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Identification of semi-domesticated reindeer (Rangifer tarandus tarandus, Linnaeus 1758) and wild forest reindeer (R.t. fennicus, Lönnberg 1909) from postcranial skeletal measurements
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ORIGINAL INVESTIGATION
Identification of semi-domesticated reindeer (Rangifer tarandus tarandus, Linnaeus 1758) and wild forest reindeer (R.t. fennicus, Lo¨nnberg 1909) from postcranial skeletal measurements Anna-Kaisa Puputti, Markku Niskanen Laboratory of Archaeology, University of Oulu, P.O. Box 1000, FIN-90014 Oulun yliopisto, Finland Received 24 October 2007; accepted 10 March 2008
Abstract Reindeer bones are common finds from archaeological sites from prehistoric and historic Fennoscandia. The interpretation of the reindeer bone finds, however, is often hindered by the difficulty to separate the different subspecies of reindeer using the postcranial skeletal morphology. In this paper, skeletal measurements of modern semidomesticated reindeer and wild forest reindeer are explored with multivariate statistical methods in order to find suitable methods for subspecies identification. The results are then applied to archaeological reindeer bone finds from Northern Finland and archaeological implications of the results are discussed. r 2008 Deutsche Gesellschaft fu¨r Sa¨ugetierkunde. Published by Elsevier GmbH. All rights reserved. Keywords: Rangifer tarandus; Zooarchaeology; Identification; Finland
Introduction In this study, we will use discriminant analysis and logistic regression to separate sets of postcranial skeletal measurements of modern semi-domesticated reindeer from wild forest reindeer. In bioarchaeology, these methods are often used, for instance, in taxonomic identification, sex assessment or habitat prediction from skeletal measurements (e.g. Goldberg, 1999; DeGusta and Vrba, 2003; Cardoso 2008). Also, the issue of sexual dimorphism of reindeer is addressed by employing principal component analysis (PCA). The results are then applied to archaeological reindeer bone remains from urban archaeological excavations from two towns in early modern (ca. 1600–1800 AD) Northern Finland, Tornio and Oulu. Corresponding author. Tel.: +358 8 553 3371.
E-mail address: anna-kaisa.puputti@oulu.fi (A.-K. Puputti).
Different subspecies of reindeer have been extensively exploited by humans in the northern hemisphere from the Palaeolithic period to present-day and reindeer bones are common finds in archaeological sites throughout the area (e.g. Weinstock 2000; Aaris-Sørensen et al. 2007). However, the interpretation of archaeological reindeer bone finds from Northern Fennoscandia is complicated by the presence of two interbreeding subspecies, mountain reindeer (includes both wild and semi-domesticated reindeer) (Rangifer tarandus tarandus) and forest reindeer (R.t. fennicus). The morphologies of these two subspecies overlap extensively (see e.g. Nieminen and Helle, 1980). Thus, identification of postcranial bones of these subspecies is difficult. Subspecies identification is of interest to archaeologists as the archaeological bone finds of these subspecies may infer different subsistence strategies and cultural interpretations. A number of studies have dealt with cranial morphology and body proportions of different reindeer
1616-5047/$ - see front matter r 2008 Deutsche Gesellschaft fu¨r Sa¨ugetierkunde. Published by Elsevier GmbH. All rights reserved. doi:10.1016/j.mambio.2008.03.002 Mamm. biol. 74 (2009) 49–58
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subspecies (e.g. Nieminen and Helle, 1980; Hakala et al., 1996), but to date, there are no zooarchaeological studies to distinguish reindeer subspecies from postcranial skeletal measurements. The geographical distribution range of reindeer (Rangifer tarandus) comprises nearly the whole circumpolar area (Banfield 1961). Reindeer has several subspecies, of which the wild mountain reindeer (R.t. tarandus) and the wild forest reindeer (R.t. fennicus) have both been extant in Northern Finland until recently. At present, wild mountain reindeer are found only in Southern Norway and inland Kola Peninsula and the forest reindeer in Eastern Finland, Ostrobothnia and Russia (Nieminen and Helle, 1980). However, historically, the ranges of wild mountain reindeer and forest reindeer comprised, respectively, almost the whole Northern Fennoscandia and Kola Peninsula, and the coniferous belt of Southern Finland and Southern Lapland (Nieminen and Helle, 1980). The withers height of forest reindeer is 10–15 cm higher than that of mountain reindeer, mostly due to longer legs of the forest reindeer. Forest reindeer are also slenderer in body and the cranial morphology differs from the mountain reindeer (Nieminen and Helle, 1980; Hakala et al., 1996). Morphological similarity suggests that the semidomesticated reindeer is most likely domesticated from the wild mountain reindeer of Scandinavia (Nieminen and Helle, 1980; Hakala et al., 1996). There is some debate among researchers as to when the reindeer was domesticated and estimates vary from the Mesolithic to the Middle Age in Scandinavia. It is generally assumed that small-scale reindeer husbandry began in Scandinavia in early Middle Age (ca. 200–900 AD) and large scale reindeer husbandry probably began in Northern Finland in the late Middle Age (ca. 1400–1500 AD) (see e.g. Ingold, 1980; Halinen, 2005 for a more detailed discussion). Reindeer were also a part of the urban subsistence in the early modern Northern Finland. Urban archaeological excavations in the area generally yield small quantities of reindeer bones (e.g. Puputti, 2006, 2007). It is unknown, if these reindeer bone finds originate from semi-domesticated reindeer or wild forest reindeer. For instance, in the case of the 17th and 18th century archaeological sites at Oulu and Tornio, both options are possible because wild forest reindeer were still hunted in Northern Finland during the early modern period and semi-domesticated reindeer were kept in the area (Virrankoski, 1973).
