Fire History on the California Channel Islands Spanning Human Arrival in the Americas

Page 1 of 27 For the Philosophical Transactions of the Royal Society B 1 2 3 4 Fire history on the California Channel Islands 5 6 spanning human arrival in the Americas 7 8 Mark Hardiman[1], Andrew C. Scott[2], Nicholas Pinter[3], 9 10 R. Scott Anderson[4], Ana Ejarque[5,6], Alice Carter-Champion[7], 11 Richard Staff[8] 12 1 Department of Geography, University of Portsmouth, U.K. 13 2 Department of Earth Sciences, Royal Holloway, University of London, U.K. 14 3 Department of Earth and Planetary Sciences, University of California Davis, U.S.A 15 4 School of Earth Sciences and Environmental Sustainability, Northern Arizona University, U.S.A. 16 5 CNRS, UMR 6042, GEOLAB, 4 rue Ledru, F-63057 Clermont-Ferrand cedex 1, France. 17 6 Université Clermont Auvergne, Université Blaise Pascal, GEOLAB, BP 10448, F-63000 Clermont- 18 Ferrand, France. 7 Department of Geography, Royal Holloway University of London, Egham, Surrey, UK. 19 8 Oxford Radiocarbon Accelerator Unit (ORAU), Research Laboratory for Archaeology and the History of Art 20 (RLAHA), University of Oxford, Dyson Perrins Building, South Parks Road, Oxford, UK. 21 22 Keywords: Fire, Charcoal, Radiocarbon dating, Arlington Springs Man, Clovis Culture, Landscape history, 23 Islands 24 25 Summary 26 27 28 Recent studies have suggested that the first arrival of humans in the Americas during the end of the 29 last Ice Age is associated with marked anthropogenic influences on landscape, in particular with the 30 31 use of fire which would have given even small populations the ability to have broad impacts on the 32 landscape. Understanding the impact of these early people is complicated by the dramatic changes in 33 34 climate occurring with the shift from glacial to interglacial conditions. Despite these difficulties we 35 here attempt to test the extent of anthropogenic influence using the California Channel Islands as a 36 37 smaller, landscapescale test bed. These islands are famous for the discovery of the ‘Arlington Springs 38 Man’, which are some of the earliest human remains in the Americas. 39 40 41 A unifying sedimentary charcoal record is presented from Arlington Canyon, Santa Rosa Island based 42 43 on over 20 detailed sedimentary sections from eight key localities. Radiocarbon dating was based on 44 45 thin, fragile, long fragments charcoal in order to avoid the ‘old wood’ problem. Radiocarbon dating of 46 49 such fragments has allowed inferences regarding the fire and landscape history of the Canyon c.19 47 48 11 ka BP. A significant period of charcoal deposition is identified ~1412.5 ka BP and bears 49 remarkable closeness to an estimated appearance age range of the first human arrival on the islands. 50 51 52 53 54 1.0 Detecting anthropogenic fire signals in the geological record 55 56 Significant evidence exists for human use of fire dating as far back as 0.8.1.0 million years 57 58 from sites in South Africa, where burnt bone with butchery marks has been discovered [1, 2]. 59 60 1 Page 2 of 27 1 2 3 By c.400 ka BP, similar evidence of hearths is found from sites across Europe, including 4 5 Beeches Pit in eastern England, which also includes the suggestion of fireside stone tool 6 production [3, 4]. Such evidence of direct human interaction with fire [see also 5] is rare in 7 8 the archaeological record, particularly at open, rather than cave or more sheltered, sites [6]. 9 10 Whereas modern hunter gatherer communities globally use fire at the landscape scale [711], 11 understanding how fire was used as a tool by past human populations is a complex task, 12 13 particularly in geographic regions with abundant natural ignition sources, including 14 15 Mediterranean climates. 16 17 One increasingly important approach is to investigate very long Quaternary records to 18 19 improve existing knowledge of fire history over long timescales, including over multiple 20 glacialinterglacial cycles. These types of investigation usually attempt to detect anomalous 21 22 levels of charcoal content and other products from the ‘combustion continuum’, such as black 23 24 carbon [12, 13], and relate this to corresponding spatial and temporal patterns in the 25 archaeological record [e.g. 1416]. This approach allows detailed comparison between 26 27 climatically similar periods (e.g., interglacials) where people are known to have been present 28 29 and periods where they were likely absent [e.g. 17]. However long terrestrial records are 30 often limited geographically, particularly in areas that have undergone repeated Quaternary 31 32 glaciation. 