Old archaeological radiocarbon dating lore has it that caribou antler and bone give different dating results, and that for some fundamental reason antler is unreliable as a dating material. We tested this idea by measuring radiocarbon concentrations in the bone and antler of two caribou (one recent, one ancient) for which the antler was still attached to the cranium. No significant differences were found. Thus, it seems that this old myth is groundless.Selon de vieux dires, la radiodatation archéologique des bois et des os du renne donnerait des résultats différents et, pour une raison fondamentale, les bois ne représenteraient pas un matériau fiable pour la radiodatation. On a testé cette idée en mesurant les concentrations de radiocarbone dans les os et les bois de deux rennes (l'un mort récemment, l'autre il y a longtemps), où les bois étaient encore rattachés au crâne. On n'a pas trouvé de différence notable, ce qui semblerait signifier que l'ancien mythe est sans fondement

Møhl, J.

Nelson, D.E.

English

ABSTRACT. Old archaeological radiocarbon dating lore has it that caribou antler and bone give different dating results, and that for some fundamental reason antler is unreliable as a dating material. We tested this idea by measuring radiocarbon concentrations in the bone and antler of two caribou (one recent, one ancient) for which the antler was still attached to the cranium. No significant differences were found. Thus, it seems that this old myth is groundless. Key words: radiocarbon dating, caribou, antler RÉSUMÉ. Selon de vieux dires, la radiodatation archéologique des bois et des os du renne donnerait des résultats différents et, pour une raison fondamentale, les bois ne représenteraient pas un matériau fiable pour la radiodatation. On a testé cette idée en mesurant les concentrations de radiocarbone dans les os et les bois de deux rennes (l’un mort récemment, l’autre il y a longtemps), où les bois étaient encore rattachés au crâne. On n’a pas trouvé de différence notable, ce qui semblerait signifier que l’ancien mythe est sans fondement. Mots clés: radiodatation, renne, bois Traduit pour la revue Arctic par Nésida Loyer

D. E. Nelson

J. Møhl

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Radiocarbon Dating Caribou Antler and Bone: Are They Different?