Material and methods A total of 46 nearly complete and partial skeletons of modern semi-domesticated reindeer and wild forest reindeer
from the collection of the Zoological Museum of University of Oulu were measured in this study. The semi-domesticated reindeer originate from reindeer keepers in Northern Finland or the University of Oulu Zoo. The wild forest reindeer originate from Eastern Finland. These animals have been prepared in the Zoological Museum and the sex and subspecies assessments have been conducted by the Zoological Museum’s staff from complete carcasses prior to the preparation. Hybrids of wild forest reindeer and semi-domesticated reindeer were not included in our study. Only mature individuals, i.e., individuals with fully fused epiphyses, were included in the study material. This means the age of approximately 42–54 months (Hufthammer 1995). Some individuals were represented only by metapodials; the age of these individuals can only be assessed as over 18–30 months, the age in which metapodial distal epiphyses fuse (Hufthammer 1995). The skeletons of the semi-domesticated reindeer include eight males, 11 females and 10 individuals of unknown sex. One skeleton of male semi-domesticated reindeer was complete and seven individuals were represented only by metapodials. One skeleton of female semi-domesticated reindeer was complete except for scapula, two were represented by humerus, radius and metacarpal, one by femur, tibia and metatarsal, and seven only by metapodials. The skeletons of individuals of unknown sex were complete. The wild forest reindeer sample includes six males, 10 females and one individual of unknown sex. These skeletons were complete, except for two males without scapulae. Some measurements were not obtained from all the bones because of, for instance, breakage or infectious tissue. The numbers of elements used in each analysis are presented in Table 1. Measurements were taken from the limb bones according to von den Driesch (1976), Berteaux and Guintard (1995) and Puputti and Niskanen (in press). Full details of the measurements, taken with a digital vernier and recorded in millimetres, are presented in Puputti and Niskanen (in press). Only limb bones were included in this study, because the cranial morphology of semi-domesticated reindeer and forest reindeer somewhat differs, making morphological identification possible (Hakala et al., 1996). Moreover, limb bones or limb bone fragments are common finds in archaeological sites because of their better durability in comparison with cranial bones, and they are easily identified to species level, unlike, for instance, vertebral and rib fragments. Measurement error can bias the analysis especially in such cases when true variation in skeletal dimensions is small, for instance, in intraspecific comparisons (Arnqvist and Ma( rtenson 1998). In our study, measurement error was estimated by measuring six individuals twice and calculating the ratio of the variance due to differences among individuals (Arnqvist and Ma( rtenson, 1998). This was done by performing a model II one-way analysis of variance with individual as categorical factor, and calculating the variance ratio R ¼ S2A =ðS2W þ S2A Þ, where S2W ¼ MSwithin and S2A ¼ ðMSamong MSwithin Þ=n. The variance in measurements was mostly due do differences between individuals, with variance ratios of 0.95–1.00, except for scapula and femur greatest lengths, with variance ratios of 0.77–0.88. Discriminant analysis and logistic regression were applied to reindeer skeletal measurements to identify the subspecies. The analysis were performed (SPSS 14.0) to complete bones and
The discriminant functions and logistic regression equations N (tarandus/ fennicus)
Correctly classified in DA
Cutoff (mean of centroids)
Correctly classified in LR
Measurement
Discriminant function coefficient
Logistic regression coefficient
SCAP
24 (10/14)
83
0.00
100
SCAP Bg SCAP LG SCAP GLP SCAP HS SCAP Ld Constant
0.07599429 0.088210739 0.140519429 0.070440793 0.07107723 14.7850995
12.5628768 7.51915075 16.9884304 25.8322241 0.86490518 493.534075
SCAP prox
25 (11/14)
68
0.00
72
SCAP Bg SCAP LG SCAP GLP Constant
0.125 0.124 0.265 13.249
HUM
29 (13/16)
93
0.00
100
HUM GL HUM GLC HUM BT HUM Bd HUM TH HUM Bp HUM HHAP Constant
0.09166274 0.238885172 0.09629042 0.057095578 0.08101913 0.027913868 0.39762584 13.0713218
HUM prox
29 (13/16)
76
0.00
90
HUM Bp HUM HHAP Constant
HUM dist
31 (14/17)
77
0.00
81
HUM Bd HUM TH HUM BT Constant
0.14657495 0.13256978 0.41846949 19.6580963 9.07362846 0.55809377 2.88449587 17.0426097 7.83830538 9.8571414 17.7966693 733.447732
0.35 0.253 9.675
1.07356524 0.76913246 28.7335005
0.5 0.295 0.45 14.501
0.90298332 0.81959462 0.68550181 23.3201552
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Table 1.
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Table 1. (continued ) Anatomical element
N (tarandus/ fennicus)
Correctly classified in DA
Cutoff (mean of centroids)
Correctly classified in LR
Measurement
RAD
30 (14/16)
90
0.00
100
RAD GL RAD PRAP RAD Bp RAD Bd Constant
RAD prox
31 (14/17)
71
0.00
71
RAD Bp RAD PRAP Constant
0.253 0.902 10.565
1.50517749 0.45684667 15.7310711
RAD dist
30 (14/16)
70
0.00
73
RAD Bd Constant
0.307 12.913
0.30754705 12.7259868
FEM
27 (11/16)
85
0.00
96
FEM GL FEM GLC FEM Bp FEM DC FEM Bd Constant
0.0724336 0.137466054 0.08208765 0.32696626 0.141792574 11.5464244
0.33863685 0.46322725 0.04123183 0.90356355 0.3937111 26.7757827
FEM prox
28 (11/17)
75
0.00
79
FEM Bp FEM DC Constant
0.149 0.099 13.573
0.22092731 0.13285413 18.9640014
FEM dist
27 (11/16)
78
0.00
82
FEM Bd Constant
0.226 14.074
0.35116322 21.1090532
TIB
28 (12/16)
93
0.00
100
TIB GL TIB Bp TIB PTAP TIB Bd Constant
TIB prox
29 (12/17)
79
0.00
86
TIB Bp TIB PTAP Constant
0.44 0.251 12.293
1.79300403 1.28007822 32.5522983
TIB dist
28 (12/16)
68
0.00
68
TIB Bd Constant
0.377 15.449
0.36390866 14.5461617
MC
44 (27/17)
89
0.00
93
MC GL MC Bp MC dp MC Bd MC dd Constant
13.9570416 18.8129845 11.10900021 2.969632149 9.458567947 83.3450581
0.15376715 1.92932531 1.24966988 0.59899048 1.21368569 48.4173786
Discriminant function coefficient 0.102702772 0.01818626 0.46255787 0.007700067 7.7566147
36.4915647 266.020331 202.76252 171.695711 95.3795556
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4.61243056 48.5164523 60.7410296 10.441994 371.758938
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0.066245604 0.06003107 0.19574231 0.20980155 5.36750403
Logistic regression coefficient
86
0.00
89
MC Bp MC dp Constant
0.362 1.039 13.496
0.84254489 2.21452935 26.9984535
MC dist
44 (27/17)
84
0.00
89
MC Bd MC dd Constant
0.026 0.839 17.527
0.10746882 1.59772289 31.4982382
MT
42 (25/17)
83
0.00
93
MT GL MT Bp MT dp MT Bd MT dd Constant
0.069472332 0.18679277 0.10266686 0.06641686 0.625113043 21.6576285
0.14859781 0.56216904 0.40466771 0.10678402 1.36063102 46.9825381
MT prox
43 (26/17)
81
0.00
81
MT Bp MT dp Constant
0.313 0.119 13.731
0.56462562 0.13680287 22.6977055
MT dist
43 (26/17)
84
0.00
84
MT Bd MT dd Constant
0.072 0.976 20.012
0.20685019 1.98222614 38.8156475
The numbers of individuals in the analysis per subspecies, proportion of correctly classified individuals in logistic regression and crossvalidated discriminant analysis, the cutoff value of discriminant analysis, the discriminant function coefficients and the logistic regression coefficients are presented.
