (VT6, TM7) show a rapid decline in tree pollen (although Pandanus, generally a disturbance indicator, disappears at this time in VT6), an increase in fern, and the first appearance of charcoal at about 2500 b.p. The third core (TIR-1), from the same basin as VT6 and initially published (Kirch et al. 1991) as disclosing similar changes from about 1600 b.p., has now been re-interpreted as showing the forest decline also beginning at about 2400 b.p. (Kirch & Ellison 1994). These data are held to demonstrate the presence of people on Mangaia by 2500 b.p., which is 1500 years earlier than the first known archaeological evidence.

My first objection to this proposition is that the reinterpretation of TIR-1 is too convenient. Without benefit of any new evidence different palynologists have perceived the beginning of deforestation at points 900-1100 years apart.

Secondly, while much is made of the initial appearance of charcoal at about 2500 b.p. in VT6 and TM7, it is not acknowledged by Kirch & Ellison (1994) that charcoal was also present by about 7000 b.p. in TIR-1 (Kirch et al. 1992: 177) and from similarly low down in TIR-2 (Kirch et al. 1991: 322). There are no charcoal counts for these cores, but quantification is misleading in any case. How much charcoal ends up in a sampled basin, and its pattern of distribution in a core, are dependent on various factors: size, type and proximity of fires, efficiency and modes of charcoal transportation, intervening trapping mechanisms, etc. It cannot be simply correlated with a presumed scale and origin of burning events.

Thirdly, since the early charcoal in TIR-1 occurs at about the time of a substantial forest decline, the argument that similar phenomena mark human colonization in the late Holocene should apply also to events around 7000-6000 b.p. (interpreted by Kirch et al. (1992: 177) as resulting from a drier climate at that time). Kirch & Ellison (1994) implicitly refute this point by arguing that it is the replacement of peat by clay infill, from extensive erosion, which confirms the anthropogenic status of the later events as against those earlier. But the chronology of clay infill is not at all clear. They note (1994: 314), that a transition from peat to clay infill is dated in four cores between about 3000 and 1600 b.p. They do not report that exactly the same phenomenon is also dated at 6260 [+ or -] 80 b.p. in core KA3 (but 2980 [+ or -] 80 b. …