hawkey 1995

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International Journal of Osteoarchaeology, Vol. 5: 324-33 8 (1 995) Activity-induced Muscu los keletal Stress Markers (MSM) and Subsistence Strategy Changes among Ancient Hudson Bay Eskimos DIANE E. HAWKEY7 AND CHARLES F. MERBS Department of Anthropology, Arizona State University, Box 872402, Tempe, AZ 85287-2402, USA ABSTRACT Although archaeological evidence may express the results of several seasons of activity, the human skeleton, when correlated with archaeological and ethnographic data, provides information concerning daily activities performed throughout an individual’s lifetime. Studies in occupational and sports medicine, along with electromyographic analysis of movement, have shown that different activities place different amounts of stress on human bone. In the present study, analysis of upper extremity musculoskeletal stress markers (MSM) has been used to clarify habitual activity patterns of two ancient Thule Eskimo groups from northwest Hudson Bay, Canada. Distinct pattern differences in muscle use occurred between Thule adult males and females and suggest possible gender-specific activity patterns that are not always discernible from the archaeological record alone. Temporal applications of the MSM data for Early and Late Period Thule support McCartney’s theory of a substantial change in subsistence strategies through time, particularly among the adult males. Keywords: activity-induced stress markers; Eskimo; northwest Hudson Bay; subsistence strategies. Introduction The daily life of ancient populations continues to be of immense interest to researchers. Although demographic data can supply information on who the people were and what they looked like, and palaeopathological analysis can indicate what went awry in a population, skeletal markers of occupational stress (MOS)‘ can clarify daily activity patterns. More importantly, analysis of activity-induced markers offers a unique way to use osteological remains to independently test hypotheses generated from archaeological data. Although the term MOS includes a variety of activity-induced changes produced by stress on human bone, we use the term musculoskeletal stress markers (MSM) to refer specifically to a distinct skeletal mark that occurs where a muscle, tendon or ligament inserts onto the periosteum and into the underlying bony cortex. In general, the periosteum is well vascularized, and the ccc l047-482X/95/040324-15 0 1995 by John Wiley & Sons, Ltd. number of capillaries that supply the periosteum increases when the muscle/tendon/ligament-bone junctions are regularly subjected to minor stress. Osteon remodelling is stimulated by this increased blood flow, and develops where there is greatest muscular activity. Hypertrophy of bone, in the form of a robust muscle attachment, is the direct result of this increased stress, and continual stress of a muscle in daily, repetitive tasks creates a well-preserved skeletal record of an individual’s habitual activity patterns. The use of MSM for habitual activity analysis operates under the assumption that degree and type of marker are related directly to the amount and duration of habitual stress placed on a specific muscle. The assumption that the data are correlated with specific activities is based on a wide variety of kinematic and electromyographic studies performed in the past 50 years. Although these studies have concentrated on the effect of stress on muscle, more recent research in sports Received $2 September 1994 Accepted $1 March $995

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Activity-induced Musculoskeletal strss markers (MSM) and Subsistence Strategy changes among Ancient Hudson bay Eskimos

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  • International Journal of Osteoarchaeology, Vol. 5: 3 2 4 - 3 3 8 (1 995)

    Activity-induced Muscu los keletal Stress Markers (MSM) and Subsistence Strategy Changes among Ancient Hudson Bay Eskimos DIANE E. HAWKEY7 AND CHARLES F. MERBS Department of Anthropology, Arizona State University, Box 872402, Tempe, AZ 85287-2402, USA

    ABSTRACT Although archaeological evidence may express the results of several seasons of activity, the human skeleton, when correlated with archaeological and ethnographic data, provides information concerning daily activities performed throughout an individuals lifetime. Studies in occupational and sports medicine, along with electromyographic analysis of movement, have shown that different activities place different amounts of stress on human bone. In the present study, analysis of upper extremity musculoskeletal stress markers (MSM) has been used to clarify habitual activity patterns of two ancient Thule Eskimo groups from northwest Hudson Bay, Canada. Distinct pattern differences in muscle use occurred between Thule adult males and females and suggest possible gender-specific activity patterns that are not always discernible from the archaeological record alone. Temporal applications of the MSM data for Early and Late Period Thule support McCartneys theory of a substantial change in subsistence strategies through time, particularly among the adult males.