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MC prox
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also to distal and proximal ends separately, as it is common that archaeological finds consist mostly of broken bone fragments. Discriminant analysis describes the relationship between a set of predictor variables and a grouping variable. Such sets of variables can be then used to predict the allocation of unknown cases to pre-defined groups. The classification function uses the following formula (Baxter, 1994): F ¼ a0 þ a1 X 1 þ a2 X 2 þ þ ak X k , where F is the discriminant score of the function, a0 is the constant, a1k are the discriminant coefficients and X1k are the predictor variables. The discriminant score is calculated for each bone sample and the subspecies identification is made in relation to the cutoff value, i.e., the weighted mean of group centroids. There are some constrains to discriminant analysis, namely, the data should preferably be normally distributed and the covariance matrices should be equal (Klecka, 1980). The preliminary examination of the data with the Kolmogorov– Smirnov test for normality and the Box’s M-test of covariance equality revealed that most of the data met the standards in 99% confidence level. However, the metacarpal greatest length was not normally distributed (p ¼ 0.05) and covariance matrices were not equal (p ¼ 0.02). Thus, the discriminant analysis of the metacarpal was run with ln-transformed data. The jacknife procedure of SPSS was performed, as the proportion of correct identifications may be artificially too high if the same data set is used in creating the discriminant functions and calculating the proportions of correctly classified individuals (Baxter, 1994; DeGusta and Vrba, 2003). Logistic regression is a form of regression that can be used in predicting a binary dependent, such as subspecies, from sets of independent variables. On the contrary to discriminant analysis, logistic regression does not require normally distributed variables and has overall less strict assumptions (Menard, 1995). Logistic regression uses the following formula (Menard, 1995): logitðY Þ ¼ b0 þ b1 X 1 þ b2 X 2 þ þ bk X k , where b0 is the constant, b1k are the regression coefficients, X1k are the predictor variables and elogit(Y) are the odds of an individual belonging to group 1, which in this study is wild forest reindeer. The cutoff value of 0.5 is used in assessing the subspecies of an individual. The issue of sexual dimorphism was addressed by exploring the skeletal measurements with PCA. We examined, whether PCA discriminates subspecies and/or sex from skeletal measurements. PCA transforms the variables into a smaller number of uncorrelated variables (Manly, 1994, p. 76) with no prior groupings of the individuals according to, e.g., sex or subspecies. In morphological studies, it is common that a ‘size’ component, comprising majority of the variation in the original variables, arises in stead of ‘relative size’ or ‘shape’ components (Baxter, 1994, p. 71; Jungers et al., 1995). Thus, we used size-adjusted measurements, created by dividing the individual measurements by the cubic root of the bone volume (Jungers et al., 1995), in this analysis. Finally, the discriminant functions and logistic regression equations based on modern reindeer skeletons were applied to archaeological reindeer (Rangifer tarandus) bone finds from Northern Finland to identify the subspecies. The archaeological reindeer bone finds originate from four Northern Finland urban archaeological excavations from the 17th and 18th century Tornio, and the 18th and early 19th century Oulu. The skeletal measurements from these finds are presented in detail
in Puputti and Niskanen (in press), and there were no statistically significant differences in measurements between the sites (t-test, 99% confidence level). Very few complete limb bones were found among the archaeological material, partly because of the fragmentary state of the bone material and partly because the bones were often broken to obtain the marrow. Marrow extraction was favoured from the metapodials, indicated by the frequently broken distal and proximal ends (Puputti, 2007). Hence, mainly distal or proximal bone fragments could be used in the subspecies identification and only one complete radius was found. The archaeological contexts of the reindeer bone finds are described in more detail in Puputti and Niskanen (in press).
Results and discussion The discriminant functions and logistic regression equations The results of the analyses are presented in Table 1. In discriminant analysis, the eigenvalues were above one for all the complete bones and also for proximal humerus, proximal metacarpal and distal metatarsal. Canonical correlations were above 0.6 for all the elements except for distal radius and distal tibia. The Chi-squares of the logistic regression models were significant in 99% confidence level, except for distal radius and distal tibia with p-values of 0.011 and 0.014, respectively. Nagelkerke’s R-squares were above 0.5 for all elements except for proximal scapula, distal radius and distal tibia. Discriminant functions based on complete limb bones were accurate with the proportion of correctly classified cases above 80%. Discriminant functions based on the proximal or distal ends were slightly less accurate than those based on complete bones. Nevertheless, the proportion of correctly classified cases was above 70%, except for distal tibia and proximal scapula. Logistic regression was slightly more efficient in discriminating the subspecies; the proportions of correct allocations was over 90% for complete limb bones and over 70% for bone ends, excluding distal tibia and proximal scapula. The poorer discriminating ability of scapula and bone condyles can be expected, because semidomesticated reindeer and wild forest reindeer differ in body dimensions most dramatically in limb length. Wild forest reindeer have longer limbs as a result of adaptation to the heavy snow cover in the forests, as the limb length of semi-domesticated reindeer is an adaptation to the lighter snow cover in the mountains (Nieminen and Helle, 1980). Also, scapula may be a poorer discriminator of subspecies because its morphology is considerably affected by weight-bearing and locomotion. There is thus more phenotypic plasticity than in case of other bones included in this study.
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Sexual dimorphism In both discriminant analysis and logistic regression, the same eight individuals were misclassified in most cases, totalling 85% of all misclassified cases. These individuals were large male semi-domesticated reindeer and small female wild forest reindeer. The withers heights, body weights and skeletal dimensions of semidomesticated reindeer and wild forest reindeer overlap considerably (Nieminen and Helle, 1980). Because of the larger size of wild forest reindeer and the sexual dimorphism of this species, especially the body sizes of large male semi-domesticated reindeer and small female wild forest reindeer overlap, making subspecies discrimination from skeletal measurements more erroneous in the case of these individuals. Also, the number of male
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semi-domesticated reindeer in the analysis was only one, except for the metapodials. This may have biased the analysis. PCA was employed in exploring the effect of sexual dimorphism in subspecies identification of reindeer. The scatterplots of 1st and 2nd principal components of tibia, femur, metacarpal and radius are presented in Fig. 1 as examples. There were differences in PCA’s ability to discriminate the subspecies. In general, however, PCA did dot discriminate sex. Upper limb bones, namely, scapula, humerus and femur, did not show a clear clustering of subspecies, and no clustering of sexes at all. Lower limb bones, i.e., radius, tibia and metapodials showed a clear clustering of subspecies, and tibia and metapodials showed no explicit clustering of sexes. However, radius and proximal and distal humerus
Fig. 1. The scatterplots of first and second principal components of tibia, femur, metacarpal and radius. (J) R.t.tarandus; (K) R.t. tarandus male; ( ) R.t. tarandus female; (&) R.t. fennicus; (’) R.t. fennicus male; and ( ) R.t. fennicus female.
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showed also a clustering of sexes. This is probably due to the different weight-bearing functions of the skeletal elements. Bones of the forelimb carry a greater share of the body weight and also the weight of antlers, which is why forelimb bones of reindeer are good discriminators of sex (Weinstock, 2000). The metacarpal measurements in our study, however, did not show any clustering of sexes, but only clustering of subspecies. This may be due to the larger sample of metacarpals. The metacarpal sample included several male semi-domesticated reindeer, which makes the segregation of subspecies and sex more reliable than in analyses where the number of male semi-domesticated reindeer is only one. Thus, sexual dimorphism of reindeer is observable especially in upper forelimb skeletal dimensions, and caution must be taken when assessing the subspecies from such dimensions, as well as the subspecies of individuals of intermediary size. These may include for instance malnourished or young individuals. Moreover, in fragmentary archaeological assemblages, the maturity of individuals represented only by early fusing elements such as proximal metapodials, proximal radius or distal humerus, remains unclear. Inclusion of such elements may bias the results and cause misidentifications (see also Weinstock, 2000). Other possible sources of error include also the presence of hybrids of wild forest reindeer and semi-domesticated reindeer in the archaeological assemblages.