33 34 35 Alternatively, marine records are increasingly used to identify potential anthropogenic 36 burning in the past [e.g. 18]. Marine records typically have more straightforward depositional 37 38 histories (i.e., are often isotaphanomic), allowing for easy calculation of charcoal 39 40 concentrations, which are typically reported as number, area or volume. Although marine 41 records are undeniably valuable, they also have limitations, such as complex or undefined 42 43 charcoal source areas. Such limitations can make reliable interpretation difficult, particularly 44 45 as it is often microcharcoal, <125 µm [19] which is the charcoal size fraction present at sites 46 distal from terrestrial source areas. There are many challenges of interpreting microcharcoal 47 48 fragments in palaeorecords [see 20]; studies in pollen source areas are also informative, with 49 50 some suggesting that marine pollen records are heavily biased towards pollen from higher 51 mountain areas and river outflows [21, 22]. Another issue is that pollen source areas may 52 53 change significantly over time in marine records [23]. Thus it is always desirable to combine 54 55 these data with fire records from proximal terrestrial sequences. 56 57 58 59 60 2 Page 3 of 27 1 2 3 For the late Quaternary, the spatial coverage of terrestrial palaeorecords improves markedly 4 5 and, during the last ~50 kyrs, radiocarbon dating allows reasonable chronologies to be 6 formed. The majority of Quaternary charcoal records covering this time come from lacustrine 7 8 or peat bog sequences, mostly with relatively straightforward depositional histories, allowing 9 10 the construction of charcoal statistics such as CHAR [see 24]. Because these records 11 minimize local variations, they contribute to regional and global syntheses of charcoal 12 13 patterns over time [e.g. 2527]. For example, in New Zealand, (which was colonised ~1280 14 15 A.D.) anthropogenic fire detected in terrestrial archives comes as asynchronous increases in 16 charcoal contemporaneous with a wave of human arrival across the country [28, 29]. 17 18 Detecting the clear arrival of people and the associated shift in fire regime in this region was 19 20 helped by 1) New Zealand's low background of natural wildfire and 2) the relatively stable 21 climate during this period. 22 23 24 Less attention has been focused on understanding fire regimes over millennial timescales 25 recorded in more complex sedimentary environments, such as fluvial deposits, probably 26 27 because depositional heterogeneity precludes simple age models and generation of statistical 28 29 indices such as CHAR. This is unfortunate as these settings have long been recognised as rich 30 sources of archaeological information [e.g. 30] and are excellent records of longer term 31 32 landscape evolution [31]. Often secondary geomorphic effects associated with wildfire, such 33 34 as postfire erosion, are preserved in this part of the landscape sedimentary system [3235]. 35 36 37 Within this investigation we look to use these more complex sedimentary environments, 38 39 specifically a fluvial fill sequence, attempting to answer questions surrounding the potential 40 present or absence of anthropogenic fire signals. Our case study is the Northern California 41 42 Channel Islands during the last glacial–interglacial transition (LGIT), c.1510 ka BP. Before 43 44 outlining our work in detail, first the North American context is introduced, in terms of the 45 key environmental and archaeological evidence and also the complexities of investigating 46 47 humanfire interactions during this timeframe. 48 49 50 51 2.0 Fire and the arrival of people in North America 52 53 It is well understood that intentional landscape burning has been practiced by humans in 54 55 North America over much or all of the Holocene[3641]. More controversial is the suggestion 56 that the first arrival of humans in the Americas during the end of the last ice age can be 57 58 associated with nontrivial anthropogenic influences on landscape, in particular with the use 59 60 3 Page 4 of 27 1 2 3 of fire [42, 43]. Proponents of this idea suggest that even small transient human populations 4 5 could have had broad impacts on ignitionlimited portions of the landscape [42]. 6 7 8 The late Pleistocene Clovis culture is the oldest welldefined archaeological technocomplex 9 10 of North America and is thought to have appeared c.13.4 ka BP and disappeared around 11 ~12.7 ka BP [4450]. Despite the fairly short interval, Clovis technology is found over a large 12 13 spatial range [50]. Less secure evidence of a human presence in the Americas during the two 14 15 millennia before Clovis (~15.5 until ~13.8 ka BP) has also been suggested [e.g. 5153] and 16 hotly debated [5458]. The exact timing of human arrival in the Americas remains uncertain. 17 18 19 20 Understanding the impact of the human vanguard into North America is further complicated 21 by the contemporaneous changes in climate during the LGIT [5963]. In particular, the 22 23 Younger Dryas cold event (c.12.9 ka BP) [6467] contributed to rapid environmental shifts at 24 25 a key time during human arrival in, and/or migration through the Americas.

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