AWA: Academic Writing at Auckland

Abstract

The settlement of the Pacific has been a contentious area of study between academics. Within the literature, several methods have been applied in order to date the first human (Polynesian) settlement in New Zealand. Academics have argued for both short and long settlement chronologies, both of which have returned conflicting results and thus hindered academic understanding of human settlement in the Pacific. Radiocarbon dates obtained from the 14^th century have been largely ambiguous, given the variation in the curve which returns a wide spectrum of possible dates. Accelerator Mass Spectrometry (AMS) dating of rat-bone has featured heavily in academics understanding of the subject, however this has been followed up with researchers employing the use of dated pollen and charcoal records and tephrochronology in order to obtain sound human settlement dates. Recent bodies of work conclude permanent human settlement dates of c.1200 – c.1400, which excludes the possibility of the early settlement chronologies proposed.

Introduction

It is known that New Zealand was the last large land mass to be colonised (Hogg et al., 2003), however the date in which this colonisation occurred has proved to be a topic that has plagued academics. Early research by Sutton (1987), Holdaway (1996) and Holdaway and Bevan (1999) argued for a date of settlement around 50-150 AD, proposing the idea of an early, transient population. Academics were quick to argue that this was not the case, on the basis of dated archaeological sites with did not pre-date the 12^th century, proposing a “long” settlement chronology (Anderson, 1991), as well as issues with the earlier dating methods employed.

Further research has since been undertaken by academics in an attempt to understand the date of human arrival and therefore Polynesian settlement to New Zealand. These methods have employed the use of dated rat-bone and rat gnawed seeds, pollen and charcoal records as well as the use of tephrochronology in order to identify when Polynesian settlement occurred. These methods have largely excluded the earlier issues that arose within dating, such as lab error and misinterpretation of results, thus giving a more accurate representation of colonisation dates. This review aims to present the research available to date in the proxies mentioned and summarise the potential issues and gaps given the current understanding.

More recent research has been able to confirm academics early understanding of a “long” settlement chronology, with settlement occurring around c.1250-c.1300 AD, which supported knowledge on the earliest known dated archaeological sites (Anderson, 1991). This was able to be identified on the basis of environmental change occurring which signalled human occupation (Hogg et al., 2003).

Methods

AMS Dated Rat Bone as a tool for establishing Polynesian settlement in New Zealand

The use of accelerator mass spectrometry (hereafter, AMS) dated rat-bone has been contentious as a tool for dating first human settlement in New Zealand. Despite this, AMS dating is the most commonly applied method used for dating human-era sites. Within the early literature, AMS dated rat bone returned highly differing results between academic’s research, and thus has been highly critiqued. More recent bodies of literature have offered explanations for the controversial results returned in earlier studies. The rat-bone used within these studies is that of the Pacific Rat, which is known to be fast breeding (Ruscoe, 2004; Brook, 2000) and have a large impact on plants and animals (Atkinson and Moller, 1990). Human contact was necessary for the arrival of the Pacific Rat in New Zealand, which is undisputed in the literature, however when this contact occurred has plagued academics.  

In a 1996 study, Holdaway argued for a date of human arrival 1000 years prior to what had been estimated as a plausible contact period in New Zealand, assumed to be 850 years BP when the most noticeable environmental disturbance occurred in the records. This was used to argue the early or “long settlement” prehistory chronology in which a near invisible population arrived >1,100 years prior to the oldest archaeological and palaeoecological dated sites which suggested human presence and were dated at 1280 AD (Wilmshurst et al., 2008).  On the basis of the dating of rat-bone gelatin, Holdaway (1996) proposed that a transient population had arrived in New Zealand and lived almost invisibly, or left soon after contact.  His study returned dates of 1775 + 94 yr BP in the North Island and 2,155 + 130 yr BP in the South Island and thus suggested that the Pacific Rat had been in New Zealand for almost 2000 years (Holdaway, 1996). This seemingly matched that of Sutton’s, (1987) work who also argued for an invisible population settled at around this time on the basis of pollen records. A further study by Holdaway and Bevan (1999), which used rat-bone gelatin samples from the Hukanui Pool limestone cave and returned dates within plausible human settlement dates, would be used to confirm that the first studies dates were reliable.

