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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 112:217-238 (2000)

Changes in Long Bone Diaphyseal Strength With HorticulturalIntensification in West-Central Illinois

PATRICIA S, BRIDGES,' JOHN H, BLITZ," AND MARTIN C, SOLAN03''Department of Anthropology, Queens College and Graduate Center,CUNY, Flushing, New York 113672Department of Anthropology, University of Alabama, Tuscaloosa,Alabama 35487-02103Department of Anthropology, University at Albany, SUNY, Albany,New York 12222

KEY WORDS biomechanics; agriculture; Lower Illinois Valley

ABSTRACT This study examines changes in long bone diaphysealstrength in west-central Illinois from the Middle Woodland through theMississippian periods. Significant differences occur between the MiddleWoodland and the Late Woodland periods, at the time when use of nativeseed crops intensifies. In females, both humeral and femoral strength in-creases, which may be related to their role in growing and processing thesecrops. In males, right arm strength declines, which may be tied in part to thereplacement of the atlatl by the bow. Fewer significant changes occur be-tween the earlier and later Late Woodland periods, at the time when maizeis introduced as a dietary staple, possibly because maize is at first grown asonly one of a series of other starchy seeds. Finally, in the Mississippianperiod, when maize use intensifies, female left arm strength declines. Thismay be because maize is easier to process than native seeds, or it may reflectinnovations in processing technology in the Mississippian period. Extemaldimensions and shape indices, in part, reflect the trends seen in biomechani-cal strength. Comparisons are made to similar studies in other regions. AmJ Phys AnthropoI112:217-238, 2000. " 2000 Wiley-Liss, Inc,

In recent years, biomechanical analysesof long bone diaphyses have provided in-sights into changes in the level of physicalactivities in prehistory, especially in associ-ation with the adoption of maize agriculturein eastem North America. In general, thesestudies show that changes in subsistencetechnology, associated with modifications ofbehavior (e.g., processing, mobility), re-sulted in the remodeling of bone to meet thechanges in physical demands on the skele-ton. However, these studies have yieldedconflicting results. On the Georgia coast,long bone strength declines with the intro-duction of agriculture (Ruff and Larsen,1990; Ruff et aI., 1984), while in northwest-em Alabama, the opposite is true (Bridges,1989). Moreover, these regions show vari-

" 2000 WILEY-LISS, INC,

able changes between the sexes and for dif-ferent bones. This diversity is likely due to acombination of factors: variability in envi-ronment, cultural systems, and subsistencepractices in agricultural groups, amongother reasons. Variability in the preagricul-tural samples is even greater, since thesestudies utilize groups from different timeperiods and of differing adaptations to com-pare with later agriculturalists.

Grant sponsor: PSC-CUNY Research Awards; Grant sponsor:Queens College Research Award in Social Sciences; Grant spon-sor; Wenner-Gren Foundation for Anthropological Research.

Dr. Bridges deceased.*Corresponrlence to: Martin C. Solano, Department of Anthro-

pology, University at Albany, SUNY, Albany, NY 12222.E-mail: ms6248®Cnsvax.albany.edu

Received 2 October 1998; accepted 12 February 2000.

218 P.S. BRIDGES ET AL.

This study attempts to resolve some,though not all, of these problems by exam-ining long bone diaphyseal dimensions andstructure in several cultural groups fromwest-central Illinois, dating from the MiddleWoodland (50 BC-AD 200), the Late Wood-land (AD 600-1050), and the Mississippian(AD 1050-1250) periods. All of these groupsgrew at least some food crops by hoe culti-vation, although their reliance on them in-creased over time (Asch and Asch, 1985a;Asch et aI., 1979). Native seed crops werecultivated in the Middle Woodland period.Maize was present in small quantities be-fore AD 600 in this region, but stable carbonisotope studies have revealed that it did notbecome a measurable part of the diet untilafter AD 800. Later, maize use rose sharplyin Mississippian times (Bender et aI., 1981;Buikstra, 1992; Buikstra et aI., 1987; vander Merwe and Vogel, 1978). Because thetiming of these events is relatively well-known in this region, it is possible to exam-ine more closely activity levels associatedwith native seed horticulture, early maizegrowing, and maize intensification.

This study concentrates on the transitionin hoe cultivation from small-scale crop pro-duction ("horticulture") through large-scalecrop production ("agriculture"). Previousstudies assumed that the introduction ofmaize agriculture was the seminal event incausing changes in activities in late prehis-tory. In order to best characterize thischange, studies of biomechanical variableslargely focused on the ends of the spectrum(hunter-gatherers vs. full-scale maize agri-culturalists), ignoring transitional horticul-tural societies. As a result, earlier biome-chanical studies do not provide an analysisof the process of initial introduction com-pared to later intensification of food crops.Because of the fine-grained chronologypresent in this region, it can distinguishbetween: 1) low-level horticulturalists rely-ing on native seeds (Middle Woodland peri-od), 2) intensive horticulturalists using thesame crops ("earlier" Late Woodland peri-od), 3) societies which relied on native seedsbut also incorporated some maize into thediet ("later" Late Woodland period), and 4)intensive maize agriculturalists (Mississip-pian period). Therefore, this study can link

activity levels with specific subsistenceeconomies, rather than with somewhat sim-plistic categories such as "agriculturalists."If the assumption that the introduction ofmaize caused a radical change in usual ac-tivities is correct, diaphyseal strengthshould change most at that time, or perhapslater, when its use intensified.

MATERIALS AND METHODS

West-central Illinois has been the site ofextensive archaeological excavations formany years, and has yielded a large quan-tity of human skeletal remains. These col-lections consist primarily of burials from theMiddle Woodland through the Mississip-pian periods, although a few Archaic indi-viduals are represented as well. Inventoriesfor the majority of the remains are availableat the Universities of Chicago and Indiana,where the remains are curated, and includepreviously determined age and sex assess-ments. The sample for this study is drawnprimarily from sites which lie within theLower Illinois Valley, although a few, suchas Kuhlmann, lie within the nearby sectionof the Mississippi River Valley. MiddleWoodland sites include Pete Klunk, Gibson,and L'Orient (Buikstra, 1976; Perino, 1968).Late Woodland remains also come from PeteKlunk, as well as Koster, Schild, Yokem,Ledders, Hacker, and Kuhlmann (Atwelland Conner, 1991; Conner, 1984; Perino,1971a, 1973a-c). The large Mississippiancemetery at the Schild site is the singlesource for burials of that period (Perino,1971b).

Several studies have linked a decline inhealth, especially in children, during theLate Woodland period with the introductionof maize as a dietary staple (Cook, 1979,1984). Since maize becomes a dietary staplemidway through the Late Woodland period,it is important to subdivide Late Woodlandsamples into "pre-" and "postmaize," withcirca AD 800 as the dividing point. How-ever, subdividing the Late Woodland periodcan be problematic, given the error rangesseen in radiocarbon dates. One additionalproblem is that the earliest Late Woodlandperiod is not represented by significant skel-etal remains in this region. Nonetheless, itis possible to sort Late Woodland societies

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BONE STRENGTH IN WEST-CENTRAL ILLINOIS 219into earlier and later subsamples. A reviewof calibrated radiocarbon dates (Conner,1984) from the sites in question reaffirmsthat the majority of the Late Woodland atthe Pete Klunk Mounds comes from the ear-lier part of this period (between AD 600-800). The Koster Mounds Late Woodlanddates largely overlap this period, falling be-tween the late 600s and late 800s. In thisstudy, these sites will be referred as "earlierLate Woodland." Other Late Woodland sitesin this study are younger in age (with radio-carbon dates mostly falling after AD 900),and are designated "later Late Woodland."

The sample used in this research is com-posed primarily of adults under the age of50 years. (Although some adults over theage of 50 years were measured, they are notincluded in the biomechanical analysis toavoid the possibility of age-related osteopo-rosis.) For the purposes of this study,"adult" is taken to represent any individualwith at least one long bone with both epiph-yses fused. Each individual measured hadto contain at least one complete long bone.Age and sex determinations were made un-der the direction of Jane Buikstra (previous-ly of Northwestern University and the Uni-versity of Chicago), and Della Cook (IndianaUniversity).

From the entire collection, 372 individu-als were chosen for osteometric analysis.Measurements included standard lengths,and diaphyseal and articular dimensions.Bones with pathological conditions were ex-cluded from the sample, whether or not thesite of measurement was affected. When apathology affected a large portion of theskeleton, the entire individual was droppedfrom the sample. From this larger sample, asmaller group was selected for computedtomographic (CT) scanning and subsequentbiomechanical analysis. This subsamplecomprised 80 individuals, 20 from each timeperiod (Middle Woodland, earlier LateWoodland, later Late Woodland, and Mis-sissippian periods), half of which were ofeach sex. To be selected for this subsample,each individual had to possess at least onecomplete femur. The left femur was used ifpresent and in good condition. If not, theright femur was substituted for it. In addi-tion, each individual had to have a right

humerus. When present and in good condi-tion, both humeri were included, to allow foran examination of bilateral asymmetry.

Next, the humeri and femora of the 80individuals chosen for biomechanical analy-sis had to be oriented properly to ensurethat the resulting CT scans would be takenin the appropriate plane. This process,which follows the procedures of Ruff (1981)and Ruff and Hayes (1983), is described inmore detail elsewhere (Bridges, 1985). Es-sentially, it involves aligning the femoraand humeri along three reference axes: thelongitudinal axis of the diaphysis, the an-teroposterior axis, and the mediolateralaxis. All bones to be scanned for each indi-vidual were aligned together on a singlesheet of heavy cardboard, and firmly affixedin place. Leveling ofthe bones was achievedwith the use of individually cut Styrofoamcubes. The midshaft of each bone wasaligned along the same plane so that a sin-gle CT image could be taken of each individ-ual at midshaft, reducing scanning time.Bones were scanned at the Department ofRadiology, Indiana University Medical Cen-ter (Indianapolis, IN), using a GE 9800 CTscanner. Each scan was reproduced as anenlarged X-ray image.