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ARCTICVOL. 56, NO. 3 (SEPTEMBER 2003) P. 262–265Radiocarbon Dating Caribou Antler and Bone: Are They Different?D.E. NELSON1 and J. MØHL2(Received 17 July 2002; accepted in revised form 2 December 2002)ABSTRACT. Old archaeological radiocarbon dating lore has it that caribou antler and bone give different dating results, and thatfor some fundamental reason antler is unreliable as a dating material. We tested this idea by measuring radiocarbon concentrationsin the bone and antler of two caribou (one recent, one ancient) for which the antler was still attached to the cranium. No significantdifferences were found. Thus, it seems that this old myth is groundless.Key words: radiocarbon dating, caribou, antlerRÉSUMÉ. Selon de vieux dires, la radiodatation archéologique des bois et des os du renne donnerait des résultats différents et,pour une raison fondamentale, les bois ne représenteraient pas un matériau fiable pour la radiodatation. On a testé cette idée enmesurant les concentrations de radiocarbone dans les os et les bois de deux rennes (l’un mort récemment, l’autre il y a longtemps),où les bois étaient encore rattachés au crâne. On n’a pas trouvé de différence notable, ce qui semblerait signifier que l’ancien mytheest sans fondement.Mots clés: radiodatation, renne, boisTraduit pour la revue Arctic par Nésida Loyer.1 The Greenland Research Centre, National Museum of Denmark, Frederiksholmskanal 12, Dk-1220 Copenhagen, Denmark; permanentaddress: Archaeology Department, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada; Erle_Nelson@sfu.ca2 Zoological Museum, University of Copenhagen, Universitetsparken 15, DK-2100 Copenhagen Ø, Denmark© The Arctic Institute of North AmericaINTRODUCTIONRadiocarbon dating is a topic of continuing interest andcontroversy in Arctic archaeology. In a recent note, Nel-son and McGhee (2002) re-examined a Thule arrowheadthat had a radiocarbon age far too old for a Thule artefactand concluded that the point had been made on antlermaterial that was already 2500 years old at the time ofmanufacture. During a casual discussion of this observa-tion at the Greenland Research Centre of the NationalMuseum of Denmark, another apparent problem with dat-ing of caribou antler surfaced. It seems that during theearly days of radiocarbon dating, archaeologists workingin the Arctic noted that caribou antler could give anoma-lous radiocarbon results when compared to other terres-trial sample materials (cf. McGhee and Tuck, 1976). Incontrast to caribou bone, antler came to be regarded as anunreliable dating material, an idea that remains a part ofpresent-day Greenlandic research lore (M. Appelt and J.Meldgaard, pers. comm. 2002).What could underlie this old concept? There is nofundamental reason to suspect that caribou antler shouldgive a radiocarbon age significantly different from thatgiven by bone from the same animal. Antler is a veryrapidly growing tissue that is formed in a few weeks andthen discarded a few months later, while bone tissue isformed over a period of a year or two and then very slowlyremodeled over the lifetime of the animal. While antlermight then reflect short-term atmospheric radiocarbonconcentration fluctuations that would be absent from thelonger-term average of the bone, this would not result inage differences of more than a decade or two at most (e.g.,compare the annual and decadal radiocarbon calibrationdata in Stuiver et al., 1998) and thus seems unlikely to bethe source of the problems noted in the past. Anothertechnical explanation might be the very serious contami-nation problems encountered with both bone and antler inthe early days of radiocarbon dating, when measurementswere often taken on the material as a whole. Other possi-bilities are that the differences were archaeological innature, if the associative interpretations of the humanevents and artefacts were erroneous, or if the differencesreflected other instances of the reuse of old antler for toolmanufacture. A test of caribou antler and bone seemed tobe in order.Modern methods for extracting bone collagen havegreatly reduced the problems with dating bone, and it hasbecome a material of choice for radiocarbon dating. Asimple test would then be to date both bone and antler fromthe same animal, thus eliminating any possibility of asso-ciative misinterpretation or reuse of old material. Twosuch sets of Greenlandic samples were chosen for thestudy. The first was the remains of a recent animal, whichwas very well suited for detailed testing; the second, thecranium of an ancient animal from a Saqqaq midden—anexample of a real archaeological application. As will beseen below, in neither case was a significant differencefound between the radiocarbon ages of bone and antler.SAMPLES AND METHODSThe samples from both animals were obtained from theosteological collections at the Zoological Museum, Uni-versity of Copenhagen. The first animal comprised thecomplete skeletal remains of a dead caribou collected on20 July 1979 by M. Meldgaard near Kangerlussuaq, WestGreenland. It was an adult female with antlers still at-tached and, given the state of decay (there was still softtissue present), it was estimated that at most a few yearshad elapsed since the animal’s death. This animal mayhave succumbed to a severe winter. An estimate of its agecould be made at the Zoological Museum by comparing itsteeth with those in a collection of mandibles from caribouof known age. Tooth wear indicated that this animal wasapproximately nine years old at the time of its death.Its death in the 1970s made this animal