    Keywords: activity-induced stress markers; Eskimo; northwest Hudson Bay; subsistence strategies.

    Introduction

    The daily life of ancient populations continues to be of immense interest to researchers. Although demographic data can supply information on who the people were and what they looked like, and palaeopathological analysis can indicate what went awry in a population, skeletal markers of occupational stress (MOS) can clarify daily activity patterns. More importantly, analysis of activity-induced markers offers a unique way to use osteological remains to independently test hypotheses generated from archaeological data.

    Although the term MOS includes a variety of activity-induced changes produced by stress on human bone, we use the term musculoskeletal stress markers (MSM) to refer specifically to a distinct skeletal mark that occurs where a muscle, tendon or ligament inserts onto the periosteum and into the underlying bony cortex. In general, the periosteum is well vascularized, and the

    ccc l047-482X/95/040324-15 0 1995 by John Wiley & Sons, Ltd.

    number of capillaries that supply the periosteum increases when the muscle/tendon/ligament-bone junctions are regularly subjected to minor stress. Osteon remodelling is stimulated by this increased blood flow, and develops where there is greatest muscular activity. Hypertrophy of bone, in the form of a robust muscle attachment, is the direct result of this increased stress, and continual stress of a muscle in daily, repetitive tasks creates a well-preserved skeletal record of an individuals habitual activity patterns.

    The use of MSM for habitual activity analysis operates under the assumption that degree and type of marker are related directly to the amount and duration of habitual stress placed on a specific muscle. The assumption that the data are correlated with specific activities is based on a wide variety of kinematic and electromyographic studies performed in the past 50 years. Although these studies have concentrated on the effect of stress on muscle, more recent research in sports

    Received $ 2 September 1994 Accepted $ 1 March $995

  • Musculoskeletal Stress Markers 325

    medicine has examined the resultant stress pattern left on the skeleton.2-4

    Studies of activity-induced markers have been well-documented in the anthropological literature. Kennedy' has chronicled more than 80 research studies that have used skeletal and dental markers to determine habitual activities in a variety of contexts, from fossil hominids to modern forensic cases. Recent years have seen an increase in the use of MSM analysis in historic population^,^-'^ in which activities can be correlated with written records. Another promising area of research is the correlation of the internal architecture of bone with musculo- skeletal stress marker data; Berget and ChurchillI6 examined the robusticity and internal geometry of Aleut humeri and found the results to be consistent with habitual behaviour patterns reflected in MSM data.17,'8

    Application of MSM data to test specific archaeologically derived hypotheses in pre- history has been a relatively recent deve- 1 0 p m e n t . ' ~ - ~ ~ A degreee of caution should be exercised when attempting to test hypotheses using small sample size skeletal series, particularly because artefactual and modern ethnographic information may not always correlate accurately with the skeletal record.14 Ideal criteria for a study of activity-induced changes in a population must include not only a relatively large sample size with good skeletal preservation, but also three other factors: ( i ) a relatively narrow time span, ( i i ) cultural and genetic isolation, and (i i i ) a limited number of specialized, but known, activities.22 The Thule culture/early historic skeletal series from the sites of Silumiut and Kamarvik, northwest Hudson Bay, meet these minimum criteria.

    Analysis of the upper extremity MSM of these two Thule groups can clarify possible subsistence strategy adjustments made as a result of increased climatic deterioration in the Canadian Arctic after AD 1200. Although Mathiassen28 identified whale-hunting initially as the major subsistence strategy of the Classic Thule culture (ca. AD 1000-historic contact), the degree of whaling activities practised by specific populations appears strongly correlated with local environmental ~ o n d i t i o n s . ~ ~ - ~ 2 A reduction of pack ice during a major climatic warming trend

    during AD400-120033 originally led to an abundance of whales in Hudson Bay, and it is believed 29,34-36 that the presence of bowhead whales (Balaena mysticetus) first attracted Thule populations into the region. But M ~ C a r t n e y ~ ~ has suggested that the later climatic conditions of the 'Little Ice Age' (beginning after AD 1200) initiated a major and abrupt change in subsistence strategies among the later Thule people of the area. Because Hudson Bay probably froze very early in the season, summer pack ice would have taken longer to melt and whale migration into the Bay region would have been limited. However, the ringed seal (Pboca bispida), which breeds on ice, is thought to have increased significantly with the abundance of sea ice in the area.37 A noticeable shift away from the active hunting and utilization of the bowhead whale may then have occurred because this strategy was no longer economically advantageous.