The images were digitized on a SummaS-ketch II Plus 12" x 12" graphics pad, usinga program called SLCOMM, modified by Pe-ter Eschman from the program SLICE(Eschman, 1990). Before digitizing the im-ages, an error analysis was performed onboth a series of standardized circles and onnine bone cross sections (three femora andsix humeri). The average error in area forthe standard circles was less than 2%. Vari-ation in cortical area of the nine cross sec-tions averaged less than 3%. A subsequenterror analysis was also performed at the endofthe digitizing process on 14 sections. Thisyielded an average error of only 1.2% incortical area. Together, these tests indicatethat the level of error in digitizing was ac-ceptably low.

Data from the digitized images are usedby the SLCOMM program to produce esti-mates of mechanical rigidity, or what iscommonly referred to as "strength" undervarious kinds of forces. Cross-sectional areais a measure of resistance to compression.

220 P.S. BRIDGES ET AL.

TABLE 1. Femoral midshaft cross-sectional propertiesl

Males FemalesMW eLW lLW Miss MW eLW lLW Miss

Unstandardized (raw) cross-sectional variables

Cortical area, mean 400 418 424 428 278 316 299 311SE 18.3 14.9 11.7 18.1 8.4 10.9 9.5 16.9Imin, mean 20,675 19,268 23,064 22,552 11,471 13,500 12,517 13,412SE 1,568 1,225 1,252 1,501 666 597 685 1,281Imax, mean 28,392 27,505 29,601 33,050 14,535 17,731 14,850 17,132SE 3,075 1,822 1,875 2,526 718 950 848 1,903J, mean 49,066 46,773 52,665 55,602 26,006 31,231 27,367 30,545SE 4,558 2,605 2,979 3,766 1,234 1,336 1,426 3,158

Size-standardized cross-sectional variables2

Cortical area, mean 435 437 444 429 367 414 434' 401SE 16.4 21.8 14.6 14.0 18.7 14.4 11.6 13.8Min bending strength, mean 145.3 129.5 153.0 139.1 114.5 133.9 150.5' 127.8SE 8.2 12.2 8.8 9.2 8.3 6.1 10.4 7.2Max bending strength, mean 194.8 179.6 194.1 203.5 146.1 174.8 175.8 162.0SE 9.6 11.3 9.0 13.9 10.7 7.7 7.9 11.7Torsional strength, mean 340.2 309.1 347.1 342.6 260.6 308.8 326.4' 289.8

. SE 15.9 22.5 16.8 21.4 18.0 11.4 17.8 18.5Shape index, Imax/Imin, mean 135 146 128 147 129 132 119 126SE 6.3 11.2 4.7 7.5 7.2 7.6 4.7 3.6

1 MW. Middle Woodland; eLW, earlier Late Woodland; ILW, later Late Woodland; Miss, Mississippian; L, left; R, right; Max,maximum; Min, minimum. Sample size for each group = 10.2 Cortical area (in mm2) divided by length3 and multiplied by 108; I and J (in mm4) divided by length5.33 and multiplied by 1012.

* Significantly different (P < 0.05) from the Middle Woodland.** Significantly different (P < 0.05) from the early Late Woodland.*** Significantly different (P < 0.05) from the late Late Woodland.

Second moments of area (designated "1")es-timate resistance to various bending forces(Lovejoy et aI., 1976). Commonly used 1val-ues include lap and Iml (resistance to bend-ing forces around the anteroposterior andmediolateral axes), or Imax and Imin (max-imum and minimum second moments ofarea). The polar second moment of area (J)estimates the section's strength under tor-sional or twisting forces, and is computed byadding 1 values from axes at right angles(i.e., lap + Iml = J).

The resistance of a long bone is also influ-enced by its length; therefore, biomechani-cal values must be size-standardized. How-ever, there is some controversy, especiallyregarding the humerus, as to what consti-tutes the most appropriate means of stan-dardization. One possibility is to divide areaby length2, and 1 or J by length4 (Churchill,1994). This study follows Ruff et al. (1993)in dividing 1 and J by bone lengths.33, tocreate a standardized estimate of bendingstrength. Cortical area is divided by bonelength3. Size standardization of external di-aphyseal measurements is accomplished by

computing standard indices, such as the ro-busticity index (circumference/length X100). To determine whether groups weresignificantly different from each other,Tukey's HSD tests were performed at a 95%confidence interval.

RESULTS

Femur

Males show no significant differencesamong time periods for any size-standard-ized femoral midshaft cross-sectional prop-erties (Table 1). Male femoral external mea-surements, however, reveal a significantincrease in size for three variables in the -Mississippian samples compared to MiddleWoodland samples: midshaft AP diameter,subtrochanteric ML diameter, and subtro-chanteric circumference (Table 2).

Females, on the other hand, show agreater number of significant differencesover time, both in external dimensions andstructural variables. For three of the biome-chanical variables (cortical area, minimumbending strength, and torsional strength),

BONE STRENGTH IN WEST-CENTRAL ILLINOIS 221TABLE 2. Femoral dimensional data (in mm) and indices1

~ MW eLW lLW MissL R L R L R L R

MalesBicondylar length, mean 453 448 459 453 451 448 451 446

SE 3.7 3.6 4.0 4.2 3.0 3.0 3.6 3.6N (27) (24) (27) (15) (44) (38) (34) (35)

MidshaftAP diameter, mean 29.0 29.3 30.5 30.1 29.9 29.6 31.0* 30.0SE 0.54 0.53 0.52 0.48 0.42 0.41 0.46 0.36N (27) (27) (28) (24) (43) (35) (33) (35)ML diameter, mean 26.2 25.2 26.1 25.6 26.7 26.0 26.4 26.1SE 0.37 0.30 0.36 0.33 0.25 0.28 0.27 0.25N (27) (27) (28) (25) (43) (35) (33) (35)Circumference, mean 86.9 86.1 88.5 86.7 88.3 87.3 89.8 88.1SE 1.13 1.08 0.95 0.90 0.87 0.87 0.84 0.82N (27) (27) (27) (22) (41) (35) (33) (35)

SubtrochantericAP diameter, mean 24.9 25.0 25.5 25.0 25.2 24.7 25.5 25.0SE 0.34 0.32 0.36 0.29 0.25 0.29 0.33 0.29N (36) (37) (34) (37) (52) (47) (37) (39)ML diameter, mean 33.4 32.8 34.0 33.5 34.3 33.8 34.0 34.2*SE 0.30 0.30 0.39 0.46 0.34 0.33 0.37 0.33N (36) (36) (33) (37) (51) (47) (37) (39)Circumference, mean 91.9 91.0 93.9 92.8 94.8 93.0 94.4 94.1*SE 0.83 0.88 0.94 0.96 0.82 0.82 0.82 0.74N (35) (36) (51) (34) (47) (45) (36) (39)Vertical head 45.4 45.3 46.1 46.1 46.3 46.2 46.1 46.1diameter, meanSE 0.32 0.32 0.41 0.33 0.32 0.37 0.40 0.34N (29) (30) (26) (33) (36) (31) (31) (32)

Shape indicesPilasteric, mean 111 117 117 117 112 114 118 115SE 2.1 2.3 2.1 2.3 1.6 1.7 2.0 1.4N (27) (27) (28) (24) (43) (35) (33) (35)Platymeric, mean 75 76 75 75 74 73 75 73SE 0.96 0.95 0.83 0.87 0.78 0.96 0.98 0.91N (36) (36) (33) (37) (51) (47) (37) (39)

FemalesBicondylar length, mean 421 420 421 421 418 415 418 417SE 2.8 4.9 2.9 4.0 3.3 2.8 3.2 3.4N (29) (19) (30) (23) (38) (42) (37) (37)Midshaft

AP diameter, mean 25.6 24.7 26.2 25.7 25.7 25.8 26.8 26.5*SE 0.36 0.40 0.37 0.37 0.36 0.32 0.30 0.31N (29) (21) (31) (29) (36) (43) (37) (37)ML diameter, mean 24.2 23.4 24.7 24.4 24.8 24.4 24.7 23.9SE 0.30 0.34 0.31 0.29 0.26 0.22 0.29 0.32N (29) (21) (31) (29) (36) (42) (37) (37)Circumference, mean 77.4 75.5 79.3 78.3 79.2 78.6 80.3 79.2*SE 0.81 1.04 0.87 0.86 0.93 0.82 0.78 0.82N (29) (21) (29) (29) (33) (40) (37) (37)

SubtrochantericAP diameter, mean 22.0 22.1 22.7 22.4 22.3 22.2 22.6 22.6SE 0.30 0.26 0.26 0.29 0.22 0.21 0.25 0.27N (40) (41) (36) (35) (56) (58) (39) (40)ML diameter, mean 30.2 30.3 31.2 30.8 30.8 30.8 31.0 31.0SE 0.23 0.22 0.26 0.27 0.28 0.26 0.31 0.32N (40) (41) (37) (34) (55) (58) (39) (41)Circumference, mean 83.1 83.1 85.4 84.5 83.9 84.4 85.1 85.1SE 0.69 0.65 0.69 0.82 0.71 0.70 0.79 0.84N (39) (40) (35) (31) (49) (51) (39) (40)Vertical head, mean 40.6 40.7 41.5 41.2 40.8 40.6 40.1 ** 40.0SE 0.27 0.31 0.40 0.39 0.39 0.33 0.37 0.40N (36) (35) (31) (34) (38) (42) (35) (38)