Application to archaeological reindeer bone finds The discriminant functions and regression equations were applied to a total of 48 archaeological reindeer bone finds from urban archaeological excavations from early modern Oulu and Tornio, Northern Finland. The results of both these methods were virtually identical and thus, only the identifications based on discriminant
functions are presented in Fig. 2. One complete radius was included in the sample, whereas the other finds were individual bone ends. Probability of membership of 0.8 was used as a threshold in choosing the statistically significant subspecies identifications. Along the same line with DeGusta and Vrba (2003), we calculated the confidence value that allowed only 5% misclassified cases and it was under 0.8 for all the elements in our material. Based on these identifications, both subspecies are represented in the urban archaeological material from Northern Finland. A clear distinction in the shares of wild forest reindeer and semi-domesticated reindeer bones was observed between Oulu and Tornio. Semidomesticated reindeer dominate the assemblages from Tornio (nine out of 12 identifications) and wild forest reindeer those from Oulu (seven out of eight identifications). Minimum numbers of individuals were two wild forest reindeer and eight semi-domesticated reindeer in Tornio, and four wild forest reindeer and one semidomesticated reindeer in Oulu. There is, however, a possibility that some of the bones identified as semidomesticated reindeer actually derive from wild mountain reindeer, as our analysis does not distinguish between animals within the same subspecies. Wild mountain reindeer were not extant in Oulu and Tornio areas, but the bone type and skeletal frequency data of marketplace animal bone assemblages in Lapland indicate that quality meat cuts that may have been exported (Lahti 2006). Moreover, several identifications were based on early fusing elements, i.e., distal humerus and proximal radius, which may derive from young individuals. However, as the age profiles extracted from early modern urban reindeer bone finds indicate that mortality was confined mostly to adult individuals (Puputti 2007), it is likely that also these elements derive from adult reindeer. Also, there is a possibility that
Fig. 2. Identifications of archaeological reindeer bone finds from Oulu and Tornio (confidence level 0.95).
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hybrids of semi-domesticated and wild forest reindeer are included in the archaeological sample. According to historical data, the townsfolk of Tornio, especially wealthy burghers, owned often several semidomesticated reindeer during the 17th and 18th centuries. They were used as draught animals during the winter trade trips to Lapland, and during the summer, they were kept in the care of reindeer keepers in Lapland (Ma¨ntyla¨, 1971). In contrast, there is less information on reindeer husbandry in the Oulu area; and moreover, there are no mentions of townsfolk in Oulu owning semi-domesticated reindeer (Virrankoski, 1973). This pattern is supported by our results. Another possibility is that the bigger share of wild forest reindeer bones in Oulu is due to the fact that all the archaeological bones from Oulu originate from excavations conducted on Pikisaari Island. This island was, although located in the close proximity of the town, sparsely inhabited by a few craftsmen during the early modern period. Thus, the proportion of wild reindeer bones may reflect the marginal status of the inhabitants of Pikisaari, who may have had to rely more on hunting in their subsistence. This hypothesis, however, cannot be confirmed, as no contemporaneous animal bone assemblages have been analysed from downtown Oulu.
Conclusion The discriminant functions and logistic regression equations based on sets of postcranial measurements from semi-domesticated reindeer and wild forest reindeer performed generally well in discriminating these subspecies. The performances of these two methods were fairly similar with classification accuracy of 70–100%. Complete bones were the best discriminators, but also bone ends produced good identification results. However, subspecies assessments from bones showing strong sexual dimorphism, i.e., the bones of the forelimb, are more prone to error, when sample sizes are small. Also, caution has to be taken when assessing the subspecies of individuals of intermediate size. The application of our results to archaeological reindeer bone finds from urban archaeological excavations from early modern Northern Finland indicated that both subspecies were present in the archaeological bone assemblages. However, semi-domesticated reindeer bones dominate the archaeological animal bone assemblages from Tornio, whereas the in Oulu, wild forest reindeer were more common. This pattern may be due to regional differences in reindeer husbandry, or, alternatively, socioeconomic factors influencing the role of hunting in the subsistence economy of the urban population.
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Acknowledgements We would like to thank the staff of the Zoological Museum at the University of Oulu for access to the reindeer skeleton collection and the anonymous referees for valuable comments on the earlier version of this article. This research was partially supported by the Finnish Graduate School in Archaeology.
References Aaris-Sørensen, K., Mu¨hldorff, R., Brinch Petersen, E., 2007. The Scandinavian reindeer (Rangifer tarandus L.) after the last glacial maximum: time, seasonality and human exploitation. J. Archaeol. Sci. 34, 914–923. Arnqvist, G., M(artenson, T., 1998. Measurement error in geometric morphometrics: empirical strategies to assess and reduce its impact on measures of shape. Acta Zoolog. Acad. Sci. Hungar. 44 (1), 73–96. Banfield, A.W.F., 1961. A Revision of the Reindeer and Caribou, Genus Rangifer. National Museum of Canada Bulletin 177. Baxter, M.J., 1994. Exploratory Multivariate Analysis in Archaeology. Edinburgh University Press, Edinburgh. Berteaux, D., Guintard, C., 1995. Osteometric study of the metapodials of Amsterdam Island feral cattle. Acta Theriol. 40 (1), 97–110. Cardoso, H.F.V., 2008. Sample-specific (universal) metric approaches for determining the sex of immature human skeletal remains using permanent tooth dimensions. J. Archaeol. Sci. 35, 158–168. DeGusta, D., Vrba, E., 2003. A method for inferring paleohabitats from the functional morphology of bovid astragali. J. Archaeol. Sci. 30, 1009–1022. Goldberg, P.M., 1999. Statistical comparisons of the osteology of Southwestern Columbidae. J. Archaeol. Sci. 26, 1459–1471. Hakala, A.V.K., Heikura, K., Markovsky, V.A., Bljudnik, L., Pulliainen, E., Danilov, P.I., 1996. On the taxonomy and geographical variation of the European reindeer with special reference to the wild forest reindeer, Rangifer tarandus fennicus Lo¨nnberg 1909. Aquilo Ser. Zool. 29, 3–23. Halinen, P., 2005. Prehistoric Hunters of Northernmost Lapland. Settlement Patterns and Subsistence Strategies. The Finnish Antiquarian Society, Helsinki. Hufthammer, A.K., 1995. Age determination of reindeer (Rangifer tarandus L.). Archaeozoologia 7 (2), 33–42. Ingold, T., 1980. Hunters, Pastoralists and Ranchers. Reindeer Economies and Their Transformations. Cambridge University Press, Cambridge. Jungers, W.L., Falsetti, A.B., Wall, C.E., 1995. Shape, relative size and size-adjustments in morphometrics. Yearbook of Physical Anthropology, vol. 38, pp. 137–161. Klecka, W.R., 1980. Discriminant Analysis. Sage Publications, Beverly Hills. Lahti, E., 2006. Bones from Sa´pmi: reconstruction of the everyday life of two ancient Saami households. In: Herva, V. (Ed.), People, Material Culture and Environment in the North. Proceedings of the 22nd Nordic Archaeological Conference, University of Oulu, Oulu, pp. 284–295.