    Use of faunal data to interpret the earlier utilization of bowhead whales may be somewhat unreliable at eastern Canadian Arctic sites.3',38 Large mammalian fauna, such as whales, were probably butchered at (or near) kill sites, with the meat, blubber and skins transported back to camp. Unfortunately, it is unlikely that these items would be preserved in the archaeological record. The whalebone and baleen found in Early Period Thule sites were often removed and reutilized by later Eskimo, also leading to an underrepresentation of whale remains in earlier northwest Hudson Bay sites.3'

    McCartney, therefore, has based his view primarily on settlement pattern evidence, particularly the absence (after AD 1200) of semi- subterranean winter houses composed of whale bone, sod and stone. The possible lack of bowhead whales, along with the abandonment of the relatively large and stable winter base camps, led McCartney to suggest that whale hunting was no longer a reliable subsistence strategy. Instead, he proposed that an increased dependency on smaiIer sea mammals as the primary subsistence source had occurred.

    Cold temperatures appear to have reached the extreme in the area by the sixteenth century,37 along with an abundance of the sea-ice- dependent ringed seal. Maintenance of domed snow houses on the ice during the winter months

  • 326 D. E. Hawkey and C. F. Merbs

    Table 1. Site, sex, and temporal breakdown of 136 Thule adults utilized for statistical analysis.

    Silumiut Karnarvik Total

    Male Female Male Female Male Female

    Early Thule (Classic Period) 39 39 25 22 64 61

    Total 44 39 31 22 75 61 Later Thule (TransitionallHistoric) 5 0 6 0 1 1 0

    would have enabled a more efficient exploitation of the ringed seal when they surfaced at their breathing hole ( a h ) locations. During the summer, the Thule may have moved inland, relying on migratory caribou, fish, birds and small game.

    Materials and methods

    Our study utilized human skeletal material recovered by the Northwest Hudson Bay Thule Project ( 1967-1 969), and represents the most extensive collection of human remains (n=3 18) from the Thule culture currently available. The remains were obtained from two large winter base camp sites, Silumiut (KkJg-t), a small island attached to the mainland at low tide north of Chesterfield Inlet (63'41'N, 9O0O5'W), and Kamarvik (LeHv-t) , a coastal site south of Wager Bay on Roes Welcome Sound (64"45'N, 87" 1 O'W). Both sites have an initial radiocarbon corrected date of ca. AD 1 205,29 and show continued occupation into historic times.

    A total of 318 skeletons from these two sites were examined initially, but only 136 individuals (43 per cent) were chosen for descriptive statistical comparison (Table 1). A variety of factors led to the exclusion of many of the skeletal remains. The acidity of the soil (pH 5.0- 6.3) at the two sites affected skeletal preservation, and those skeletons that were incomplete or poorly preserved were excluded from our study. Individuals with evidence of healed fractures or severe degenerative joint disease were not included, because these conditions could increase the amount of stress placed on the non-pathological side. Also excluded were adult skeletons that could not be aged or sexed reliably. Children and subadults were not considered for analysis because the presence of secondary

    osteons at subadult insertion sites appears to be independent of localized stress on the bone, and may actually indicate continuity of muscle- bone attachment in a rapidly growing skeleton.39

    All upper extremity bones (clavicles, scapulae, humeri, radii, ulnae) from the remaining individuals were examined visually and scored for MSM type and severity. The sample was then subdivided by age, sex, and geographic location, with individuals assigned a temporal category based on McCartney's analysis of burial artefacts.40 Dental morphological features and craniometric evidence suggest a close phenetic similarity between Kamarvik and S i l ~ m i u t , ~ ' , ~ ~ and because preliminary analysis indicated no statistically significant differences between MSM scores from either site (p

  • Musculoskeletal Stress Markers 327

    Figure 1. Robusticity category at the pectoralis majorinsertion site. Scores from left to right are: Absent 0, Rl=faint. The cortex is only slightly rounded, and often not visible without viewing under a strong light. The elevation is, however, apparent to the touch, although no distinct crests or ridges have formed. RS=rnoderate. The cortical surface is uneven, with a mound-shaped elevation that is easily observable. No sharp ridges or crests have formed. RS=strong. Distinct, sharp crests or ridges have formed. Often there may be a slight depression between two crests (especially noticeable between pecforalis major and feres major insertions), but the depression does not extend into the coltex.