Shape indicesPilasteric, mean 106 106 106 105 104 106 109*** 112*,**,***., SE 1.7 1.6 1.5 1.3 1.1 1.2 1.3 1.5N (29) (21) (31) (29) (36) (42) (37) (37)Platymeric, mean 73 73 73 73 73 72 73 73SE 0.97 0.86 0.83 0.86 0.78 0.68 0.83 0.85N (40) (41) (36) (34) (55) (58) (39) (40)

1 See Table 1 for notes.

222 P.S. BRIDGES ET AL.

400

350

i 300

e 250

~ 200.ci 150oI- 100

50

MW B.W LLW MISS

Fig. 1. Torsional strength (standardized) of femalefemora. Means. MW, Middle Woodland; ELW, earlyLate Woodland; LLW, late Late Woodland;MISS, Mis-sissippian.

there is a significant increase in strength inlater Late Woodland females in comparisonto Middle Woodland females (Table 1).Though the early Late Woodland is not sig-nificantly different from these adjacent pe-riods, it exhibits intermediate values be-tween the two, supporting a trend ofincreased strength through the late LateWoodland. The trend in torsional strengthof female femora is also expressed in Figure1. In the dimensional data, female midshaftAP diameter and circumference both in-crease significantly on the right side in Mis-sissippian times compared to earlier LateWoodland samples. The pilasteric index in-dicates a left-side significant difference be-tween later Late Woodland and Mississip-pian females, and a right-side significantdifference between Mississippian and allother period samples. Thus there appears tobe increased stress at the female femoralmidshaft up to the later Late Woodland interms ofbiomechanical variables, but with acontinued increase only in external dimen-sions at midshaft in Mississippian times.Together, these data suggest an increase infemoral strength through the chronologicalsequence, though this trend is more dra-matic for females.

Tibia

Following from the femoral data, onewould expect relatively few differences inmale tibial measurements, but somewhatsurprisingly, there are a number of signifi-cant changes in external dimensions (asnoted above, tibiae were not selected for bio-

mechanical analysis). For males, midshaftAP diameters increase and ML diametersdecrease significantly in the earlier LateWoodland period (Table 3). As a result,there are also a number of significantchanges in shape indices of the tibial diaph-ysis, all indicating an increase in forcesplaced along the anteroposterior directionduring the earlier Late Woodland, and con-tinuing into the later Late Woodland period.Mississippian males show significant in-creases in both midshaft and minimumshaft dimensions. Coinciding with thesechanges, shape indices of the middle anddistal diaphysis more closely approach 100,indicating more rounded diaphyses in Mis-sissippian males.

Female tibiae also show increased diaph-yseal dimensions and indices, but signifi-cant change occurs somewhat later thanmales, in the later Late Woodland period(Table 3), which was unexpected consider-ing the data on femoral external dimen-sions. For Mississippian females, the con-trast with Middle Woodland females is evengreater, with significant changes in moredimensions, particularly midshaft and min-imum shaft variables. Both the left andright sides are affected. However, in con-trast to males, Mississippian female tibialshape indices register little change, exceptthat the shape index of the distal diaphysisincreases at this time, indicating a morerounded shaft (as was the case for themales).

Humerus

Biomechanical measures of male humeralstrength fail to show significant changethrough time (Table 4), a parallel to the lackof significant change in structural measuresof male femora. Similarly, there are rela-tively few significant changes in male di-aphyseal external dimensions (Table 5).However, these data show subtle indica-tions of a trend towards bilateral symmetryin male humeral torsional strength throughtime, due to a decline in overall forcesplaced on the right humerus (Fig. 2). Leftminimum shaft minimum diameter, andboth left and right minimum shaft shapeindices, decline significantly in earlier Late

BONE STRENGTH IN WEST-CENTRAL ILLINOIS 223TABLE 3. Tibial dimensional data (in mm) and indices'

!! MW eLW lLW MissL R L R L R L R

MalesLength, mean 387 385 381 380 384 380 382 382

SE 4.3 4.4 3.7 4.0 4.0 3.6 4.3 4.7N (23) (22) (14) (16) (27) (29) (19) (18)

MidshaftAP diameter, mean 31.3 31.0 33.0 32.7* 32.6 32.4 33.3* 33.2*SE 0.43 0.43 0.49 0.43 0.42 0.41 0.34 0.43N (21) (22) (13) (15) (25) (27) (19) (18)ML diameter, mean 21.6 21.9 20.1* 20.1* 20.8 20.6 22.2**'*** 21.9**SE 0.44 0.47 0.49 0.45 0.25 0.31 0.24 0.34N (22) (22) (14) (15) (26) (28) (19) (18)Circumference, mean 84.9 84.3 86.1 84.7 85.5 84.6 89.3*'*** 88.4*SE 1.17 1.20 0.84 1.23 1.00 1.17 0.82 0.76N (18) (21) (11) (13) (20) (22) (19) (18)

Nutrient foramenAP diameter, mean 35.5 35.5 36.9 36.3 36.2 36.6 37.0 36.6SE 0.52 0.52 0.56 0.51 0.43 0.42 0.37 0.35N (26) (24) (15) (20) (28) (33) (22) (21)ML diameter, mean 23.2 24.1 22.6 23.0 23.0 22.9 23.6 23.1SE 0.43 0.54 0.62 0.42 0.33 0.30 0.39 0.39N (26) (24) (15) (20) (29) (33) (22) (22)Circumference, mean 92.5 93.4 94.2 93.2 93.5 94.0 96.6 95.2SE 1.45 1.46 1.37 1.49 0.98 1.24 0.94 0.85N (21) (20) (12) (14) (22) (24) (22) (21)

Minimum shaftAP diameter, mean 26.2 26.1 27.3 26.6 27.2 27.5* 27.1 26.7SE 0.33 0.40 0.64 0.47 0.33 0.31 0.28 0.34N (26) (26) (15) (18) (28) (29) (22) (22)ML diameter, mean 21.8 21.8 21.2 21.6 21.1 21.6 23.1 *,**.*** 23.0***SE 0.35 0.34 0.45 0.48 0.29 0.40 0.34 0.35N (26) (26) (15) (18) (28) (29) (22) (22)Circumference, mean 76.0 76.2 77.1 76.2 77.2 77.5 79.8*'*** 79.6*SE 0.89 0.89 0.95 0.83 0.66 0.93 0.64 0.83N (26) (26) (15) (18) (28) (29) (22) (22)

Shape indicesMidsbaft, mean 69 71 61* 62* 64* 64* 67 66SE 1.41 1.69 1.98 1.45 1.09 0.84 0.92 1.37N (21) (22) (13) (15) (25) (27) (19) (18)Cnemic, mean 66 68 61 64* 64 63* 64 63*SE 1.04 1.33 1.62 0.96 0.94 0.83 1.10 1.11N (26) (24) (15) (20) (28) (33) (22) (21)Minimum Shaft, 83 84 78 82 78 79 86**'*** 86***

meanSE 1.3 1.5 2.7 2.7 1.5 1.4 1.3 1.6N (26) (26) (15) (18) (28) (29) (22) (22)

FemalesLength, mean 354 351 350 352 347 346 356 354SE 4.5 4.3 4.0 3.3 2.8 2.7 3.5 3.3N (17) (14) (18) (18) (24) (28) (25) (25)

MidshaftAP diameter, mean 26.8 26.6 26.9 27.6 27.9 28.2 28.7*'** 28.6*SE 0.34 0.58 0.39 0.54 0.35 0.32 0.45 0.42N (17) (14) (16) (18) (23) (28) (24) (25)ML diameter, mean 18.4 18.7 18.9 18.6 18.9 19.1 19.7* 19.4SE 0.38 0.44 0.32 0.23 0.29 0.31 0.34 0.33N (17) (14) (17) (18) (24) (28) (25) (25)Circumference, mean 71.9 71.9 73.8 74.5 75.9* 76.0* 77.1* 77.2*SE 0.82 1.02 0.66 1.14 0.95 0.86 1.21 1.03N (17) (13) (15) (15) (22) (27) (22) (24). (Continued)

.,

224 P.S. BRIDGES ET AL.

TABLE 3. (continued.)

MW eLW lLW Miss

L R L R L R L R

Nutrient ForamenAP diameter, mean 30.0 30.1 30.2 30.8 31.3 31.5 31.6 32.0*SE 0.46 0.56 0.40 0.49 0.32 0.33 0.51 0.44N (21) (17) (18) (18) (34) (38) (25) (27)ML diameter, mean 20.2 20.7 20.2 20.2 20.9 21.0 20.9 20.7SE 0.34 0.47 0.41 0.35 0.28 0.31 0.40 0.37N (21) (17) (19) (18) (37) (37) (25) (27)Circumference, mean 80.5 79.7 81.1 81.4 84.2 83.5 84.3 84.0SE 1.10 1.46 0.94 1.01 1.01 0.88 1.30 1.10N (20) (14) (15) (16) (29) (33) (24) (26)

Minimum shaftAP diameter, mean 22.2 22.5 23.3 23.3 23.7* 24.1* 23.6* 24.0*SE 0.29 0.49 0.25 0.32 0.24 0.27 0.41 0.40N (21) (17) (18) (17) (36) (36) (25) (28)ML diameter, mean 19.1 19.0 19.2 19.4 19.3 19.3 20.8*'**'*** 20.1SE 0.30 0.32 0.35 0.30 0.28 0.25 0.40 0.32N (21) (17) (18) (17) (36) (36) (25) (28)Circumference, mean 66.1 66.5 68.1 68.1 68.9* 69.3 71.0* 70.3*SE 0.76 1.06 0.58 0.91 0.60 0.63 0.99 0.92N (21) (17) (18) (17) (36) (36) (25) (28)

Shape indicesMidshaft, mean 69 71 71 68 68 68 69 68SE 1.34 1.87 1.58 1.42 0.98 1.06 1.10 0.85N (17) (14) (16) (18) (23) (28) (24) (25)Cnemic, mean 68 69 67 66 67 67 66 65SE 1.16 1.19 1.65 1.74 0.64 0.90 0.99 0.85N (21) (17) (18) (18) (34) (37) (25) (27)Minimum shaft, 86 85 83 83 82 80 88**'*** 84

meanSE 1.5 1.8 1.6 1.4 1.3 1.1 1.3 1.3N (21) (17) (18) (17) (36) (36) (25) (28)

1 See Table 1 for notes.

Woodland when compared to the precedingMiddle Woodland sample.