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Manly, B.F.Y., 1994. Multivariate Statistical Methods. A Primer, second ed. Chapman & Hall, London. Ma¨ntyla¨, I., 1971. Tornion kaupungin historia. 1. osa. 1621–1809. Tornion kaupunki, Tornio. Menard, S., 1995. Applied Logistic Regression Analysis. Sage Publications, Thousand Oaks. Nieminen, M., Helle, T., 1980. Variation in body measurements of wild and semi-domestic reindeer (Rangifer tarandus) in Fennoscandia. Ann. Zool. Fennici 17, 275–283. Puputti, A., 2006. Animal Husbandry and Game Exploitation in 17th Century Tornio, Northern Finland, META 1/2006, pp. 13–28. Puputti, A., 2007. Ruuanja¨tteita¨ tunkiolla. Oulun Pikisaaren kesa¨n 2006 kaivausten ela¨inluulo¨ydo¨t. Faravid 31, 9–22.
Puputti, A., Niskanen, M. The estimation of body weight of the reindeer (Rangifer tarandus L.) from skeletal measurements. Environ. Archaeol., in press. Virrankoski, P., 1973. Pohjois-Pohjanmaan ja Lapin historia III. 1600-luku. Pohjois-Pohjanmaan, Kainuun ja Lapin yhteinen historiatoimikunta, Oulu. von den Driesch, A., 1976. Das Vermessen von Tierknochen aus Vor- und Fru¨hgeschichtlichen Siedlungen. Univerista¨t Mu¨nchen, Mu¨nchen. Weinstock, J., 2000. Osteometry as a source of refined demographic information: sex ratios or reindeer, hunting strategies, and herd control in the Late Glacial site of Stellmoor, Northern Germany. J. Archaeol. Sci. 27, 1187–1195.
www.elsevier.de/mambio
ORIGINAL INVESTIGATION
Identification of semi-domesticated reindeer (Rangifer tarandus tarandus, Linnaeus 1758) and wild forest reindeer (R.t. fennicus, Lo¨nnberg 1909) from postcranial skeletal measurements Anna-Kaisa Puputti, Markku Niskanen Laboratory of Archaeology, University of Oulu, P.O. Box 1000, FIN-90014 Oulun yliopisto, Finland Received 24 October 2007; accepted 10 March 2008
Abstract Reindeer bones are common finds from archaeological sites from prehistoric and historic Fennoscandia. The interpretation of the reindeer bone finds, however, is often hindered by the difficulty to separate the different subspecies of reindeer using the postcranial skeletal morphology. In this paper, skeletal measurements of modern semidomesticated reindeer and wild forest reindeer are explored with multivariate statistical methods in order to find suitable methods for subspecies identification. The results are then applied to archaeological reindeer bone finds from Northern Finland and archaeological implications of the results are discussed. r 2008 Deutsche Gesellschaft fu¨r Sa¨ugetierkunde. Published by Elsevier GmbH. All rights reserved. Keywords: Rangifer tarandus; Zooarchaeology; Identification; Finland
Introduction In this study, we will use discriminant analysis and logistic regression to separate sets of postcranial skeletal measurements of modern semi-domesticated reindeer from wild forest reindeer. In bioarchaeology, these methods are often used, for instance, in taxonomic identification, sex assessment or habitat prediction from skeletal measurements (e.g. Goldberg, 1999; DeGusta and Vrba, 2003; Cardoso 2008). Also, the issue of sexual dimorphism of reindeer is addressed by employing principal component analysis (PCA). The results are then applied to archaeological reindeer bone remains from urban archaeological excavations from two towns in early modern (ca. 1600–1800 AD) Northern Finland, Tornio and Oulu. Corresponding author. Tel.: +358 8 553 3371.
E-mail address: anna-kaisa.puputti@oulu.fi (A.-K. Puputti).
Different subspecies of reindeer have been extensively exploited by humans in the northern hemisphere from the Palaeolithic period to present-day and reindeer bones are common finds in archaeological sites throughout the area (e.g. Weinstock 2000; Aaris-Sørensen et al. 2007). However, the interpretation of archaeological reindeer bone finds from Northern Fennoscandia is complicated by the presence of two interbreeding subspecies, mountain reindeer (includes both wild and semi-domesticated reindeer) (Rangifer tarandus tarandus) and forest reindeer (R.t. fennicus). The morphologies of these two subspecies overlap extensively (see e.g. Nieminen and Helle, 1980). Thus, identification of postcranial bones of these subspecies is difficult. Subspecies identification is of interest to archaeologists as the archaeological bone finds of these subspecies may infer different subsistence strategies and cultural interpretations. A number of studies have dealt with cranial morphology and body proportions of different reindeer
1616-5047/$ - see front matter r 2008 Deutsche Gesellschaft fu¨r Sa¨ugetierkunde. Published by Elsevier GmbH. All rights reserved. doi:10.1016/j.mambio.2008.03.002 Mamm. biol. 74 (2009) 49–58
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subspecies (e.g. Nieminen and Helle, 1980; Hakala et al., 1996), but to date, there are no zooarchaeological studies to distinguish reindeer subspecies from postcranial skeletal measurements. The geographical distribution range of reindeer (Rangifer tarandus) comprises nearly the whole circumpolar area (Banfield 1961). Reindeer has several subspecies, of which the wild mountain reindeer (R.t. tarandus) and the wild forest reindeer (R.t. fennicus) have both been extant in Northern Finland until recently. At present, wild mountain reindeer are found only in Southern Norway and inland Kola Peninsula and the forest reindeer in Eastern Finland, Ostrobothnia and Russia (Nieminen and Helle, 1980). However, historically, the ranges of wild mountain reindeer and forest reindeer comprised, respectively, almost the whole Northern Fennoscandia and Kola Peninsula, and the coniferous belt of Southern Finland and Southern Lapland (Nieminen and Helle, 1980). The withers height of forest reindeer is 10–15 cm higher than that of mountain reindeer, mostly due to longer legs of the forest reindeer. Forest reindeer are also slenderer in body and the cranial morphology differs from the mountain reindeer (Nieminen and Helle, 1980; Hakala et al., 1996). Morphological similarity suggests that the semidomesticated reindeer is most likely domesticated from the wild mountain reindeer of Scandinavia (Nieminen and Helle, 1980; Hakala et al., 1996). There is some debate among researchers as to when the reindeer was domesticated and estimates vary from the Mesolithic to the Middle Age in Scandinavia. It is generally assumed that small-scale reindeer husbandry began in Scandinavia in early Middle Age (ca. 200–900 AD) and large scale reindeer husbandry probably began in Northern Finland in the late Middle Age (ca. 1400–1500 AD) (see e.g. Ingold, 1980; Halinen, 2005 for a more detailed discussion). Reindeer were also a part of the urban subsistence in the early modern Northern Finland. Urban archaeological excavations in the area generally yield small quantities of reindeer bones (e.g. Puputti, 2006, 2007). It is unknown, if these reindeer bone finds originate from semi-domesticated reindeer or wild forest reindeer. For instance, in the case of the 17th and 18th century archaeological sites at Oulu and Tornio, both options are possible because wild forest reindeer were still hunted in Northern Finland during the early modern period and semi-domesticated reindeer were kept in the area (Virrankoski, 1973).