These controversial findings would not be without their critique. In 2004, Wilmshurst and Higham used rat-gnawed seeds as a proxy in order to try and solve some of the issues that rat-bone dating had in earlier studies and found that seeds offered several advantages over rat-bone (Wilmshurst and Higham, 2004). Although the use of rat-gnawed seeds had been used as a proxy in earlier studies by academics, the dates had largely been ignored in terms of the debate surrounding arrival of the Pacific Rat to New Zealand (Molloy, 1995 and Clarkson et al., 1992 as cited in Wilmshurst and Higham, 2004).  Rat-gnawed seeds are able to be well preserved in peat and forest litter, buried by flood or volcanic ash deposits (Wilmshurst and Higham, 2004). Furthermore, individual seed cases have a high carbon content and are reliable sources for AMS dating (Wilmshurst and Higham, 2004). The Pacific Rat largely consumes the main forest tree seeds found in New Zealand, and leaves very distinctive gnaw marks (Wilmshurst and Higham, 2004). This is an advantage to the research, given that gnaw marks on seeds that pre-date European contact will have only been left by the Pacific Rat given that there were no terrestrial mammals at that time that would also have left such obvious marks (Wilmshurst and Higham, 2004). Using two Taranaki sites and one in the Coromandel Peninsula, 1000 seed cases were obtained from peaty deposits. Wilmshurst and Higham would conclude from this study that the Pacific Rat was present in Eastern and Western Coastal forests at the same time as human arrival, but not before the thirteenth century (2004). This largely contradicted Holdaway’s 1996 and 1999 findings, which would have thus meant that the Pacific Rat had arrived around AD 50-150. If this were the case, it would have been expected that there was an immediate predation on the native flora and fauna which is not evident in past records until the thirteenth century, aligning with suspected human arrival (Wilmshurst and Higham, 2004).

The 1996 findings would again be tested and critiqued in Wilmshurst et al., 2008 which sought to identify if early human presence, as suggested in the early literature, was plausible. The study would date rat-bone from the same caves and stratigraphic layers as used in the earlier study (Wilmshurst et al., 2008). Their research found that none of the original 1995 and 1996 dates overlapped with the new rat bone dates, which all returned younger than 1280 AD (2008). This would rule the 1996 findings to be incorrect, and conclude that the Pacific Rat arrived with the first human colonists to New Zealand, as widely assumed, and therefore rule out the long-prehistory model (Wilmshurst et al., 2008). These findings would offer new suggestions around the issues with rat-bone dating which will be discussed.  

Within the literature, it was suggested that rat bones offered little sound evidence for dating human arrival, given that there was neither archaeological nor palaeoecological evidence of humans or rats in New Zealand until the thirteenth century AD (Wilmshurst and Higham, 2004). Furthermore, technical issues arose when rat-bones were found to be older than dated archaeological cultural materials, such as wood and eggshells, found in the same layer (Wilmshurst and Higham, 2004). Research by Smith and Anderson (1998) suggested that rat bones at archaeological sites were unreliable for dating, which was thought to be because of unremoved contamination or due to the reservoir effect (Anderson, 1996; Anderson, 1998b). This finding was on the basis of dates returning 1000 years older than the archaeologically dated counterparts (Smith and Anderson, 1998). This was rebutted by Wilmshurst et al., 2008, who concluded that this was unlikely given that stable isotope measurements showed a strong terrestrial signal and thus a low probability of large reservoir effects.  Holdaway and Bevan (1999) would suggest that rat-bone from archaeological sites was unreliable given that they tended to be situated in dune sites, which was an unsuitable preserver of bone for AMS dating, however Higham and Petchey (2000) would argue that this would then have implications for dated “naturally” preserved bone. A later study by Anderson (2000) however, would conclude that rat bones dated in 1995-1996 were unreliable, but later dated rat bone tended to offer a more expected date range (Anderson, 2000 as cited in Higham and Petchey, 2000). This was supported by findings in Wilmshurst et al. 2008, in which it was suggested that the earlier dated rat bones were handled inadequately in pre-treatment and therefore old carbon had failed to be removed or was added from a laboratory source. Academics also argued that rat bones returned older dates due to the dietary uptake of carbon depleted in ¹⁴C (Bevan and Sparks 1998 as cited in Wilmshurst et al., 2008).

Pollen and Charcoal records

Pollen and charcoal records have also offered evidence for dating the arrival of humans to New Zealand. Pollen and charcoal are used to date environmental changes and disturbances, particularly that of deforestation and firing (Hogg et al., 2003) Charcoal in soils and pollen found in lakes and bogs have provided a baseline in order for academics to interpret how the New Zealand environment has changed (Mcglone, 1989). Much like AMS dating of rat-bone however, this has been contentious. Issues around old carbon contamination are duly noted within the literature, stemming from different environments and their susceptibility to contamination (McGlone and Wilmshurst, 1999). This is reflected within the research, which has returned several wide-spread results for the dating of initial Maori impact on New Zealand (Mcglone and Wilmshurst, 1999).