Compared to males, females show agreater number of significant differencesover time, both in structural variables andexternal dimensions. Several female hu-meral cross-sectional measures increasesignificantly from Middle Woodlandthrough later Late Woodland periods, on theleft side only (Table 4). Then, in the Missis-sippian sample, there is a dramatic de-crease in most variables in comparison toboth Late Woodland periods. Again, thischange is significant on the left side only(the trend is apparent on the right side butdoes not attain significance). The changes infemale humeral torsional strength are de-picted in Figure 3.

Female humeri increase in external dinIen-sions from the Middle Woodland to the laterLate Woodland, but these increases attainsignificance for the midshaft maximum diam-eter and minimum shaft circumference only(Table 5). Note that a different set of variables

is affected in females than is the case formales. These changes occur variously on boththe left and right sides. For Mississippian fe-males, many values are maintained with littlechange, but there is a significant decrease atright midshaft maximum diameter comparedto later Late Woodland. This change is re-flected in the Mississippian right midshaftshape index, which shows a significant devel-opment towards circularity of shape in com-parison to both Late Woodland period sam-ples. So while there is an overall increase instrength affecting both left and right femalehumeri through time, upper arms apparentlyexperienced less directional stress in Missis-sippian times. As mentioned above, the bio-mechanical data show a similar pattern ofstrength increase in the Late Woodland peri-ods and decrease in Mississippian times, butunlike tlIe external dimensional data, tlIeseoccur mostly on the left side, and are moreobvious in the earlier Late Woodland period.The large increase in cortical area of the lefthumerus after Middle Woodland times is un-

BONE STRENGTH IN WEST-CENTRAL ILLINOIS

TABLE 4. Humeral midshaft cross-sectional properties1

225

Males

LMW

R LeLW

R LlLW

R LMiss

R

Unstandardized (raw) cross-sectional variables

Cortical area, meanSElmin, meanSEImax, meanSEJ, meanSE

16810.5

4,286430

7,171839

11,4581,266

1877.7

5,371479

9,9611,073

15,3321,542

16310.9

3,539234

6,227517

9,766720

1819.5

4,105313

7,882401

11,988688

15512.2

5,275**651

7,997450

13,2721,060

1726.3

5,100297

8,758369

13,858620

1607.1

4,755373

7,528564

12,283927

1749.3

5,239549

9,289707

14,5281,239

Size-standardized cross-sectional variables

Cortical area, meanSEMin bending strength, meanSEMax bending strength, meanSETorsional strength, meanSEShape Index, Imax/Imin meanSENFemales

1718.1

16715.6

27729.8

44544.8

1655.36

1886.0

20415.7

37632.5

58047.5

1845.5

10

16311.5

12812.7

22523.9

35335.8

1768.99

18210.1

15216.1

28821.5

44037.2

1957.4

10

1539.2

18630.2

28033.5

46662.0

15611.24

1726.7

18414.9

31623.6

49937.4

1747.0

10

1594.9

1667.9

2628.6

42916.1

1593.47

1728.8

18120.8

32126.7

50246.9

1826.7

10

Unstandarsized (raw) cross-sectional variables

Cortical area, meanSEImin, meanSEImax, meanSEJ, meanSE

1034.6

2,056117

3,518195

5,574307

1206.9

2,442194

4,832433

7,274611

125*5.0

2,560206

4,820*340

7,379*524

1216.2

2,552199

5,240409

7,792589

1234.3

2,679183

4,816394

7,495*519

1203.7

2,570162

5,217350

7,787489

97**'***7.2

2,238136

3,503**345

5,742471

1168.2

2,555244

4,482524

7,037756

Size-standardized cross-sectional variables

Cortical area, meanSEMin bending strength, meanSEMax bending strength, meanSETorsional strength, meanSEShape index, Imax/Imin meanSEN

1 See Table 1 for notes.

1135.7

1216.3

20814.5

33020.6

1714.07

1296.9

13110.4

25717.5

38826.6

1988.6

10

1384.7

1486.4

280*11.1

42814.6

1919.19

1316.3

1357.3

27816.3

41321.6

20912.110

138*3.5

178*14.2

315*20.0

493*31.4

18213.37

131 105**'***3.5 7.5

154 127***11.6 16.3

310 194**'***20.8 23.9

464 321**'***31.3 39.6

204 155**8.3 8.0

10 7

1258.0

14114.0

24122.6

38235.4

1748.7

10

doubtedly a factor in overall greater strength.External dimensions, while correlated withdiaphyseal strength, ignore internal struc-tural features such as cortical area, and aretherefore an imperfect reflection of bonestrength.

In summary, the greatest number ofchanges in both male and female humeri oc-

cur after the Middle Woodland period, in theearlier Late Woodland period. Males declinein right humeral strength, while at the sametime females increase in strength on the leftside. As a result, earlier Late Woodlandwomen have left humeri that are, on average,stronger than their right humeri. Female bio-mechanical strength decreases in Mississip-

226 P.s.BRIDGES ET AL.TABLE 5. Humeral dimensional data (in mm) and indices}

MW eLW lLW Miss

L R L R L R L R

MalesLength, mean 330 329 332 332 327 330 325 327

BE 3.1 2.8 2.2 2.4 2.1 2.0 2.5 2.2N (26) (27) (28) (27) (33) (36) (30) (35)

MidshaftMax diameter, mean 21.9 23.0 22.3 23.0 21.9 22.8 22.3 22.9BE 0.36 0.35 0.34 0.29 0.32 0.26 0.28 0.27N (25) (28) (28) (30) (32) (37) (30) (35)Min diameter, mean 16.6 17.1 16.3 16.6 16.5 17.0 16.8 16.9BE 0.27 0.24 0.27 0.23 0.27 0.22 0.24 0.23N (25) (28) (28) (30) (32) (37) (30) (35)Circumference, mean 64.2 67.0 65.0 66.8 64.0 66.7 65.2 67.0BE 1.01 0.98 1.00 0.85 0.80 0.70 0.71 0.71N (24) (28) (26) (29) (32) (35) (30) (35)

Minimum shaftMax diameter, mean 18.5 19.2 19.0 19.5 18.5 19.1 18.9 19.6BE 0.23 0.21 0.17 0.20 0.15 0.15 0.22 0.25N (35) (34) (31) (35) (42) (47) (34) (36)Min diameter, mean 19.5 20.4 18.9* 19.2 19.2 19.5 19.5 19.7SE 0.30 0.30 0.37 0.31 0.27 0.26 0.28 0.26N (35) (34) (31) (35) (42) (47) (34) (36)Circumference, mean 60.2 62.7 61.0 61.9 60.3 61.7 61.6 62.9BE 0.61 0.57 0.71 0.65 0.54 0.51 0.57 0.59N (35) (34) (31) (35) (42) (47) (34) (36)

Shape indicesMidshaft, mean 76 75 73 72 75 75 76 74BE 1.07 0.84 0.76 0.80 0.78 0.79 0.96 0.74N (25) (28) (28) (30) (32) (37) (30) (35)Minimum shaft, 105 107 100* 99* 104 102 103 101'

meanBE 1.5 1.8 1.8 1.5 1.4 1.2 1.3 1.3N (35) (34) (31) (35) (42) (47) (34) (36)

FemalesLength, mean 303 307 304 308 302 304 302 307BE 2.7 2.4 2.3 2.2 2.2 2.1 2.3 2.5N (25) (25) (26) (33) (43) (38) (34) (39)

MidshaftMax diameter 1 mean 19.6 20.1 20.7 21.1 * 20.6* 21.3* 20.0 20.3*BE 0.27 0.27 0.27 0.24 0.25 0.24 0.32 0.30N (28) (29) (26) (35) (43) (42) (34) (38)Min diameter, mean 14.5 14.6 15.0 14.8 15.0 14.9 15.0 15.2BE 0.27 0.22 0.29 0.21 0.19 0.15 0.26 0.20N (28) (29) (26) (35) (43) (42) (34) (38)Circumference, mean 57.1 59.0 59.3 61.0 59.6 61.2 58.9 60.0BE 0.65 0.71 0.82 0.71 0.70 0.62 0.82 0.72N (28) (28) (24) (34) (42) (40) (34) (38)

Minimum shaftMax diameter, mean 16.4 16.8 17.0 17.2 16.9 17.2 17.2 17.5BE 0.21 0.21 0.25 0.25 0.15 0.17 0.28 0.24N (33) (36) (29) (34) (54) (51) (38) (41)Min diameter, mean 16.7 16.9 17.4 17.4 17.5 17.5 17.1 17.2BE 0.27 0.24 0.34 0.26 0.18 0.19 0.29 0.24N (33) (36) (29) (34) (54) (51) (38) (41)Circumference, mean 53.6 54.1 55.6 56.0 55.7* 55.9 55.6 56.1*BE 0.54 0.53 0.66 0.62 0.45 0.41 0.71 0.61N (33) (36) (29) (34) (54) (51) (38) (41)

Shape indicesMidshaft, mean 74 73 73 70 73 70 75 75**'***BE 1.42 1.12 1.21 1.07 0.90 0.67 1.06 1.02N (28) (29) (26) (35) (43) (42) (34) (38) ,",Minimum shaft, 102 101 103 102 104 102 99 99

meanBE 2.0 1.6 2.1 1.8 1.2 1.2 1.5 1.4N (33) (36) (29) (34) (54) (51) (38) (41)

1 See Table 1 for notes.

BONE STRENGTH IN WEST-CENTRAL ILLINOIS 227

Fig. 3. Torsional strength (standardized) of femalehumeri. Means. (See Fig. 1 for notes.)