Material and methods A total of 46 nearly complete and partial skeletons of modern semi-domesticated reindeer and wild forest reindeer
from the collection of the Zoological Museum of University of Oulu were measured in this study. The semi-domesticated reindeer originate from reindeer keepers in Northern Finland or the University of Oulu Zoo. The wild forest reindeer originate from Eastern Finland. These animals have been prepared in the Zoological Museum and the sex and subspecies assessments have been conducted by the Zoological Museum’s staff from complete carcasses prior to the preparation. Hybrids of wild forest reindeer and semi-domesticated reindeer were not included in our study. Only mature individuals, i.e., individuals with fully fused epiphyses, were included in the study material. This means the age of approximately 42–54 months (Hufthammer 1995). Some individuals were represented only by metapodials; the age of these individuals can only be assessed as over 18–30 months, the age in which metapodial distal epiphyses fuse (Hufthammer 1995). The skeletons of the semi-domesticated reindeer include eight males, 11 females and 10 individuals of unknown sex. One skeleton of male semi-domesticated reindeer was complete and seven individuals were represented only by metapodials. One skeleton of female semi-domesticated reindeer was complete except for scapula, two were represented by humerus, radius and metacarpal, one by femur, tibia and metatarsal, and seven only by metapodials. The skeletons of individuals of unknown sex were complete. The wild forest reindeer sample includes six males, 10 females and one individual of unknown sex. These skeletons were complete, except for two males without scapulae. Some measurements were not obtained from all the bones because of, for instance, breakage or infectious tissue. The numbers of elements used in each analysis are presented in Table 1. Measurements were taken from the limb bones according to von den Driesch (1976), Berteaux and Guintard (1995) and Puputti and Niskanen (in press). Full details of the measurements, taken with a digital vernier and recorded in millimetres, are presented in Puputti and Niskanen (in press). Only limb bones were included in this study, because the cranial morphology of semi-domesticated reindeer and forest reindeer somewhat differs, making morphological identification possible (Hakala et al., 1996). Moreover, limb bones or limb bone fragments are common finds in archaeological sites because of their better durability in comparison with cranial bones, and they are easily identified to species level, unlike, for instance, vertebral and rib fragments. Measurement error can bias the analysis especially in such cases when true variation in skeletal dimensions is small, for instance, in intraspecific comparisons (Arnqvist and Ma( rtenson 1998). In our study, measurement error was estimated by measuring six individuals twice and calculating the ratio of the variance due to differences among individuals (Arnqvist and Ma( rtenson, 1998). This was done by performing a model II one-way analysis of variance with individual as categorical factor, and calculating the variance ratio R ¼ S2A =ðS2W þ S2A Þ, where S2W ¼ MSwithin and S2A ¼ ðMSamong MSwithin Þ=n. The variance in measurements was mostly due do differences between individuals, with variance ratios of 0.95–1.00, except for scapula and femur greatest lengths, with variance ratios of 0.77–0.88. Discriminant analysis and logistic regression were applied to reindeer skeletal measurements to identify the subspecies. The analysis were performed (SPSS 14.0) to complete bones and
The discriminant functions and logistic regression equations N (tarandus/ fennicus)
Correctly classified in DA
Cutoff (mean of centroids)
Correctly classified in LR
Measurement
Discriminant function coefficient
Logistic regression coefficient
SCAP
24 (10/14)
83
0.00
100
SCAP Bg SCAP LG SCAP GLP SCAP HS SCAP Ld Constant
0.07599429 0.088210739 0.140519429 0.070440793 0.07107723 14.7850995
12.5628768 7.51915075 16.9884304 25.8322241 0.86490518 493.534075
SCAP prox
25 (11/14)
68
0.00
72
SCAP Bg SCAP LG SCAP GLP Constant
0.125 0.124 0.265 13.249
HUM
29 (13/16)
93
0.00
100
HUM GL HUM GLC HUM BT HUM Bd HUM TH HUM Bp HUM HHAP Constant
0.09166274 0.238885172 0.09629042 0.057095578 0.08101913 0.027913868 0.39762584 13.0713218
HUM prox
29 (13/16)
76
0.00
90
HUM Bp HUM HHAP Constant
HUM dist
31 (14/17)
77
0.00
81
HUM Bd HUM TH HUM BT Constant
0.14657495 0.13256978 0.41846949 19.6580963 9.07362846 0.55809377 2.88449587 17.0426097 7.83830538 9.8571414 17.7966693 733.447732
0.35 0.253 9.675
1.07356524 0.76913246 28.7335005
0.5 0.295 0.45 14.501
0.90298332 0.81959462 0.68550181 23.3201552
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Table 1.