    Figure 2. Robusticity category (tendinous attachment type) at the biceps brachii insertion site. Scores from left to right are: R1 =faint. There is a slight indentation at the site of attachment, but no well-defined sourrounding margin of bone. RP=moderate. Roughening of the attachment site occurs, most often with well-defined surrounding margin of bone. R3=strong. Deep indentation occurs with a clearly defined margin of bone. Usually the roughened area has developed crests of bone.

    (DEH)ZO was used for our study. Standardization score, but also eliminates total reliance on of the gross morphological expressions provided a observer experience. Inter- and intra-observer simple, consistent way to score MSM type and error have proven negligible (p

  • 328 D. E. Hawkey and C. F. Merbs

    Figure 3. Stresss lesion category at the pectoralis majorinsertion site. Scores from left to right are: Sl=faint. There is a shallow 'furrow', a pitting into the cortex that has a lytic-like appearance. It is less than 1 mm in depth. SP=moderate. The pitting is deeper and covers more surface area. It is greater than 1 mm, but less than 3 mm in depth. It may vary in length, but not longer than 5 rnm. SS=strong. The pitting is marked, and greater than 3 rnm in depth, or more than 5 mm in length.

    Figure 4. Ossification category on the humerus (various attachment sites). Scores from left to right are: OSl=faint. A slight exostosis occurs, usually rounded in appearance, and extends less than 2 mm from the cortical surface. OSP=moderate. There is a distinct exostosis, varied in shape, that extends more than 2 rnm, but less than 5 mm from the surface of the cortex. Two examples of OSS=strong. The exostosis extends more than 5 mm from the surface of the bone, or else covers an extensive amount of cortical surface.

    four specific grades (see Figures 1-4). Absence of expression is noted as grade=O.

    daily activities that produce rugged markings at the musculoskeletal site of attachment. It is seen in its most extreme expression as sharp ridges, or crests, of bone. A variation of the robusticity

    Robusticity marker (Figure 1 ) category is seen at sites of tendinous attachment to bone. A mesenchymal cell barrier (layers of

    This category describes the normal reaction of calcified and uncalcified hyaline cartilage) the skeleton to habitual muscle usage and reflects between the tendon and bone prevents

  • Musculoskeletal Stress Markers 329

    resorption or formation of new bone at the attachment site.43 However, the areas imme- diately adjacent to the tendinous attachment do reflect the stress of muscular pull, as seen at the insertion of brucbialis on the radius (Figure 2). In part, the difference in MSM appearance reflects the larger area needed for muscle-to-bone attachment, because muscles have a lower tensile strength than tendons, and require a more substantial attachment area to prevent rupture.44

    Stress lesion [Figure 3)

    The stress lesion is defined here as a pitting, or 'furrow', into the cortex to the degree that it superficially resembles a lytic lesion. There is little in the literature to suggest the aetiology of this poorly understood MSM. Microscopic examination of the area affected reveals bone remodelling and is easily differentiated from post- mortem erosion. Because the stress lesion is also isolated and non-random in nature (occurring only at insertion sites), it is unlikely to be disease- related, such as seen in the inflammatory articular lesions of ankylosing spondylitis.45 Instead, the stress lesion appears to be activity-induced as a result of continual microtrauma at the attachment site.

    A continuum often occurs between the robusticity and stress lesion markers. Some individuals exhibit a combination of the strongest robusticity score (R3), and the faintest stress lesion grade (S l ) at a single insertion site, suggesting a severe use pattern. When a muscle is utilized beyond its intended capacity, it begins to lose the ability to properly absorb stress.46 Histological evidence suggests further that prolonged and habitual tension can cause small muscle fibres to tear and reattach to the periosteum, disrupting the blood supply to the bone.39,47,48 If the disruption is severe and continuous, bone necrosis may occur.49 Bone resorption also takes place at a much faster rate than bone formation, and continual, daily microtrauma would prevent the healing process from successfully concluding, resulting in a deep pitting into the cortex.