Fig. 2. Torsional strength (standardized) of malehumeri. Means. (See Fig. 1 for notes.)

pian times, with a concomitant change in theshape of the right midshaft suggesting a re-duction of stress at that point, while otherexternal dimensions are maintained com-pared to the preceding time period.

Radius and ulna

Males show few significant changes in ra-dial diaphyseal dimensions (Table 6). Leftmaximum shaft minimum diameter in-creases significantly in Mississippian malescompared to earlier Late Woodland males.Correspondingly, left radial shape indicesalso register significant increases in Missis-sippian males compared to earlier LateWoodland samples. Taken together, thesedata suggest more robust distal forearms inMississippian times. There are no signifi-cant changes in male ulna through time(Table 7).

Females show a variety of differences inforearm properties which are only partiallypredicted by the humeral biomechanicaldata. Neither the radius nor the ulnachanges significantly in the earlier LateWoodland period (with the exception of

DISCUSSION

right side ulna length), though the trend istowards an increase, as in the humeral andfemoral data. However, in the later LateWoodland, numerous ulnar variables in-crease significantly in females, mostly whencompared to the Middle Woodland. Interest-ingly, this trend towards greatest size di-mensions in the late Late Woodland alsooccurs when female humeral biomechanicalstrength is at its greatest. However, radialdimensions exhibit few significant changesthrough the late Late Woodland, indicatingthat activities may have differentially af-fected areas of the arm and forearm, or per-haps indicating a lack of correspondence be-tween external dimensions and internaldiaphyseal structure.

For Mississippian females, there is asteep decline in radial maximum shaft di-mensions compared to the Late Woodlandsamples. At the same time, radial shapeindices for Mississippian females increaseon both sides, a development towards circu-larity of shape. This pattern parallels fe-male humeral strength, again suggestingdecreased stress on the upper limb. As forthe ulna, two right-side midshaft dimen-sions decrease significantly in Mississippianfemales compared to earlier periods. Ulnashape indices of Mississippian femalesmaintain the significant decrease of thelater Late Woodland over earlier samples.

Diaphyseal measurements and biome-chanical variables reveal a complex patternof changes over the time span from the Mid-dIe Woodland to the Mississippian periods·in west-central Illinois, a pattern that is notidentical to that seen in other areas of theEastern Woodlands for which similar stud-ies have been carried out. One expectedfinding is that the sexes differ in the natureand timing of changes in strength indica-tors. Generally, these differences are lesspronounced for the lower limb than for theupper limb, and less pervasive for malesthan for females. Females show significantincreases in lower limb strength over thetime span examined, with the greatest dif-ferences occurring between the MiddleWoodland and the earlier Late Woodlandperiods. Males, on the other hand, show no

MISS

MISS

LLW

LLW

ELW

ELW

MW

MW

100

600

500

== 400!!u;<; 300co~ 200...

600

SOD

=g'400~'"~3000

~ 200...100

228 P.S. BRIDGES ET AL.

TABLE 6. Radial dimensional data (in mm) and indices 1

MW eLW lLW Miss

L R L R L R L R

MalesLength, mean 258 254 261 260 259 260 258 259SE 3.0 4.2 2.5 2.8 2.4 1.8 2.2 2.0N (24) (15) (25) (22) (28) (31) (26) (31)

MidshaftMax diameter, mean 14.9 15.1 15.1 15.1 14.6 14.9 14.5 15.1SE 0.33 0.48 0.26 0.33 0.20 0.24 0.31 0.29N (23) (15) (25) (21) (28) (31) (25) (30)Min diameter, mean 12.3 11.8 12.0 11.9 12.1 12.1 12.5 12.1SE 0.18 0.35 0.21 0.26 0.12 0.16 0.19 0.17N (23) (14) (25) (21) (28) (31) (26) (30)Circumference, mean 43.4 43.2 43.4 43.7 42.6 43.4 43.2 43.5SE 0.66 1.07 0.65 0.87 0.42 0.53 0.66 0.61N (22) (14) (24) (20) (28) (30) (25) (29)

Maximum ShaftMax diameter, mean 16.4 16.6 16.6 16.8 16.2 16.5 16.5 16.5SE 0.26 0.27 0.28 0.29 0.18 0.23 0.27 0.26N (29) (27) (28) (31) (42) (40) (28) (34)Min diameter, mean 12.2 12.4 11.6 11.7 11.9 11.8 12.5** 11.5SE 0.18 0.29 0.22 0.23 0.14 0.16 0.20 0.24N (29) (27) (28) (31) (42) (40) (28) (34)Circumference, mean 45.1 46.2 45.0 46.3 44.6 45.5 45.5 45.8SE 0.57 0.67 0.54 0.59 0.37 0.47 0.62 0.56N (29) (27) (34) (30) (41) (39) (28) (34)Max head diameter, mean 23.1 22.9 22.9 23.1 23.3 23.5 22.8 23.0SE 0.28 0.29 0.27 0.21 0.23 0.30 0.44 0.30N (15) (12) (18) (22) (21) (22) (10) (19)Min head diameter, mean 21.9 21.9 21.7 22.2 22.1 22.3 21.5 21.8SE 0.24 0.26 0.27 0.23 0.19 0.29 0.38 0.35N (13) (15) (17) (21) (22) (23) (15) (16)

Shape indicesMidshaft, mean 83 78 80 79 84 81 87** 80SE 1.6 2.4 1.5 1.9 1.3 1.2 1.6 1.5N (23) (14) (25) (21) (28) (31) (25) (30)Maxshaft, mean 75 75 70 70 74 72 76** 70SE 1.4 1.5 1.5 1.5 1.1 1.2 1.4 1.4N (29) (27) (28) (31) (42) (40) (28) (34)

FemalesLength, mean 232 234 239 242 231** 233** 236 237SE 2.2 1.7 2.4 2.3 1.5 2.0 2.4 2.0N (21) (21) (25) (29) (36) (31) (28) (40)

MidshaftMax diameter, mean 13.4 13.7 13.6 14.0 13.6 14.3 13.2 13.6SE 0.25 0.34 0.29 0.21 0.21 0.22 0.22 0.20N (21) (21) (24) (29) (35) (30) (28) (40)Min diameter, mean 10.5 10.1 10.8 10.5 10.5 10.5 10.9 10.7SE 0.19 0.17 0.23 0.13 0.13 0.14 0.21 0.17N (21) (21) • (25) (28) (35) (29) (28) (40)Circumference, mean 38.3 38.5 39.1 40.0 39.0 40.1 39.2 39.1SE 0.59 0.66 0.55 0.43 0.42 0.48 0.50 0.45N (21) (21) (24) (27) (35) (29) (27) (40)

Maximum shaftMax diameter, mean 14.7 14.8 15.2 15.4 15.4 15.6 14.8 14.8***SE 0.27 0.29 0.24 0.22 0.19 0.19 0.28 0.21N (26) (26) (28) (32) (48) (42) (34) (42)Mill diameter, mean 10.4 10.2 10.6 10.5 10.5 10.4 10.9 10.4SE 0.16 0.20 0.19 0.13 0.13 0.14 0.21 0.17N (26) (26) (28) (32) (48) (41) (34) (42)Circumference, mean 40.3 40.8 41.2 42.1 41.5 41.8 40.8 40.8SE 0.58 0.56 0.44 0.50 0.37 0.40 0.51 0.48N (25) (26) (27) (30) (48) (40) (33) (42)Max head diameter, mean 20.5 20.4 21.0 21.3 20.7 21.1 19.8** 20.2**SE 0.25 0.20 0.30 0.29 0.25 0.23 0.26 0.27N (18) (20) (19) (17) (23) (16) (15) (26)Min head diameter, mean 19.5 19.6 19.8 20.1 19.7 20.0 19.2 19.1**'*** .'SE 0.22 0.22 0.23 0.22 0.19 0.24 0.28 0.24N (20) (20) (20) (20) (22) (18) (19) (27)

Shape indicesMidshaft, mean 79 75 80 76 77 74 83*** 78***SE 1.6 1.6 2.0 1.4 1.3 1.2 1.9 1.2N (21) (21) (24) (28) (35) (29) (28) (40)Maxshaft, mean 71 69 70 69 69 67 74*** 70SE 1.33 1.70 1.09 1.23 0.84 1.07 1.84 1.08N (26) (26) (28) (32) (48) (41) (34) (42)

] See Table 1 ior notes.