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Table 1. (continued ) Anatomical element
N (tarandus/ fennicus)
Correctly classified in DA
Cutoff (mean of centroids)
Correctly classified in LR
Measurement
RAD
30 (14/16)
90
0.00
100
RAD GL RAD PRAP RAD Bp RAD Bd Constant
RAD prox
31 (14/17)
71
0.00
71
RAD Bp RAD PRAP Constant
0.253 0.902 10.565
1.50517749 0.45684667 15.7310711
RAD dist
30 (14/16)
70
0.00
73
RAD Bd Constant
0.307 12.913
0.30754705 12.7259868
FEM
27 (11/16)
85
0.00
96
FEM GL FEM GLC FEM Bp FEM DC FEM Bd Constant
0.0724336 0.137466054 0.08208765 0.32696626 0.141792574 11.5464244
0.33863685 0.46322725 0.04123183 0.90356355 0.3937111 26.7757827
FEM prox
28 (11/17)
75
0.00
79
FEM Bp FEM DC Constant
0.149 0.099 13.573
0.22092731 0.13285413 18.9640014
FEM dist
27 (11/16)
78
0.00
82
FEM Bd Constant
0.226 14.074
0.35116322 21.1090532
TIB
28 (12/16)
93
0.00
100
TIB GL TIB Bp TIB PTAP TIB Bd Constant
TIB prox
29 (12/17)
79
0.00
86
TIB Bp TIB PTAP Constant
0.44 0.251 12.293
1.79300403 1.28007822 32.5522983
TIB dist
28 (12/16)
68
0.00
68
TIB Bd Constant
0.377 15.449
0.36390866 14.5461617
MC
44 (27/17)
89
0.00
93
MC GL MC Bp MC dp MC Bd MC dd Constant
13.9570416 18.8129845 11.10900021 2.969632149 9.458567947 83.3450581
0.15376715 1.92932531 1.24966988 0.59899048 1.21368569 48.4173786
Discriminant function coefficient 0.102702772 0.01818626 0.46255787 0.007700067 7.7566147
36.4915647 266.020331 202.76252 171.695711 95.3795556
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4.61243056 48.5164523 60.7410296 10.441994 371.758938
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0.066245604 0.06003107 0.19574231 0.20980155 5.36750403
Logistic regression coefficient
86
0.00
89
MC Bp MC dp Constant
0.362 1.039 13.496
0.84254489 2.21452935 26.9984535
MC dist
44 (27/17)
84
0.00
89
MC Bd MC dd Constant
0.026 0.839 17.527
0.10746882 1.59772289 31.4982382
MT
42 (25/17)
83
0.00
93
MT GL MT Bp MT dp MT Bd MT dd Constant
0.069472332 0.18679277 0.10266686 0.06641686 0.625113043 21.6576285
0.14859781 0.56216904 0.40466771 0.10678402 1.36063102 46.9825381
MT prox
43 (26/17)
81
0.00
81
MT Bp MT dp Constant
0.313 0.119 13.731
0.56462562 0.13680287 22.6977055
MT dist
43 (26/17)
84
0.00
84
MT Bd MT dd Constant
0.072 0.976 20.012
0.20685019 1.98222614 38.8156475
The numbers of individuals in the analysis per subspecies, proportion of correctly classified individuals in logistic regression and crossvalidated discriminant analysis, the cutoff value of discriminant analysis, the discriminant function coefficients and the logistic regression coefficients are presented.
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MC prox
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also to distal and proximal ends separately, as it is common that archaeological finds consist mostly of broken bone fragments. Discriminant analysis describes the relationship between a set of predictor variables and a grouping variable. Such sets of variables can be then used to predict the allocation of unknown cases to pre-defined groups. The classification function uses the following formula (Baxter, 1994): F ¼ a0 þ a1 X 1 þ a2 X 2 þ þ ak X k , where F is the discriminant score of the function, a0 is the constant, a1k are the discriminant coefficients and X1k are the predictor variables. The discriminant score is calculated for each bone sample and the subspecies identification is made in relation to the cutoff value, i.e., the weighted mean of group centroids. There are some constrains to discriminant analysis, namely, the data should preferably be normally distributed and the covariance matrices should be equal (Klecka, 1980). The preliminary examination of the data with the Kolmogorov– Smirnov test for normality and the Box’s M-test of covariance equality revealed that most of the data met the standards in 99% confidence level. However, the metacarpal greatest length was not normally distributed (p ¼ 0.05) and covariance matrices were not equal (p ¼ 0.02). Thus, the discriminant analysis of the metacarpal was run with ln-transformed data. The jacknife procedure of SPSS was performed, as the proportion of correct identifications may be artificially too high if the same data set is used in creating the discriminant functions and calculating the proportions of correctly classified individuals (Baxter, 1994; DeGusta and Vrba, 2003). Logistic regression is a form of regression that can be used in predicting a binary dependent, such as subspecies, from sets of independent variables. On the contrary to discriminant analysis, logistic regression does not require normally distributed variables and has overall less strict assumptions (Menard, 1995). Logistic regression uses the following formula (Menard, 1995): logitðY Þ ¼ b0 þ b1 X 1 þ b2 X 2 þ þ bk X k , where b0 is the constant, b1k are the regression coefficients, X1k are the predictor variables and elogit(Y) are the odds of an individual belonging to group 1, which in this study is wild forest reindeer. The cutoff value of 0.5 is used in assessing the subspecies of an individual. The issue of sexual dimorphism was addressed by exploring the skeletal measurements with PCA. We examined, whether PCA discriminates subspecies and/or sex from skeletal measurements. PCA transforms the variables into a smaller number of uncorrelated variables (Manly, 1994, p. 76) with no prior groupings of the individuals according to, e.g., sex or subspecies. In morphological studies, it is common that a ‘size’ component, comprising majority of the variation in the original variables, arises in stead of ‘relative size’ or ‘shape’ components (Baxter, 1994, p. 71; Jungers et al., 1995). Thus, we used size-adjusted measurements, created by dividing the individual measurements by the cubic root of the bone volume (Jungers et al., 1995), in this analysis. Finally, the discriminant functions and logistic regression equations based on modern reindeer skeletons were applied to archaeological reindeer (Rangifer tarandus) bone finds from Northern Finland to identify the subspecies. The archaeological reindeer bone finds originate from four Northern Finland urban archaeological excavations from the 17th and 18th century Tornio, and the 18th and early 19th century Oulu. The skeletal measurements from these finds are presented in detail
in Puputti and Niskanen (in press), and there were no statistically significant differences in measurements between the sites (t-test, 99% confidence level). Very few complete limb bones were found among the archaeological material, partly because of the fragmentary state of the bone material and partly because the bones were often broken to obtain the marrow. Marrow extraction was favoured from the metapodials, indicated by the frequently broken distal and proximal ends (Puputti, 2007). Hence, mainly distal or proximal bone fragments could be used in the subspecies identification and only one complete radius was found. The archaeological contexts of the reindeer bone finds are described in more detail in Puputti and Niskanen (in press).
Results and discussion The discriminant functions and logistic regression equations The results of the analyses are presented in Table 1. In discriminant analysis, the eigenvalues were above one for all the complete bones and also for proximal humerus, proximal metacarpal and distal metatarsal. Canonical correlations were above 0.6 for all the elements except for distal radius and distal tibia. The Chi-squares of the logistic regression models were significant in 99% confidence level, except for distal radius and distal tibia with p-values of 0.011 and 0.014, respectively. Nagelkerke’s R-squares were above 0.5 for all elements except for proximal scapula, distal radius and distal tibia. Discriminant functions based on complete limb bones were accurate with the proportion of correctly classified cases above 80%. Discriminant functions based on the proximal or distal ends were slightly less accurate than those based on complete bones. Nevertheless, the proportion of correctly classified cases was above 70%, except for distal tibia and proximal scapula. Logistic regression was slightly more efficient in discriminating the subspecies; the proportions of correct allocations was over 90% for complete limb bones and over 70% for bone ends, excluding distal tibia and proximal scapula. The poorer discriminating ability of scapula and bone condyles can be expected, because semidomesticated reindeer and wild forest reindeer differ in body dimensions most dramatically in limb length. Wild forest reindeer have longer limbs as a result of adaptation to the heavy snow cover in the forests, as the limb length of semi-domesticated reindeer is an adaptation to the lighter snow cover in the mountains (Nieminen and Helle, 1980). Also, scapula may be a poorer discriminator of subspecies because its morphology is considerably affected by weight-bearing and locomotion. There is thus more phenotypic plasticity than in case of other bones included in this study.