In 1987, Sutton argued that noticeable disturbances in pollen occurring before known deforestation, such as an increase in bracken, was due to a small invisible population having settled around c.1300 AD. It was suggested that this population was made up of early Polynesian colonists, and that the increase in the record was due to human-lit fires dating to AD 0-500 (Sutton, 1987) (Hogg et al., 2003). Further bodies of work following Sutton also deduced from vegetation and landscape disturbances that early human influence was apparent (McGlone and Wilmshurst, 1999). Holdaway’s (1996) findings using rat-bone gelatin mirrored this suggestion, and both were used to argue the ‘early’ settlement chronology.

This theory has been rebutted by academics, who believe that this increase in charcoal and bracken within the pollen records can be explained through natural occurrences. Fire disturbances have occurred in New Zealand throughout the Holocene, and were evident prior to human arrival albeit at a lower frequency (Wilmshurst and Higham, 2004; Hogg et al., 2003; Perry et al., 2014). These natural disturbances may have included storms, volcanic eruptions and droughts, which were seen to have had an increase in frequency throughout the Holocene but were also evident in pollen records dated pre-Holocene (Mcglone, 1989; Wilmshurst et al., 1997; Ogden et al., 1998; Newnham et al., 1998a and McGlone and Wilmshurst, 1999 as cited in Hogg et al., 2003). Furthermore, increases in pollen and charcoal are shown to be consistent with the deposition of the Kaharoa Tephra, seen a key indicator of human arrival in the literature (Hogg et al., 2003).

Several studies have since used pollen and charcoal records to gain an understanding of when environmental impact occurred, and therefore when initial settlement of New Zealand was. Charcoal by itself can show that vegetation has been destroyed, however pairing this with pollen can accurately depict deforestation (McGlone, 1989). A study by McGlone (1989) used Pollen records from areas in Otago, which dated deforestation through fire to 2500 yr BP, a date which supports natural firing and is further supported by known weather patterns at the time. No permanent deforestation occurred however, which is also supported by pollen records from volcanic centres which also depict no permanent deforestation after natural events (McGlone, 1989). Given that it is known permanent deforestation has occurred at some point, and this is not supported by natural known events, anthropogenic causes of environmental change seem likely (McGlone, 1989). Despite anthropogenic firing being hard to indicate in the records, McGlone’s research found that continuous influxes of charcoal tend to offer evidence of anthropogenic firing, which was dated to 700-750 years BP (1989). A later study by McGlone and Wilmshurst using dated lake, bog and swamp sediment, returned timeframes of impact through deforestation occurring post 1200 AD, with 65% of this analysis coming from bog samples which are less prone to contamination (1999). Extending on this, these dates aligned with Anderson’s (1991) dating of archaeological sites, and thus returned some confidence for these dates (McGlone and Wilmshurst, 1999).

It is widely documented within the literature that the loss of New Zealand forest, through human-lit fires, occurred post human settlement (Perry et al., 2014). Pollen and charcoal records have induced that the first evidence of Polynesian arrival to New Zealand on the basis of this extensive environmental change, occurred around c.1200-1400 AD, which has been supported by evidence that shows this change occurred simultaneously across New Zealand (Hogg et al. 2003; Mcglone and Wilmshurst, 1999).

Tephrochronology

In order to counter-act the issues that arose through AMS dating of rat-bone and pollen and charcoal records, tephrochronology has also been enlisted in the literature. The use of tephra as a proxy has been used in New Zealand for 160 years (Lowe and Newnham, 2004). Tephra layers are used to establish “marker beds”, in which numerical or relative ages can be discovered (Hogg et al., 2003). As Hogg et al., (2003) explains, tephra layers provide isochrons which are able to be correlated between sites. The relative advantage of tephra is the locality; tephra is able to be found at both palaeo-environmental (natural) and archaeological sites and thus can be correlated in an unambiguous manner (Hogg et al., 2003).

In the literature, the eruption of the Kaharoa Tephra, is marked as an important event to consider when dating the arrival of Polynesians to New Zealand and is largely considered a key settlement layer in the North Island (Hogg et al., 2003). Several academics have commented on the layer’s distinctiveness and the wide dispersal over 30,000 kilometres. This layer originates from the Mount Tarawera volcano (Hogg et al., 2003). As the literature discusses, no cultural artefacts have been recorded beneath this layer (Anderson, 1991) however, the palynological data, or human induced environmental disturbances, occur closely to the layer’s deposition (Hogg et al., 2003). Within the literature it is noted that radiocarbon dating of the Kaharoa Tephra has returned results which cannot definitively date the layer, due to the wiggles in the calibration curve, and thus cannot be interpreted alone (Lowe and Newnham, 2004). Earlier studies by Lowe et al., (1998) determined an age of the Kaharoa Tephra of around 665 +/- 25 radiocarbon years BP (Hogg et al., 2003). This was problematic, as the wiggle in the calibration curve meant that the eruption of the Tephra could have occurred anywhere between c.1290 and c.1400 and thus any environmental impacts thought to have occurred by Polynesians was largely ambiguous (Hogg et al., 2003). In order to achieve a more precise date of this layer, and establish a sound date for Polynesian settlement, wiggle-matching has been employed by some academics.