BONE STRENGTH IN WEST-CENTRAL ILLINOIS 229TABLE 7. Ulnar dimensional data (in mm) and indices1

~ MW eLW lLW Miss

L R L R L R L R

MalesLength, mean 277 272 281 281 277 282 275 277SE 3.2 3.6 2.8 3.0 1.9 2.0 2.5 2.3N (16) (17) (22) (21) (27) (30) (24) (30)

MidshaftMax diameter, mean 16.4 16.5 16.2 16.8 16.7 16.8 16.5 16.5SE 0.44 0.34 0.30 0.43 0.24 0.28 0.30 0.23N (16) (15) (20) (20) (27) (28) (24) (29)Min diameter, mean 12.3 12.3 11.8 12.2 12.4 12.8 11,8 12.5SE 0.27 0.27 0.20 0.22 0.17 0.15 0.21 0.22N (16) (15) (20) (20) (27) (29) (24) (29)Circumference, mean 46.9 47.6 47.3 48.9 48.5 49.0 47.8 49.4SE 0.78 0.91 0.69 0.93 0.50 0.60 0.50 0.57N (16) (14) (19) (20) (26) (27) (24) (29)

Maximum shaftMax diameter, mean 17.1 17.1 17:6· 17.4 17.6 17.5 17.3 17.5SE 0.34 0.35 0.39 0.43 0.24 0.22 0.33 0.27N (28) (26) (27) (27) (42) (39) (27) (33)Min diameter, mean 13.0 13.1 12.6 13.0 12.8 13.4 12.3 12.9SE 0.20 0.20 0.19 0.18 0.13 0.14 0.23 0.20N (28) (26) (27) (27) (42) (39) (27) (33)Circumference, mean 49.3 49.7 50.4 50.9 50.5 51.1 49.5 51.1SE 0.70 0.76 0.86 0.87 0.44 0.48 0.61 0.53N (27) (25) (26) (26) (40) (39) (27) (33)

Shape indicesMidshaft, mean 75 75 74 73 74 76 73 76SE 1.9 1.2 1.6 1.5 1.5 1.3 1.9 1.6N (16) (15) (20) (20) (27) (28) (24) (29)Maxshaft, mean 76 77 72 75 73 77 72 74SE 1.5 1.3 1.5 1.6 1.2 1.2 1.9 1.3N (28) (26) (27) (27) (42) (39) (27) (33)

FemalesLength, mean 251 253 260 263* 251** 253** 255 257SE 2.5 2.8 2.5 2.2 2.1 1.6 2.3 2.3N (17) (15) (25) (26) (29) (32) (26) (33)

MidshaftMax diameter, mean 14.9 14.5 15.6 15.5 16.0 16.3* 15.4 15.1***SE 0.38 0.37 0:32 0.27 0.32 0.26 0.31 0.26N (17) (14) (25) (26) (28) (32) (25) (32)Min diameter, mean 10.9 11.1 11.0 11.4 10.9 11.0 10.5 10.5**SE 0.26 0.22 0.18 0.18 0.17 0.15 0.23 0.16N (17) (14) (25) (26) (28) (32) (26) (32)Circumference, mean 42.5 42.8 44.3 45.0 45.2 46.3' 44.0 44.3SE 0.79 0.74 0.61 0.57 0.77 0.54 0.61 0.57N (16) (13) (23) (26) . (27) (31) (24) (32)

Maximum shaftMax diameter, mean 15.4 15.5 16.4 16.3 16.5* 16.7* 16.4 16.0SE 0.27 0.33 0.29 0.27 0.26 0.23 0.27 0.26N (26) (21) (26) (32) (42) (41) (36) (41)Min diameter, mean 11.4 11.3 11.5 11.7 11.2 11.2 11.1 11.2SE 0.20 0.22 0.18 0.18 0.15 0.13 0.16 0.19N (26) (21) (26) (32)· (42) (41) (36) (41)Circumference, mean 44.3 44.5 46.6 46.8 46.5* 47.1* 46.5* 46.1SE 0.62 0.59 0.60 0.54 0.54 0.50 0.55 0.55N (26) (21) (26) (32) (42). (39) (36) (41)

Shape indicesMidshaft, mean 74 77 71 74 69 68*,** 68 70*SE 2.2 2.2 1.7 1.5 1.3 1.1 1.8 1.2N (17) (14) (25) (26) (28) (32) (25) (32)Max shaft, mean 74 73 71 73 68* 68*,** 68* 70

~ SE 1.48 2.14 1.66 1.41 1.12 0.98 1.23 1.26N (26) (21) (26) (32) (42) (41) (36) (41)

1 See Table 1 for notes.

230 P.s. BRIDGES ET AL.

major differences in femoral size or strengththroughout all the time periods, and amixed pattern of a few increases and de-creases in various tibial dimensions and in-dices.

For the upper limb, a different patternemerges. Females show a large number ofsignificant increases in humeral dimensionsand strength indicators in the earlier LateWoodland period. The female ulna is char-acterized by larger dimensions in the laterLate Woodland, as opposed to the earlierpart of this period, and the radius exhibitsalmost no change from Middle Woodland toLate Woodland times. In Mississippian fe-males, all three long bones show a signifi-cant decline in a number of external dimen-sions and strength variables. Males exhibitvery few significant changes in the upperlimb over time. There is a general pattern ofdecline in humeral strength from the Mid-dle Woodland to early Late Woodland,though these changes failed to show signif-icance. There are no changes in the ulna,and the radius displays only a few signifi-cant differences between the Mississippianand early Late Woodland, but only on theleft side.

In short, females exhibit significant in-creases from Middle Woodland to LateWoodland periods in many measures oflongbone strength and external dimensions, andshow a decline in the Mississippian periodin the arms only; males show very few sig-nificant differences over time, restrictedmainly to increases in the tibia and radiusin the Mississippian period. One of the ma-jor implications from this work is that manychanges in activities do not occur with theadoption of maize agriculture, but ratherpredate this event. In order to understandthe timing of the changes in activities, it isnecessary to examine more closely specificfood-production activities in prehistoric Illi-nois, both predating and postdating the useof maize.

The Late Woodland period:intensification of native seeds

The results described here show that sig-nificant changes in (female) diaphyseal di-mensions and strength occurred before theadoption of maize as a dietary staple. This

discovery could, of course, reflect impreci-sion in the radiocarbon dates assigned tothese sites or perhaps an insufficient under-standing of the process of maize adoption. Itis equally plausible that in· this region theinitial introduction of maize was less impor-tant in terms of workload than was the in-tensification of other cultivated crops. Inother words, the focus on maize ignores thesignificant antecedent role played by nativecultigens in a number of prehistoric societ-ies in the Midwest (Illinois, Missouri) andMidsouth (Kentucky, Tennessee).

Intentional cultivation of a variety ofhard-shelled squash began during the Mid-dle Archaic period (circa 5000 BC) in west-central Illinois. By the Middle Woodland pe-riod in the Midwest, a variety of native seedcrops were also grown. In west-central Illi-nois, these included two oily seeded annu-als, sumpweed or marsh elder (fua annualand sunflower (Helianthus), and fourstarchy seeds, goosefoot (Chenopodium ber-landieri), erect knotweed (Polygonum erec-tum), maygrass (Phalaris caroliniana), andlittle barley (Hordeum pusillum), as well assquash (Cucurbita pepo) (Asch and Asch,1985a). Several of these plants (squash,sumpweed, sunflower, and goosefoot) showsigns of domestication, and it is now widelyaccepted that independent domestication ofnative plants occurred in the Midwest andMidsouth regions prior to the introductionof maize and other tropical domesticatesfrom Mesoamerica (Smith, 1989).

Although there is no dramatic change inthe nature of botanical assemblages be-tween the Middle Woodland and Late Wood-land periods, there is evidence for increas-ing intensification of existing crops by LateWoodland times. Caches of seeds first ap-pear in the archaeological record of west-central Illinois during the early Late Wood-land period, pointing to an increase in bothstorage and use of cultigens (Asch and Asch,1981; Johannessen, 1993; Styles, 1981,1985). Significantly, the increase in femalefemoral and humeral strength occurs at thetime of intensification of native seed crops,suggesting that females played a major rolein this process.

Other bioarchaeological studies also indi-cate changes in activities in the Late Wood-

BONE STRENGTH IN WEST-CENTRAL ILLINOIS 231land period. In a study on cortical thicknessand remodeling rates of the femur based onthe same groups used in the current work,Hanson (1988) found a significant increasein female cortical area in the earlier LateWoodland, similar to that seen in this study.Deltoid tuberosity rugosity in females alsoincreases greatly at this time, leading to areduction in sexual dimorphism of this fea-ture (Hamilton, 1982).

In addition, fertility rates increase withthe onset of the Late Woodland period, co-inciding with a rise in juvenile caries, andoften coincident with enamel hypoplasia(Buikstra et aI., 1986; Cook and Buikstra,1979). This increase in caries may be due toa change in weaning diet, which correlateswith the introduction of pottery types de-signed for efficient boiling (Buikstra et aI.,1986). Innovations in pottery include thin-ner vessel walls, finer temper, and differentvessel forms, all of which suggest that resis-tance to thermal stress was the most impor-tant factor in their manufacture (Braun,1983). Therefore, in the Late Woodland pe-riod, a number of interrelated factors maybe seen: an increase in the use of starchyseeds, an increase in female arm strength(possibly linked with growing or processingthese seeds), a transition to pottery vesselsbetter suited for boiling (resulting in softerfoods such as gruel), a concomitant increasein juvenile caries, and finally, increased fer-tility related to the introduction of an appro-priate food (gruel) for early weaning of in-fants (Buikstra et aI., 1986). Given thetemporal changes in bone rigidity, perhapsthese data reflect the assumption of femalesubsistence activities at an earlier age, re-sulting in attainment of greater bone mass.There appears to be a fundamental shift inthe life history pattern associated with theLate Woodland intensification of starchyseeds: early weaning and assumption offood-production tasks by females at an ear-lier age. These life history changes are con-sonant with intensification of hoe cultiva-tion cross-culturally (Cohen and Armelagos,1984; Ember, 1983).