    Oss$cation exostosis (F$ure 4 )

    This particular type of MSM is due usually to an abrupt r n a c r ~ t r a u m a , ~ ~ such as a muscle rupture that could result from a sudden fall on the ice. When a bone avulsion injury occurs, new bone formation may be incorporated into the ligament or muscle tissue, and result in a exostosis, or bony 'spur'.

    Expression scores were assessed for statistical analysis with the following numerical values: O=no expression, 1 =robusticity grade 1 (faint), 2 =robusticity grade 2 (moderate), 3 =robusticity grade 3 (strong), 4=stress lesion grade 1 (faint), 5=stress lesion grade 2 (moderate), and 6=stress lesion grade 3 (strong). Because ossification MSM are considered to be due to abrupt macrotrauma, and not to continual muscle use, they were analysed separately. Total weighted mean scores for both males and females were also calculated in order to determine a statistical break-point between stronger and more moderate use of muscles within the specific samples. Those muscles that were higher than the weighted mean breakpoint were considered to have been the most utilized; those below the breakpoint were less utilized.

    A total of 20 muscle insertion sites, three clavicular ligament insertion sites, and two common muscle origin sites, were examined for each individual. Insertion sites were chosen because contraction of a muscle generalIy produces the maximum amount of pull at its insertion.' Three ligaments (one sternoclavicular and two acromioclavicular) were of particular interest in analysis of rotational shoulder movements. Because a total of four flexor muscles originate from the medial epicondyle of the humerus, and four extensors from the lateral epicondyle, both sites were considered to be adequate, if not definitive, indicators of maximum muscular pull.

    Results

    Analyses of side use dominance within individuals who had more than ten bilateral attachment sites present (n=25), indicate that 80 per cent of adults

  • 3 30 D. E. Hawkey and C. F. Merbs

    body size dimorphism and resultant biomechanical advantages involved in lever arm movement. Although a paired t-test revealed statistically significant differences (p

  • Musculoskeletal Stress Markers 331

    Table 4. Largest degrees of difference in rank order score between Early Period adult Thule males and females.

    Rank scorea Rank

    Muscle/liaament Male Female difference

    Biceps brachii Pronator teres Supraspinatus Conoid ligament Anconeus Trapezius Supinator lnfraspinatus

    15.5 8.0 11.0 4.5 9.5 15.0 8.0 13.0 7.0 11.5 5.0 9.0 6.0 3.0

    13.0 10.0

    7.5 6.5 5.5 5.0 4.5 4.0 3.0 3.0

    "Bold face type indicates higher ranked and stronger usage.

    activities consistent with these patterns of muscle usage are repetitive tasks involved in the preparation of animal skins for clothing, and habitual activities involving rowing a boat, possibly an umiak, in which oars were usually attached to the g~nwales .5~ Unfortunately, relatively few individuals ( n = I 1 ) could be identified conclusively as Later Period Thule, and all were males.

    Pectoralis major, teres major, the costoclavicular ligaments, flexors, and deltoideus (Table 5) remained among the most utilized muscles, in both Early and Later Period males. When mean differences greater than 0.5 (the equivalent of an intermediate grade on the severity scale of 1-6) were determined (Table 6 ) , the Later Thule scores increased for pectoralis major (adductor and rotator of the arm, drawing the arm across the chest), and pronator quadratus (pronation of the forearm), two muscles that would be utilized heavily when harpooning at a downward angle. Decreases in use were found to occur with brachialis (bending the elbow), subclaoius (lowering the shoulder blade), supinator

    Table 5. MSM scores for 19 specific muscles, ranked from most utilized to least utilized, for all Later Period adult Thule males, right side.

    MSM Number of MuscleAigament score individuals utilized Location

    5.29 7 Pectoralis major Humerus 3.86 7 Teres major Humerus 3.50 4 Costoclavicular ligament Clavicle 2.17 6 Flexors, common origin Humerus 2.13 8 Deltoideus Humerus 2.00 6 Trapezoid ligament Clavicle 2.00 3 Pronator teres Radius

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

    1.80 5 lnfraspinatus Humerus 1.57 7 Latissmus dorsi Humerus 1.50 6 Brachialis Utna 1.40 5 Conoid ligament Clavicle 1.25 4 Supraspinatus Humerus 1.20 5 Pronator quadratus Radius 1.10 5 Pectoralis minor Scapula 1.00 6 Subclavius Clavicle 1.00 4 Coracobrachialis Humerus 0.75 4 Supinator Radius 1.67 3 Trapezius Scapula 0.00 4 Teres minor Humerus

    _ _ _ - statistical break-point between stronger and more moderate use of muscles.