ideal for thisexperiment, as its tissue should reflect the large changes inatmospheric radiocarbon concentration that were then tak-ing place as a consequence of atmospheric nuclear weap-ons testing. These concentration changes would be solarge over the lifetime of this animal that radiocarbonmeasurement uncertainty is not an issue in interpretation,and one might expect the bone and antler concentrations toprovide detailed information on the animal’s life thatcould be compared to the zoological information. If thereare fundamental differences between bone and antler, theyshould be clearly evident in this animal.The ancient samples were taken from a cranium with anantler portion still attached that was excavated by A.Gotfredsen and T. Møbjerg from the Nipisat site nearmodern-day Sisimiut, West Greenland. This site was clearlyof Saqqaq cultural affiliation, and the caribou was ex-pected to yield a radiocarbon age of approximately 3000 –3500 years. Unlike the modern specimen, this one was notwell preserved; while it was likely an adult animal, it wasnot possible to determine its sex. This bone-antler pairprovides a test of a real archaeological sample in whichany dating problems with the antler should be evident.Both bone and antler were sampled by boring with aslow-speed drill. The area to be sampled was selected byappearance, and the surface was removed using a sphericalmilling bit. A drill bit 2 mm in diameter was then used tobore into the cleaned area, yielding about 60 mg of drillingsfrom each sample. For the recent animal, the antler and afemur were sampled. For the ancient animal, a sample ofantler was taken from a portion that remained connected tothe cranium, and the bone sample was taken from thecranium itself.Collagen was extracted using the usual method em-ployed at the Simon Fraser University (SFU) ArchaeometryLaboratory (details are given in Takahashi and Nelson,2002). In short, the method isolates from the sample onlythose remaining collagen fragments with a molecularweight greater than about 30 kDaltons. During this sam-pling and extraction procedure, there are numerous tests ofthe quality of the material under study.A portion of each extract was burned to yield CO2,which was then sent to the Center for Accelerator MassSpectrometry (CAMS) Group at the Lawrence LivermoreNational Laboratory for radiocarbon determination byaccelerator mass spectrometry. A second aliquot was sentto the Earth and Ocean Sciences Department of the Uni-versity of British Columbia for measurement of carbonand nitrogen concentrations and stable carbon (δ13C) andnitrogen (δ15N) values.RESULTSThe material thus extracted from the recent samples hasthe characteristics (carbon and nitrogen concentrationsand C/N ratio) expected for well-preserved bone andantler, as shown in Table 1. Those from the ancient animalwere not well preserved, but nevertheless gave extractsthat satisfy the requirements for isotopic measurement, asmay be seen by comparison to those from the recentanimal. The stable isotope results give a further test of thequality of the extract. For both animals, these values arevery similar to those of numerous other Greenlandic cari-bou samples measured at the SFU laboratory. (To comparethe recent and the ancient animals directly, one must add1.5‰ (Friedli et al., 1986) to the recent δ13C values tocorrect for the impact on atmospheric CO2 of fossil fuelburning.) There is thus every indication that the radiocar-bon determinations are reliable.Since the basic concern here is the possible differencein radiocarbon concentration between bone and antler, thedata are presented in Table 1 as ∆14C values, which are themeasured 14C concentrations in the samples as compared(in parts per thousand) to that of the International radiocar-bon standard (Stuiver and Polach, 1977). This allowsdirect comparison of the recent animal with the so-called‘bomb curve’ data for the Northern Hemisphere, whichgives the atmospheric radiocarbon concentrations sinceA.D. 1950 (Levin et al., 1985).The data for the bone and antler of the recent caribou(Table 1) differ by 5.4‰. In statistical terms, this differ-ence corresponds to 0.9 standard deviations (e.g.,5.4 / √ (4.42 + 4.42), so these are results that could beexpected for repeat measurements on the same sample. InFigure 1, these determinations are placed on the plot foratmospheric radiocarbon concentrations for the bomb-testperiod (Levin et al., 1985). The antler measurement pro-vides a very precise time for the death of this animal, sincecaribou form and cast their antlers annually, and femaleskeep theirs throughout the winter. The attachment of theantler to the cranium thus indicates that the death of thisfemale occurred during late fall or winter. Given themeasured concentration, there are two possible years inRADIOCARBON DATING ANTLER AND BONE • 263264 • D.E. NELSON and J. MØHLwhich this death could have occurred, either 1963 or 1971.The former is inconsistent with the collector’s observa-tions on the state of the carcass, and so we may concludethat the animal died in very early or very late 1971, asshown in Figure 1.The femur result also indicates (Fig. 1) that the animalformed its bone collagen in either 1963 or 1971. The latterpossibility is very unlikely, as the animal was an adult. Ifits femur radiocarbon concentration reflected that of the1971 atmosphere, it must have been remodeling its bonecollagen as rapidly as it formed antler. That is not reason-able, and so the most probable date for the animal’s birthand growth period is 1962 – 63, indicating that the animalwas about eight or nine years old at the time