Another technological change of the LateWoodland period is the introduction of thebow-and-arrow (Blitz, 1988). Small triangu-lar arrowpoints are present even at the ear-

liest Late Woodland sites in this sample,dating to shortly after AD 600 (Perino,1973c). Besides documenting the introduc-tion of the bow, these points suggest an in-crease in interpersonal violence at this time(Milner, 1995). The Koster Mounds, for ex-ample, of earlier Late Woodland age, con-tain several multiple burials with associ-ated points, some embedded in bone(Perino, 1973c). The introduction of the bowcoincides with a decrease in right humeralstrength in males in the earlier Late Wood-land period. This skeletal change is consis-tent with that expected when the atlatl(spearthrower) is replaced by the bow, sincethe atlatl presumably would have placedgreater forces on the throwing arm. Becausethe bow imposes forces on both the left andright sides, a decline in bilateral asymmetryshould occur (Bridges, 1990). Although hu-meral torsional strength does become moreequivalent in both arms in earlier LateWoodland, left arm strength does not in-crease as expected. Instead, left armstrength is at its lowest levels in the earlierLate Woodland period, when the bow is in-troduced. Therefore, although decreasedmale right arm strength is consistent withreplacement of the atlatl by the bow, otherchanges in left arm strength are not, butrather postdate this event. This suggeststhat weapon technology can account for atmost only part of the change in male armstrength in these groups; other activitiesmust also be responsible.

The later Late Woodland period: theadoption of maize as a dietary staple

Although maize has been found in MiddleWoodland contexts in the Eastern Wood-lands (Riley et aI., 1994; Smith, 1989), itsfirst appearance at archaeological sites inthis region occurs well into the Late Wood-land period, at about AD 580 (Asch andAsch, 1985b). Carbon isotope analyses dem-onstrate that maize is not a measurablepart of the diet until after AD 800 (Benderet aI., 1981; Buikstra et aI., 1987; van derMerwe and Vogel, 1978). Although maize iswidely grown after that time, it does nottotally displace the native crops grown ear-lier. When maize is initially adopted, itseems to be added to the preexisting suite of

232 P.S. BRIDGES ET AL.

native crops and treated as just anotherstarchy seed (Rindos and Johannessen,1991; Watson, 1988). If this scenario is cor-rect, it would go far towards explaining therelative dearth of changes in diaphysealstrength between the earlier and later LateWoodland periods. Because maize is incor-porated into an already operational horti-cultural system, its initial cultivation andprocessing may have been similar to thoseof the starchy seeds that had been grown forthousands of years. In short, fewer changesin activities, especially female activities, oc-cur with the initial introduction of maize asa staple crop because the physical activitiesinvolved in its cultivation and processing (atleast in the beginning) are similar to thoseemployed for growing native crops. Thisconclusion is also supported by other re-search on femoral cortical area (Hanson,1988) and humeral rugosity (Hamilton,1982), which found no significant differ-ences occurring at this time.

Pickering (1984) found an increase in fe-male arthritis which apparently occurs atthe time of the introduction of maize. How-ever, that study lumped Middle Woodlandand earlier late Woodland periods into a"premaize" sample, and later Late Wood-land and Mississippian periods into a "post-maize" grouping. Although there is a clearincrease in female arthritis over time, thesegross temporal groupings make it difficult toascertain exactly when in the sequence thischange occurred.

The Mississippian period: intensificationof maize

Carbon isotope analysis indicates thatmaize use increases strongly in the Missis-sippian period (Bender et a!., 1981; van derMerwe and Vogel, 1978). Native crops con-tinue to constitute a significant part of thediet as well (Asch and Asch, 1985a). Sun-flower and sumpweed achenes reach theirlargest size in the Mississippian period, in-·dicating that selection for favored nativecultigens operates into late prehistory(Yarnell, 1978). One native plant, erectknotweed, may even be initially domesti-cated during Mississippian times (Asch andAsch, 1985a).

The increasing reliance on starchy seeds,especially maize, in the Mississippian pe-riod would be expected to coincide with agreater need for processing, a chore tradi-tionally carried out by females. If so, femalearm strength should continue to increase inthe Mississippian period. That it did not,but actually decreases, requires rethinkingthis hypothesis. Several alternative expla-nations are possible: that maize is physi-cally less demanding to grow or processthan native seeds; that processing becomesmore efficient in the Mississippian era (per-haps through soaking, boiling, or parchingthe maize prior to pounding it in a woodenmortar); or that other activities unrelated tomaize agriculture decrease significantly atthis time.

In historic times, the hard kernels ofdried or stored corn had to be softened orground before use, a process that requiredconsiderable time and physical strength. Itis not clear how the earlier seeds were pre-pared, but historic analogues are availablefor maize processing in Mississippian soci-eties. Throughout the Eastern Woodlands,the wooden mortar and pestle were used byintensive maize farmers for this chore. Oneearly observer likened pounding corn inwooden mortars to blacksmithing (Tuggle,1973). Ethnographically, women in societiesthat utilize simple technology for processingmaize have been observed to spend, on theaverage, 2 hr a day in pounding or grindingcorn (Foster, 1967). A recipe for makinghominy from prepared corn in a woodenmortar, published in the 1978 ChoctawNews Fair Edition, instructs one to "beat itwith a pestle for at least six hours ... "Maize processing would have been evenmore rigorous if Eastern Woodland Indiansocieties had not adopted several key ad-vances in soaking and cooking technologythat significantly reduced the amount ofpounding and grinding required: lye pro-cessing and boiling.

Many groups, as part of the initial pro-cessing, first soaked the kernels overnight,sometimes in a lye (alkali) solution made ofwood or other ashes, to remove their outerhull (e.g., Campbell, 1959; Swanton, 1979;Tuggle, 1973). Processing in this mannerwould have lessened the need for pounding

"

BONE STRENGTH IN WEST-CENTRAL ILLINOIS 233

or grinding corn. Although wood-ash lyeprocessing is well-established for historicIndian societies in the Eastern Woodlands(Linton, 1924), it may not require any dis-tinctive artifacts, and therefore, may be dif-ficult to confirm prehistorically. However,there are two forms of evidence for prehis-toric lye processing. One clue comes fromcarbonized corn kernels preserved at ar-chaeological sites. The majority of kernelsfrom late prehistoric archaeological sitesclosely resemble hominy, or maize that iseither boiled or treated with alkali process-ing, rather than unprocessed corn (King,1994). This suggests that some kind of ini-tial soaking process softened the kernelsprior to pounding or grinding them. A sec-ond possible indicator of prehistoric lye pro-cessing is the distinctive pottery artifactsknown as "stumpware" and "juice presses."In form, these artifacts appear to be funnelsand strainers. Although their function is notdefinitely established, these ceramic con-tainers have been interpreted as artifactsused in lye-processing maize (Emerson andJackson, 1984), and first appear in Missis-sippian times.

Alkali processing of corn, or nixtamaliza-tion, has been suggested to improve thequality of protein in maize, and increase theavailability of niacin (Katz et aI., 1974).However, its overall effect on nutrients isunclear. Certainly, any cooking or soakingtechnique tends to remove nutrients, espe-cially water-soluble vitamins (Penny, 1983).Mississippian diets, at least in this region,were diverse enough that pellagra and othernutritional deficiencies associated with cornwere unlikely to have posed a serious prob-lem. Therefore, there is no reason to suspectthat nixtamalization was adopted in thisregion primarily as a nutritional strategy.Instead, it functioned to aid processing, pos-sibly adapted from earlier techniques asso-ciated with either leaching tannins fromacorns, or processing native seed crops(Blitz and Welch, 1998; Linton, 1924).

Along with innovations in food prepara-tion involving soaking, boiling technology isenhanced in late prehistoric societies. Inwest-central Illinois, thin-walled potteryvessels adapted to boiling appear prior tosignificant maize use, in the Late Woodland

period, coincident with the increase in na-tive seed production. With maize intensifi-cation, Mississippian pottery was producedin more diverse forms, and included innova-tive wide-mouth globular pots suitable forboiling large quantities. Analysis of Missis-sippian pottery technology supports historicreports that indigenous diets emphasizedboiling, which would have resulted in softer,more palatable foods (Hally, 1986; Swanton,1979). Clearly, Mississippian populationscontinued and may even have expanded theLate Woodland emphasis on boiling asmaize production was intensified.

In short, in historic times, and by exten-sion, prehistoric Mississippian societies, avariety of methods for processing or cookingmaize were in use, supplementing the nec-essary but physically strenuous pounding ofcorn. Of course, the starchy seeds used byearlier Woodland peoples might also haverequired tremendous amounts of processingor boiling. Maize may have been originallyprepared in a similar way as the nativeseeds it supplemented, but perhaps ad-vances in processing technology (woodenmortar and pestle, more efficient cookingpots, nixtamalization) meant that less phys-ical labor was required to render it palat-able. Regardless, at the time of intensifica-tion of maize, female arm strength declines.Innovations in processing technology are aplausible reason for this change, but otherfactors, including greater ease of cultiva-tion, may have been responsible as well.

This summary of the prehistory of west-central Illinois shows that many of thechanges in activity patterns may be linkedto local subsistence or technologicalchanges. With these in mind, the findingsmay be compared with other regions, whichhave shown different results.

Comparisons with other regions

Similar biomechanical studies have beencarried out for two other regions of the East-ern Woodlands: northwestern Alabama andcoastal Georgia. These two previous studiescame to vastly different conclusions: onefound that activities increased with agricul-ture, and the other that they decreased. Inaddition, changes differed between thesexes. The results from the current study do

234 P.8. BRIDGES ET AL.

not completely match either ofthe previoustwo, but there are some similarities witheach.