Hogg et al. (2003) used known sequences which included tree ring series and superposed peat layers in order to establish a likely date for the Kaharoa Tephra layer. With the use of tree-ring series, the study suggested that the eruption of the Kaharoa Tephra occurred between the months of May to September, on the basis of known tree ring studies (Hogg et al., 2003). Through wiggle-matching, the study was able to determine a date of around 1314 +/- 12 AD, with dates being in agreeance using both the Southern Hemisphere Calibration curve and a Bayesian approach (Hogg et al., 2003).

Academics following this study have also been in agreeance with the suggested dates for the eruption and thus the likely age of the Kaharoa Tephra. Lowe and Newnham believe that in accordance with the suggested date of the tephra, archaeological sites do date younger than c.1314 (2004). However, there is evidence within the palynological records that early human induced environmental effects occurred around 50 years prior to the eruption (Lowe and Newnham, 2004). If these records are correct, and the dating of the Tephra is in fact accurate, this offers a sound date of Polynesian settlement occurring around c. 1250- c.1300 (Lowe and Newnham, 2004). These dates are in agreeance with the earliest known dated archaeological sites and palynological records (Lowe and Newnham, 2004).  

The implications of this research almost rules out the possibility of a transient population as proposed by Sutton (1987) and further by Holdaway (1996), given that no archaeological or palynological records have supported such findings (Lowe and Newnham, 2004). This date also offers firm support for Wilmshurst et al., (2008) findings in AMS records, that there was indeed no invisible population that occurred, and that Polynesian arrival was around 1280 AD.

Discussion

All records have a source of error attached to them, and thus we could deduce that finding an exact date of human settlement in New Zealand is not entirely possible. One large issue for dating occurs within the limitations of the calibration curve in the 14^th century, returning several possible dates (Hogg et al., 2003) therefore some records remain uncalibrated (McGlone and Wilmshurst, 1999). Dates are important for obtaining the settlement history of New Zealand and this error has hindered academics ability to soundly interpret results (McFadgen et al. 1994). Wiggle-matching is one method in which more sound dates can be achieved (Hogg et al., 2003). Pairing data with known dated records, such as archaeological evidence, is also a way that potential error within research may be accounted for.

Tephrochronology used for dating also offers some limitations, given that the Kaharoa Tephra only occurs in some known locations in the North Island (Hogg et al., 2003). The author has accounted for the geographical limitation that this proxy imposes on the research and furthermore the possibility that younger dates may exist outside of the Kaharoa Tephra fallout zone (Hogg et al., 2003).

Issues with pollen and charcoal records to obtain environmental disturbance signals has been noted within the literature, and authors have remarked on the susceptibility of sites to carbon in-wash and contamination. This may mean that dates that have been established through the use of these proxies may not be entirely accurate and may need to be paired with other proxies and records to establish whether the dates are plausible. Furthermore, there is no environmental signal in which academics can accurately pin point environmental change occurring through human action rather than naturally, therefore the dates are largely uncertain in this respect. Work in this area tends to predate the 2000’s, so further study may be required.

The dating of rat-bone and rat-gnawed seeds has to date provided a useful and sound proxy of dating human arrival, and academics have continued to publish supporting literature to back-up or build on past knowledge (Wilmshurst and Highman, 2008; Wilmshurst et al., 2004). Perhaps one identified issue within the literature is that human contact once the Pacific Rat arrived in New Zealand was not necessary for its dispersal (Wilmshurst et al., 2004). This could therefore be an issue if trying to look at the spread of Polynesians through New Zealand post initial settlement.

The literature suggests that human arrival occurred in the thirteenth century, and no earlier. All records, when authors have accounted for error, tend to return dates of around 1200 AD-1400 AD, which is in line with Anderson (1991) dating of archaeological settlement sites. The dating therefore rules out earlier suggestions by Sutton (1987), followed by Higham (1996), of an invisible, transient population arriving in New Zealand prior to the thirteenth century. Academics are largely confident in their work to date.

References

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