of its death in1971. This age corresponds extremely well with the nine-year age estimate made on the basis of tooth wear. The dataprovided by the antler and bone radiocarbon measure-ments can thus be combined with zoological observationto provide detailed information on this animal’s birth anddeath. This would not be the result if there were somesystematic problem with antler determinations, and weconclude that there is no fundamental basis for the ideathat antler gives deviant radiocarbon ages.The bone and antler data for the ancient caribou (Table 1)differ by an almost identical amount, 5.6‰. As the meas-urement accuracy obtained for these samples was higherthan that for the recent ones, this is a statistical differenceof 1.3 standard deviations, which is a little more than onewould expect for two measurements on the same preparedsample. This minor difference could reflect one or more ofseveral possible causes: 1) simple random measurementprobability, 2) a small overestimate of measurement accu-racy by the laboratory, 3) slight differences in the level ofcontaminant elimination in these two poorly preservedsamples, or 4) a real difference in the short-term and long-term averages for the antler and bone. It would be verydifficult to establish which of these contribute to the ob-served radiocarbon concentration difference, but as it cor-responds to an age difference of only 65 radiocarbon years,the outcome would be of no significance for either futuremeasurement procedure or archaeological interpretation.Conventional radiocarbon ages (as defined by Stuiverand Polach, 1977) for the ancient samples may then becalculated as 2920 ± 25 B.P. for the antler and 2985 ± 45B.P. for the cranium. At the present level of archaeologicalanalysis, the 65 14C-year difference is not significant, andeither date is in complete accord with expectation for thesite. Thus, the best dating estimate for this animal is theweighted average of these two results, or 2935 ± 22 B.P.This is well within the expected time range, and thearchaeological implications of this determination are to bediscussed by the excavators (T. Møbjerg and A.B.Gotfredsen, pers. comm. 2002).CONCLUSIONSRadiocarbon concentration measurements on an antlerand a bone sample from each of a recent and an ancientcaribou showed no age differences of significance toradiocarbon dating of these materials. It would appear thatthe old myth of a general problem with dating caribouantler is groundless. Caribou antler may in fact be amaterial of choice for radiocarbon dating, because it wasso often used for tool manufacture and because, unlikemarine materials, it requires no reservoir correction. How-ever, there remains the possibility that the ancient hunterTABLE 1. AMS and stable isotope results for the recent and ancient caribou.SFU# CAMS# Sample C conc. (%) N conc. (%) C/N ratio δ13C (‰ vPDB) δ15N (‰ vAIR) ∆14C (‰)Recent:Rens–25 82922 antler 45.1 16.4 2.7 -21.1 2.4  498.2 ± 4.4Rens–26 82923 femur 44.9 16.1 2.8 -19.7 2.1  503.6 ± 4.4Ancient:Rens–27 82924 antler 45.3 15.6 2.8 -18.0 2.6 -309.0 ± 2.2Rens–28 82925 cranium 44.7 15.6 2.9 -17.9 2.9 -314.6 ± 3.6FIG. 1. Measured bone and antler radiocarbon concentrations for the recentcaribou plotted as horizontal lines crossing the atmospheric radiocarbon “bombcurve” for the Northern Hemisphere (Levin et al., 1985). The intersections ofthe caribou determinations with the curve give the possible times for bone andantler formation, as shown by the arrows. The height of the bar in the inset boxrepresents measurement uncertainty over the range of ±1 standard deviation; itis too small to influence interpretation.σ)   RADIOCARBON DATING ANTLER AND BONE • 265used even more ancient antler or bone for tool manufac-ture. It may have been that this practice was the basis of theearly difficulties with caribou antler dating.ACKNOWLEDGEMENTSWe thank Martin Appelt and Jørgen Meldgaard for raising theproblem, Tinna Møbjerg and Gitte Gotfredsen for providing theancient sample, Cheryl Takahashi for the laboratory chemistry, andthe Lawrence-Livermore CAMS Group and the University ofBritish Columbia Ocean Sciences Group for the isotopicdeterminations. D. Erle Nelson thanks the Greenland ResearchCentre at the National Museum of Denmark (SILA) for a year’shospitality. Funding was provided by the Natural Sciences andEngineering Research Council of Canada (NSERC).REFERENCESFRIEDLI, H., LOSTSCHER, H., OESHGER, H.,SIEGENTHALER, U., and STAUFFER, B. 1986. Ice record of13C/12C ratio of atmospheric CO2 in the past two centuries. Nature324:237 –238.LEVIN, I., KROMER, B., SCHOCH-FISCHER, H., BRUNS, M.,MÜNNICH, M., BERDAU, D., VOGEL, J.C., and MÜNNICH,K.O. 1985. 25 years of tropospheric 14C observations in centralEurope. Radiocarbon 27(1):1 –19.NELSON, D.E., and McGHEE, R. 2002. Aberrant radiocarbondates on an Inuit arrowhead. Arctic 55(4):345 –347.STUIVER, M., and POLACH, H.A. 1977. Discussion: Reportingof 14C data. Radiocarbon 19(3):355 –363.STUIVER, M., REIMER, P.J., and BRAZIUNAS, T.F. 1998.High-precision radiocarbon age calibration for terrestrial andmarine samples. Radiocarbon 40(3):1127 –1151.TAKAHASHI, C.M., and NELSON, D.E. 2002. Radiocarbon datingand stable isotope analysis of antler and bone from Greenland.Archaeometry Laboratory Internal Report 2002–2, ArchaeologyDepartment, Simon Fraser University, Burnaby, British ColumbiaV5A 1S6, Canada.

Radiocarbon Dating Caribou Antler and Bone : Are They Different?

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Radiocarbon Dating Caribou Antler and Bone : Are They Different?

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