In northwestern Alabama, Archaic-periodskeletons were compared to a Mississippianskeletal sample (there being no large collec-tions of Woodland burials in the region).Although Archaic groups in this region mayhave cultivated some plants, their subsis-tence was largely based on hunting andgathering. The Mississippians in this sam-ple are thought to have been intensivemaize agriculturalists (Walthall, 1980).Mississippian males had much stronger legsthan Archaic males, but relatively fewchanges occurred between the male samplesin the arms (Bridges, 1985, 1989). Femalesshowed increases in both arm and legstrength in the later period, but the morestriking difference between groups was inthe arms, especially on the left side. Themore widespread nature of the changes infemale strength was attributed to theirgreater participation in agricultural tasks,while the specific patterning of arm robust-icity in Mississippian females (reduced bi-lateral asymmetry and a strengthening cen-tered around the left elbow region) wassuggested to be related to pounding maizein wooden mortars (Bridges, 1985, 1989).

The coastal Georgia study came to verydifferent conclusions. There, a spectrum ofpreagricultural skeletal samples was com-pared with maize agriculturalists (Ruff andLarsen, 1990; Ruff et a!., 1984). The latergroup showed declines in both leg and armstrength, compared to the preagriculturalsample. Also in contrast to the Alabamastudy, males showed the most significantchanges, not females. Males decreased instrength at the subtrochanteric level of thefemur and the distal humerus. Females hadno significant changes in size-standardizedstrength measures for either the humerusor femur. The coastal Georgia study sug-gests a major decrease in male activitieswith the introduction of agriculture, but lit-tle or no change in female chores (Ruff andLarsen, 1990; Ruff et a!., 1984).

The results from the present study, whilenot identical to those from either Alabamaor Georgia, show some similarities witheach. Change in female strength in Illinois

in many ways mirrors that from Alabama,although the timing of events is eithersomewhat different, or perhaps obscured inthe Alabama study by the fact that only twoends of the spectrum (hunter-gatherers vs .agriculturalists) are represented, ratherthan intermediate horticultural groups. Inboth regions, females showed more differ-ences over time than males, encompassingboth the arms and legs. In both places, anincrease in female strength in the legs, andthe left arm, was associated with either in-tensification oflocal seeds (Illinois) or adop-tion of maize agriculture (Alabama). How-ever, the drop in female arm strength inIllinois with maize intensification is puz-zling. As discussed above, it may be that thenative seeds grown in Illinois are simplymore difficult to grow or process than maize,or that cultivation and processing tech-niques improve in that region at the timethat maize use intensifies.

Unfortunately, we cannot yet compare therelative importance of maize in west-centralIllinois with northwestern Alabama, sinceappropriate isotopic studies have not yetbeen carried out in the latter region. West-central Illinois societies, although relyingon maize to a large degree in the Mississip-pian period, did not utilize it to the sameextent as Fort Ancient and other societies tothe east and south (Buikstra, 1992; Buik-stra et a!., 1987). If the northwestern Ala-bama groups shared this characteristic withFort Ancient and nearby Tennessee Missis-sippian populations, some of the variationbetween them and Illinois Mississippian so-cieties may be due to the relative impor-tance of maize in the diet. If true, this re-gional variation in maize productionintensity could also explain some of the dif-ferences in activity levels between femalesin the Alabama and Georgia studies, sincethe amount of corn consumption, as judgedby carbon isotope levels, is lower in bothcoastal and inland Georgia groups than inthose from Tennessee (Buikstra, 1992;Hutchinson et a!., 1998).

Changes in male strength in Illinois,which mostly involve a decline in right armstrength, are not congruent with those fromAlabama. However, the studies are not com-pletely comparable, since only left (not

..

BONE STRENGTH IN WEST-CENTRAL ILLINOIS 235right) humeri were analyzed biomechani-cally from Alabama. However, external di-aphyseal dimensions actually increasesomewhat in agricultural males from Ala-bama, further supporting the idea thatchanges in male strength are different fromthose in Illinois. For Illinois males, the dataare more similar to those from coastal Geor-gia, which show a decline in male humeralstrength (left and right sides combined) overtime. Once again, this change occurs in Illi-nois populations with the early Late Wood-land period, prior to the adoption of maizeagriculture, and coincident with the intro-duction of the bow-and-arrow. Like the Al-abama agriculturalists, male leg strength inthe Illinois sample increases (although lessdramatically); such was not the case for theGeorgia coast.

It is likely that a number of reasons mayaccount for the differences in results be-tween these studies. The environment, ag-ricultural practices, and processing tech-niques may have varied in different regions.And, as noted above, significant regionalvariation in maize use may correlate withactivity levels, especially for females. Atleast as important is the fact that the pre-maize groups used for comparison differeddramatically-from Archaic hunter-gather-ers to Woodland horticulturalists to coastalfisherfolk. In spite of the variation seen inthese three studies, there is an importantcommonality. The point at which activitieschange in all three regions is similar: thechange occurred when use of crops intensi-fied, either as a result of a long endemicprocess, or as the result of a relatively rapid,full-scale introduction of maize agriculture.Recent comparative research has revealedthat intensive cultivation of native seedcrops was primarily a Midwestern (includ-ing Kentucky and Tennessee) phenomenon(Fritz, 1993). In the Southeast, on thecoastal plain, the native crops were not cul-tivated, at least not to the extent seen in theMidwest. In other words, there were reallytwo crop-intensification transitions in theMidwest, the first with native seed cropsand the second with maize, whereas coastalGeorgia populations participated in only thesingle food-production transition to maize

(there are no data on premaize cultivationin northwestern Alabama).

The current study, while not conformingcompletely to either ofthe previous works interms of results, may help to clarify theobserved differences in regional activitypatterns. The primary factors affecting re-gional activity variation are the agriculturalintensification process and the differentialparticipation of males and females in thenew activities that accompany the process.For example, the crucial event in Illinois inchanging activities may not have occurredat the moment of initial adoption of maizeagriculture, but as a process of intensifica-tion of plant husbandry that occurredthroughout the Woodland and into the Mis-sissippian periods in this region. As individ-uals began to increase food production, ac-tivity levels may have risen early in theprocess. It is possible that, as more efficientmeans of growing and processing crops de-veloped, activities may have later declined.

In all three regions, males and femalesshow differing patterns of change with theintroduction or intensification of agricul-ture. While male arm strength either de-clines or remains the same, changes in maleleg strength are highly variable, possiblydue to differences in male mobility amongregions. Changes in female strength maydepend more on the degree of reliance onagriculture, with more intensive maize ag-riculturalists showing greater increasesthan those groups with less reliance onmaize. For example, the decrease in malearm strength in the earlier Late Woodlandperiod of west-central Illinois occurs at thesame time as a number of female strengthmeasures increase, clearly indicating thatchanges in male and female activities arenot closely linked. Overall, male and femalechanges in strength occur largely indepen-dent of each other, suggesting that theirroles in society differed as well, as is sup-ported by early ethnographic accounts(Swanton, 1979). Given that females histor-ically conducted the majority of agriculturaltasks, including both growing and process-ing crops, and that variation in femalestrength in this study fits well with the ob-served archaeological sequence of subsis-tence change, it can be assumed that fe-

236 P.S. BRIDGESET AL.

males were also largely responsible forgrowing crops in the Woodland period aswell as later in Mississippian times. For thisreason, it is highly probable that most ofthechanges seen in subsistence and processingtechnology are female innovations (Watsonand Kennedy, 1991).

CONCLUSIONS

In west-central Illinois, the level of phys-ical activities does not change with theadoption of maize as a staple crop, but priorto this time, when use of native seed cropsintensifies. Femoral and left humeralstrength increase in females at this time,corresponding with historical evidence thatfemales are the primary individuals respon-sible for growing and processing of crops inprehistoric Eastern Woodland societies.Male changes are fewer in number, and arelargely restricted to a decrease in the righthumerus, which may be tied to the replace-ment of the atlatl by the bow.

Fewer changes in activities occur whenmaize becomes a dietary staple in the laterLate Woodland period, possibly becausemaize is at first treated as just another seedcrop. Later, female left humeral strengthdeclines significantly in the Mississippianperiod when maize use intensifies. Thiscould occur because maize is easier to culti-vate or process than native small seeds, oras a result of significant improvements inprocessing, or changes in other types of ac-tivities.

Results from this study differ from thoseseen in previous research on skeletal sam-ples from Alabama and Georgia, supportingthe notion that significant regional diversityis present in levels of activity associatedwith prehistoric agriculture. This variabil-ity is of particular interest, since it maycorrelate with differences in the nature orintensity offood production across the East-ern Woodlands, which in turn has funda-mental implications for the interpretation ofprehistoric health, demography, sexual di-vision of labor, and sociopolitical develop-ment. Additional comparative work onthese topics is necessary to resolve theseIssues.

ACKNOWLEDGMENTS

The Pete Klunk, Koster, Yokem, andSchild sites were excavated by GregoryPerino of the Gilcrease Institute (Tulsa,OK). This material is housed at IndianaUniversity, and curated by Dr. Della Cook.Dr. Jane Buikstra directed the excavation ofthe other sites, first at Northwestern Uni-versity, and later at the University of Chi-cago. We thank Drs. Buikstra and Cook fortheir aid and hospitality while gatheringdata at their institutions. Dr. Ethan Braun-stein of the Department of Radiology, Indi-ana University Medical Center in Indianap-olis, directed the computed tomographicscans at that facility. Drs. Warren DeBoer,Paul Welch, and our other colleagues atQueens College endured endless questionson archaeology, agricultural intensification,and food preparation. An earlier version ofthis paper was delivered by Dr. Bridges at afestschrift in honor of Dr. C. Loring Brace atthe 64th Annual Meeting of the AAPA in1995. Final revisions of the manuscriptwere completed by John H. Blitz and MartinC. Solano, after the death of Dr. Bridges.

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