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Sexual dimorphism In both discriminant analysis and logistic regression, the same eight individuals were misclassified in most cases, totalling 85% of all misclassified cases. These individuals were large male semi-domesticated reindeer and small female wild forest reindeer. The withers heights, body weights and skeletal dimensions of semidomesticated reindeer and wild forest reindeer overlap considerably (Nieminen and Helle, 1980). Because of the larger size of wild forest reindeer and the sexual dimorphism of this species, especially the body sizes of large male semi-domesticated reindeer and small female wild forest reindeer overlap, making subspecies discrimination from skeletal measurements more erroneous in the case of these individuals. Also, the number of male
55
semi-domesticated reindeer in the analysis was only one, except for the metapodials. This may have biased the analysis. PCA was employed in exploring the effect of sexual dimorphism in subspecies identification of reindeer. The scatterplots of 1st and 2nd principal components of tibia, femur, metacarpal and radius are presented in Fig. 1 as examples. There were differences in PCA’s ability to discriminate the subspecies. In general, however, PCA did dot discriminate sex. Upper limb bones, namely, scapula, humerus and femur, did not show a clear clustering of subspecies, and no clustering of sexes at all. Lower limb bones, i.e., radius, tibia and metapodials showed a clear clustering of subspecies, and tibia and metapodials showed no explicit clustering of sexes. However, radius and proximal and distal humerus
Fig. 1. The scatterplots of first and second principal components of tibia, femur, metacarpal and radius. (J) R.t.tarandus; (K) R.t. tarandus male; ( ) R.t. tarandus female; (&) R.t. fennicus; (’) R.t. fennicus male; and ( ) R.t. fennicus female.
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showed also a clustering of sexes. This is probably due to the different weight-bearing functions of the skeletal elements. Bones of the forelimb carry a greater share of the body weight and also the weight of antlers, which is why forelimb bones of reindeer are good discriminators of sex (Weinstock, 2000). The metacarpal measurements in our study, however, did not show any clustering of sexes, but only clustering of subspecies. This may be due to the larger sample of metacarpals. The metacarpal sample included several male semi-domesticated reindeer, which makes the segregation of subspecies and sex more reliable than in analyses where the number of male semi-domesticated reindeer is only one. Thus, sexual dimorphism of reindeer is observable especially in upper forelimb skeletal dimensions, and caution must be taken when assessing the subspecies from such dimensions, as well as the subspecies of individuals of intermediary size. These may include for instance malnourished or young individuals. Moreover, in fragmentary archaeological assemblages, the maturity of individuals represented only by early fusing elements such as proximal metapodials, proximal radius or distal humerus, remains unclear. Inclusion of such elements may bias the results and cause misidentifications (see also Weinstock, 2000). Other possible sources of error include also the presence of hybrids of wild forest reindeer and semi-domesticated reindeer in the archaeological assemblages.
Application to archaeological reindeer bone finds The discriminant functions and regression equations were applied to a total of 48 archaeological reindeer bone finds from urban archaeological excavations from early modern Oulu and Tornio, Northern Finland. The results of both these methods were virtually identical and thus, only the identifications based on discriminant
functions are presented in Fig. 2. One complete radius was included in the sample, whereas the other finds were individual bone ends. Probability of membership of 0.8 was used as a threshold in choosing the statistically significant subspecies identifications. Along the same line with DeGusta and Vrba (2003), we calculated the confidence value that allowed only 5% misclassified cases and it was under 0.8 for all the elements in our material. Based on these identifications, both subspecies are represented in the urban archaeological material from Northern Finland. A clear distinction in the shares of wild forest reindeer and semi-domesticated reindeer bones was observed between Oulu and Tornio. Semidomesticated reindeer dominate the assemblages from Tornio (nine out of 12 identifications) and wild forest reindeer those from Oulu (seven out of eight identifications). Minimum numbers of individuals were two wild forest reindeer and eight semi-domesticated reindeer in Tornio, and four wild forest reindeer and one semidomesticated reindeer in Oulu. There is, however, a possibility that some of the bones identified as semidomesticated reindeer actually derive from wild mountain reindeer, as our analysis does not distinguish between animals within the same subspecies. Wild mountain reindeer were not extant in Oulu and Tornio areas, but the bone type and skeletal frequency data of marketplace animal bone assemblages in Lapland indicate that quality meat cuts that may have been exported (Lahti 2006). Moreover, several identifications were based on early fusing elements, i.e., distal humerus and proximal radius, which may derive from young individuals. However, as the age profiles extracted from early modern urban reindeer bone finds indicate that mortality was confined mostly to adult individuals (Puputti 2007), it is likely that also these elements derive from adult reindeer. Also, there is a possibility that
Fig. 2. Identifications of archaeological reindeer bone finds from Oulu and Tornio (confidence level 0.95).
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hybrids of semi-domesticated and wild forest reindeer are included in the archaeological sample. According to historical data, the townsfolk of Tornio, especially wealthy burghers, owned often several semidomesticated reindeer during the 17th and 18th centuries. They were used as draught animals during the winter trade trips to Lapland, and during the summer, they were kept in the care of reindeer keepers in Lapland (Ma¨ntyla¨, 1971). In contrast, there is less information on reindeer husbandry in the Oulu area; and moreover, there are no mentions of townsfolk in Oulu owning semi-domesticated reindeer (Virrankoski, 1973). This pattern is supported by our results. Another possibility is that the bigger share of wild forest reindeer bones in Oulu is due to the fact that all the archaeological bones from Oulu originate from excavations conducted on Pikisaari Island. This island was, although located in the close proximity of the town, sparsely inhabited by a few craftsmen during the early modern period. Thus, the proportion of wild reindeer bones may reflect the marginal status of the inhabitants of Pikisaari, who may have had to rely more on hunting in their subsistence. This hypothesis, however, cannot be confirmed, as no contemporaneous animal bone assemblages have been analysed from downtown Oulu.
Conclusion The discriminant functions and logistic regression equations based on sets of postcranial measurements from semi-domesticated reindeer and wild forest reindeer performed generally well in discriminating these subspecies. The performances of these two methods were fairly similar with classification accuracy of 70–100%. Complete bones were the best discriminators, but also bone ends produced good identification results. However, subspecies assessments from bones showing strong sexual dimorphism, i.e., the bones of the forelimb, are more prone to error, when sample sizes are small. Also, caution has to be taken when assessing the subspecies of individuals of intermediate size. The application of our results to archaeological reindeer bone finds from urban archaeological excavations from early modern Northern Finland indicated that both subspecies were present in the archaeological bone assemblages. However, semi-domesticated reindeer bones dominate the archaeological animal bone assemblages from Tornio, whereas the in Oulu, wild forest reindeer were more common. This pattern may be due to regional differences in reindeer husbandry, or, alternatively, socioeconomic factors influencing the role of hunting in the subsistence economy of the urban population.
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Acknowledgements We would like to thank the staff of the Zoological Museum at the University of Oulu for access to the reindeer skeleton collection and the anonymous referees for valuable comments on the earlier version of this article. This research was partially supported by the Finnish Graduate School in Archaeology.
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