    (supination of the forearm), and teres minor (rotation of the arm outward), muscles consistent with launching a harpoon. The use of the costoclavicular ligament (associated with kayaking) was also found to decrease through time.

    Discussion

    Early Period Thuk Eskimo Clothing Preparation

    Artefactual finds at S i l ~ m i u t ~ ~ included ulus (women's knives) and a variety of scrapers and scraper blades, confirming that clothing

    Table 6. Mean MSM differences (greater than 0.5 points) between Early and Late Period Thule adult males

    Early Thule males Later Thule males

    Muscle/ligament Mean N Mean N Mean differences

    Subclavius 2.00 24 1 .oo 6 1 .oo Costoclavicular ligament 4.24 17 3.50 4 0.74 Brachialis 2.07 29 1.50 6 0.57 Teres minor 0.57 14 0.00 4 0.57 Supinator 1.29 14 0.75 4 0.54 Pronator quadratus 0.69 16 1.20 5 0.51

    Pectoralis major 3.17 36 5.29 7 2.12

  • 332 D. E. Hawkey and C. F. Merbs

    Figure 5. Stress lesion MSM at the pectoralis major and teres major insertion site, right humerus. Both MSM are grade 53 (strong expression).

    preparation was an important habitual activity at the site. Females would have utilized mainly the wrist flexor muscles when cutting animal skins with an ulu, whereas repeated flexion and extension of the elbow would have been the primary movements used when scraping skins to remove hair. The supra spinatus muscle would have played a role in the abduction of the arm, and would have helped to fix the humeral head in the glenoid fossa, an action that is instrumental in lifting relatively heavy objects. When seen in conjunction with both pectoralis major and teres major muscles, the pattern is suggestive of a habitual action in which the arm is regularly held below a 90" horizontal angle with the humerus held anteriorly adducted toward the chest, perhaps holding heavy animal skins during the clothing preparation process.

    Umiak utilization A less common female activity may have

    involved the retroversion and lowering of both arms consistent with rowing a boat. Although Lyon5' noted an absence of umiaks in this region

    at the time of European contact, this may be due to the depletion of whales prior to the introduction of European and U.S. whalers into the region,58 and it seems unlikely that the people of Silumiut and Kamarvik had not made use of this craft. Although termed a 'women's boat' the umiak undoubtedly was utilized by both sexes for a variety of purposes, including transportation of salvaged whale bones to winter camp sites for house construction.38 However, it is unknown if whale-hunting umiak crews included women,30 because religious taboos may have forbidden females from active participation in whale hunting.59

    When modern Labrador lnuit females use wooden umiaks,60 the boats are rowed with oars; male whale-hunting umiak crews, however, use single-bladed paddles. Adult Thule females were found to have used the muscles involved in rowing activities bilaterally (pectoralis major, teres major, deltoideus, trapezius, latissimus dorsi, triceps brachii, anconeus, coracobrachialis, biceps brachii, flexors, bracbialis and brachioradialis). Also of interest is the extremely strong use of both teres major (mean=3.40) and pectoralis major (mean=2.65), which often scored into the stress lesion category (Figure 5). This severe degree of muscle usage indicates that a substantial amount of stress was placed bilaterally on both humeri, a form of microtrauma that would have been caused by more strenuous, continual activity than the actions involved in the animal skin preparation process alone.

    Evidence for kayak use Although no archaeological evidence of kayaks

    has been found at either Silumiut or Kamarvik, this is not unusual given the fragile nature of these skin boats. However, ethnographic evidence of kayak use among eastern Canadian Inuit, the Sadlermiut of Southampton I ~ l a n d , ~ ~ , ~ ~ and Labrador Eskimo,60 along with eastern and central Thule artefacts depicting single-man kayaks,30 lends credence to the utilization of kayaks by the Hudson Bay Thule. Furthermore, a common Thule open-sea whale-hunting technique used several single-man kayaks to chase and harpoon the whales, followed and assisted by crews in the slower moving, but sturdier, ~ m i a k s . ~ ~ , 5 9

    The highest MSM scores for the Early Period

  • Musculoskeletal Stress Markers 333

    adult males occurred at three sites, the costoclavicular ligament, pectoralis major, and teres major, attachment sites consistent with the distinct alternating, rotary movements performed when kayaking with a double-bladed paddle. Pulling on the paddle to propel the kayak forward would also involve the strenuous contraction of both pectoralis major and teres major, with the costoclavicular ligament preventing excessive displacement of the clavicle during rapid and repetitive movement of both arms. Adult males with both clavicles and humeri present (n= 1 1) displayed signs of heavy stress placed bilaterally at these attachment sites. Other muscles utilized in this action would include deltoideus (lifting the paddle out of the water), extensors, flexors, biceps bracbii, and triceps bracbii (straightening and bending the elbow), all of which scored in the strong or moderate use categories.

    A distinct ?'-shaped stress lesion at the costoclavicular ligament site, termed 'kayaker's clavicIe',2 was observed to occur bilateralIy among the northwest Hudson Bay males (Figure 6). The ligament would be most stressed during the distinct rotary movement associated with using a double-bladed paddle. A costoclavicular sulcus was first noted by Houghton6' in New Zealand skeletons and was attributed to the actions involved in canoe paddling. Since that time, the occurrence of either a sulcus or robust attachment at the costoclavicular site has been observed in other maritime populations, including prehistoric and historic Hawaiians,62 M i c r o n e ~ i a n s , ~ ~ ancient A l e ~ t s , ~ ~ , ~ ~ historic Hudson Bay trappers,8 and mariners on the Mary R0se.1~ Although these markers of stress occur predominately in males, and in most cases are attributed to the actions involved in paddling movements, none of the samples appear to exhibit the distinct bilateral ?'-shape stress lesion found in all the Early Period Thule males.

    Analysis of prehistoric adult male remains from the eastern Aleutian Islands suggests another distinct kayak-use difference between the Aleut and T h ~ l e . ' ~ , ~ ~ Lower extremity MSM comparisons indicate that Aleut males sat with their legs laterally rotated at the hip and in full extension, placing considerable bilateral stress on the obturator extemus muscles. Thule males lacked this pattern and may have kayaked while in a

    kneeling position, similar to historic Koniag Eskimos.

    Later Period Tbule Eskimo

    Methods of hunting the ringed seal The change in muscle usage from Early to Late

    Thule males may be understood best in conjunction with the Silumiut faunal record. Although the minimum number of individual (MNI) counts for whales are unreliable, there was an abundance of ringed seal remains (MNI=247) recovered from S i l ~ m i u t . ~ ~ Both the modern Grise Fiord Inuit65 and the North Alaska Eskimo66 hunt the ringed seal by a variety of methods, which are determined by local ice conditions. During winter months, allu hunting through the ice is a common method of sealing. Men in North Alaska who still practice the traditional methods of allu sealing utilize the toggle harpoon head,66 similar to the harpoon heads recovered from both Silumiut and Kamarvik. The MSM data collected for the Later Period Thule support evidence for increased allu hunting, because actions involved in the forceful downward thrust of the harpoon through the allu when the seal surfaced, would involve primarily the strenuous use of pectoralis major. Moreover, the differences in pectoralis major use between Early and Late Thule males were found to be significant statistically (p

  • 3 34 D. E. Hawkey and C. F. Merbs

    Figure 6. 'Kayaker's clavicle' (KA-15 XIV-C:545). Bilateral stress lesion MSM occurring at the costoclavicular ligament insertion site.

    and latissimus dorsi). This distinctive pattern was not observed in the eight males with complete upper extremities present. Although remains of at least 1 18 caribou (Rangfer tarandus) were recovered at S i l ~ m i u t , ~ ~ pointed out that summer co-operative hunting with a bow and arrow would not be particularly profitable, because caribou could be hunted more efficiently in the inland lakes and rivers by hunters utilizing kayaks and lances.

    Conclusions

    The MSM data from this study suggest that discernible differences in muscle use exist between Early Period Thule adult males and females of northwest Hudson Bay. Although both sexes continued to lead an active, strenuous life into old age, severe macrotrauma to the upper extremity (in the form of ossification MSM) apparently did not occur. However, daily, continuous microtrauma at the attachment sites (in the form of robusticity markers and stress lesions) helped clarify possible gender-specific activity patterns that were not always apparent from the archaeological record alone.

    A very high prevalence of activity-induced stress lesions occurred among the Early Thule

    females at insertion sites that were consistent with the actions involved in rowing an umiak. Although in the past the presence of umiaks in Hudson Bay has been questioned, the skeletal evidence suggests that the tasks of females in northwest Hudson Bay may have been somewhat underestimated. While females were unlikely to have actively participated in umiak hunting crews (due to religious taboos), they may have been partially responsible for family transportation by umiak, and quite possibly scavenged for whale bones along the shoreline, bringing the remains back to camp via this large, skin boat.

    Similarly, although physical evidence for kayaks has been lacking from the archaeological record, distinctive skeletal stress markers (i.e, 'kayaker's clavicle', strong bilateral use of the muscles utilized in paddling with a double-bladed paddle) indicate that Early Period Thule males may have used the kayak extensively. The question of its use in open- sea whale hunting may be impossible to determine from the MSM data alone, although the presence of whale remains at the Early Period winter camps strongly supports this possibility. Also of interest is the absence of statistically significant MSM diferences between the Early Kamarvik and Silumiut skeletal series. Because both are large winter camp sites, consisting of relatively large

  • Musculoskeletal Stress Markers 335

    groups involved in similar activities, communal whale hunting is certainly a possibility.

    Temporal applications of the MSM data support McCartney's theory of a substantial change in subsistence strategies among the northwest Hudson Bay Thule males, suggesting that a variety of hunting methods were utilized through time. An increase in caribou hunting may have been practised by the Late Period Thule, probably utilizing the kayak and spear thrust kill, because a variety of lance heads were recovered at S i l ~ m i u t . ~ ~ Use of the composite bow and arrow does not appear to have been a major form of hunting among the Late Thule males, and may have been used primarily for birds and small game. Differing temporal methods of harpoon utilization, and a decrease in kayak use, as indicated by the skeletal evidence, suggests that if open-sea hunting of whales had once been practised, it was abandoned after the Early Period, when a shift towards the exploitation of an increased ringed seal population occurred.

    Finally, the high prevalence of the activity- induced stress lesion accounted for the high MSM scores for many of the muscle attachment sites in both males and females. Although the prehistoric Aleut exhibited strong bilateral robusticity scores at the costoclavicular ligament attachment sites, they lacked the stress lesion 'kayaker's clavicle' condition seen among the Thule males. Two factors may explain the discrepancy in MSM type: ( i ) preconditioning to the rigours of kayaking at an early age, and ( i i ) temperature/climatic change. Modern ethno- graphic evidence67 indicates that physical training of young Aleut boys is an important part of conditioning for the rigours of adulthood, and may have helped to prevent damage to muscle attachment sites. The greater degree of microtraumatic stress lesions in the Thule sample suggests that early preconditioning may not have been a common practice among Thule males.

    In addition, cold temperatures have been found to accelerate musculoskeletal trauma68 owing to vasoconstriction of the capillaries, an action that lessens the supply of blood to the periosteum. The Thule lived in a region where the current (1931-1960) temperature can drop as low as - 60 O F ( - 5 1 "C), with an average January wind chill factor (KgCal/m2hr) of 1950, well below

    the 1400 point where exposed flesh freezes.29 Conditions during the 'Little Ice Age' would have been considerably colder. The added environ- mental stress, especially when viewed in conjunction with the long, cold wait and rapid, sudden movements involved in harpooning seals by the allu method, might well explain the remarkably high MSM score for the pectoralis major muscle found among the later Thule males. Apparently, local climatic deterioration had a significant effect not only on temporal sub- sistence strategies, but on the human skeleton as well.

    Acknowledgements

    The authors thank Kenneth A. R. Kennedy, Mary W. Marzke, Christy G. Turner 11, and the anonymous reviewers, for their comments and suggestions. In addition, we wish to thank the Archaeological Survey of Canada, Canadian Museum of Civilization, Ot tawd Hull, for the opportunity to study the skeletal series.

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